Patent Publication Number: US-8992235-B2

Title: Terminal fitting and a connection structure for a terminal fitting

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a terminal fitting and a connection structure for terminal fitting. 
     2. Description of the Related Art 
     Japanese Unexamined Patent Publication No. 2005-174615 discloses a structure for press-fitting a press-fit type terminal fitting into a through hole of a busbar for connection. Two projections are formed on the outer edges of two resilient deforming portions of the terminal fitting that are deformed resiliently when the terminal fitting is press-fit into the through hole. The terminal fitting is press-fit into the through hole so that the projections engage front and rear opening edges in a pressing direction to retain the terminal fitting. 
     The front projection in the press-fitting direction interferes with the inner peripheral surface of the through hole as the above-described terminal fitting is press-fit into the through hole and the deforming portions displace. The deforming portions restore resiliently when the projections align with the opening edges of the through hole. Thus, the amount of resilient displacements of the deforming portions decreases. Accordingly, resilient restoring forces accumulated in the deforming portions when the terminal fitting is connected to the through hole become smaller than a maximum value in the press-fitting process. The lower resilient restoring forces accumulated in the resilient deforming portions when the terminal fitting is connected to the through hole means a reduced holding force of the terminal fitting in the through hole. 
     The invention was completed in view of the above situation and an object thereof is to increase a holding force of a terminal fitting in a through hole. 
     SUMMARY OF THE INVENTION 
     The invention relates to a terminal fitting with a plurality of resilient deforming portions that are to be press-fit into a hole of a connection target while being resiliently displaced substantially toward each other. At least one lock is formed by recessing an outer edge of the resilient deforming portion and can engage the inner peripheral surface of the hole when the deforming portions are press-fit in the hole. 
     Resilient restoring forces of the deforming portions cause the lock to engage the inner peripheral surface of the hole when the deforming portions are press-fit in the hole and the resilient restoring forces hold the deforming portions in the hole. The lock is formed by recessing the outer edge of the resilient deforming portion. Thus, the amount of resilient displacement of the deforming portion, i.e. the resilient restoring forces accumulated in the deforming portion, becomes a maximum when the lock is engaged with the hole, and a holding force of the terminal fitting in the hole is large. 
     A part of an area of the resilient deforming portion facing the inner peripheral surface of the through hole defines a maximum displacement area where the amount of resilient displacement becomes a maximum in a press-fitting process. The lock is arranged only in an area different from the maximum displacement area. 
     Stresses generated in the resilient deforming portions while press-fitting the deforming portions into the through hole become a maximum in the maximum displacement areas. However, a stress also is generated in the lock when the lock engages the inner peripheral surface of the through hole. Thus, the lock is arranged only in the area other than the maximum displacement area to avoid a concentration of stress. 
     At least one opening edge of the lock defines a biting edge for engaging the inner peripheral surface of the hole. 
     Groups of locks may be formed. 
     A dimension of each resilient deforming portion in a width direction preferably is substantially constant over the entire length of the resilient deforming portion. 
     The invention also relates to a connection structure that includes the above-described terminal fitting and at least one hole formed in a connection target of the terminal fitting and into which the resilient deforming portions are to be press-fit while being displaced resiliently toward each other. 
     The hole preferably is a through hole in a circuit board. 
     These and other objects, features and advantages of the invention will become more apparent upon reading the following detailed description of preferred embodiments and accompanying drawings. Even though embodiments are described separately, single features may be combined to additional embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view showing a state where a terminal fitting is press-fitted in a through hole in a first embodiment. 
         FIG. 2  is a front view of the terminal fitting. 
         FIG. 3  is a partial enlarged front view of the terminal fitting. 
         FIG. 4  is a side view of the terminal fitting. 
         FIG. 5  is a sectional view along X-X of  FIG. 1 . 
         FIG. 6  is a side view of a terminal fitting according to a second embodiment, 
         FIG. 7  is a partial enlarged front view of the terminal fitting. 
