Abstract:
In a connector which is loaded to the end of a cable including an internal conductor and an external conductor arranged radially outside of the internal conductor via an insulation layer therebetween. The internal conductor covering part has a covering piece capable of being bent inside. The covering piece is formed between an electric connection part of the external conductor terminal and the external conductor crimping part. A covering insulation member is formed by an electric insulator. The covering insulation member covers an inner side surface of the internal conductor covering part. The covering piece of the internal conductor covering part and the covering insulation member are integrally bending inside. The covering piece of the internal conductor covering part and the covering insulation member have a shape to cover the internal conductor covering part from outside.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to technology of a connector connected to the end of a co-axial cable and a shield cable. 
   2. Description of the Related Art 
   Of conventional cables, there are some cables which are equipped with both an internal conductor and an external conductor, for example, a co-axial cable and a shield cable. Connectors to be connected to the end of such cable are those equipped with an internal conductor terminal and an external conductor terminal connected respectively to the end of the internal conductor and that of the external conductor and in which a terminal insulation member comprising an electric insulator lies between the electric connection parts of these terminals. 
   One example is shown in  FIG. 9 . 
   An illustrated cable  10  is provided with an internal conductor  12  and, for example, a braided external conductor  16 , in which an insulation layer  14  lies between both conductors  12  and  16  and an exterior of the external conductor  16  is covered with a sheath  18 . 
   On the other hand, a connector connected to the cable  10  is provided with an internal conductor terminal  100 , external conductor terminal  110  and terminal insulation member  120 . 
   The internal conductor terminal  100  is provided with an electric connection part  102  fitted into an opposing internal conductor terminal and an internal conductor barrel  104  crimped to the end in such a manner that embraces the end of the internal conductor  12 . The external conductor terminal  110  is provided with an electric connection part  112  fitted into an opposing external conductor terminal, an external conductor barrel  114  crimped to the end in such a manner that embraces the end of the external conductor  16  and an insulation barrel  116  crimped to the end in such a manner that embraces the end of the sheath  18 . The terminal insulation member  120  is a cylindrical form lying between the electric connection part  102  of the internal conductor terminal  100  and the electric connection part  112  of the external conductor terminal  110 , and the internal conductor barrel  104  is provided immediately therebehind. 
   Incidentally, the thus structured connector is necessary to match the impedance of the connector to that of the cable  10  as much as possible, particularly in sending high-frequency wave electric signals, and insufficiency of such matching will cause a great reflection of the signals and result in disadvantage of a significant decrease in transmission efficiency of the signals. In this instance, an part where electric connection parts  102  and  112  of the connector are overlapped is relatively large in the sectional area, and a terminal insulation member  120  higher in dielectric constant than air lies between the electric connection parts  102  and  112 , thereby making it easy to reduce the impedance accordingly and match the impedance with that of the cable  10 . In contrast, a part where the internal conductor barrel  104  is crimped to the internal conductor  12  immediately therebehind (hereinafter referred to as “internal conductor crimping part”) is small in the sectional part and the internal conductor barrel  104  is in a condition which is opened outside and surrounded with air, thereby keeping the impedance high and making it difficult to match the impedance with that of the cable  10 . Therefore, it is a serious problem in adjusting the impedance at the internal conductor crimping part. 
   As a means to solve such a problem, JP-A-2001-185302 shown below has disclosed a method in which while an internal conductor crimping part is inserted into a heat-shrinkable tube having an electrically conductive layer inside, the tube is subjected to heat shrinkage and the electrically conductive layer of the tube is closely attached to the internal conductor crimping part, by which the internal conductor crimping part is covered with the tube. 
   SUMMARY OF THE INVENTION 
   JP-A-2001-185302 requires an operation for accurately positioning a heat-shrinkable tube to an internal conductor crimping part and an operation for heating the heat-shrinkable tube, with such a positioning being kept. These operations are not necessarily easy. Further, an excessively great shrinkage of the heat-shrinkable tube may result in an excessive contact pressure of an electrically conductive layer with the internal conductor crimping part, whereas insufficiency of the shrinkage may result in removal of the heat-shrinkable tube from the internal conductor crimping part. Therefore, it is difficult to control the shrinkage. 
