Patent Publication Number: US-9425532-B2

Title: Connector terminal

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a connector terminal including an elastic contact piece provided with a part projecting out of a body of thereof when the connector terminal is inserted into a housing. 
     2. Description of the Related Art 
     A known connector terminal includes an elastic contact piece with a part (a contact part) projecting out of a body thereof when the connector terminal is inserted into a terminal space formed in a housing. The connector terminal contacts another terminal through the part of the elastic contact piece projecting out of the terminal body. The connector terminal is, however, accompanied with the following problems. First, the part may be damaged and/or deformed when a cable is compressed onto the connector terminal to be fixed to the connector terminal. Second, the part may be grazed with an inner surface of the terminal space to be damaged when the connector terminal is inserted into the terminal space. 
       FIG. 32  is a perspective view of a connector disclosed in Japanese Utility Model Publication No. 2598581 with a partial cross-sectional view thereof. As illustrated in  FIG. 32 , a spring  1003  is housed in a box  1004  to be protected when a terminal  1001  has not been yet inserted into a connector housing  1016 . And then, the terminal  1001  is inserted thereinto, a sliding portion  1008  of the spring  1003  slides along a tapered guide surface, and is pressed by a pressing projection  1021  to be lifted up. Thus, a contact part  1010  of the spring  1003  projects out of the box  1004  through an opening  1011 . 
     The spring  1003  is neither damaged nor deformed when a cable is compressed onto and thus fixed to the terminal  1001  or when the terminal  1001  is inserted into the connector housing  1016 . The connector provides enhanced reliability to electrical connection between the terminal  1001  and another terminal (not illustrated) through the contact part  1010 . 
     In the connector illustrated in  FIG. 32 , the spring  1003  is wholly lifted up by the projection  1021  when the terminal  1001  is inserted into the connector housing  1016 . The spring  1003  is fixed at a proximal end thereof to the box  1004  by collapsing a piece  1007  to thereby fix the spring  1003  onto the box  1004 . Thus, the spring  1003  is supported by the box  1004  in a canti-lever. Consequently, the connector is accompanied with a problem that the spring  1003  cannot have a sufficient spring length, and hence, when the contact part  1010  of the spring  1003  projects out of the opening  1011  of the box  1004  to contact another terminal, the spring  1003  may be plastically deformed, resulting in that there cannot be ensured a sufficient contact pressure between the spring  1003  and another terminal. 
     SUMMARY OF THE INVENTION 
     In view of the above-mentioned problems, an object of the present invention is to provide a connector terminal capable of preventing an elastic contact piece from being damaged and/or deformed when the connector terminal is inserted into a housing, and further, ensuring a sufficient spring length after the connector terminal has been inserted into a housing, to thereby ensure a sufficient contact pressure between the elastic contact piece and another terminal. 
     A first aspect of the present invention provides a connector terminal, comprising: a terminal body operable to be inserted into a terminal space formed in a housing, and; an elastic contact piece arranged in the terminal body, the terminal body including: a bottom wall possessing an first opening; and a top wall facing the bottom wall spaced away therefrom, wherein the elastic contact piece includes: a first end fixed to the bottom wall; a second end abutting on the top wall and being a free end; and a substantially U-shaped folded portion located between the first and second ends, the terminal space includes a raised portion having a height from the bottom wall towards the top wall, when the terminal body is inserted into the terminal space, the folded portion runs onto the raised portion, and a part of the elastic contact piece moves out of the opening, and the second end abuts on the bottom wall. 
     In the connector terminal according to the present invention, when the connector terminal has not been yet inserted into a terminal space formed in a housing, the elastic contact piece is housed in the terminal body. Upon inserting it into the terminal space, the folded portion of the elastic contact piece runs onto the raised portion, and thus, the elastic contact piece projects at the part (a contact part) thereof out of the terminal body through the opening. That is, the part of the elastic contact piece can be exposed out of the terminal body by merely inserting the connector terminal into the terminal space. Since the second end of the elastic contact piece is a free end, the second end contacts the bottom wall and acts as a fulcrum when the folded portion runs onto the raised portion. Thus, the elastic contact piece can be supported with both the folded portion and the second end. 
     A second aspect of the present invention provides a connector terminal in addition to the first aspect, wherein: the elastic contact piece further includes an angle changer changing an angle by which the elastic contact piece is bent between the first end and the folded portion; and a first direction in which the elastic contact piece extends between the first end and the angle changer differs from a second direction in which the elastic contact piece extends between the angle changer and the folded portion from each other. 
