Patent Publication Number: US-8986020-B2

Title: Inter-terminal connection structure

Description:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT 
     The present invention relates to an inter-terminal connection structure, and a board terminal and a connection connector thereof. More specifically, the present invention relates to an inter-terminal connection structure for electrically connecting a conductive member to be connected to a connection connector to a board terminal mounted on a circuit board through a connection terminal of the connection connector. 
     Patent Reference has disclosed a conventional inter-terminal connection structure. In the inter-terminal connector structure disclosed in Patent Reference, a receptacle terminal (a board terminal) is mounted on each of two circuit boards placed on a same level plane. A plug connector provided with a plug terminal (a connection terminal) having a plate shape is configured to connect the receptacle terminals in a state that the receptacle terminals are arranged along one direction, so that the receptacle terminals are electrically connected. The plug terminal is arranged such that a plate surface of the plug terminal is aligned with a plane perpendicular to a surface of the circuit board, so that the plug terminal saddles between the two circuit boards. Then, the plug connector is attached to the receptacle terminals from above. 
     Patent Reference: Japanese Patent Publication No. 2012-043764 
     In the conventional inter-terminal connection structure disclosed in Patent Reference, the receptacle terminal includes a base portion disposed to face the corresponding circuit board and extending an arrangement direction of the receptacle terminal. The receptacle terminal further includes a pair of first sandwiching pieces as a locking portion and a pair of second sandwiching pieces as a contact portion extending from the base portion. The first sandwiching pieces have an engaging protrusion as a locking protrusion, and the second sandwiching pieces have a sandwiching protrusion as a contact protrusion. 
     Further, in each of the receptacle terminals, the first sandwiching pieces and the second sandwiching pieces have one thereof situated on one surface side and another thereof situated on the other surface side of the plug terminal with the plate shape, and they are arranged at positions shifted with each other in the arrangement direction. In other words, the four sandwiching pieces, that is, the pair of the first sandwiching pieces and the pair of the second sandwiching pieces are arranged in a staggered arrangement pattern, so that the first sandwiching pieces is situated at shifted positions between the second sandwiching pieces in the arrangement direction. 
     In the conventional inter-terminal connection structure disclosed in Patent Reference, as described above, the pair of the first sandwiching pieces and the pair of the second sandwiching pieces of the receptacle terminal are situated at the shifted positions on both sides of the surface of the plug terminal in the arrangement direction, so that the first sandwiching pieces and the second sandwiching pieces sandwich the plug terminal with the plate shape of the plug connector. As a result, the first sandwiching pieces and the second sandwiching pieces contact with the one surface and the other surface of the plug terminal at the different locations in the arrangement direction. 
     In the conventional inter-terminal connection structure disclosed in Patent Reference, as described above, the plug terminal of the plug connector is formed in the plate shape extending in the arrangement direction. The plug terminal is configured to contact with the receptacle terminals sandwiching the plug connector at both end portions thereof. At the same time, the plug terminal is locked in a connector pull out or insertion direction. More specifically, at the both end portions of the plug terminal, the plate surface situated at a position corresponding to the sandwiching protrusions (the contact protrusions) of the second sandwiching pieces is configured to function as a corresponding contact portion. Further, the both end portions of the plug terminal, though holes as a locked portion are formed in the plug connector at a position corresponding to engaging protrusions (locking protrusions) of the first sandwiching pieces for engaging with the engaging protrusions. 
     In general, the receptacle terminals may be shifted from a standard position relative each other in a width direction of the receptacle terminal (a direction perpendicular to the arrangement direction and the connector pull out or insertion direction) due to a deviation of the placement of the circuit board or the mounting position of the receptacle terminal relative to the circuit board. 
     In the conventional inter-terminal connection structure disclosed in Patent Reference, as described above, the first sandwiching pieces and the second sandwiching pieces press against and contact with the both surfaces of the plug terminal at the different locations in the arrangement direction. Accordingly, when the receptacle terminals are shifted in the width direction thereof, a middle portion of the plug terminal in the arrangement direction is configured to be deformed elastically in the width direction to absorb the shift of the receptacle terminals, so that the connection state between the receptacle terminals is maintained. 
     In the conventional inter-terminal connection structure disclosed in Patent Reference, as described above, when the plug connector is connected to the receptacle terminals, the plug terminal is configured to be deformed elastically to absorb the shift of the receptacle terminals in the width direction. Accordingly, as long as the connection state is maintained, in which the plug terminal is deformed elastically to absorb the shift of the receptacle terminals, a stress is applied to the plug terminal for a long period of time due to the elastic deformation, thereby causing damage in the plug terminal. Further, when the plug terminal is deformed elastically, it is difficult to maintain the connection state between the plug terminal and the receptacle terminals, thereby deteriorating contact reliability between plug terminal and the receptacle terminals. 
     Further, in the conventional inter-terminal connection structure disclosed in Patent Reference, even when a cable or the plug terminal having other conductive member is connected to the receptacle terminal mounted on the circuit board as the board terminal, it is difficult to prevent the problem due to the elastic deformation of the plug terminal in the connection state, as far as the first sandwiching pieces and the second sandwiching pieces of the receptacle terminal press against and contact with the both surfaces of the plug terminal at the different locations in the arrangement direction. 