   There is another method in which the internal conductor crimping part is wrapped with a metal tape so as to increase the sectional area of the conductor at this part. However, it is practically difficult to stably obtain a desired sectional area by wrapping with the metal tape. Further, the metal tape may act as an intermediate to cause short-circuiting between an internal conductor and an external conductor. 
   In addition, considered is an idea that a terminal insulation member  120  shown in  FIG. 9  is extended in axial length so that not only the electric connection part  102  of the internal conductor terminal  100  but also the internal conductor crimping part can be inserted into the terminal insulation member  120  (namely, the terminal insulation member  120  exists also outside the internal conductor crimping part). However, the internal conductor  120  of the cable  10  and the insulation layer  14  may be easily buckled on such insertion, resulting in a poor workability, which is disadvantageous. Further, where a larger clearance is provided between the terminal insulation member  120  and the internal conductor crimping part in order to make the operation easier, an air layer is increased and results in elevation of the impedance. 
   It is an object of the present invention to provide a connector or cable with the connection which make it possible to easily and appropriately adjust the impedance at the crimping part of the internal conductor of the cable and the internal conductor terminal by using a simply-structured device. 
   According to one aspect of the invention, there is provided with a connector which is loaded to the end of a cable including an internal conductor and an external conductor arranged radially outside of the internal conductor via an insulation layer therebetween, the connector including: an internal conductor terminal having: an electric connection part contacting with an opposing terminal; and an internal conductor crimping part being arranged behind the electric connection part, and the internal conductor crimping part being crimped to an end of the internal conductor; an external conductor terminal having: an electric connection part having a shape to cover the electric connection part of the internal conductor terminal outside in a radial direction thereof, and the electric connection part of the external conductor terminal contacting with the opposing terminal; and an external conductor crimping part being arranged behind the electric connection part of the external conductor terminal, and the external conductor crimping part being crimped to an end of the external conductor; a terminal insulation member being formed by an electric insulator and being disposed between the electric connection part of the internal conductor terminal and the electric connection part of the external conductor terminal, an internal conductor covering part having an covering piece capable of being bent inside, the covering piece being formed between the electric connection part of the external conductor terminal and the external conductor crimping part, a covering insulation member being formed by an electric insulator and covering an inner side surface of the internal conductor covering part. The internal conductor covering part is at least partially covered from outside by integrally bending at least one of the covering piece of the internal conductor covering part and the covering insulation member inside. 
   By thus configuration, for example, the internal conductor crimping part of the internal conductor terminal and the external conductor crimping part of the external conductor terminal are crimped respectively to the internal conductor and the external conductor of the cable to fabricate the terminal, terminal insulation member and covering insulation member, and an covering piece of the external conductor terminal and an covering insulation member arranged therein are bent inside together so that the covering piece and the insulation member are given such a configuration that covers the internal conductor crimping part from the outside, thereby making it possible to reduce the impedance at the internal conductor crimping part. 
   In this instance, the covering piece is formed on the external conductor terminal having the external conductor crimping part, it is not necessary to separately perform positioning of operation the covering piece to the internal conductor crimping part, other than positioning operation of the external conductor crimping part to the external conductor and also making it possible to adjust the impedance easily and appropriately by a simple step of bending the covering piece and the covering insulation member after they are set, similar to crimping the external conductor crimping part by pressure. Since a covering insulation member is provided inside the covering piece, short-circuiting between the external conductor terminal and the internal conductor terminal can be avoided and an impedance can also be further reduced. 
   Further, unlike the heat-shrinkable tube disclosed in JP-A-2001-185302, the covering insulation member is not necessarily required to be closely attached to the internal conductor pressure part, thereby making the operation easier. In addition, by actively forming an air layer between the covering insulation member and the internal conductor crimping part in association with such separation it becomes possible to utilize the thickness of the air layer for adjustment of the impedance. 
   The covering piece of the external conductor terminal may be available singularly, however, it is more preferably formed both on the right and left sides of the internal conductor crimping part. Such configuration makes it possible to divide the bending amount required for the covering piece into right and left, thus resulting in an easier bending work. 
   In this instance, if a connection part connecting the right and left covering pieces of the external conductor terminal and a part of the covering insulation member corresponding to the connection part are given an inwardly recessed configuration, the impedance at these parts can be further reduced. 
   Further, if the covering insulation member is provided with a thin bent part, which is locally made thin for bending, the bent part may be more easily treated and also the impedance can be set by referring to a site where the locally thin part is formed. 