     The angle changer arranged between the first end and the folded portion changes an angle by which the elastic contact piece extends from the first end, and further, changes an angle by which the elastic contact piece extends from the angle changer. 
     A third aspect of the present invention provides a connector terminal in addition to the first aspect, wherein the angle changer is constituted of a curved portion directing the folded portion to the bottom wall. 
     A fourth aspect of the present invention provides a connector terminal in addition to the second aspect, wherein: a first portion of the elastic contact piece between the first end and the angle changer inclines toward the top wall; and a second portion of the elastic contact piece between the angle changer and the folded portion inclines toward the bottom wall. 
     Even if the folded portion is located at the same height as the raised portion, a portion of the elastic contact piece between the curved portion and the first end can be deformed, and the curved portion can be widened, resulting in that the contact terminal can be housed in the terminal space without a portion of the elastic contact piece between the curved portion and the folded portion being deformed. 
     A fifth aspect of the present invention provides a connector terminal in addition to the fourth aspect, wherein: the top wall possesses a second opening; and a part of the folded portion outwardly projects from the terminal body through the second opening. 
     A sixth aspect of the present invention provides a connector terminal in addition to the second aspect, wherein: the angle changer is constituted of an area having a width smaller than the remainder of the elastic contact piece. 
     The elastic contact piece can be readily deformed at the area. 
     A seventh aspect of the present invention provides a connector terminal in addition to the first aspect, wherein: the elastic contact piece includes a curved portion forming a convex from the top wall to the bottom wall; the second end is continuous to the curved portion; and when the folded portion runs onto the raised portion, not the second end but the top wall abuts on the bottom wall. 
     Since the second end is continuous to the curved portion, the elastic contact piece contacts the bottom wall at the curved portion. Accordingly, it is possible to prevent the bottom wall from being damaged. Furthermore, since the curved portion slides on the bottom wall, the elastic contact piece can readily move on the bottom wall. 
     An eighth aspect of the present invention provides a connector terminal in addition to the first aspect, wherein: the elastic contact piece extends in an axial direction of a cylindrical terminal contacting therewith; and the part of the elastic contact piece possesses an arc outer surface along a peripheral surface of the cylindrical terminal. 
     Thus, even if the arc contact surface does not have a uniform curvature, the elastic contact surface can stably contact the arc contact surface of the cylindrical terminal. 
     By designing the part of the elastic contact piece to have the arc outer surface along the peripheral surface of the cylindrical terminal, the part can stably contact the peripheral surface of the cylindrical terminal. 
     A ninth aspect of the present invention provides a connector terminal in addition to the eighth aspect, wherein: a plurality of projections extending in an axial direction of the cylindrical terminal are formed on an outer surface of the part of the elastic contact piece; and the plurality of projections are arranged in a peripheral direction of the cylindrical terminal. 
     By forming the plurality of the projections, even if at least one of the peripheral contact surface and the arc outer surface does not have a uniform curvature, the elastic contact piece contacts the cylindrical terminal at two or more points. Accordingly, the contact terminal can be kept in stable contact the cylindrical terminal. 
     A tenth aspect of the present invention provides a connector terminal in addition to the first aspect, wherein: the raised portion includes a slope inclining from the bottom wall to the top wall; a horizontal portion continuous with a top of the slope; and the folded portion runs onto the horizontal portion such that a part of the folded portion contacts a surface of the horizontal portion. 
     It is possible for the part of the folded portion contacting the horizontal portion to uniformly receive contact pressure acting on the part of the elastic contact piece, and to be supported by the horizontal portion when the part of the elastic contact piece contacts the cylindrical terminal. Accordingly, the part of the elastic contact piece can be uniformly compressed onto the cylindrical terminal. 
     The advantages obtained by the aforementioned present invention will be described hereinbelow. 
     The connector terminal according to the present invention is inserted into the terminal space, and thus, the folded portion of the elastic contact piece runs onto a raised portion, resulting in that the part of the elastic contact piece is exposed out of the terminal body, and further, the second end of the elastic contact piece, which is a free end, contacts the bottom wall to thereby act as a fulcrum for supporting the elastic contact piece. Thus, when having not been yet inserted into a housing, the connector terminal according to the present invention makes it possible to prevent the elastic contact piece from being damaged and/or deformed, and further, to ensure a sufficient spring length when the connector terminal is inserted into the housing, to thereby ensure a necessary contact pressure between the elastic contact piece and another terminal. 