     In view of the problems described above, an object of the present invention is to provide an inter-terminal connection structure capable of solving the problems of the conventional inter-terminal connection structure. Another object of the present invention is to provide a board terminal and a connection connector of the inter-terminal connection structure. In the inter-terminal connection structure of the present invention, it is possible to prevent a connection terminal of the connection connector from being damaged even when the board terminal and a conductive member are shifted from a standard position, and to maintain a good connection state between the board terminal and the connection terminal. 
     Further objects and advantages of the invention will be apparent from the following description of the invention. 
     SUMMARY OF THE INVENTION 
     In order to attain the objects described above, according to a first aspect of the present invention, an inter-terminal connection structure includes a board terminal mounted on a circuit board and a terminal of a connection connector connected to the board connector in a connector pull out or insertion direction as a direction perpendicular to the circuit board. As a result, a conductive member connected to the terminal of the connection connector is electrically connected to the board terminal. 
     According to the first aspect of the present invention, in the inter-terminal connection structure, the board terminal includes a base portion arranged to face the circuit board and having a side portion extending in a longitudinal direction thereof, a pair of contact pieces extending from both side portions of the base portion, and a locking pieces extending from the both side portions of the base portion. The contact pieces and the locking pieces have elastic arm portions capable of elastically deforming in a terminal width direction connecting the both side portions of the base portion viewed in the longitudinal direction. The elastic arm portions are formed in a curved shape, so that the elastic arm portions become close together in the terminal width direction. The elastic arm portions of the contact pieces are formed as contact portions, and the elastic arm portions of the locking pieces are formed as locking portions. 
     According to the first aspect of the present invention, in the inter-terminal connection structure, the connection connector includes a connection terminal having a plate shape portion inserted between the contact portions and the locking portions of the board terminal in the pull out or insertion direction viewed in the longitudinal direction. The connection connector further includes a housing for holding the connection terminal. The plate shape portion of the connection terminal has a plate surface perpendicular to the longitudinal direction and the terminal width direction. Further, the plate shape portion includes a corresponding contact portion contacting with the contact portions of the board terminal. 
     According to the first aspect of the present invention, in the inter-terminal connection structure, ones of the contact pieces and the locking pieces of the board terminal are situated on an edge portion side of the circuit board relative to the other ones in the longitudinal direction. Each of the locking portions of the locking pieces is provided with a locking protrusion approaching with each other in the terminal width direction viewed in the longitudinal direction. Further, the plate shape portion of the connection terminal includes a locked portion formed as a hole portion or a cut portion penetrating in the terminal width direction within a range including the locking protrusions of the board terminal in a connection state between the board terminal and the connection terminal in the longitudinal direction and the connector pull out or insertion direction. Accordingly, in the connection state, the contact portions of the contact pieces of the board terminal pressingly sandwich the corresponding contact portions of the connection terminal in the terminal width direction, so that the contact portions contact with the corresponding contact portions. At the same time, the locking protrusions of the locking pieces of the board terminal enter and are situated in the locked portion of the connection terminal with a play, so that the locking protrusions are movable in the terminal width direction. 
     According to the first aspect of the present invention, in the inter-terminal connection structure, ones of the contact pieces and the locking pieces of the board terminal are situated on the edge portion side of the circuit board relative to the other ones in the longitudinal direction. In other words, as opposed to the conventional inter-terminal connection structure, the contact pieces and the locking pieces do not have a mixed range in the longitudinal direction. 
     Further, the locking protrusions of the locking pieces of the board terminal enter and are situated in the locked portion of the connection terminal with a play, so that the locking protrusions are movable in the terminal width direction. In other words, the locking pieces regulate the connection terminal to be capable of locking in a non-sandwiched state. 
     As described above, according to the first aspect of the present invention, in the inter-terminal connection structure, the contact pieces and the locking pieces do not have the mixed range in the longitudinal direction, and the locking pieces regulate the connection terminal in the non-sandwiched state. Accordingly, when the board terminal and the conductive member are shifted from the standard position, the connection terminal is moved only to an inclined state relative to the standard position (the position where the connection terminal extends in the arrangement direction) in the terminal width direction while following the shift with the position of the corresponding contact portions sandwiched with the contact portions of the board terminal as a pivot, so that the connection terminal is not elastically deformed. As a result, a stress is not applied to the connection terminal, thereby preventing the connection terminal from being damaged. Further, it is possible to securely maintain the good connection state between the connection terminal and the board terminal. 
     According to a second aspect of the present invention, in the inter-terminal connection structure according to the first aspect, two circuit boards may be arranged such that edge portions thereof are situated next to each other. The board terminal having an identical configuration is disposed on each of the two circuit boards. The connection connector includes the corresponding contact portions and the locked portions on both end portions of the connection terminal. Accordingly, it is possible to connect the board terminal on one of the circuit boards to the board terminal on the other of the circuit boards as the conductive member on the other of the circuit boards with the connection terminal of the connection connector. 