   The terminal insulation member and the covering insulation member may be formed independently. However, when an insulation member is provided in which a terminal insulation part lying between an electric connection part of the internal conductor terminal and that of the external conductor terminal is formed integrally with an covering insulation part covering the inner plane of the internal conductor covering part, the number of parts can be reduced to more easily assemble the connector. 
   In this instance, when the insulation member is provided with an inwardly recessed part at an area corresponding to the connection part of the external conductor terminal and the recessed part of the external conductor terminal is from behind brought into contact with a projected part formed between the recessed part and a part anterior to the recessed part, by which the insulation part is constituted so as not to be removed from the external conductor terminal, the insulation member can be locked on the external conductor terminal due to the configuration of the recessed part and such locking is able to prevent the insulation member from removing backward from the external conductor terminal. 
   According to another aspect of the invention, there is provided with a method for manufacturing a cable with a connector, including: crimping the internal conductor crimping part to an end of the internal conductor of a cable including an internal conductor and an external conductor arranged radially outside of the internal conductor via an insulation layer therebetween; assembling the connector; crimping an external conductor crimping part of an external conductor terminal of the connector to the end of the external conductor of the cable; and bending the covering piece of the external conductor terminal and the covering insulation member arranged therein inside together covering the internal conductor crimping part from the outside by the covering piece and the covering insulation member, thereby to connect the crimping member to the electric connection member. 
   By thus method, there is no particular restriction on types of cable, and where the cable is a shield cable on which the outer conductor is grounded, the shield performance can also be improved. 
   According to the above aspects of the invention, the connector or the cable with the connector are simple in structure, are effective in making an easy and appropriate adjustment of the impedance at the crimping part between the internal conductor of the cable and the internal conductor terminal. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an exploded perspective view showing an outline structure of a male connector of the embodiment in the present invention. 
       FIG. 2A  is a cross side view of a male connector, and  2 B is a partial cross side view of the male connector. 
       FIG. 3A  is a front view of an insulation member built into the male connector, and  3 B is a cross side view of the insulation member. 
       FIG. 4A  is a perspective view of the male connector in an integrated state, and  4 B is a cross sectional view of  4 A taken along line A—A. 
       FIG. 5A  is a cross side view of a female connector joined to the male connector, and  5 B is a fragmentary cross plane view of the female connector. 
       FIG. 6A  is a cross sectional view of an insulation member built into the female connector, and  FIG. 6B  is a front view of the insulation member. 
       FIG. 7  is a graph showing the relationship between the axial position with the impedance in a state where the male connector is connected with the female connector. 
       FIGS. 8A and 8B  are perspective views showing an example where the external conductor terminal of the male connector is divided into an electric connection member and a crimping member. 
       FIG. 9  is an exploded perspective view showing one example of a conventional cable connector. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   An explanation will be made for a preferred embodiment of the present invention by referring to  FIG. 1  through  FIG. 8 . The embodiment discloses a male connector Cm and a female connector Cf which are fittable each other and connected to the end of a cable  10 . The cable  10  is provided with an internal conductor  12  and an external conductor  16  arranged via an insulation layer  14  radially outside of the internal conductor, in which the external conductor  16  is externally covered with a sheath  18  and which is applicable either to a co-axial cable or a shield cable. 
   First, an explanation will be made for the structure of the male connector Cm by referring to  FIG. 1  to  FIG. 4 . The male connector Cm is provided with an internal conductor terminal  20 , an external conductor terminal  30  and an insulation member  40 . 
   A male tab  22  is formed at a front end of the internal conductor terminal  20  as an electric connection part, and an internal conductor barrel  24  is formed at the rear end. The internal conductor barrel  24  is constituted with a pair of right and left erect pieces, and bent in such a manner to embrace the internal conductor  12  from right and left, by which it is crimped to the internal conductor  12 . Further, a stabilizer  26  for preventing a reverse insertion projects upward at a location between the internal conductor barrel  24  and the tab  22 . 
   The external conductor terminal  30  is provided with an electric connection part  32  at the front end and with an external conductor barrel  34  and insulation barrel  36  therebehind. The electric connection part  32  is in an approximately tubular form, and configured so as to cover from radially outwardly a tab  22  on the internal conductor terminal  20 . The external conductor barrel  34  is constituted with a pair of right and left erect pieces and bent so as to embrace an external conductor  16  of the cable  10  from right and left, by which it is crimped to the external conductor  16 . Similarly, the insulation barrel  36  is also constituted with a pair of right and left erect pieces and bent so as to embrace a sheath  18  of the cable  10  from right and left, by which it is crimped to the sheath  18 . 