         FIG. 8  is a sectional view showing a state where the terminal fitting is press-fitted in a through hole. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A first embodiment of the invention is described with reference to  FIGS. 1 to 5 . A connection structure for a terminal fitting  20  according to the first embodiment is for connecting the terminal fitting  20  to a circuit board  10 . In the following description, the circuit board  10  is arranged horizontally and the terminal fitting  20  is mounted into the circuit board  10  substantially from above and in an inserting direction ID. 
     A substantially circular through hole  11  penetrates the circuit board  10  in a plate thickness direction, as shown in  FIGS. 1 and 5 . In the following description, the plate thickness direction of the circuit board  10 , a penetrating direction of the through hole  11  and a vertical direction all mean the same. A plating layer (not shown) is formed on the inner peripheral surface of the through hole  11  and is connected to a printed circuit (not shown) of the circuit board  10 . An inner diameter of the through hole  11  is substantially constant over the entire length of the through hole  11  from the upper surface to the lower surface of the circuit board  10 . A board connecting portion  21  of the terminal fitting  20  is press-fit into the through hole  11  from above and in the inserting direction ID. 
     The terminal fitting  20  is mounted in a housing (not shown) that is to be mounted on the circuit board  10 . A housing-side connecting portion (not shown) is formed at one end of the terminal fitting  20  and is configured for connection to a wiring harness (not shown). The board connecting portion  21  is formed at the other end of the terminal fitting  20  and is configured for connection to the circuit board  10 . 
     As shown  FIGS. 2 and 4 , the board connecting portion  21  is long and narrow vertically along the inserting direction ID and the leading end faces down in the inserting direction ID. The board connecting portion  21  has two substantially bilaterally symmetric resilient deforming portions  22  that are long and narrow in a length direction that is substantially parallel to the inserting direction ID into the through hole  11 . In the following description, the length direction of the board connecting portion  21 , a length direction of the resilient deforming portions  22  and the vertical direction all mean the same direction. A length dimension of the resilient deforming portions  22  in the inserting direction ID is larger than a dimension of the through hole  11  in the thickness direction of the circuit board  10 . 
     As shown in  FIGS. 1 to 3 , the resilient deforming portions  22  are spaced apart laterally in a width direction WD of the board connecting portion  21 , which is substantially normal to the inserting direction ID. A deformation space  23  is formed between the resilient deforming portions  22  and permits the resilient deforming portions  22  to be deformed resiliently toward each other in the width direction WD. The deformation space  23  penetrates through the board connecting portion  21  in forward and backward directions. In the following direction, the width direction WD of the board connecting portion  21 , a width direction of the resilient deforming portions  22  and an arranging direction of the resilient deforming portions  22  all mean the same direction. The width direction WD of the board connecting portion  21  is substantially perpendicular to the vertical press-fitting or inserting direction ID into the through hole  11 . 
     As shown in  FIGS. 2 and 3 , each resilient deforming portion  22  has a substantially constant dimension in the width direction WD over the entire length of the resilient deforming portion  22 . Further, the resilient deforming portions  22  are curved so that a spacing between central parts thereof in the length direction is largest when the board connecting portion  21  is not press-fit in the through hole  11 . That is, the pair of resilient deforming portions  22  are curved so that outer edges  24  of the board connecting portions  21  project out in the width direction WD. Accordingly, the width of the board connecting portion  21  is maximum at longitudinal central parts of the resilient deforming portions  22  in the longitudinal direction. As shown in  FIGS. 2 and 3 , maximum displacement areas  25  of the resilient deforming portions  22  are defined where the board connecting portion  21  is widest and where the resilient displacements of the resilient deforming portions  22  in the width direction WD becomes maximum in the press-fitting process into the through hole  11 . 
     A maximum width of the board connecting portion  21  when board connecting portion  21  is not press-fit in the through hole  11  is larger than the inner diameter of the through hole  11 . Thus, the resilient deforming portions  22  are displaced resiliently toward each other in the width direction WD and toward a longitudinal center of the terminal fitting  20  when the board connecting portion  21  is press-fit in the through hole  11 , and resilient restoring forces accumulate in the resilient deforming portions  22 . The outer edges  24  of the resilient deforming portions  22  contact the inner peripheral surface of the through hole  11  and the resilient restoring forces of the resilient deforming portions  22  ensure a specified contact pressure between the terminal fitting  20  and the through hole  11 . 