     According to the second aspect of the present invention, the board terminal having an identical configuration is disposed on each of the two circuit boards. A circuit portion of the other of the circuit boards corresponds to the conductive member. The contact portions of the board terminals on the circuit boards are connected through the plate shape portion of the connection terminal of the connection connector. When one of the circuit boards and the other one of the circuit boards are shifted from a standard position, the connection terminal is inclined and moved to a position on a line between the contact portions of the board terminals on the two circuit boards without being elastically deformed. Accordingly, the locking portion enters the locked portion, so that it is possible to maintain the state capable of locking without a pressing force. 
     According to a third aspect of the present invention, in the inter-terminal connection structure according to the first aspect, the locking pieces of the board terminal may be situated on a position closer to the edge portion of the circuit board relative to the contact pieces in the longitudinal direction of the base portion. 
     According to the third aspect of the present invention, the locked portion is situated closer to the edge portion of the circuit board than the contact pieces. Accordingly, when the board terminal is shifted from the standard position, even if the locked portion is situated on the same inclined line as the contact portions, the locked portion is moved for a distance smaller than a deformation amount of the contact portions of the board terminal, thereby making it possible to prevent the locking pieces from coming off. 
     According to a fourth aspect of the present invention, in the inter-terminal connection structure according to the first aspect, the locking pieces of the board terminal may include a plurality of pairs disposed at different positions in the longitudinal direction of the base portion. 
     According to the fourth aspect of the present invention, the pairs of the locking pieces become independent with each other. Accordingly, when the circuit board is shifted and the inclined line becomes large, ones of the locking pieces are moved for a distance smaller than that of the other ones of the locking pieces, thereby securing the locking positions thereof. 
     According to a fifth aspect of the present invention, a board connector mounted on a circuit board is connected to connection connector a in a connector pull out or insertion direction as a direction perpendicular to the circuit board. As a result, a conductive member connected to the terminal of the connection connector is electrically connected to the board terminal. 
     According to the fifth aspect of the present invention, the board terminal includes a base portion arranged to face the circuit board and having a side portion extending in a longitudinal direction thereof, a pair of contact pieces extending from both side portions of the base portion, and a locking pieces extending from the both side portions of the base portion. The contact pieces and the locking pieces have elastic arm portions capable of elastically deforming in a terminal width direction connecting the both side portions of the base portion viewed in the longitudinal direction. The elastic arm portions are formed in a curved shape, so that the elastic arm portions become close together in the terminal width direction. The elastic arm portions of the contact pieces are formed as contact portions, and the elastic arm portions of the locking pieces are formed as locking portions. 
     According to the fifth aspect of the present invention, in the connection connector, ones of the contact pieces and the locking pieces of the board terminal are situated on an edge portion side of the circuit board relative to the other ones in the longitudinal direction. Each of the locking portions of the locking pieces is provided with a locking protrusion approaching with each other in the terminal width direction viewed in the longitudinal direction. Accordingly, in the connection state, the contact portions of the contact pieces of the board terminal pressingly sandwich the corresponding contact portions of the connection terminal in the terminal width direction, so that the contact portions contact with the corresponding contact portions. At the same time, the locking protrusions of the locking pieces of the board terminal enter and are situated in the locked portion of the connection terminal with a play, so that the locking protrusions are movable in the terminal width direction. 
     According to a sixth aspect of the present invention, a terminal of a connection connector is connected to a board connector mounted on a circuit board in a connector pull out or insertion direction as a direction perpendicular to the circuit board. As a result, a conductive member connected to the terminal of the connection connector is electrically connected to the board terminal. 
     According to the sixth aspect of the present invention, the connection connector includes a connection terminal having a plate shape portion inserted between the contact portions and the locking portions of the board terminal in the pull out or insertion direction viewed in the longitudinal direction. The connection connector further includes a housing for holding the connection terminal. The plate shape portion of the connection terminal has a plate surface perpendicular to the longitudinal direction and the terminal width direction. Further, the plate shape portion includes a corresponding contact portion contacting with the contact portions of the board terminal. 
     According to the sixth aspect of the present invention, in the connection connector, the plate shape portion of the connection terminal includes a locked portion formed as a hole portion or a cut portion penetrating in the terminal width direction within a range including the locking protrusions of the board terminal in a connection state between the board terminal and the connection terminal in the longitudinal direction and the connector pull out or insertion direction. Accordingly, in the connection state, the contact portions of the contact pieces of the board terminal pressingly sandwich the corresponding contact portions of the connection terminal in the terminal width direction, so that the contact portions contact with the corresponding contact portions. At the same time, the locking protrusions of the locking pieces of the board terminal enter and are situated in the locked portion of the connection terminal with a play, so that the locking protrusions are movable in the terminal width direction. 