   In addition, the external conductor terminal  30  is characterized in that an internal conductor covering part  37  which covers an internal conductor barrel  24  of the internal conductor terminal  20  is formed between the electric connection part  32  and the external conductor barrel  34 . As with the external conductor barrel  34  and the insulation barrel  36 , the internal conductor covering part  37  is provided with covering pieces  38 , which are a pair of right and left erect pieces, and the covering pieces  38  are bent inside, as with both barrels  34  and  36 , thereby making it possible to give such a configuration that the covering pieces  38  cover the internal conductor barrel  24  from above, the details of which will be explained later. 
   A part connecting a bottom wall  37   a  of the internal conductor covering part  37 , namely, these covering pieces  38 , is given a configuration which is recessed radially inwardly (upward in the figure). In the figure, the recessed part is formed by giving a so-called hammering finish to the bottom wall  37   a  from the outside. 
   An insulation member  40  is an integral formation of a terminal insulation part  42  with an insulation part  47  by using an insulating material. 
   The terminal insulation part  42  is configured so as to lie between the electric connection part  32  of the external conductor terminal  30  and the tab  22  of the internal conductor terminal  20 . More concretely, it is given an outer configuration that can be fitted into the electric connection part  32  and provided with an insertion hole  41  through which the tab  22  can be inserted into the axial center. Further, an insertion groove  46  into which the stabilizer  26  of the internal conductor terminal  20  is inserted is formed at an area around the rear end of the insertion hole  41 . 
   The terminal insulation part  42  is provided at the ceiling wall with a through hole  43  provided radially. A piece to be locked  23  of the internal conductor terminal  20  that is shown in  FIGS. 2A and 2B  is inserted into the through hole  43 , by which the internal conductor terminal  20  is to be locked on the insulation member  40 . 
   The covering insulation part  47  is given a configuration that covers an inner plane of the internal conductor covering part  37  at the external conductor terminal  30 . To be more specific, it is provided with an insulation covering piece  44  and a bottom wall  47   a  respectively corresponding to the right and left covering pieces  38  of the internal conductor covering part  37  and the bottom wall  37   a , and the bottom wall  47   a  is given a configuration which is recessed inwardly (upward in the figure). The bottom wall  37   a  of the internal conductor covering part  37  is from behind brought into contact with a projected part  48   a  formed between the bottom wall  47   a  and a part anterior thereto, by which the insulation member  40  is prevented from being removed backward from the external conductor terminal  30 . 
   Further, in this embodiment, as shown in  FIG. 2A , a projected part  48   b  is also formed at a part anterior to the projected part  48   a , and a locking piece  31  formed on the external conductor terminal  30  is from the front brought into contact with the projected part  48   b , by which the insulation member  40  is prevented from being removed forward as well. 
   Next, an explanation will be made for the structure of a female connector Cf by referring to  FIGS. 5A ,  5 B and  FIGS. 6A ,  6 B. The female connector Cf is provided with an internal conductor terminal  50 , an external conductor terminal  60  and an insulation member  70 . 
   The internal conductor terminal  50  is provided at the front end with a female electric connection part  52  into which the tab  22  of the male connector Cm can be fitted and at the rear end with an internal conductor barrel  54 . The internal conductor barrel  54  is constituted with a pair of right and left erect pieces and bent so as to embrace the internal conductor  12  from right and left, by which it is crimped to the internal conductor  12 . Further, a stabilizer  56  for preventing a reverse insertion projects upward at a location between the internal conductor barrel  54  and the electric connection part  52 . 
   The external conductor terminal  60  is provided at the front end with an electric connection part  62  and at a location therebehind with an external conductor barrel  64  and an insulation barrel  66 . 
   The electric connection part  62  is in an approximately tubular form and configured so as to cover radially outwardly the electric connection part  52  of the internal conductor terminal  50 , and the electric connection part  32  of the male connector Cm can be fitted into the electric connection part  62 . An electric contact piece  63  which is bent elastically and deformed in association with fitting of the electric connection part  32  is formed on the side wall of an electric connection part  62 , and the electric connection part  62  is brought into contact with the outer circumferential wall of the electric connection part  32  by the elastic force, thereby ensuring the conduction between the external conductor terminals  30  and  60 . 
