Abstract:
A bus bar  31  to be inserted in a circular through hole provided in a casing  10  and connecting both terminals provided inside and outside the casing  10  to be brought in a conduction state has a circular section in a portion passing through a through hole  11 A. The outer periphery of the section is covered with a grommet  32  having a circular section and the ratios in vertical and transverse directions of the grommet  32  are equal to each other. Accordingly, when a bus bar body  30  including the bus bar  31  and the grommet  32  is fitted in the through hole  11 A, the grommet  32  has compression ratios equal to each other in the vertical and transverse directions. Consequently, the fitting portions of the bus bar  31  and the grommet  32  uniformly come in close contact with each other, and a sealing property can fully be maintained in the fitting portions of the grommet  32  and the bus bar  31.

Description:
BACKGROUND OF THE INVNTION  
         [0001]    1. Industrial Field of Application  
           [0002]    The present invention relates to a terminal connecting device.  
           [0003]    2. Related Art  
           [0004]    In a controller for controlling a motor of an electric vehicle, for example, a controller body is covered with a case and is thus protected. In order to connect the controller body to the motor, accordingly, it is necessary to lead out a terminal of the controller body to the outside of the case. The Unexamined Japanese Patent Application Publication No. Hei11-26050 has described an example of connection to be employed in that case.  
           [0005]    As shown in FIG. 13, a flat conductor bent like an L-shape is used for a bus bar  1 , a through hole  3 A provided in a case  3  is caused to penetrate through a grommet  2  formed of an insulating material and the grommet  2  is fixed to the case  3  with a screw  7 .  
           [0006]    On the other hand, a terminal  5  of the bus bar and a terminal  4  on the controller side are fixed to each other with a bolt  6  in the case  3 , and the other terminal of the bus bar which is not shown is lead out through the through hole of the case  3 .  
           [0007]    In this case, it is necessary to maintain insulating and sealing properties between the case  3  and the bus bar  1 . Therefore, the grommet  2  formed of an insulating material is fitted in the through hole  3 A of the case  3  by pressure.  
         SUMMARY OF THE INVENTION  
         [0008]    Problems that the Invention is to Solve  
           [0009]    According to such a structure, the sealing property should be improved between an opening  2 A of the grommet  2  and the bus bar  1 . More specifically, the flat conductor is used for the bus bar  1 . Therefore, the ratios in vertical and transverse directions of the bus bar  1  are different from each other. Accordingly, when the grommet  2  (circular section) is fitted in the through hole  3 A (circular) of a case  3 , the fitting portions of the bus bar  1  and the grommet  2  do not uniformly come in close contact with each other because the grommet  2  has the compression ratios in the vertical and transverse direction which are different from each other. Thus, there is a fear for the sealing property.  
           [0010]    The invention has been completed based on such circumstances and has an object to provide a terminal connecting device having a high sealing property.  
           [0011]    Means for Solving the Problems  
           [0012]    In order to achieve the object, a first aspect of the invention is directed to a terminal connecting device for connecting both outer and inner terminals provided outside and inside a casing through a conductive bus bar inserted into a circular through hole opened on a wall surface of the casing, wherein a portion of the bus bar which passes through the through hole has a circular section, a hole wall of the through hole is attached, by pressure, to an outer periphery of the portion having the circular section, and a grommet formed of an insulating material which is to be sealed along a whole periphery of the hole wall is fitted and attached.  
           [0013]    A second aspect of the invention is directed to the terminal connecting device according to the first aspect of the invention, wherein the bus bar is formed of a round bar member and an end side to be connected to the outer and inner terminals is provided with a terminal connecting portion crushed like a flat plate.  
           [0014]    A third aspect of the invention is directed to the terminal connecting device according to the first or second aspect of the invention, wherein a contact portion is formed along a whole outer peripheral surface of the grommet, and when the bus bar provided with the grommet is to be inserted into the through hole, the contact portion is attached by pressure with being sealed to a hole wall of the through hole to attach a whole bus bar.  