     As described above, according to the present invention, when the board terminal and the conductive member are shifted from the standard position, the connection terminal is moved only to an inclined state relative to the standard position in the terminal width direction while following the shift with the position of the corresponding contact portions sandwiched with the contact portions of the board terminal as a pivot, so that the connection terminal is not elastically deformed. As a result, a stress is not applied to the connection terminal, thereby preventing the connection terminal from being damaged. Further, it is possible to securely maintain the good connection state between the connection terminal and the board terminal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing a board terminal and a connection connector of an inter-terminal connection structure just before the board terminal is connected to the connection connector according to an embodiment of the present invention; 
         FIG. 2  is an enlarged perspective view showing the board terminal of the inter-terminal connection structure according to the embodiment of the present invention; 
         FIG. 3  is an enlarged perspective view showing the connection connector of the inter-terminal connection structure in an inverted state from  FIG. 1  according to the embodiment of the present invention; 
         FIG. 4  is an enlarged perspective view showing the board terminal and the connection connector without a housing thereof of the inter-terminal connection structure just before the board terminal is connected to the connection connector according to the embodiment of the present invention; 
         FIGS. 5(A) and 5(B)  are sectional views showing the board terminal and the connection connector of the inter-terminal connection structure in a state that the board terminal is connected to the connection connector according to the embodiment of the present invention, wherein  FIG. 5(A)  is a sectional view showing the connection connector of the inter-terminal connection structure taken along a line  5 (A) in  FIG. 1 , and  FIG. 5(A)  is a sectional view showing the connection connector of the inter-terminal connection structure taken along a line  5 (B) in  FIG. 1 ; and 
         FIG. 6  is a plan view showing the board terminal and the connection connector of the inter-terminal connection structure in the state that the board terminal is connected to the connection connector at a standard position (represented with a solid line) and in a state that the board terminal is shifted relative to the connection connector from the standard position (represented with a projected line) according to the embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereunder, embodiments of the present invention will be explained with reference to the accompanying drawings. In the accompanying drawings, similar components are designated with the same reference numerals, and repeated explanations thereof are omitted. 
       FIG. 1  is a perspective view showing a board terminal  10  and a connection connector  30  of an inter-terminal connection structure just before the board terminal  10  is connected to the connection connector  30  according to an embodiment of the present invention. 
     As shown in  FIG. 1 , the board terminals  10  having an identical configuration are mounted on two circuit boards P 1  and P 2  such that the board terminals  10  are connected to corresponding circuit portions (not shown) on the circuit boards P 1  and P 2 . Further, the connection connector  30  is to be connected to the board terminals  10  in a state that edge portions P 1 A and P 2 A of the circuit boards P 1  and P 2  face each other, so that the connection connector  30  connects the board terminals  10 . 
     In the embodiment, it may be configured such that the connection connector  30  is arranged to connect the board terminal  10  on the circuit board P 1  to a conductive member other than the board terminal  10  on the circuit board P 2 . The conductive member may include, for example, a cable to be connected to the connection connector  30  or other electric parts. As far as the connection connector  30  is capable of connecting two components, the conductive member is not limited to a specific one. 
     In the embodiment, the board terminals  10  on the circuit boards P 1  and P 2  have an identical configuration, and are arranged to face opposite each other in symmetry relative to the side edge portions P 1 A and P 2 A of the circuit boards P 1  and P 2 . In the following description, only the board terminal  10  on the circuit board P 1  will be explained in more detail. It should be noted that a direction along with the board terminals  10  are arranged is referred to as an arrangement direction of the board terminals  10 . Further, the board terminals  10  are formed to have a longitudinal direction as one direction. In other words, the board terminals  10  are arranged in the longitudinal direction as the arrangement direction. 
     A configuration of the connection connector  30  will be explained in more detail.  FIG. 3  is an enlarged perspective view showing the connection connector  30  of the inter-terminal connection structure in an inverted state from  FIG. 1  according to the embodiment of the present invention. 
     As shown in  FIG. 1  and  FIG. 3  that shows the up side down (vertically) inverted state, the connection connector  30  includes a housing  31  formed of an electrically insulation material and a connection terminal  32  held with the housing  31 . The housing  31  is arranged to extend in the arrangement direction of the board terminals  10  as the longitudinal direction thereof, and the connection connector  30  is arranged to extend in the longitudinal direction as well. 
     In the embodiment of the present invention, the connection connector  30  has a configuration symmetrical relative to a symmetrical line X situated at a center of the connection connector  30  in the longitudinal direction and extending perpendicular to the longitudinal direction. Accordingly, in the following description, one half of the connection connector  30  will be explained. When the connection connector  30  is connected to the board terminals  10 , the symmetrical line X is situated in a space between the edge portions P 1 A and P 2 A of the circuit boards P 1  and P 2 . Accordingly, the connection connector  30  having the symmetrical configuration relative to the symmetrical line X is arranged to saddle between the board terminals  10  on both sides of the edge portions P 1 A and P 2 A of the circuit boards P 1  and P 2 . 
       FIG. 4  is an enlarged perspective view showing the board terminal  10  and the connection connector  30  without the housing  31  thereof of the inter-terminal connection structure just before the board terminal  10  is connected to the connection connector  30  according to the embodiment of the present invention. 
     As shown in  FIG. 1  and  FIG. 4 , the connection terminal  32  is formed through processing a metal plate with a band shape. The connection terminal  32  includes a plate portion  33  extending in the longitudinal direction and having a band width in the vertical direction. Further, the connection terminal  32  includes an edge portion held portion  34  at both end portions of the plate portion  33  having a plate surface perpendicular to that of the plate portion  33  (one of the edge held portions  34  is not shown in  FIG. 4 ). 
     In the embodiment, it is suffice that the connection terminal  32  includes the plate portion  33 , and it may be configured such that a portion the connection terminal  32  is bent relative to the plate portion  33  as other portion including the edge portion held portion  34 . For example, the connection terminal  32  may include a bent portion bent at an upper edge of the plate portion  33 , so that the bent portion is embedded in the connection connector  30  to increase strength of the connection terminal  32  as a whole. 