     The above and other objects and advantageous features of the present invention will be made apparent from the following description made with reference to the accompanying drawings, in which like reference characters designate the same or similar parts throughout the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a first electrical connector in a preferable embodiment according to the present invention; 
         FIG. 2  is a front view of the first electrical connector illustrated in  FIG. 1 ; 
         FIG. 3  is a perspective view of a connector terminal; 
         FIG. 4  is a side view of the connector terminal illustrated in  FIG. 3 ; 
         FIG. 5  is a partial cross-sectional view of the connector terminal illustrated in  FIG. 4 ; 
         FIG. 6  is a front view of the connector terminal illustrated in  FIG. 3 ; 
         FIG. 7  is a side view of the connector terminal illustrated in  FIG. 4 , showing that the elastic contact piece is lifted up, resulting in that the elastic contact piece projects out of a terminal body; 
         FIG. 8  is a front view of the connector terminal illustrated in  FIG. 7 ; 
         FIG. 9  is a perspective view of a projecting terminal illustrated in  FIG. 1 ; 
         FIG. 10  is a perspective view of a second electrical connector in the preferable embodiment according to the present invention; 
         FIG. 11  is a front view of the second electrical connector illustrated in  FIG. 10 ; 
         FIG. 12  is a perspective view of a first cylindrical terminal of in the second electrical connector illustrated in  FIG. 10 ; 
         FIG. 13  is a perspective view of a second cylindrical terminal of the second electrical connector illustrated in  FIG. 10 ; 
         FIG. 14  is a cross-sectional view showing a state where the first connector terminal illustrated in  FIG. 1  and the second connector terminal illustrated in  FIG. 10  are fitted with each other; 
         FIG. 15  is a perspective cross-sectional view showing a state where the first connector terminal illustrated in  FIG. 1  and the second connector terminal illustrated in  FIG. 10  are fitted with each other; 
         FIG. 16  is a perspective cross-sectional view showing a state where the first connector terminal illustrated in  FIG. 1  and the second connector terminal illustrated in  FIG. 10  are fitted with each other next to  FIG. 15 ; 
         FIG. 17  is a cross-sectional view showing a state where the first connector terminal and the second connector terminal illustrated in  FIG. 14  are fitted with each other; 
         FIG. 18  is a partially enlarged cross-sectional view showing a state where the first connector terminal and the second connector terminal illustrated in  FIG. 15  are fitted with each other; 
         FIG. 19  is a partially enlarged cross-sectional view showing a state sifted from the state where the first connector terminal and the second connector terminal are fitted with each other in  FIG. 18 ; 
         FIG. 20  is a partial cross-sectional view showing a contacting state between the first connector terminal in  FIG. 3  illustrated in  FIG. 3  and the first cylindrical terminal illustrated in  FIG. 12 ; 
         FIG. 21  is a perspective view showing a contacting state between the first connector terminal in  FIG. 3  illustrated in  FIG. 3  and the first cylindrical terminal illustrated in  FIG. 12 ; 
         FIG. 22  is a partial cross-sectional view showing a contacting state between the first connector terminal and the first cylindrical terminal illustrated in  FIG. 21 ; 
         FIG. 23A  is a partial cross-sectional view of a terminal space into which the connector terminal illustrated in  FIG. 3  is inserted; 
         FIG. 23B  is a partial cross-sectional view of a terminal space in which the elastic contact piece runs onto a raised portion next to  FIG. 23A ; 
         FIG. 24  is a side view of the connector terminal including an elastic contact piece according to a variant; 
         FIG. 25  is a bottom view of the connector terminal illustrated in  FIG. 24  according to the variant; 
         FIG. 26  is a partial cross-sectional view showing the connector terminal illustrated in  FIG. 3 , showing a state before being inserted into a terminal space; 
         FIG. 27  is a partial cross-sectional view showing the connector terminal illustrated in  FIG. 3 , showing a state after having been inserted into a terminal space next to  FIG. 26 ; 
         FIG. 28  is a partial cross-sectional view of the connector terminal illustrated in  FIG. 3  according to a first variant, showing a state before being inserted into the terminal space; 
         FIG. 29  is a partial cross-sectional view of the connector terminal, showing a state after having been inserted into the terminal space next to  FIG. 28 ; 
         FIG. 30  is a partial cross-sectional view of the connector terminal illustrated in  FIG. 3  according to the second variant, showing a state before being inserted into the terminal space; 
         FIG. 31  is a partial cross-sectional view of the connector terminal, showing a state after having been inserted into the terminal space next to  FIG. 30 ; and 
         FIG. 32  is a perspective view of a conventional connector recited in Reference  1 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A connector terminal according to the first embodiment of the present invention will be explained hereinbelow with reference to drawings. 