   The external conductor barrel  64  is constituted with a pair of right and left erect pieces and bent so as to embrace the external conductor  16  of the cable  10  from right and left, by which it is crimped to the external conductor  16 . Similarly, the insulation barrel  66  is also constituted with a pair of right and left erect pieces and bent so as to embrace a sheath  18  of the cable  10  from right and left, by which it is crimped to the sheath  18 . 
   In addition, the external conductor terminal  60  is characterized in that an internal conductor covering part  67  covering an internal conductor barrel  54  of the internal conductor terminal  50  is formed between the electric connection part  62  and the external conductor barrel  64 . As with the external conductor barrel  64  and the insulation barrel  66 , the internal conductor covering part  67  is provided with covering pieces  68 , which are a pair of right and left erect pieces, and the covering pieces  68  are bent inside, as with the both barrels  64  and  66 , thereby making it possible to give such a configuration that the covering pieces  68  cover the internal conductor barrel  54  from above, the details of which will be explained later. 
   A part connecting a bottom wall  67   a  of the internal conductor covering part  67 , namely, the covering pieces  68 , is configured so as to be recessed radially inwardly (upward in the figure). For example, as with the bottom wall  37   a  of the external conductor terminal  30 , a recessed part can be formed on the bottom wall  67   a  as well by giving a so-called hammering finish. 
   An insulation member  70  is an integral formation of a terminal insulation part  72  with an insulation part  77  by using an insulating material. 
   The terminal insulation part  72  is configured so as to lie between the electric connection part  62  of the external conductor terminal  60  and the electric connection part  52  of the internal conductor terminal  50 . Concretely, it is given an outer configuration that can be fitted into the electric connection part  62 , available in a tubular form which permits the electric connection part  52  to fit into the axial center, and provided at the front tip with a tab insertion hole  71  for accommodating the tab  22  of the male connector Cm. Further, an insertion groove  76  into which a stabilizer  56  of the internal conductor terminal  50  is inserted is formed at the rear end of the electric connection part  62 . 
   The terminal insulation part  72  is provided at the ceiling wall with a through hole  73  provided radially. A piece to be locked  53  of the internal conductor terminal  50  that is shown in  FIGS. 2A and 2B  is inserted into the through hole  73 , by which the internal conductor terminal  50  is locked on the insulation member  70  side. 
   The covering insulation part  77  is configured so as to cover an inner plane of the internal conductor covering part  67  at the external conductor terminal  60 . To be more specific, it is provided with an insulation covering piece  74  and a bottom wall  77   a  respectively corresponding to the right and left covering pieces  68  of the internal conductor covering part  67  and the bottom wall  77   a , and the bottom wall  77   a  is configured so as to be recessed inwardly (upward in the figure). The bottom wall  67   a  of the internal conductor covering part  67  is from behind brought into contact with an projected part  78   a  formed between the bottom wall  77   a  and a part anterior thereto, by which the insulation member  70  is prevented from being removed backward from the external conductor terminal  60 . Further, as shown in  FIG. 5A , a projected part  78   b  is also formed at a part anterior to the projected part  78   a , and a locking piece  61  formed on the external conductor terminal  60  is from the front brought into contact with the projected part  78   b , by which the insulation member  70  is prevented from being removed forward as well. 
   In addition, in this embodiment, as shown in  FIGS. 6A and 6B , a horizontal groove  75  is formed on the inner plane of the intermediate part at the individual insulation covering pieces  74 , which is to be used as a bent part made locally thin. It is, therefore, possible to bend these insulation covering pieces  74  inside easily at the part. 
   There is no particular restriction on materials of the insulation member  40  or  70 , and those with a relatively high dielectric constant, for example, polybutylene terephthalate or those with a relatively low dielectric constant, for example, polymethyl pentane, may be used. In either case, it is more preferable to optimize an outer diameter of the internal conductor terminal and an inner diameter of the external conductor terminal so as to obtain desired impedance properties, with the dielectric constant taken into account. 
   Next, an explanation will be made for an example of a method for connecting the connectors Cm and Cf with the end of the cable  10 , namely, a method for manufacturing a connector-equipped cable. 