           [0015]    Function and Effect of the Invention  
           [0016]    Invention of Claim 1  
           [0017]    According to the first aspect of the invention, the bus bar to be inserted in the circular through hole provided in the casing has a circular section in the portion passing through the through hole. The grommet having the circular section is fitted and attached into the outer periphery of the portion having the circular section and the ratios in the vertical and transverse directions of the grommet are equal to each other. Accordingly, when the whole bus bar including the bus bar and the grommet is fitted in the through hole and is attached by pressure, the compression ratios of the grommet are equal to each other over the whole periphery. Consequently, the fitting portions of the external wall of the bus bar and the inner peripheral surface of the grommet and the fitting portions of the hole wall of the through hole and the outer peripheral surface of the grommet uniformly come in contact with each other. Consequently, a sealing property can be maintained along the whole periphery of the through hole of the casing.  
           [0018]    Invention of Claim 2  
           [0019]    Conventionally, a base material formed of a flat plate is used for the bus bar. Consequently, if the connecting portion of the terminals is to be constituted on both ends and they are to be set into positions twisted by 90 degrees, at least one of them should be formed by bending a predetermined expanded shape. In this case, a great deal of labor and time are required for the processing and yield is also deteriorated.  
           [0020]    In this respect, according to the second aspect of the invention, the bus bar is formed of a round bar member. Therefore, the connecting terminal portions formed on both ends can be crushed by pressure in a free direction, and they can also be set easily in the twisted positions and the yield can also be enhanced.  
           [0021]    Invention of Claim 3  
           [0022]    Conventionally, the bus bar body including the bus bar and the grommet and the casing are fixed with a screw. According to the third aspect of the invention, however, a contact portion is formed along a whole outer peripheral surface of the grommet, and when the bus bar provided with the grommet is to be inserted into the through hole, the contact portion is attached by pressure with being sealed to a hole wall of the through hole to attach a whole bus bar without slip-off.  
           [0023]    Accordingly, the screw for fixing is not required so that the number of parts can be reduced and an excellent assembling property can also be obtained.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]    [0024]FIG. 1 is an exploded perspective view showing a part of a first embodiment,  
         [0025]    [0025]FIG. 2 is a perspective view showing a single bus bar according to the first embodiment,  
         [0026]    [0026]FIG. 3 is a perspective view showing a single grommet according to the first embodiment,  
         [0027]    [0027]FIG. 4 is a longitudinal sectional view showing the periphery of the bus bar according to the first embodiment (before the bus bar is attached),  
         [0028]    [0028]FIG. 5 is a longitudinal sectional view showing the periphery of the bus bar according to the first embodiment (after the bus bar is attached),  
         [0029]    [0029]FIG. 6 is a cross-sectional view showing the periphery of the bus bar according to the first embodiment (after the bus bar is attached),  
         [0030]    [0030]FIG. 7 is a sectional view showing a maximum diameter portion of the bus bar according to the first embodiment (after the bus bar is attached),  
         [0031]    [0031]FIG. 8 is a top view showing a single terminal base according to the first embodiment,  
         [0032]    [0032]FIG. 9 is a rear view showing the single terminal base according to the first embodiment,  
         [0033]    [0033]FIG. 10 is a sectional view showing the single terminal base according to the first embodiment,  
         [0034]    [0034]FIG. 11 is a top view showing the terminal base in a nut attachment state according to the first embodiment,  
         [0035]    [0035]FIG. 12 is a sectional view showing the terminal base in a nut attachment state according to the first embodiment, and  
         [0036]    [0036]FIG. 13 is a sectional view showing a conventional embodiment. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0037]    Mode for Carrying Out the Invention  
         [0038]    Preferred embodiments of the invention will be described below with reference to the accompanying drawings.  
         [0039]    First Embodiment  
         [0040]    A first embodiment of the invention will be described with reference to FIGS.  1  to  12 .  