     In the specification, with respect to words of “front and rear,” a word of “front” means a side through which the two electrical connectors are fit into each other, and a word of “rear” means the opposite side of the “front”. 
     A first electrical connector  10  illustrated in  FIG. 1  and a second electrical connector  20  illustrated in  FIG. 10  can be used for connecting various kinds of sensors with a wire harness, for example. The second electrical connector  20  is the connector terminal according to the present invention. 
     First, the first electrical connector  10  is explained hereinbelow with reference to  FIGS. 1 to 9 . 
     As illustrated in  FIGS. 1, 2 and 14 , the first electrical connector  10  includes: an outer housing  11  (a first housing) into which the second electrical connector  20  illustrated in  FIG. 10  is fit; a plurality of first contact terminals  12  (connector terminals) through which the first electrical connector  10  is electrically connected with the second electrical connector  20 ; and a projecting terminal  13  through which the first electrical connector  10  is electrically connected with the second electrical connector  20 . 
     The outer housing  11  is cylindrical in shape. The outer housing  11  is constituted of a first member  111  and a second member  112 . 
     The first member  111  includes a cover portion  111   a  at a rear end of the outer housing  11 . The cover portion  111   a  protects a connector through which cables C are connected with terminals (the first contact terminals  12  and the projecting terminal  13 ), and houses a seal  124  (See,  FIG. 3 .) therein. The first member  111  further includes a first shaft  114  provided with a terminal space R 1  into which the projecting terminal  13  is to be inserted. The first shaft  114  extends coaxially with a central axis L 1  of the outer housing  11 . 
     As illustrated in  FIG. 15 , the first shaft  114  is designed to have three stages each having a diameter increasing toward a proximal end from an open end thereof. Specifically, the first shaft  114  includes: a front end stage; a middle stage; and a rear end stage, in which the front stage has a diameter smaller than that of the middle stage, and the middle stage has a smaller diameter than that the rear end stage. 
     A guide hole  114   a  extending axially of the first shaft  114  to lead to the terminal space R 1  is formed in the first shaft  114 . 
     The first member  111  includes: a peripheral wall part  111   c  provided with a terminal space R 2  between itself and the first shaft  114  for allowing the first contact terminals  12  to be inserted thereinto; and a locking piece  111   f  through which the first member  111  is engaged with the second member  112 . 
     The second member  112  is cylindrical, and a first fitting hole  115  between the first shaft  114  and itself is formed when coupled to the first member  111 . The second electrical connector  20  (See,  FIG. 16 .) is fit into the thus formed first fitting hole  115 . 
     As illustrated in  FIG. 2 , a plurality of linear grooves  111   g  arranged radially of the central axis L 1  of the outer housing and extending in a length-wise direction F 1  the first electrical connector  10  formed on an inner surface of the first fitting hole  115  surrounded by the second member  112 . In the second member  112  of the first embodiment, the linear grooves  111   g  are formed on the inner surface of the first fitting hole  115  at five locations among nine locations spaced away from one another by 40 degrees in a peripheral angle. 
     As illustrated in  FIG. 14 , a seal member  113  of a ring shape is provided inside of a coupling part between the first member  111  and the second member  112  illustrated in  FIG. 1 . 
     As illustrated in  FIGS. 2 and 14 , each of the first contact terminals  12  is arranged on an outer surface of the first shaft  114  in parallel with a central axis of the first shaft  114 . In front view of the first fitting hole  115 , the first contact terminals  12  are peripherally equally spaced away from one another around the first shaft  114 . In the first embodiment, the three first contact terminals  12  are arranged according to the three diameter stages of the first shaft  114  by 120 degrees of a peripheral angle of the outer housing  11 . 
     As illustrated in  FIGS. 3 to 6 , each of the first contact terminals  12  includes: an electrically conductive elastic contact piece  121  formed by having a metal piece bent into a U-shape; a first terminal body  122  to be inserted into the terminal space R 2  (See,  FIG. 14 .); and a bundling portion  123  onto which a cable C 1  is compressed. 
