Patent Publication Number: US-7714693-B2

Title: Slow blow fuse and electric junction box

Description:
TECHNICAL FIELD 
   The present invention relates to a slow blow fuse and an electric junction box and more particularly the present invention is intended to decrease the height of the slow blow fuse having the fuse element and facilitate a work of mounting the slow blow fuse in the electric junction box. 
   BACKGROUND ART 
   Conventionally to protect a circuit from eddy current, a fuse is mounted on the electric junction box for distributing a power supply to electric component parts mounted on a car. As disclosed in Japanese Patent Application Laid-Open No. 2004-281078 (patent document 1), the slow blow fuse 1 shown in FIG. 11 is proposed. 
   In the slow blow fuse 1, the fuse element 5 having the female terminal-shaped input terminal part 2 and the output terminal part 3 connected thereto by the coupling part 4 having the fusing portion 4a is accommodated inside the box-shaped housing 6 made of an insulating resin. The insertion ports (not shown in FIG. 11) through which mating terminals are inserted into the housing 6 are formed through the bottom wall of the housing 6 at positions confronting the input terminal part 2 and the output terminal part 3 of the fuse element 5 so that the mating terminals inserted into the housing 6 through the insertion ports are connected to the input terminal part 2 and the output terminal part 3 respectively. 
   In the slow blow fuse 1 disclosed in the patent document 1, the coupling part 4 of the fuse element 5 is projected from the input terminal part 2 and the output terminal part 3 in a terminal plugging direction. Thus the fuse element 5 is long in the terminal plugging direction. 
   In addition in the fuse element 5 of the slow blow fuse 1 disclosed in the patent document 1, the mating terminals can be inserted into the input terminal part 2 and the output terminal part 3 from only the side of the housing 6 where the coupling part 4 is not provided. Therefore in inserting the slow blow fuse 1 accommodating the fuse element 5 into the fuse accommodation portion of the electric junction box, the bottom wall of the housing 6 should be set as the front end at the insertion side. 
   Ordinarily, the slow blow fuse is inserted into the fuse accommodation portion by using mechanical equipment. In inserting the slow blow fuse 1 into the fuse accommodation portion, it is necessary to position the slow blow fuse 1 in which component parts are irregularly arranged in such a way that the bottom wall of the housing 6 is set as the front end at the insertion side. Thus it is necessary to use a dedicated equipment to do so, which makes the production cost high. 
   Patent document 1: Japanese Patent Application Laid-Open No. 2004-281078 
   DISCLOSURE OF THE INVENTION 
   Problem to be Solved by the Invention 
   The present invention has been made in view of the above-described problems. It is an object of the present invention to make the height of a fuse element of a slow blow fuse low, allow terminals to be inserted into a female terminal part of the slow blow fuse in two directions, and simplify equipment for inserting the slow blow fuse into a fuse accommodation portion of an electric junction box to decrease a production cost. 
   Means for Solving the Problem 
   To solve the above-described problems, the present invention provides a slow blow fuse in which a fuse element is accommodated in a housing made of an insulating resin; and insertion ports into which mating terminals can be inserted from upper and lower sides of the housing; 
   Wherein the fuse element comprises a pair of female terminal parts, disposed in parallel, into which the mating terminals are plugged; and 
   a fusing portion coupling a pair of the female terminal parts to each other in a direction orthogonal to a direction in which the mating terminals are plugged into the female terminal parts; and 
   the female terminal parts have plugging ports for the mating terminals at vertical upper and lower ends thereof; an edge of a left side surface or a right side surface of one of the female terminal parts and an edge of a left side surface or a right side surface of the other female terminal part are coupled to each other by a coupling part having the fusing portion at a center thereof; and the coupling part is located at a position proximate to one of the plugging ports disposed at the vertical upper and lower ends of the female terminal parts. 
   In the above-described construction, unlike the conventional art, the coupling part of the fuse element is not projected in the direction in which the mating terminals are inserted into the female terminal parts respectively, but orthogonally to the direction in which the mating terminals are inserted thereinto respectively. Therefore it is possible to shorten the dimension of the female terminal parts in the direction in which the mating terminals are inserted thereinto respectively and thus make the height of the slow blow fuse low. 