         [0041]    A terminal connecting device according to the first embodiment is applied to a driving motor for an electric vehicle. The reference numeral  10  denotes a joint case which is formed of metal and has an almost box shape, for example. A terminal base  21  is attached into the joint case  10 , and as shown in FIG. 5, is positioned by a concave portion  13  provided on the bottom face of the joint case  10  and a fitting projection  24  provided on the bottom face of the terminal base  21  and is fixed with a double coated adhesive tape  28  stuck to the bottom face portion of the terminal base  21 . The terminal base  21  thus fixed is divided into three chambers through a partition board  22 . Each chamber is provided with a nut housing chamber  23  having a rectangular shape. As shown in FIG. 8, a nut  50  for fixing a connecting terminal is attached to the nut housing chamber  23 . For the positioning, a two-bar positioning piece  25  is protruded inwards in a vertical direction on each side wall of the nut housing chamber  23 . An escape hole  26  is provided on the bottom face of the nut housing chamber  23 , and a bolt  51  screwed to the nut  50  is escaped.  
         [0042]    Three circular through holes  11 A are formed on a front wall  11  of the joint case  10  in a transverse direction corresponding to the chambers partitioned by the partition board  22  on the terminal base  21 . On the other hand, three electric wire inserting holes  11 C for inserting a shielding electric wire are formed on a surface opposite to the through hole  11 A in the joint case  10 .  
         [0043]    By utilizing each through hole  11 A, three bus bars  31  are attached.  
         [0044]    As shown in FIG. 2, the bus bar  31  is formed of a round bar member and terminal connecting portions  31 A and  31 B obtained by crushing the round bar member like a flat plate are formed on both end sides thereof.  
         [0045]    The terminal connecting portion  31 A is connected to a stator terminal of a motor which is not shown and the terminal connecting portion  31 B is connected to a terminal fixture  42  attached to an end of the shielding electric wire  41 .  
         [0046]    The joint case  10  is provided in a motor casing which is not shown. At this time, the terminal connecting portion  31 A provided on one of ends of the bus bar  31  is plunged into the motor casing and is exposed to oil in the casing.  
         [0047]    A grommet  32  for insulating an adjacent apparatus such as the joint case  10  from the bus bar  31  is fitted and attached into the outer periphery of the bus bar  31 , and is formed of a rubber material having elasticity, for example. Thus, the bus bar body  30  according to the embodiment is constituted by the bus bar  31  and the grommet  32 . In a processing procedure, both ends of the bus bar  31  is processed to form the terminal connecting portions  31 A and  31 B, and then, a grommet  32  is fitted and attached thereto.  
         [0048]    As shown in FIGS. 3 and 4, moreover, the grommet  32  has such an almost cylindrical shape as to insert the bus bar  31  therein, and a central portion thereof is formed to gradually increase a thickness from both sides toward the center. In other words, two angle portions  33  (maximum diameter portions) and one valley portion  34  are annularly provided over the whole surface in the vicinity of the central portion on the outer peripheral surface of the grommet.  
         [0049]    By the way, since the outer diameter of the maximum diameter portion  33  of the grommet  32  is larger than the hole diameter of the through hole  11 A, in condition that the whole bus bar body  30  is fitted by pressure without slip-off into a predetermined position to mount the whole bus bar body  30  to the joint case  10 , owing that the maximum diameter portion  33  of the grommet  32  is attached by pressure onto the hole wall of the through hole  11 A as shown in FIG. 5, the whole bus bar body  30  is fitted and attached.  
         [0050]    Therefore, in this embodiment, the maximum diameter  33  provided on the outer peripheral surface of the grommet  32  functions as a contact portion which is attached by pressure onto the hole wall of the through hole  11 A.  
         [0051]    Further, when the bus bar body  30  is attached to the joint case  10 , the terminal connecting portion  31 B on one ends of the bus bar  31  is positioned on the nut  50  of the nut housing chamber  23  and is fastened to the terminal based  21  with a bolt  51  together with the terminal fixture  42  of the shielding electric wire  41 .  
         [0052]    As described above, since both maximum diameter portions  33  interposing the valley portion  34  in the grommet  32  therebetween is attached by pressure to the hole wall of the through hole  11 A by elastic force, and therefore also functions as a sealing edge. At this time, a corresponding portion of a bus bar  31  to which the grommet  32  is fitted has a circular section. Therefore, the grommet  32  is uniformly compressed over the whole periphery.  
         [0053]    Consequently, each contact portion of the grommet  32  uniformly comes in close contact with and is sealed against the hole wall of the through hole  11 A and an external wall  31 C of the bus bar.  