   1) Internal conductor crimping step: In the male connector Cm, the end of the internal conductor  12  of the cable  10  is set inside an internal conductor barrel  24  of the internal conductor terminal  20 , the internal conductor barrel  24  is bent inside, with this state being kept, by which the internal conductor barrel  24  is configured so as to embrace the internal conductor  12  from right and left. To be specific, the internal conductor barrel  24  is crimped to the end of the internal conductor  12 . Similarly, in the female connector Cf, an internal conductor barrel  54  of an internal conductor terminal  50  is crimped to the end of the internal conductor  12 . 
   2) Assembly step: The connectors Cm and Cf are assembled. In the male connector Cm, the terminal insulation part  42  of the insulation member  40  is fitted into the electric connection part  32  of the external conductor terminal  30 , and the tab  22  and the stabilizer  26  of the internal conductor terminal  20  are inserted into the insertion hole  41  and the insertion groove  46  of the terminal insulation part  42 . Similarly, in the female connector Cf, the terminal insulation part  72  of the insulation member  70  is fitted into the electric connection part  62  of the external conductor terminal  60 , then, the electric connection part  52  of the internal conductor terminal  50  is inserted into the terminal insulation part  72 , and the stabilizer  56  is inserted into the insertion groove  76 . After completion of this assembly, internal conductor barrels  24  ( 54 ) of the internal conductor terminal  20  ( 50 ), the end of the external conductor  16  of the cable  10  and the end of a sheath  18  are positioned to the locations respectively corresponding to internal conductor covering parts  37  ( 67 ) of external conductor terminals  30  ( 60 ), external conductor barrels  34  ( 64 ) and insulation barrels  36  ( 66 ), and covering insulation parts  47  ( 77 ) of insulation members  40  ( 70 ) are positioned inside the internal conductor covering parts  37  ( 67 ). 
   A step in which the terminal insulation parts  42  and  72  are inserted into the electric connection parts  32  and  62  of the external conductor terminals  30  and  60  may be done before or after a step in which the internal conductor terminal is crimped. However, in view of supplying parts, it is more preferable to complete at first a step of inserting the terminal insulation parts  42  and  72  and then a step of assembling the external conductor terminal, followed by a step of crimping the internal conductor terminal. 
   3) External conductor crimping step and sheath crimping step: In the male connector Cm, the external conductor barrel  34  and the insulation barrel  36  of the external conductor terminal  30  are bent inside, by which the barrels  34  and  36  are configured so as to embrace respectively the end of the external conductor  16  and that of the sheath  18  from right and left. To be specific, these barrels  34  and  36  are respectively crimped to the end of the external conductor  16  and that of the sheath  18 . Similarly, in the female connector Cf, the external conductor barrel  64  and the insulation barrel  66  of the external conductor terminal  60  are respectively bent inside and crimped to the external conductor  16  and the sheath  18  of the cable  10 . 
   This step may be conducted at the same time with the subsequent covering step, or may be conducted after the covering step. 
   4) Covering step: In the male connector Cm, the covering piece  38  of the internal conductor covering part  37  at the external conductor terminal  30  and the insulation covering piece  44  of the covering insulation part  47  arranged therein are bent inside integrally, by which, as shown in  FIGS. 4A and 4B , the covering piece  38  and the insulation covering piece  44  are configured so as to cover the internal conductor barrel  24  from outside. Similarly, in the female connector Cf, the covering piece  68  of the internal conductor covering part  67  at the external conductor terminal  60  and the insulation covering piece  74  of the covering insulation part  77  arranged therein are bent inside integrally, by which the covering piece  68  and the insulation covering piece  74  are configured so as to cover the internal conductor barrel  54  from outside. 
   This step makes a condition where the internal conductor barrels  24  and  54  are covered by the covering insulation parts  47  and  77  of the insulation members  40  and  70  and also by the internal conductor covering parts  37  and  67  of the external conductor terminals  30  and  60 , thereby providing a remarkable reduction in impedance, as compared with a case where the internal conductor barrels  24  and  54  are opened outside. Further, where the cable  10  is a shield cable, namely, a cable to which the external conductor  16  is grounded, it is also effective in improving the shield performance. 
   In this instance, if the bottom walls  47   a  and  77   a  of the covering insulation parts  47  and  77  and the bottom walls of  37   a  and  67   a  of the internal conductor covering parts  37  and  67  are configured so as to be recessed inwardly, as shown in the figure, the impedance will be reduced further by such a recess. 