   By projecting the coupling part orthogonally to the direction in which the mating terminals are inserted into the female terminal parts respectively, it is possible to make the height of the slow blow fuse lower than that of the conventional slow blow fuse by 20 to 50%. 
   The female terminal parts of the fuse element are so configured that the mating terminals can be inserted thereinto respectively from both ends in the terminal plugging direction, and the housing accommodating the fuse element is provided with the insertion ports confronting the plugging ports of the female terminal parts disposed at the vertical upper and lower ends thereof. Therefore it is possible to insert the mating terminals to be connected with the female terminal parts respectively into the female terminal parts respectively from the upper and lower sides of the housing. 
   As described above, the slow blow fuse of the present invention allows the mating terminals to be inserted into the female terminal parts respectively in the two opposite directions. Thus it is unnecessary to regulate the insertion direction of the slow blow fuse to the upward direction or the downward direction. Therefore it is possible to mount the slow blow fuse inside a fuse accommodation portion of an electric junction box in both the upward direction or the downward direction. 
   Conventionally in equipment for inserting the slow blow fuse into the fuse accommodation portion of the electric junction box, it is necessary to use an apparatus for regulating the posture of the slow blow fuse so that a wall portion thereof through which the insertion port is formed is located at the lower side thereof. But owing to the use of the slow blow fuse of the present invention, it is unnecessary to provide the equipment with an apparatus for regulating the insertion direction of the slow blow fuse to the upward direction or the downward direction. Therefore it is possible to simplify the construction of the equipment and decrease the cost. 
   Because the insertion ports are formed through the confronting walls of the housing, the heat radiation performance can be enhanced. 
   The housing has a main body, uncovered at an upper portion thereof, which is composed of a bottom wall, a side wall, and a cover for closing said uncovered upper portion of said main body; and 
   said insertion ports are formed through said bottom wall of said main body and said cover confronting said bottom wall. 
   The main body of the housing and the cover are coupled to each other by locking the main body and the cover to each other after the fuse element is accommodated inside the main body of the housing. 
   The housing may be provided with upper and lower covers for closing the main body of the housing uncovered at the upper portion thereof. In this case, one of the covers constitutes the bottom wall of the main body of the housing. 
   Probe pin insertion ports, for examining electrical conductivity, continuous with the insertion ports respectively are provided. 
   The probe pin insertion port is formed through the bottom wall formed continuously with the insertion port formed through the bottom of the main body of the housing and the insertion port formed through the cover. Therefore it is possible to conduct a conductivity test by inserting a probe pin into the probe pin insertion port when the housing is used upside down or not. 
   A flange portion is projected from a periphery of the bottom wall of the main body of the housing. 
   The peripheral edge of the cover for closing the uncovered upper portion of said main body is projected from the side wall of the main body of the housing. Thus the flange portion is projected from the periphery of the bottom wall of the main body of the housing so that the outer configuration of the flange portion and that of the cover are identical to each other. By forming the flange portion on the bottom wall of the main body of the housing in such a way that the slow blow fuse is accommodated in a box with the flange portion closely engaging a mounting portion of the box, the cover closely engages the mounting portion of the box without being loosened, when the cover is mounted on the mounting portion of the box with the slow blow fuse turned upside down. 
   It is preferable that a concave portion or/and a convex portion for placing the slow blow fuse in position in a fuse accommodation portion and preventing an erroneous connection are formed on an outer surface of the housing. 
   For example, when the concave portion is formed on the outer surface of the bottom wall of the main body of the housing, the concave portion is also formed on the outer surface of the cover at a position corresponding to the concave portion formed on the outer surface of the bottom wall. 
   The present invention provides an electric junction box having a fuse accommodation portion for accommodating a slow blow fuse. 
   It is preferable that a bottom wall of the fuse accommodation portion is provided with a convex portion or/and a concave portion which engage the concave portion or/and the convex portion formed on the housing. 
   In the above-described construction, when the predetermined slow blow fuse is accommodated in the fuse accommodation portion, the convex portion fits in the concave portion. Thus the slow blow fuse can be inserted into the fuse accommodation portion to a predetermined normal position thereof. On the other hand, when a slow blow fuse other than the predetermined slow blow fuse is accommodated in the fuse accommodation portion, the convex portion interferes with the bottom wall of the fuse accommodation portion or the insertion-side front end surface of the housing of the slow blow fuse. Thus the slow blow fuse cannot be inserted into the fuse accommodation portion to the predetermined normal position. Thereby it is possible to prevent the slow blow fuse from being erroneously inserted into the fuse accommodation portion to the predetermined normal position. 