         [0054]    As shown in FIG. 4, moreover, an axial hole  35  permitting the insertion of the bus bar  31  penetrates through the core of the grommet  32 , and an annular slit  36  is formed like a concave over the whole periphery in a position corresponding to the valley portion  34 . One end side (a left end side of FIG. 4) of the axial hole  35  comes in cloth contact with the outer peripheral surface  31 C of the bus bar  31  over the whole periphery within a range of a predetermined length by using the slit  36  as a boundary, and the other end side thereof (a right end side of FIG. 4) is enlarged like a trumpet toward the open side. Consequently, a region which is not in contact with the outer peripheral surface  31 C of the bus bar  31  is provided so that an insertion resistance generated by inserting the grommet  32  into the bus bar  31  can be reduced.  
         [0055]    Besides, one end of the grommet  32  (the left of FIG. 4) is thinned to form a hollow portion  37  of a slit provided on the outer peripheral surface  31 C of the bus bar  31 . Further, an opening portion  38  is provided by lacking at the same end of the grommet  32  so that a thermosetting adhesive  39  is injected to the hollow portion  37  therefrom. The thermosetting adhesive  39  is injected to regulate a displacement along the axis of the grommet  32  with respect to the bus bar  31 .  
         [0056]    Finally, a cover  54  is put on the upper surface of the joint case  10  through a seal plate  53  formed of a cushion material, and four corners thereof are fastened and fixed with a bolt  52 .  
         [0057]    Next, the function and effect of the embodiment having the structure described above will be described specifically. In the case in which the shielding electric wire  41  side is to be connected to the motor side, the bus bar body  30  is inserted into the through hole  11 A of the joint case  10  and the terminal connecting portion  31 A of the bus bar  31  is connected to the stator terminal of the motor with a screw. Subsequently, the shielding electric wire  41  is inserted into the joint case  10  through the electric wire inserting hole  11 C and the terminal fixture  42  connected to the end thereof is superposed on the other terminal connecting portion  31 B of the bus bar and is fastened to the nut  50  of the terminal base  21  with the bolt  51  in that state. Consequently, the terminal fixture  42  and the terminal connecting portion  31 B of the bus bar are fastened together.  
         [0058]    By repeating the connecting work for the three bus bar bodies  30 , a work for connecting the terminal to the motor is completed. Then, when the cover  54  is attached through the seal plate  53 , the whole work is completed.  
         [0059]    As described above,the maximum diameter portion  33  formed on the outer peripheral surface of the grommet  32  is larger than the through hole  11 A of the joint case  10 . Therefore, in a state in which the bus bar body  30  is assembled into the joint case  10 , the maximum diameter portion  33  of the grommet  32  comes in close contact with the hole edge of the through hole  11 A in a compression state. Since the portion of the bus bar  31  for inserting the grommet  32  has a circular section, the grommet  32  is uniformly compressed over the whole surface. Consequently, each contact portion of the grommet  32  with the hole wall of the through hole  11 A and the external wall  31 C of the bus bar uniformly comes in close contact over the whole periphery. Thus, a high sealing property can be obtained.  
         [0060]    According to the embodiment, moreover, the bus bar  31  and the grommet  32  are adhered by the thermosetting adhesion  39 . Thus, the bus bar body  30  is inserted to the through hole  11 A in the press state to fit and attach the maximum diameter portion  33  of the grommet  32  to the hole wall of the through hole  11 A with respect to the joint case  10 , and slip-off can be effectively prevented without using a screw differently from the conventional art. Accordingly, complicated screwing is not required and the number of parts can also be reduced.  
         [0061]    Other Embodiment  
         [0062]    The invention is not restricted to the embodiment described above with reference to the drawings but the following embodiment is also included in the technical range of the invention, for example, and furthermore, various changes can be made without departing from the scope of the invention.  
         [0063]    (1) While the grommet is fitted and attached into the bus bar after the terminal connecting portion of the bus bar is formed in the embodiment, the grommet may be previously fitted and attached into the bus bar and the terminal connecting portion of the bus bar is formed.