     A first end  1211  of the elastic contact piece  121  is fixed by being integrated with a bottom wall  1221  of the first terminal body  122 . The elastic contact piece  121  extends from the bottom wall  1221  and forms a U-shaped folded portion  1212  at the end thereof. The elastic contact piece  121  further extends inside of the first terminal body  122  and terminates at a second end  1213  of a free end. 
     The elastic contact piece  121  has a part acting as a contact part  1214  through which the elastic contact piece  121  contacts a later-mentioned first cylindrical terminal. The contact part  1214  has an arc possessing an outer surface along a peripheral arc surface of a later-mentioned first cylindrical terminal. 
     A plurality of slim projections  1214   a  are formed in the contact part  1214 . In the first embodiment, two projections  1214   a  are formed. The projections  1214   a  are arranged on the elastic contact piece  121  in a direction F 3  (a width direction of the elastic contact piece  121 ) perpendicular to the central axis L 1  of the first cylindrical terminal. 
     Between the first end  1211  and the folded portion  1212 , a first curved portion  1215  is formed. The first curved portion  1215  bends the folded portion  1212  toward the bottom wall  1211 . In an initial condition of the elastic contact piece  121 , the curved portion  1215  in the first embodiment is bent in a manner such that an ascent portion from the first end  1211 , which is continuous to the bottom wall  1221 , to an opening  1222   a  turns to the bottom wall  1221 , which is the opposite side of the opening  1222   a.    
     In the initial condition, the folded portion  1212  projects out of the bottom wall  1221  of the first terminal body  122 , and the contact part  1214  does not project out of the opening  1222   a  formed at a top wall  1222  of the first terminal body  122 . At the second end  1213  of the elastic contact piece  121 , a second curved portion  1216  possessing a convex towards the bottom wall  1221  is formed. 
     As illustrated in  FIG. 3 , the first terminal body  122  is designed to be hollow and have a rectangular cross-section. 
     The first terminal body  122  is formed at sidewalls  1223  thereof with a lance  1224 . The lance  1224  is formed by forming a cutting line around a part of the sidewall  1223 , and outwardly inclining the part. 
     As illustrated in  FIG. 26 , the lance  1224  prevents the first contact terminal  12  from being released out of the terminal space R 2  after the first contact terminal  12  has been inserted into the terminal space R 2  (See,  FIG. 14 .) of the outer housing  11 . 
     As illustrated in  FIGS. 3, 26 and 27 , the lance  1224  has an open end  1224   b  defining a slope  1224   c  inclining relative to the sidewall  1223  such that the open end  1224   b  is remotest from the sidewall  1213 . Furthermore, the slope  1214   c  has a width varying in a length-wise direction of the first contact terminal  12  such that the width is in maximum at the open end  1224   b.    
     The lance  1224  includes: a first slope portion  1224   m  extending from the first terminal body  122  at a first inclination angle relative to the first terminal body  122 ; and a second slope portion  1224   n  outwardly inclining from the first terminal body  122  at a second inclination angle greater than the first inclination angle relative to the first terminal body  122 , and defining the slope  1224   c.    
     As illustrated in  FIG. 4 , the bundling portion  123  compresses the cable C 1  thereonto to fix the same therein. The bundling portion  123  includes an insulation barrel  123   a  and a wire barrel  123   b . The first contact terminal  12  further includes a seal  124  into which the cable C 1  is inserted, at a rear of the bundling portion  123 . 
     The projecting terminal  13  illustrated in  FIG. 14  is housed in the terminal space R 1  formed at a proximal end of the first shaft  114 , and contacts a later-mentioned second cylindrical terminal of the second electrical connector  20 . As illustrated in  FIG. 9 , the projecting terminal  13  includes: a contact portion  131 ; a second terminal body  132 ; and a bundling portion  133 . 
     The contact portion  131  includes: a plurality of contact pieces  131   a  equally spaced away from one another; a pair of C-shaped binders  131   b  arranged at distal and proximal ends of the contact pieces  131   a ; and a cone portion  131   d  continuous to the binder  131   b  located at open ends of the contact pieces  131   a.    
     The second terminal body  132  is hollow and has a rectangular cross-section. 
     The bundling portion  133  compresses the cable C 1  thereonto to fix the same therein. The bundling portion  133  includes: an insulation barrel  133   a ; and a wire barrel  133   b.    
     Hereinbelow, a structure of the second electrical connector  20  is explained referring to  FIGS. 10 to 14 . 