   Effect of the Invention 
   As described above, according to the present invention, the coupling part of the fuse element is projected orthogonally to the direction in which the mating terminals are inserted into the female terminal parts respectively. Therefore it is possible to shorten the dimension of the female terminal parts in the direction in which the mating terminals are inserted thereinto respectively and thus make the height of the slow blow fuse low. 
   The female terminal parts of the fuse element are so configured that the mating terminals can be inserted thereinto from both ends in the terminal plugging direction, and the housing accommodating the fuse element is provided with the insertion ports confronting the plugging ports of the female terminal parts disposed at the vertical upper and lower ends thereof. Therefore it is possible to insert the mating terminals to be connected with the female terminal parts respectively into the female terminal parts respectively in two opposite directions. 
   In equipment for inserting the slow blow fuse into the fuse accommodation portion of the electric junction box, it is possible to simplify the construction of an apparatus for regulating the posture of the slow blow fuse and hence decrease the cost. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an exploded perspective view of a slow blow fuse of a first embodiment of the present invention. 
       FIG. 2  shown a fuse element of the slow blow fuse, in which (A) is a plan view, and (B) is a front view. 
       FIG. 3  shows the slow blow fuse, in which (A) is a perspective view, and (B) is a plan view. 
       FIG. 4  is a sectional view taken along a line A-A. 
       FIG. 5(A)  is a sectional view showing a state in which a terminal is inserted into the slow blow fuse from a lower surface thereof to connect the terminal to a female terminal, and  5 (B) is a sectional view showing a state in which the terminal is inserted into the slow blow fuse from an upper surface thereof to connect the terminal to the female terminal. 
       FIGS. 6(A) through 6(E)  show modification examples of a probe pin insertion port formed continuously with an insertion port of the slow blow fuse. 
       FIG. 7  is a sectional view showing a slow blow fuse of a second embodiment of the present invention. 
       FIG. 8  is an exploded perspective view of an electric junction box where the slow blow fuse is mounted. 
       FIG. 9(A)  is a sectional view showing a state in which a predetermined slow blow fuse is accommodated in a fuse accommodation portion of the electric junction box.  FIG. 9(B)  is a sectional view showing a state in which a slow blow fuse other than the predetermined slow blow fuse is accommodated in the fuse accommodation portion. 
       FIG. 10  shows a modification example of the second embodiment. 
       FIG. 11  shows an example of a conventional art. 
   

   EXPLANATION OF REFERENCE NUMERALS AND SYMBOLS 
   
       
         10 : slow blow fuse 
         11 : fuse element 
         12 : input terminal part 
         13 : output terminal part 
         14 : coupling part 
         14   a : fusing portion 
         20 : housing 
         21 : main body 
         21   a : bottom wall 
         21   a - 1 : flange 
         21   c : insertion port for terminal 
         21   p : probe pin insertion port 
         22 : cover 
         22   a : insertion port for terminal 
         22   p : probe pin insertion port 
         23 : convex portion 
         24 : concave portion 
         30 : mating terminal 
         40 : electric junction box 
         45 : fuse accommodation portion 
         45   a : bottom wall 
         45   b : concave portion 
         45   c : convex portion 
     
  
   BEST MODE FOR CARRYING OUT THE INVENTION 
   The embodiments of the present invention are described below with reference to the drawings. 
     FIGS. 1 through 5  show a first embodiment of the present invention. A slow blow fuse  10  includes a fuse element  11  having a pair of female terminal-shaped input and output terminal parts  12 ,  13  continuous with each other by a coupling part  14  having a fusing portion  14   a ; and a box-shaped housing  20 , made of an insulating resin, which accommodates the fuse element  11 . 