   The covering insulation parts  47  and  77  which lie between the internal conductor barrels  24  and  54  and the internal conductor covering parts  37  and  67  act to prevent short-circuiting between the internal conductor terminals  20  and  50  and the external conductor terminals  30  and  60 . Therefore, the covering insulation parts  37  and  67  may be crimped to the internal conductor barrels  24  and  54  in the assembly step. As shown in  FIG. 4B , a clearance is provided between the barrel and the covering insulation part to form an air layer, thereby making it possible to adjust the impedance by the thickness of the air layer. 
   In particular, as shown in the female connector Cf, if the groove  75  is provided at an appropriate location of the covering insulation part  74  to form a part made thin for bending work, the part is firmly held, thereby making it possible to adjust the impedance more accurately. 
     FIG. 7  shows a relationship of the axial position with the impedance, with both the connectors Cm and Cf connected. In a conventional connector in which the internal conductor barrels  24  and  54  are opened, as shown with the two-dot dashed line in the same figure, a greatly increased impedance is locally found at a part corresponding to the internal conductor barrel, contributing to reduction in transmission efficiency. In a case of the connectors Cm and Cf, the internal conductor barrels  24  and  54  are covered by the internal conductor covering parts  37  and  67  of the external conductor terminals  30  and  60  and by the covering insulation parts  47  and  77  arranged therein, thereby making it possible to reduce the impedance effectively also at a location of the internal conductor barrel, as shown with the solid line in  FIG. 7 . 
   Further, the present invention is not restricted to the above-described embodiment, however, may be available in various embodiments. 
     FIGS. 8A ,  8 B show the male connector Cm, the external conductor terminal  30  of which is divided into an electric connection member  30 A and a crimping member  30 B. The electric connection member  30 A includes the electric connection part  32 , and the crimping member  30 B includes the external conductor barrel  34 , the insulation barrel  36  and the internal conductor covering part  37 . Further, a connection piece  39  to be inserted between the covering insulation part  47  of the insulation member  40  and the internal conductor covering part  37  projects backward from the rear end of the electric connection member  30 A. 
   According to the connector Cm, an internal conductor crimping step and an assembly step in which the terminal insulation part  42  of the insulation member  40  and the internal conductor terminal  20  are assembled to the electric connection part  32  of the electric connection member  30 A are conducted, then, the external conductor barrel  34  and the insulation barrel  36  of the crimping member  30 B are crimped respectively to the end of the external conductor  16  of the cable  10  and that of the sheath  18 , and in a state where a connection piece  39  of the electric connection member  30 A is inserted between the internal conductor covering part  37  of the crimping member  30 B and the covering insulation part  47  of the insulation member  40 , the internal conductor covering part  37  and the insulation covering piece  47  are bent inside integrally to give such a configuration that the covering piece  38  and the insulation covering piece  44  cover the internal conductor barrel  24  from outside, thereby making it possible to reduce the impedance at the internal conductor barrel  24  and also connect the crimping member  30 B with the electric connection member  30 A. 
   The terminal insulation part  42  of the insulation member  40  and the internal conductor terminal  20  can be assembled inside the electric connection part  32  of the electric connection member  30 A more effectively by this method, without an impeditive presence of the covering piece  38  or the barrels  34  and  36 . 
   The present invention may also be available in the following embodiments. 
     FIG. 1  through  FIG. 7  show an embodiment of the present invention in which both the male connector Cm and the female connector Cf are used, but only either one of them may be used in the present invention. 
   The covering pieces  38  and  68  of the external conductor terminals  30  and  60  are not necessarily required to be formed on both the right and left sides of the internal conductor barrels  22  and  52 , and a single covering piece erecting from one of the terminal walls may be bent, for example, up to the other terminal wall. 
   In the embodiment shown in  FIGS. 6A and 6B , the groove  75  is provided on the inner plane of the covering insulation part  77  to form a part made locally thin for bending work. A similar groove or notch may be provided on the outer circumferential plane or both on the outer and inner circumferential planes. 
   It is also possible to reduce the impedance at the internal conductor barrels  24  and  54  even when the insulation members  40  and  70  and the covering insulation parts  47  and  77  of the terminal insulation parts  42  and  72  are respectively formed as individual members such as terminal insulation member and covering insulation member.