     Frictional resistance is generated between the outer edges  24  of the resilient deforming portions  22  and the inner peripheral surface of the through hole  11  as the resilient restoring forces accumulate in the resilient deforming portions  22 . This frictional resistance becomes a holding force for holding a press-fit contact state between the outer edges  24  of the terminal fitting  20  and the inner peripheral surface of the through hole  11 . In this embodiment, four pairs of locking portions  28  are formed on the outer edges  24  of the left and right resilient deforming portions  22  for further increasing the holding force of the terminal fitting  20  in the through hole  11 . 
     As shown in  FIG. 5 , the outer edge  24  of the resilient deforming portion  22  has an outer side surface  26  that is substantially perpendicular to the width direction WD and substantially parallel to forward and backward penetrating direction of the deformation space  23 , a front arcuate surface  27 F that is a substantially quarter-circular connecting the outer side surface  26  and the front surface, and a rear arcuate surface  27 F that is a substantially quarter-circular connecting the outer side surface  26  and the rear surface. As shown in  FIGS. 1 to 3 , the locking portions  28  formed on the left resilient deforming portion  22  and those formed on the right resilient deforming portion  22  are paired. The paired locking portions  28  are arranged substantially at the same heights in the vertical direction and are substantially bilaterally symmetrical. 
     As shown in  FIG. 4 , the locking portions  28  are substantially wedge-shaped recesses formed in the outer side surface  26 , the front arcuate surface  27 F and the rear arcuate surface  27 R of the outer edge  24 . An opening of each locking portion  28  on the outer edge  24  is a slit substantially perpendicular to the press-fitting inserting direction ID into the through hole  11 . That is, the opening of the locking portion  28  is a slit extending in substantially forward and backward directions when viewed in a direction perpendicular to the outer side surface  26 . As shown in  FIGS. 2 and 3 , the opening of the locking portion  28  is a slit extending substantially in the lateral direction when viewed from front and behind. The upper and lower inner surfaces of the locking portion  28  are substantially perpendicular to the outer side surface  26 , the front arcuate surface  27 F and the rear arcuate surface  27 R. 
     As shown in  FIG. 3 , opening edges of the locking portion  28  on the outer edge  24  (outer side surface  26 , front arcuate surface  27 F and rear arcuate surface  27 ) define upper and lower biting edges  29 . As shown in  FIGS. 4 and 5 , formation areas of the locking portions  28  in forward and backward directions are substantially the entire areas of the resilient deforming portions  22  in the thickness direction (forward and backward directions), i.e. areas from the front surfaces to the rear surfaces of the resilient deforming portions  22 . Further, as shown in  FIGS. 2 ,  3  and  5 , formation areas of the locking portions  28  in the width direction WD extends over substantially the entire ranges of formation areas of the front arcuate surfaces  27 F and the rear arcuate surfaces  27 R. 
     The four pairs of locking portions  28  are arranged one above another in the vertical direction. As shown in  FIGS. 2 and 3 , the uppermost locking portions  28  and the second locking portions  28  from top are arranged above the maximum displacement areas  25 . The bottommost locking portions  28  and the second locking portions  28  from bottom are arranged below the maximum displacement areas  25 . Thus, all of the locking portions  28  are arranged in areas other than the maximum displacement areas  25  in the vertical inserting direction ID into the through hole  11 . Further, as shown in  FIG. 1 , all of the locking portions  28  are within the range of an area facing the inner peripheral surface of the through hole  11  (i.e. within the range of the plate thickness of the circuit board  10 ) when the board connecting portion  21  is press-fit correctly in the through hole  11 . 
     Parts of the resilient deforming portions  22  below the maximum displacement areas  25  interfere with the opening edge on the upper surface of the through hole  11  in the process of press-fitting the board connecting portion  21  in the inserting direction ID into the through hole  11 . As a result, the resilient deforming portions  22  are displaced resiliently toward each other. The amount of the resilient displacements gradually increases as the board connecting portion  21  is press-fit into the through hole  11 . The board connecting portion  21  reaches a properly press-fit state when the maximum displacement areas  25  reach a substantially central part of the through hole  11 , as shown in  FIG. 1 . At this time, the amount of deformations of the resilient deforming portions  22  is a maximum. 