   The fuse element  11  is formed by punching a conductive metal plate into a required configuration and thereafter bending an obtained metal piece. The input terminal part  12  of the fuse element  11  and the output terminal part  13  thereof are so disposed that plugging directions of mating terminals to be connected thereto are parallel with each other. Plugging ports  12   a - 1 ,  12   a - 2 ,  13   a - 1 , and  13   a - 2  through which the mating terminals are inserted thereinto are formed at upper and lower ends of the input terminal part  12  and the output terminal part  13  in the terminal plugging direction so that the mating terminals can be inserted thereinto from opposed both sides in a terminal plugging direction X. One side wall of each of the input terminal part  12  and the output terminal part  13  is folded inward at the plugging ports  12   a - 1 ,  13   a - 1  disposed at one end of the input terminal part  12  and the output terminal part  13  in the terminal plugging direction X, and a portion of the one side wall rearward from the folded position is folded inward again at a position near the other end thereof to form elastic pieces  12   b ,  13   b . The mating terminals inserted into the input terminal part  12  and the output terminal part  13  respectively are sandwiched between the elastic piece  12   b  and a wall confronting the elastic piece  12   b  and between the elastic piece  13   b  and a wall confronting the elastic piece  13   b  respectively. Locking pieces  12   c ,  13   c  are formed on the input terminal part  12  and the output terminal part  13  respectively by cutting and raising a portion of the confronting side walls of each of the input terminal part  12  and the output terminal part  13 . 
   The coupling part  14  coupling an edge of one side wall surface of the input terminal part  12  and that of one side wall surface of the output terminal part  13  to each other is provided by projecting the coupling part  14  in a direction orthogonal to the terminal plugging direction X of the mating terminals to be plugged into the input terminal part  12  and the output terminal part  13  respectively with the coupling part  14  spanning the input terminal part  12  and the output terminal part  13 . A narrow fusing portion  14   a  is provided at a central portion of the coupling part  14  in a direction in which the coupling part  14  is extended. A circular bulged portion  14   b  is provided at both sides of the fusing portion  14   a  to enhance heat radiation performance of the coupling part  14  at the bulged portion  14   b  so that the fusing portion  14   a  can be prevented from being fused by a short-time eddy current. 
   In the first embodiment, by projecting the coupling part  14  orthogonally to the terminal plugging direction X, the height of the input terminal part  12  and that of the output terminal part  13  in the terminal plugging direction is 70% of that of the fuse element of the conventional slow blow fuse having the coupling part projected in the terminal plugging direction. That is, the height of the input terminal part  12  and that of the output terminal part  13  in the terminal plugging direction is 30% less than that of the fuse element of the conventional slow blow fuse. 
   The housing  20  accommodating the fuse element  11  includes a main body  21  having a bottom wall  21   a , a side wall  21   b  projected from the periphery of the bottom wall  21   a , and a flange portion  21   a - 1  projected from the periphery of the bottom wall  21   a ; and a flat plate-shaped cover  22  closing the uncovered main body  21 . The outer configuration of the flange portion  21   a - 1  projected from the bottom wall  21   a  and that of the cover  22  are set identically to each other. 
   Insertion ports  21   c  are formed through the bottom wall  21   a  of the main body  21  at positions confronting the plugging port  12   a - 1  of the input terminal part  12  of the fuse element  11  to be accommodated inside the housing  20  and the plugging port  13   a - 1  of the output terminal part  13  thereof. Insertion ports  22   a  are formed through the cover  22  at positions confronting the plugging port  12   a - 2  of the input terminal part  12  of the fuse element  11  to be accommodated inside the housing  20  and the plugging port  13   a - 2  of the output terminal part  13  thereof. 
   The positions of a pair of the insertion ports  21   c  formed through the bottom wall  21   a  of the main body  21  and those of a pair of the insertion ports  22   a  formed through the cover  22   c  are vertically correspondent to each other. 
   Conductivity-examining probe pin insertion ports  21   p ,  22   p  are formed continuously with an outer edge of a central position of a pair of the insertion ports  21   c  of the bottom wall  21   a  and an outer edge of a central position of a pair of the insertion ports  22   p  of the cover  22  respectively. 