     As illustrated in  FIGS. 10, 11 and 14 , the second electrical connector  20  includes: an inner housing  21  to be fit into the first electrical connector  10  illustrated in  FIG. 1 ; a first cylindrical terminal  22  capable of electrically connecting with the first contact terminals  12  of the first electrical connector  10 ; and a second cylindrical terminal  23 . 
     The inner housing  21  includes a peripheral wall part  212  in a front half of the inner housing  21 . The peripheral wall part  212  defines therein a second fixing hole  211  into which the first shaft  114  of the first electrical connector  10  (See,  FIG. 1 .) is fit. The second fixing hole  211  is constituted of a plurality of stages each having an inner diameter gradually decreasing from an opening end toward a rear. The peripheral wall part  212  has an outer peripheral surface  212   a  contacting an inner surface of the first fitting hole  115  when the first electrical connector  10  is fit into the first fitting hole  115  of the second electrical connector  20 . A front half of the peripheral wall part  212  is a cylindrical portion  212   b  on which no projection is formed. Three linear projections  212   c  each extending in a length-wise direction of the second electrical connector  20  are formed at a rear half of the peripheral wall part  212   a  radially of and around an axis L 2  (See,  FIG. 10 .) of the inner housing  21 . In the first embodiment, the linear projections  212   c  are equally spaced away from one another in a peripheral direction F 4 , that is, are arranged by 120 peripheral degrees. 
     A second shaft  213  extends in the second fixing, hole  211 . The second shaft  213  is cylindrical in shape, and includes the second cylindrical terminal  23  arranged therein. 
     The first cylindrical terminal  22  is coaxial with the second shaft  213 , and is fixed on an inner surface of the second fixing hole  211  of the inner housing  21  with a contact surface  2212  being exposed outside. As illustrated in  FIG. 12 , the first cylindrical terminal  22  includes: a cylindrical contact portion  221 ; and a linear connector portion  222 . 
     The contact portion  221  contacts the elastic contact piece  121  of the first contact terminal  12  (See,  FIG. 3 .). The contact portion  221  is formed by joining opposite ends of electrically conductive sheets to each other through a joint portion  2211 . For instance, a first end  2211   a  is designed to have a projection, and a second end  2211   b  is designed to have a recess. By fitting the projection into the recess and fixing them to each other, the ends  2211   a  and  2211   b  are joined to each other. Since the joint portion  2211  is defined by the combination of the above-mentioned projection and recess, the joint portion  2211  has a length ranging between proximal and open ends of the contact portion  221 , and a width equal to a length of the projection or the recess. 
     As illustrated in  FIG. 14 , the second fixing hole  211  of the inner housing  21  defines therein three stages each having an inner diameter different from others. Specifically, a first stage located close to an open end of the second fixing hole  211  has a greatest inner diameter, a third stage located remotest from an open end of the second fixing hole  211  has a smallest inner diameter, and a second stage located between the first and third stages has an inner diameter smaller than an inner diameter of the first stage, but greater than an inner diameter of the third stage. 
     The second electrical connector  20  includes three first cylindrical terminals  22 , each of which is arranged on an inner surface of each of the first to third stages defined in the second fixing hole  211  of the inner housing  21 . The contact portion  211  of the first cylindrical terminal  22  arranged on an inner surface of the first stage has a greatest inner diameter among the contact portions  211  of the three first cylindrical terminals  22 , the contact portion  211  of the first cylindrical terminal  22  arranged on an inner surface of the third stage has a smallest inner diameter among the contact portions  211  of the three first cylindrical terminals  22 , and the contact portion  211  of the first cylindrical terminal  22  arranged on an inner surface of the second stage has an inner diameter intermediate between the greatest and smallest inner diameters. 
     The connecting portion  222  straightly extends from the contact portion  221  towards a rear end of the inner housing  21 , and has an open end exposed out of the inner housing  21  and to be connected to a printed wiring board (not illustrated). The connecting portion  222  is formed with a lance  2221  for preventing the first cylindrical terminal  22  from being released from the inner housing  21 . 
     As illustrated in  FIGS. 10, 11 and 14 , the second cylindrical terminal  23  is housed in the second shaft  213 . The second cylindrical terminal  23  has an open end through which the projecting terminal  13  is inserted thereinto. The second cylindrical terminal  23  outwardly extends beyond the second shaft  213 , and thus, is exposed at an open end thereof out of the second shaft  213 . The second cylindrical terminal  23  is arranged to closely contact the second shaft  213  so as to be integrated therewith. 