     As shown in  FIG. 4 , the plate portion  33  includes a center held portion  35  with a band shape having a flat surface and extending on both sides of the symmetrical line X; a locked portion  36  formed as a hole portion between the center held portion  35  and the edge portion held portion  34 ; and a corresponding contact portion  37  for contacting with the board terminal  10 . Further, the plate portion  33  includes an intermediate held portion  38  having a flat surface between the locked portion  36  and the corresponding contact portion  37 . 
     In the embodiment, a surrounding portion (a portion forming an inner circumferential edge of the hole portion) of the locked portion  36  formed as the hole portion and the corresponding contact portion  37  are configured to have a width in the vertical direction larger than that of the center held portion  35  or the intermediate held portion  38 . The locked portion  36  is formed as a long hole portion extending in the longitudinal direction and penetrating in the plate thickness direction. A lower portion  36 - 1  is disposed below the locked portion  36 , and has an upper edge portion and a lower edge portion formed in a taper shape. With the tapered shape, it is possible to easily insert or pull out the lower portion  36 - 1  between a pair of locking pieces of the board terminal  10  (described later). Further, a surrounding portion of the locked portion  36  including the lower portion  36 - 1  is formed through a press molding to have a thickness slightly smaller than other portion. 
     In the embodiment, the corresponding contact portion  37  includes a corresponding contact surface  37 A extending from an upper portion  37 - 1  thereof down to a lower edge thereof for contacting with a pair of contact pieces of the board terminal  10  (described later). The lower edge of the corresponding contact portion  37  is formed in a tapered shape, so that it is possible to easily insert the corresponding contact portion  37  between the contact pieces of the board terminal  10 . Further, the corresponding contact surface  37 A is formed through the press molding to have a thickness slightly smaller than that of other portion. 
     In the embodiment, the connection terminal  32  is integrally molded with the housing  31 , so that the housing  31  holds the connection terminal  32 . More specifically, the connection terminal  32  is integrally molded and held with the housing  31 , so that the edge portion held portion  34 , the center held portion  35 , the intermediate held portion  38 , the upper edge of the locked portion  36 , and the upper edge of the corresponding contact portion  37  shown in  FIG. 4  are embedded in the housing  31 . It should be noted that the upper edge of the corresponding contact portion  37  is shown in  FIG. 3  as the lower edge in an inverted posture. Accordingly, when the connection terminal  32  is integrally molded and held with the housing  31 , the locked portion  36  and the corresponding contact portion  37  are not embedded in and are exposed from the housing  31 . 
     In the embodiment, as described above, the housing  31  holds the connection terminal  32  at the upper edge thereof in the posture (at the position) of the connection terminal  32  shown in  FIG. 4 . Accordingly, as shown in  FIG. 1 , the housing  31  covers the upper portion of the connection connector  30 . Further, the housing  31  includes an upper wall portion  31 A forming a flat upper surface thereof; holding wall portions  39  formed in a rectangular shape at a lower portion of the upper wall portion  31 A (an upper portion in  FIG. 3  showing as the inverted state from  FIG. 1 ) for surrounding the locked portion  36  and the corresponding contact portion  37  at the both end portions of the connection terminal  32 ; and intermediate holding portions  40  (refer to  FIG. 3 ) formed in an island shape and disposed inside the holding wall portions  39  with the rectangular shape. 
     In the embodiment, the housing  31  further includes a center holding protruding portion  41  (refer to  FIG. 3 ) on a lower surface of the upper wall portion  31 A. The center holding protruding portion  41  extends in the longitudinal direction to connect the holding wall portions  39  with the rectangular shape at the both end portions of the housing  31 . Further, the center holding protruding portion  41  is to be situated at the space between the edge portions P 1 A and P 2 A of the circuit boards P 1  and P 2 , and the connection terminal  32  is not exposed at the center holding protruding portion  41 . Accordingly, even when the circuit portions on the circuit boards P 1  and P 2  are exposed at the edge portions P 1 A and P 2 A, it is possible to prevent inadvertent electrical contact with the circuit portions on the circuit boards P 1  and P 2 . 
     As shown in  FIG. 3 , the housing  31  further includes outer edge wall portions  39 A arranged outside the holding wall portions  39  in the longitudinal direction, so that a majority portion of the edge portion held portion  34  of the connection terminal  32  is embedded in each of the outer edge wall portions  39 A. The intermediate held portion  38  is embedded in the intermediate holding portions  40 . Further, the center held portion  35  is embedded in the portion from an inner edge wall portion  39 B of one of the holding wall portions  39  to the inner edge wall portion  39 B of the other of the holding wall portions  39  through the center holding protruding portion  41 . Accordingly, with the configuration described above, the housing  31  holds the connection terminal  32 . As a result, the locked portion  36  and the corresponding contact portion  37  of the connection terminal  32  are situated and exposed inside the holding wall portions  39  with the rectangular shape. 