     The front and rear arcuate surfaces  27 F and  27 R of the outer edges  24  face the inner peripheral surface of the through hole  11  when the board connecting portion  21  is inserted in the through hole  11  and are pressed resiliently by the resilient restoring forces of the resilient deforming portions  22 , as shown in  FIG. 5 . Thus, the terminal fitting  20  and the through hole  11  are connected with a specified contact pressure. Further, as shown in  FIG. 1 , contact areas of the outer edges  24  of the resilient deforming portions  22  with the inner peripheral surface of the through hole  11  in the vertical direction include the entire maximum displacement areas  25 , and partial areas above and below the maximum displacement areas  25 . 
     All of the locking portions  28  are arranged within the ranges of the areas of the outer edges  24  of the resilient deforming portions  22  that are held in contact with the inner peripheral surface of the through hole  11 . Accordingly, all of the biting edges  29  formed on the locking portions  28  engage with and bite into the inner peripheral surface of the through hole  11  due to the resilient restoring forces of the resilient deforming portions  22 . Displacements of the board connecting portion  21  relative to the through hole  11  in the vertical inserting direction ID are prevented or inhibited by the locking action of the biting edges  29 . Thus, the terminal fitting  20  is held reliably in the through hole  11 . 
     As described above, the connection structure of this first embodiment includes the terminal fitting  20  with two resilient deforming portions  22  and the through hole  11  in the circuit board  10  is the connection target of the terminal fitting  10  into which the resilient deforming portions  22  are press-fit while being displaced resiliently toward each other. The resilient deforming portions  22  have the locking portions  28  formed by recessing the outer edges  24  and engage the inner peripheral surface of the through hole  11  when the resilient deforming portions  22  are press-fit in the through hole  11 . 
     The locking portions  28  are engaged with the inner peripheral surface of the through hole  11  due to the resilient restoring forces of the resilient deforming portions  22  when the resilient deforming portions  22  are press-fit in the through hole  11 , thereby holding the resilient deforming portions  22  in the through hole  11 . The locking portions  28  are recessed in the outer edges  24  of the resilient deforming portions  22 . Thus, the amount of displacements of the resilient deforming portions  22 , i.e. the restoring forces accumulated in the resilient deforming portions  22 , becomes a maximum in the press-fitting process when the locking portions  28  engage the through hole  11 . Therefore, the holding force of the terminal fitting  20  in the through hole  11  is large. 
     The locking portions  28  are arranged in the vertical inserting direction ID in areas other than the maximum displacement areas  25  of the resilient deforming portions  22  where the amount of resilient displacement becomes a maximum in the press-fitting process. More particularly, the resilient deforming portions  22  deform resiliently while being press-fit into the through hole  11  to increase a radius of curvature. The amount of resilient displacements of the resilient deforming portions  22  at this time and hence the stress generated in the resilient deforming portions  22  becomes a maximum in the maximum displacement areas  25 . On the other hand, when the biting edges  29  bite into the inner peripheral surface of the through hole  11 , a deformation occurs to change a distance between the upper and lower biting edges  29  of one locking portion  28  and a stress is generated in the locking portion  28 . Accordingly, the locking portions  28  are arranged only in the areas other than the maximum displacement areas  25  to avoid the concentration of stresses in the maximum displacement areas  25 . 
     A second embodiment of the invention is described with reference to  FIGS. 6 to 8 . The terminal fitting  20  of the first embodiment is formed with the four pairs of locking portions  28 , whereas a terminal fitting  30  of this second embodiment is formed with four groups of locking portions  31 , with each group being composed of four locking portions  31 . Since the other configuration is similar to or the same as in the above first embodiment, the similar elements are denoted by the same reference signs and the structure, functions and effects thereof are not described. 
     As shown in  FIG. 8 , one group of locking portions  31  is composed of a pair of front and rear locking portions  31  formed on a left resilient deforming portion  22  and a pair of front and rear locking portions formed on a right resilient deforming portion  22 . As shown in  FIGS. 6 and 7 , the locking portions  31  constituting one group are arranged on the same height in the vertical direction and are substantially bilaterally and front-back symmetrical. 