   Inside the main body  21 , a pair of partitioning walls  21   d  is projected upward from the bottom wall  21   a . Lances  21   f  for locking the locking piece  12   c  of the input terminal part  12  and the locking piece  13   c  of the output terminal part  13  thereto respectively are provided on outer surfaces of the partitioning walls  21   d  and inner surfaces of the side wall  21   b  confronting thereto. When the input terminal part  12  of the fuse element  11  and the output terminal part  13  thereof are accommodated between the partitioning wall  21   d  and the side wall  21   b , as shown in  FIG. 4 , the lances  21   f  lock the tip of the locking piece  12   c  formed on the input terminal part  12  and the tip of the locking piece  13   c  formed on the output terminal part  13  thereto respectively. Thereby the fuse element  11  is fixedly placed in position inside the main body  21 . 
   A locking claw  21   e  is provided at an upper end of each of the confronting side walls  21   b  of the main body  21 . A locking frame  22   b  is formed on the cover  22 . After the fuse element  11  is accommodated inside the main body  21 , the cover  22  is placed on the uncovered main body  21 , and the locking claw  21   e  of the main body  21  is locked to the locking frame  22   b  of the cover  22  to lock the main body  21  and the cover  22  to each other. 
   In the slow blow fuse  10 , the plugging ports  12   a - 1 ,  12   a - 2 ,  13   a - 1 , and  13   a - 2  are provided at the upper and lower ends of the input terminal part  12  of the fuse element  11  and the output terminal part  13  thereof in the terminal plugging direction, and the insertion ports  21   c  and  22   a  are formed through the bottom wall  21   a  of the housing  20  and the cover  22  respectively. Therefore the mating terminals  30  to be connected with the fuse element  11  can be inserted into the slow blow fuse  10  from both the upper and lower sides thereof. 
   That is, as shown in  FIGS. 5(A) and 5(B) , when the tab-shaped mating terminals  30  projected inside a fuse accommodation portion  45  of an electric junction box  40  in which the slow blow fuse  10  is to be mounted are inserted into the housing  20  through the insertion port  21   c  of the bottom wall  21   a  or the insertion port  22   a  of the cover  22 , the mating terminals  30  are sandwiched between the one elastic piece  12   b  of the input terminal part  12  and the side wall  21   b  confronting thereto and between the elastic piece  13   b  of the output terminal part  13  and the other side wall  21   b  confronting thereto respectively and connected to the input terminal part  12  and the output terminal part  13  respectively. 
   In the above-described construction, the mating terminals  30  can be connected to the input terminal part  12  and the output terminal part  13  respectively by inserting the mating terminals  30  into the slow blow fuse  10  from both the upper and lower sides thereof. Thus for example, in equipment for inserting the slow blow fuse  10  into the fuse accommodation portion  45  of the electric junction box  40 , it is unnecessary to regulate the insertion direction of the slow blow fuse  10  to the upward direction or the downward direction. Therefore it is unnecessary to provide a dedicated equipment for regulating the insertion direction of the slow blow fuse  10  to the upward direction or the downward direction and hence simplify the construction of the equipment and decrease the production cost. 
   Because the insertion ports  21   c  and  22   a  are formed through confronting upper and lower walls of the housing  20 , the heat radiation performance can be enhanced. 
   Further because the coupling part  14  having the fusing portion  14   a  is projected orthogonally to the terminal plugging direction X of the mating terminals  30  to be inserted into the input terminal part  12  and the output terminal part  13 , it is possible to shorten the dimension of the input terminal part  12  and that the output terminal part  13  in the terminal plugging direction X and thus make the height of the slow blow fuse  10  low. 
   Let it be supposed that the slow blow fuse  10  is accommodated in the fuse accommodation portion  45  of the electric junction box  40  by turning the main body  21  and the cover  22  upside down with either the main body  21  or the cover  22  located at the lower side of the slow blow fuse  10 . The probe pin insertion ports  21   p  and  22   p  are formed through the bottom wall  21   a  of the main body  21  and the cover  22  respectively. Therefore it is possible to conduct a conductivity test by inserting a probe pin (not shown in the drawings) into the probe pin insertion port formed through the main body  21  or the cover  22  located at the upper side of the slow blow fuse  10 . 
   Further the bottom wall  21   a  of the main body  21  is provided with the flange  21   a - 1  to make the outer configuration of the bottom wall  21   a  identical to that of the cover  22 . Therefore even though the slow blow fuse  10  is mounted in the fuse accommodation portion  45  with the cover  22  and the main body  21  turned upside down, it is possible to fit the slow blow fuse  10  closely in the fuse accommodation portion  45  without loosening the slow blow fuse  10  and mount the slow blow fuse  10  therein stably. 