     In the embodiment, the housing  31  further includes an undulation portion  31 A- 1  having a wave shape on each of side edges of the upper wall portion  31 A at the center thereof in the longitudinal direction. The undulation portion  31 A- 1  is provided for an operator to easily pick up the connection connector  30  when the connection connector  30  is connected to the board terminal  10 . Further, the housing  31  includes protruding portions  31 A- 2  protruding from the both edges of the upper wall portion  31 A in the longitudinal direction. The protruding portions  31 A- 2  are provided for hooking a finger of the operator when the connection connector  30  is pulled out from the board terminal  10 . 
     A configuration of the board terminal  10  will be explained in more detail next.  FIG. 2  is an enlarged perspective view showing the board terminal  10  of the inter-terminal connection structure according to the embodiment of the present invention. 
     In the embodiment, when the board terminal  10  is produced, after a metal plate is punched out and machined, the metal plate is bent to have a shape as shown in  FIGS. 1 ,  2  and  4 . As described above, the board terminals  10  have the identical configuration, and  FIG. 2  is the enlarged perspective view of one of the board terminals  10  arranged symmetrically with the symmetrical line X in between as shown in  FIG. 1 . In the following description, the configuration of the board terminal  10  will be explained with reference to  FIG. 2 . 
     As shown in  FIG. 2 , the board terminal  10  includes a base portion  11  having a plate surface extending in the longitudinal direction along the surface of the circuit board P 1 ; the contact pieces  12  standing from side edges of the base portion  11 ; the locking pieces  13  similarly standing from the side edges of the base portion  11 ; and connecting portions  14  protruding from both end portions of the base portion  11 . 
     In the embodiment, both the contact pieces  12  and the locking pieces  13  are formed to be capable of being elastically deformed. The board terminal  10  further includes width direction guiding walls  15  for connecting the contact pieces  12  and the locking pieces  13  such that the contact pieces  12  and the locking pieces  13  are capable of being freely deformd. The width direction guiding walls  15  are provided for guiding the intermediate holding portion  40  of the connection connector  30  when the connection connector  30  is connected to the board terminal  10 . Further, the board terminal  10  includes longitudinal direction guiding walls  16  in a standing posture adjacent to the contact pieces  12  such that the contact pieces  12  are capable of being freely deformed. In the following description, each of the components of the board terminal  10  will be explained in more detail. 
     In the embodiment, the contact pieces  12  include contact portions  12 A arranged to stand from both side edges of the base portion  11  in the width direction, respectively, such that the contact portions  12 A face to each other and are arranged symmetrically. The contact portions  12 A are formed as elastic arm portions capable of being elastically deformed in the width direction such that the contact portions  12 A stand from the side edges of the base portion  11  to approach each other, and are curved downwardly. The contact portions  12 A include contact protrusions  12 A- 1  at positions closest each other. The contact protrusions  12 A- 1  of the contact portions  12 A are arranged to have a distance in between, so that the contact protrusions  12 A- 1  of the contact portions  12 A are capable of sandwiching and pressing the corresponding contact portion  37  formed on the connection terminal  32  of the connection connector  30 . 
     In the embodiment, the locking pieces  13  are disposed at two locations in the longitudinal direction, that is, two pairs. Similar to the contact pieces  12 , each of the pairs of the locking pieces  13  is formed as elastic arm portions capable of being elastically deformed in the width direction such that the locking pieces  13  stand from the side edges of the base portion  11  to approach each other, and are curved downwardly. The elastic arm portions of the locking pieces  13  are provided as locking portions  13 A. The locking portions  13 A include locking protrusions  13 A- 1  at closest portions thereof. The locking protrusions  13 A- 1  as the closest portions are arranged such that a distance between the locking protrusions  13 A- 1  becomes smaller than the plate thickness of the surrounding portion of the locked portion  36  formed on the connection terminal  32  of the connection connector  30 . 
     In the embodiment, when the connection connector  30  is connected to the board terminal  10 , the locking protrusions  13 A- 1  of the locking pieces  13  are situated within a range of the locked portion  36  formed as the hole portions both in the longitudinal direction and the connector pull out or insertion direction. As described above, the distance between the locking protrusions  13 A- 1  becomes smaller than the plate thickness of the surrounding portion of the locked portion  36 . Accordingly, when the connection connector  30  is connected to the board terminal  10 , the locking protrusions  13 A- 1  are capable of entering inside the locked portion  36  without receiving any abutting force from the plate surface of the locked portion  36 . 
     In the embodiment, the width direction guiding walls  15  are provided for connecting the contact pieces  12  and the locking pieces  13 , and are configured to stand from the both side edges of the base portion  11 . The width direction guiding walls  15  have upper edges situated outside relative to the contact pieces  12  and the locking pieces  13  in the width direction. When the connection connector  30  is connected to the board terminal  10 , at the beginning or in the middle of connection, the upper edges of the width direction guiding walls  15  are situated inside the inner wall surfaces of the holding wall portions  39  of the connection connector  30  at both sides thereof in the width direction. Accordingly, the width direction guiding walls  15  are provided for guiding the connection connector  30  in the width direction. 
     In the embodiment, the width direction guiding walls  15  include tapered portions  15 A at the upper edges thereof, so that it is possible to easily guide the connection connector  30  when the connection connector  30  is connected to the board terminal  10 . With the configurations described above, when the connection connector  30  is connected to the board terminal  10 , even if the connection connector  30  is shifted from the standard position in the width direction, the width direction guiding walls  15  can guide the connection connector  30  toward the standard position. 