     The locking portions  31  are substantially are wedge-shaped recesses formed in front arcuate surfaces  27 F and rear arcuate surfaces  27 R of outer edges  24 . As shown in  FIGS. 6 and 7 , an opening of each locking portion  31  on the outer edge  24  is in the form of a slit substantially perpendicular to the press-fitting inserting direction ID into the through hole  11 . Thus, as shown in  FIG. 6 , the opening of the locking portion  31  is in the form of a slit substantially extending in forward and backward directions when viewed in a direction perpendicular to an outer side surface  26 . As shown in  FIG. 7 , the opening of the locking portion  31  is substantially in the form of a slit extending in the lateral direction when the board connecting portion  21  is viewed from the front and rear. Both upper and lower inner surfaces of the locking portion  31  are substantially perpendicular to the front arcuate surface  27 F and the rear arcuate surface  27 R. 
     As shown in  FIG. 7 , opening edges of the locking portion  31  on the outer edge  24  (front arcuate surface  27 F and rear arcuate surface  27 R) define upper and lower biting edges  32 . As shown in  FIGS. 6 and 8 , formation areas of the locking portions  31  in forward and backward directions (thickness direction of the resilient deforming portions  22 ) are the entire ranges of formation areas of the front arcuate surfaces  27 F and the entire ranges of formation areas of the rear arcuate surfaces  27 R. Further, as shown in  FIGS. 7 and 8 , formation areas of the locking portions  31  in the width direction WD also are the entire ranges of the formation areas of the front arcuate surfaces  27 F and the entire ranges of the formation areas of the rear arcuate surfaces  27 R. 
     As shown in  FIGS. 6 and 7 , the four groups of locking portions  31  are arranged one above another in the vertical direction. The uppermost locking portions  31  and the second locking portions  31  from top are arranged above maximum displacement areas  25 . The bottommost locking portions  31  and the second locking portions  31  from bottom are arranged below the maximum displacement areas  25 . Thus, all of the locking portions  31  are arranged in areas other than the maximum displacement areas  25  in the vertical press-fitting direction into the through hole  11 . Further, all of the locking portions  31  are arranged within the range of an area substantially facing the inner peripheral surface of the through hole  11  (i.e. within the range of the plate thickness of the circuit board  10 ) when the board connecting portion  21  is press-fit correctly in the through hole  11 . 
     The invention is not limited to the above described embodiments. For example, the following embodiments also are included in the scope of the invention. 
     Although the four pairs of locking portions are formed in the first embodiment, the number of the pairs of the locking portions may be fewer or more. 
     Although four groups each composed of four locking portions are provided in the second embodiment, the number of the groups of the locking portions may be three or less or five or more. 
     The paired locking portions are substantially bilaterally symmetric in the first and second embodiments. However, the paired locking portions may be bilaterally asymmetric. Moreover, there may be three or more locking portions provided resiliently deformable substantially radially towards and away from a longitudinal center line of the terminal fitting. 
     The locking portions on the right side and those on the left side are equal in number and paired in the first and second embodiments. However, the number of the locking portions on the right side and on the left side may differ. 
     Equal numbers of the locking portions are formed in the areas of the resilient deforming portion above and below the maximum displacement area in the first and second embodiments. However, the number of the locking portions above and below the maximum displacement area may differ. 
     The locking portions are arranged in area of the resilient deforming portion both above and below the maximum displacement area in the first and second embodiments. However, the locking portions may be arranged only in the area above the maximum displacement area or the area below the maximum displacement area. 
     The locking portions are arranged in areas deviated from the maximum displacement area of the resilient deforming portion in the length direction of the board connecting portion in the first and second embodiments. However, the locking portions may be arranged within the range of the maximum displacement area of the resilient deforming portion in the length direction of the board connecting portion. 
     Although the terminal fitting is connected to the circuit board in the first and second embodiments, the connection target of the terminal fitting is not limited to the circuit board and may be a busbar or the like according to the invention.