     As illustrated in  FIG. 13 , the second cylindrical terminal  23  includes: a cylindrical portion  231 ; a constricted part  232 , a closed section  233 ; and an L-shaped connecting portion  234 . 
     The constricted part  232  is located at a rear of the cylindrical portion  231 , and has a thickness reduced in a direction in which the connecting portion  234  extends. Specifically, the constricted part  232  has a width (a length in a first direction A 1 ) equal to a diameter of the cylindrical portion  231 , and has a thickness (a length in a second direction A 2  perpendicular to the first direction A 1 ) gradually decreasing in a length-wise direction of the second cylindrical terminal  23  from a diameter equal to the same of the cylindrical portion  231 . As a result of the reduction in a thickness, the constricted part  232  is finally flat. 
     The closed section  233  is located at a rear of the constricted part  232  and at a proximal end of the second cylindrical terminal  23 . The closed section  235  has a width (a length in the direction A 1 ) greater than the same of the constricted part  233 . Furthermore, the closed section  233  has a thickness smaller than a diameter of the cylindrical portion  231  and a width greater than a diameter of the cylindrical portion  231 . 
     The L-shaped connecting portion  234  is continuous to the closed section  233 . The connecting portion  234  includes: 
     a plate-shaped portion  234   a  bending perpendicularly to the closed section  233 , and further, perpendicularly bending to be in parallel with the cylindrical portion  231 ; and 
     a needle portion  234   b  outwardly extending from an open end of the plate-shaped portion  234   a.    
     How the first and second electrical connectors  10  and  20  configured as mentioned above are used is explained hereinbelow with reference to  FIGS. 15 to 20 . 
     As illustrated in  FIG. 15 , the first electrical connector  10  and the second electrical connector  20  are caused to come close to each other. Then, an open end of the peripheral wall part  212  (of the inner housing  21 ) is aligned with the first fitting hole  115  of the outer housing  11 , and an open end of the second shaft  213  (of the inner housing  21 ) is also aligned with the guide hole  114   a  (of the first shaft  114 ). 
     Then, the peripheral wall part  212  (of the inner housing  21 ) is forwarded in the length-wise direction F 1  of the first fitting hole  115 , and the second shaft  213  (of the inner housing  21 ) is also forwarded in the length-wise direction F 1  (of the guide hole  114   a ). 
     As illustrated in  FIG. 16 , a front half of the peripheral wall part  212  (of the inner housing  21 ) is the cylindrical portion  212   b  on which no projections are formed (See,  FIG. 10 .). Accordingly, when only the front half of the peripheral wall part  212  is inserted into the first fitting hole  115  (of the outer housing  11 ), the linear projections  212   c  (of the inner housing  21 ) are not yet fit into the linear grooves  111   g  (of the outer housing  11 ). Thus, a user can fit the outer housing  21  into the inner housing  11  with one of them being rotated around an axis thereof. A user can forward the inner housing  21  relative to the outer housing  11  without due care and attention to a direction of the rotation. 
     After the state in  FIG. 16 , the peripheral wall part  212  of the inner housing  21  is wholly forwarded into the first fitting hole  115  of the outer housing  11 , and then the linear projections  212   c  of the peripheral wall part  212  are fit into the linear grooves  111   g  of the outer housing  11 , thereby the outer housing  11  and the inner housing  21  are positioned relative to each other. Accordingly, the outer and inner housings  11  and  21  cannot rotate relative to each other. 
     Furthermore, when the peripheral wall part  212  is wholly forwarded into the first fitting hole  115 , the projecting terminal  13  is inserted into the second cylindrical terminal  23  to contact therewith. In addition, each of the first cylindrical terminals  22  of the second electrical connector  20  contacts the elastic contact piece  121  of each of the first contact terminals  12  of the first electrical connector  10 . 
     As mentioned above, the linear grooves  111   g  of the outer housing  11  and the linear projections  212   c  of the inner housing  21  constitute a positioning unit. The positioning unit is formed by inserting the inner housing  21  into the outer housing  11 . Once formed, the positioning unit prohibits the relative rotation between the inner housing  21  and the outer housing  11  at a position where the first cylindrical terminals  22  and the elastic contact pieces  121  contact each other. 
     That is, at the beginning of the insertion, the second electrical connector  20  can act as an electrical connector that can freely rotate from the first electrical connector  10  about a direction of the insertion. 