     In the embodiment, the longitudinal direction guiding walls  16  are disposed adjacent to the contact pieces  12 , and are curved to approach each other similarly to the contact pieces  12 , except that the longitudinal direction guiding walls  16  are not situated as closely as the contact portions  12 A of the contact pieces  12 . Further, the longitudinal direction guiding walls  16  include slant surfaces  16 A as plate thickness surfaces on side edges thereof farther from the contact pieces  12 . The slant surfaces  16 A are inclined in a direction approaching the contact pieces  12  toward distal end portions of the longitudinal direction guiding walls  16  (inwardly in the width direction). In other words, the slant surfaces  16 A are formed as side edge surfaces extending from top portions of the longitudinal direction guiding walls  16  toward the base portion  11  and away from the contact pieces  12 . 
     In the embodiment, when the connection connector  30  is connected to the board terminal  10 , at the beginning or in the middle of connection, the slant surfaces  16 A are situated inside the inner wall surfaces of the outer edge wall portions  39 A arranged at the end portions of the holding wall portions  39  of the connection connector  30  in the longitudinal direction. Accordingly, top portions of the slant surfaces  16 A can guide the inner wall surfaces of the outer edge wall portions  39 A, and the contact points move toward the base portion  11  as the connection connector  30  enters the board terminal  10  further, so that the slant surfaces  16 A guide the connection connector  30  in the longitudinal direction. When the board terminals  10  are mounted on both the circuit boards P 1  and P 2 , the slant surfaces  16 A of the board terminals  10  guide the holding wall portions  39  at the both end portions of the connection connector  30  in the longitudinal direction. Accordingly, when the connection connector  30  is shifted from the standard position in the longitudinal direction upon connection, the slant surfaces  16 A arranged symmetrically guide the connection connector  30  toward the center to the standard position. 
     An operation of connecting the connection connector  30  to the board terminals  10  of the inter-terminal connection structure will be explained next. 
     First, as shown in  FIG. 1 , the board terminals  10  are placed on and fixed to the circuit boards P 1  and P 2  at specific locations thereon with solder and the like. Accordingly, the board terminals  10  on the circuit boards P 1  and P 2  are arranged with the edge portions P 1 A and P 2 A of the circuit boards P 1  and P 2  in between in the symmetrical arrangement. As a result, the board terminals  10  disposed at the specific locations of the circuit boards P 1  and P 2  are situated with the longitudinal direction thereof aligned with the arrangement direction. It should be noted that the board terminals  10  are fixed to the circuit boards P 1  and P 2  with solder at the connecting portions  14  at the both end portions of the board terminals  10 . 
     In the next step, as shown in  FIG. 1 , the connection connector  30  is placed over the board terminals  10  on the circuit boards P 1  and P 2 , which face each other at the specific locations. Then, the connection connector  30  is pushed downwardly toward the circuit boards P 1  and P 2  to insert into the board terminals  10 . 
     In the embodiment of the present invention, when the connection connector  30  is pushed downwardly toward the circuit boards P 1  and P 2 , the connection connector  30  is fitted into and connected to the board terminals  10 . At the beginning of the connecting operation, the board terminals  10  guide the inner circumferential surface of the holding wall portions  39  with the rectangular shape formed on the housing  31  of the connection connector  30 , thereby smoothly fitting the connection connector  30  into the board terminals  10 . More specifically, in the width direction of the connection connector  30 , the width direction guiding walls  15  of the board terminals  10  guide one of the inner wall surfaces of the holding wall portions  39  on the both sides in the width direction. In the longitudinal direction, the slant surfaces  16 A of the longitudinal direction guiding walls  16  of the board terminals  10  guide the inner surfaces of the outer edge wall portions  39 A of the holding wall portions  39 . Accordingly, it is possible to smoothly insert the connection connector  30  into the board terminals  10  while correcting any shift thereof from the standard position in the width direction and the longitudinal direction. 
       FIGS. 5(A) and 5(B)  are sectional views showing the board terminal  10  and the connection connector  30  of the inter-terminal connection structure in a state that the board terminal  10  is connected to the connection connector  30  according to the embodiment of the present invention. More specifically,  FIG. 5(A)  is a sectional view showing the connection connector  30  of the inter-terminal connection structure taken along a line  5 (A) in  FIG. 1 , and  FIG. 5(A)  is a sectional view showing the connection connector  30  of the inter-terminal connection structure taken along a line  5 (B) in  FIG. 1 . 
     As shown in  FIGS. 5(A) and 5(B) , when the connection connector  30  is pushed downwardly to the standard engagement position, the corresponding contact portion  37  of the connection connector  30  contacts with the contact pieces  12  of the board terminals  10 , and the lower portion  36 - 1  of the locked portion  36  engages with the locking pieces  13 . More specifically, as shown in  FIG. 5(A) , the corresponding contact portion  37  enters between the contact pieces  12 . In particular, the corresponding contact portion  37  is sandwiched and pressed through a point contact between the contact protrusions  12 A- 1  formed on the contact portions  12 A of the contact pieces  12 . 