   As shown in  FIG. 1 , in the fuse element  11  of the slow blow fuse  10  of the first embodiment, the coupling part  14  having the fusing portion provided at its center couples a pair of the female terminal parts  12  and  13  to each other with the coupling part  14  projected outward beyond the female terminal parts  12  and  13 . But it is possible to widen the interval between the female terminal parts  12  and  13  to dispose the coupling part  14  having the fusing portion in a space between the female terminal parts  12  and  13  by folding the fusing portion  14   a . In this case, although the interval between the female terminal parts  12  and  13  is widened, it is possible to decrease the dimension of a portion of the coupling part  14  projected outward beyond the female terminal part. 
   In the first embodiment, the locking pieces  12   c ,  13   c  of the female terminal parts of the fuse element  11  are respectively locked to the lances  21   f  provided on the side wall  21   b  and the partitioning wall  21   d  to fixedly place the fuse element  11  in position inside the main body  21 . But the locking pieces  12   c ,  13   c  do not necessarily have to be locked to both lances  21   f  provided on the side wall  21   b  and the partitioning wall  21   d , but may be respectively locked to the lance  21   f  provided on the side wall  21   b  or the lance  21   f  provided on the partitioning wall  21   d . In addition, it is possible that the locking pieces  12   c ,  13   c  and the lances  21   f  are not formed, but the input terminal part  12  and the output terminal part  13  may be fixed by press fit between the side wall  21   b  of the main body  21  and the partitioning wall  21   d . Thereby it is possible to decrease the number of cut and raised portions for forming the locking pieces  12   c ,  13   c  and the number of the lances  21   f  and unnecessary to form the locking pieces  12   c ,  13   c  and the lances  21   f , which facilitates the formation of the fuse element and the housing. 
   Further the configuration of the probe pin insertion ports  21   p  and  22   p  formed continuously with the insertion port  21   c  formed on the bottom wall  21   a  of the main body  21  and the cover  22  respectively are not regulated to that shown in  FIG. 1 . For example, the probe pin insertion ports  21   p ,  22   p  may have configurations, as shown in  FIGS. 6(A) through 6(E) . 
   In  FIG. 6(A) , the probe pin insertion ports  21   p  ( 22   p ) are formed by outwardly and rectangularly cutting the bottom wall  21   a  of the main body  21  and the cover  22  continuously with longitudinal opposite ends of a pair of each of the insertion ports  21   c - 1 ,  21   c - 2  ( 22   a - 1 ,  22   a - 2 ) arranged side by side. 
   In  FIG. 6(B) , the probe pin insertion ports  21   p  ( 22   p ) are formed continuously with the insertion ports at the same-side ends thereof in the longitudinal direction thereof. 
   In  FIG. 6(C) , the probe pin insertion ports  21   p  ( 22   p ) are formed at the central position of each of the insertion ports in the longitudinal direction thereof with the probe pin insertion ports  21   p  ( 22   p ) projected inward in such a way that the probe pin insertion ports  21   p  ( 22   p ) approach each other. 
   In  FIG. 6(D) , the probe pin insertion ports  21   p  ( 22   p ) are formed at opposite ends of the insertion ports in the longitudinal direction thereof with the probe pin insertion ports  21   p  ( 22   p ) projected inward. 
   In  FIG. 6(E) , the probe pin insertion ports  21   p  ( 22   p ) are formed not rectangularly but semicircularly. 
   The position and configuration of the probe pin insertion port  21   p  ( 22 P) are so set that a probe pin inserted into the probe pin insertion port  21   p  ( 22 P) is capable of contacting the fuse element  11  with the probe pin locked at a predetermined normal position inside the housing  20 . 
     FIGS. 7 through 9  show a second embodiment of the present invention. 
   The slow blow fuse  10  of the second embodiment is connected with an internal circuit of the electric junction box  40  with the slow blow fuse  10  accommodated in the fuse accommodation portion  45  of the electric junction box  40 . 