     Further, as shown in  FIG. 5(B) , the lower portion  36 - 1  of the locked portion  36  pressingly enters between the locking portions  13 A of the locking pieces  13 . When the lower portion  36 - 1  of the locked portion  36  moves to the specific position, the locking protrusions  13 A- 1 , i.e., the closest portions of the locking portions  13 A, enter the locked portion  36 , so that the locking portions  13 A are released from the deformed state and become the free state. 
     In the embodiment of the present invention, as described above, the locking protrusions  13 A- 1  of the locking portions  13 A are situated inside the locked portion  36  formed as the hole portion in the connection terminal  32  of the connection connector  30 . Accordingly, in the longitudinal direction of the connection connector  30 , the locking protrusions  13 A- 1  of the locking portions  13 A are capable of abutting against the inner edge portions situated at the both edges of the locked portion  36  in the longitudinal direction. Further, in the connector pull out or insertion direction (the vertical direction), the locking protrusions  13 A- 1  of the locking portions  13 A are capable of abutting against the inner edge portions situated at the upper and lower edges of the locked portion  36  in the connector pull out or insertion direction. As a result, the surrounding portion of the locked portion  36  is regulated in the vertical direction in the locked state without receiving the abutting force from the locking pieces  13 . 
     Further, in the embodiment of the present invention, the inner edge portions at the upper edge and the lower edge of the locked portion  36  are capable of abutting against the surrounding portions of the locking protrusions  13 A- 1  of the locking portions  13 A. Accordingly, the locked portion  36  of the connection terminal  32  with the plate shape is regulated in the width direction as well. Accordingly, in the connection connector  30 , the corresponding contact portion  37  formed on the connection terminal  32  of the connection connector  30  contacts with the contact pieces  12  of the board terminals  10  through the point contact. Further, the surrounding portion of the locked portion  36  is maintained in the locked state without receiving the abutting force from the locking pieces  13 . 
     In general, even if the board terminals  10  are accurately fixed to the circuit boards P 1  and P 2  at the specific position, when the circuit boards P 1  and P 2  are shifted from the standard position, the board terminals  10  may be shifted from the standard position as well. Especially, if the board terminals  10  are not accurately fixed to the circuit boards P 1  and P 2  at the specific position, the board terminals  10  may be shifted from the standard position to a greater extent. In the embodiment of the present invention, the inter-terminal connection structure is configured as described above to solve the above problem without applying an excessive stress to the board terminals  10  or the connection connector  30 . 
       FIG. 6  is a plan view showing the board terminal  10  and the connection connector  30  of the inter-terminal connection structure according to the embodiment of the present invention. As shown in  FIG. 6 , the connection terminal  32  of the connection connector  30  is connected to the board terminal  10  shown in the plan view (viewed in the connector pull out or insertion direction). Please note that only one of the board terminals  10  is shown, and the other one is omitted. In  FIG. 6 , the state that the connection terminal  32  of the connection connector  30  is connected to the board terminal  10  at the standard position is represented with a solid line, and a state that the board terminal  10  is shifted from the other one is represented with a projected line. 
     As shown in  FIG. 6 , when the board terminals  10  are situated at the standard position, the corresponding contact portion  37  of the connection terminal  32  contacts with the contact protrusions  12 A- 1  of the contact portions  12 A through the pint contact with the contact pressure. A position of the point contact relative to one of the board terminals  10  is represented with an arrow P, and the point contact occurs at a similar position on the other of the board terminals  10  (not shown). Further, as represented with a hidden line in  FIG. 6 , the locking protrusions  13 A- 1  of the locking pieces  13  are situated within the locked portion  36  formed as the hole portion in the locked portion  36  of the connection terminal  32 , so that the locking protrusions  13 A- 1  of the locking pieces  13  regulate the locked portion  36  without abutting against the connection terminal  32 . 
     As shown in  FIG. 6 , the connection terminal  32  of the connection connector  30  contacts with the board terminal  10  through the pint contact. Accordingly, when the board terminals  10  are shifted with each other due to the positional shift of the circuit boards P 1  and P 2 , or the fixing positional shift of the board terminals  10  relative to the circuit boards P 1  and P 2 , the connection terminal  32  is inclined as shown in  FIG. 6 . In other words, the connection terminal  32  is sandwiched at the point contact positions at the both end portions the connection connector  30  in the longitudinal direction, so that the connection terminal  32  is inclined independently from the locking pieces  13 . 
     In the embodiment of the present invention, as described above, the locking protrusions  13 A- 1  of the locking pieces  13  do not receive the abutting force relative to the connection terminal  32 . Accordingly, when the connection terminal  32  is inclined, the connection terminal  32  stays at the original location represented with the hidden line shown in  FIG. 6 , so that the locking protrusions  13 A- 1  of the locking pieces  13  are maintained inside the locked portion  36  to engage with the inner edges of the locked portion  36 . As a result, even when the locked portion  36  is inclined, the locked portion  36  is maintained in the locked state without generating any stress. 
     The disclosure of Japanese Patent Application No. 2012-105640 filed on May 7, 2012, is incorporated in the application by reference. 
     While the invention has been explained with reference to the specific embodiments of the invention, the explanation is illustrative and the invention is limited only by the appended claims.