   As shown in  FIG. 7 , a convex portion  23  having a predetermined configuration is formed on an outer wall surface of the housing  20  through which the insertion ports  21   c ,  22   a  are formed. In one slow blow fuse  10 , the convex portion  23  formed on the bottom wall  21   a  of the main body  21  and the convex portion  23  formed on the cover  22  have the same configuration and are formed at symmetrical positions. 
   A slow blow fuse  10 ′ having a capacity different from that of the slow blow fuse  10  is provided with a convex portion having a configuration different from that of the slow blow fuse  10 . In the slow blow fuse  10 ′, the convex portions are also formed at symmetrical positions. 
   In the electric junction box  40 , an internal circuit composed of bus bars  43  formed by punching a conductive metal plate into a predetermined configuration is accommodated inside a case consisting of an upper case  41  and a lower case  42 . A tab-shaped terminal  44  provided at a distal end of the bus bar  43  is projected into the fuse accommodation portion  45  provided in the upper case  41 . On the bottom wall  45   a  of the fuse accommodation portion  45 , a concave portion  45   b  is formed in correspondence to the convex portion  23  formed on the housing  20  of the slow blow fuse  10 . 
   An upper cover  46  is placed on the upper case  41 , and a lower cover  47  is placed on the lower case  42  to waterproof the cases. 
   When the predetermined slow blow fuse  10  is accommodated in the fuse accommodation portion  45  of the electric junction box  40 , as shown in  FIG. 9(A) , the convex portion  23  formed on an insertion-side end surface of the housing  20  of the slow blow fuse  10  fits in the concave portion  45   b  formed on the bottom wall  45   a  of the fuse accommodation portion  45 , and the slow blow fuse  10  is inserted into the fuse accommodation portion  45  to a predetermined normal position thereof. At this time, the input terminal part  12  of the slow blow fuse  10  and the output terminal part  13  thereof are connected with the terminal  44  of the bus bar  43  composing the internal circuit of the electric junction box  40 . 
   In one slow blow fuse  10 , the configuration of the bottom wall  21   a  of the main body  21  and that of convex portion  23  formed on the cover  22  are identical to each other. Thus even though the slow blow fuse  10  is inserted into the fuse accommodation portion  45  with the slow blow fuse turned upside down, the convex portion  23  formed on the slow blow fuse  10  fits in the concave portion  45   b  formed on the fuse accommodation portion  45 , and the slow blow fuse  10  can be inserted into the fuse accommodation portion  45  to the predetermined normal position thereof. 
   As shown in  FIG. 9(B) , when the predetermined slow blow fuse  10 ′ having the capacity different from that of the slow blow fuse  10  is inserted into the fuse accommodation portion  45 , the configuration and disposition of a convex portion  23 ′ of the slow blow fuse  10 ′ are different from those of the convex portion  23  of the slow blow fuse  10 . Therefore the convex portion  23 ′ interferes with the bottom wall  45   a  of the fuse accommodation portion  45  and thus the slow blow fuse  10 ′ cannot be inserted thereinto to the predetermined normal position. 
   Thereby it is possible to confirm that the slow blow fuse  10 ′ has been erroneously inserted into the predetermined normal position. 
   The second embodiment has the same construction, operation, and effect as those of the first embodiment. Thus the same parts of the second embodiment as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and description thereof is omitted herein. 
     FIG. 10  shows a modification example of the second embodiment. 
   In the modification example, the housing  20  of the slow blow fuse  10  is provided with an erroneous insertion prevention concave portion  24 , and a bottom wall  45   a  of the fuse accommodation portion  45  of the electric junction box  40  is provided with a convex portion  45   c  which fits in the erroneous insertion prevention concave portion  24 . 
   In the modification example, a slow blow fuse having a capacity different from that of the slow blow fuse  10  is provided with a convex portion having a configuration different from that of the slow blow fuse  10 , and the fuse accommodation portion is provided with a convex portion whose configuration corresponds to that of the convex portion of the slow blow fuse to be inserted thereinto. 
   In the above-described construction, a slow blow fuse other than the predetermined slow blow fuse is inserted into the fuse accommodation portion  45 , the convex portion  45   c  of the fuse accommodation portion  45  interferes the insertion-side front-end surface of the housing of the slow blow fuse  10 . Thus it is possible to prevent an erroneous insertion of the slow blow fuse  10 .