     After the positioning unit of the outer housing  11  and the inner housing  21  has been formed, the first cylindrical terminals  22  contact the elastic contact pieces  121 . That is, when the first cylindrical terminals  22  contact the elastic contact pieces  121 , the relative rotation between the inner housing  21  and the outer housing  11  has been already prohibited. Consequently, the cylindrical contact portion  221  (of the first cylindrical terminal  22 ) and the elastic contact piece  121  (of the first contact terminal  12 ) are neither worn down nor damaged caused by the relative rotation between the first and second electrical connectors  10  and  20 . 
     Even if an axis of the second cylindrical terminal  23  is deviated from an axis of the projecting terminal  13 , there is no problem according to the following reason. That is, when the projecting terminal  13  starts being fit into the second cylindrical terminal  23 , the contact portion  131  slides on an inner surface of the second cylindrical terminal  23 . The sliding action automatically corrects a posture of the contact portion  131  of the projecting terminal  13 . 
     However, the projecting terminal  13  is housed in the terminal space R 1  with a gap between the projecting terminal  13  and an inner surface of the first shaft  114 , and further, is locked by the lance  134 . Accordingly, even if the posture of the contact portion  131  is corrected by the second cylindrical terminal  23 , the second terminal body  132  of the projecting terminal  13  can be shifted, within the terminal space R 1 , to a new axial direction in which the posture of the contact portion  131  is corrected. Consequently, the projecting terminal  13  can be moved to follow the new axial direction of the second cylindrical terminal  23 . 
     As illustrated in  FIG. 14 , by further inserting the second electrical connector  20  into the first electrical connector  10 , the peripheral wall part  212  of the inner housing  21  is completely fit into the first fitting hole  115  of the outer housing  11 , the first shaft  14  of the outer housing  11  is completely fit into the second fixing hole  211  of the inner housing  21 , and the second shaft  213  of the inner housing  21  is completely fit into the guide hole  114   a  of the first shaft  114 . 
     In this situation, each of the first contact terminals  12  arranged on an outer surface of the first shaft  114  contacts each of the contact portions  221  of the first cylindrical terminals  22  arranged on an inner surface of the inner housing  21 . And, the contact portion  131  of the projecting terminal  13  is inserted into the cylindrical portion  231  of the second cylindrical terminal  23  to contact therewith. 
     Thus, the first and second electrical connectors  10  and  20  are fit with each other. 
     The first contact terminals  12  are arranged on an outer surface of the first shaft  114  coaxially with a central axis of the first shaft  114 . The first cylindrical terminals  22  are arranged on an inner surface of the inner housing  21  coaxially with the second shaft  213 . Thus, when the first shaft  114  and the second shaft  213  are fit into each other, the first contact terminals  12  can stably contact the first cylindrical terminals  22 . 
     Hereinbelow is explained another positioning unit for positioning the outer and inner housings  11  and  21  in a peripheral direction when they are fit into each other as they rotate relative to each other. 
     As illustrated in  FIGS. 17 and 19 , the above-mentioned positioning unit is constituted of: the linear grooves  111   g  of the outer housing  11 ; and the linear projections  212   c  of the inner housing  21 . 
     As mentioned before, when the peripheral wall part  212  illustrated in  FIG. 10  is inserted only at a front half thereof into the first fitting hole  115  of the outer housing  11 , the linear projections  212   c  of the inner housing  21  have not yet been fit into the linear grooves  111   g  of the outer housing  11 . Thus, the outer and inner housings  11  and  21  can be fit into each other while rotating one of them  11  and  21  relative to the other. 
     As illustrated in  FIG. 17 , after the linear projections  212   c  have been fit into the linear grooves  111   g , the outer and inner housing  11  and  21  are positioned with respect to a rotative direction, and hence, they cannot rotate around an axis thereof relative to each other. 
     The linear projections  212   c  and the linear grooves  111   g  cause the elastic contact pieces  121  of the first contact terminals  12  to contact the contact surface  2212  other than the joint portion  2211 . 
     In  FIGS. 17 and 18 , the first contact terminal  12  located at an open end of the first shaft  114  (of the first electrical connector  10 ) contacts the first cylindrical terminal  22  located at the deepest position of the second fixing hole  211 . 
     As illustrated in  FIGS. 10 and 11 , the three linear projections  212   c  are arranged on the outer peripheral surface  212   a  of the inner housing  21  by 120 peripheral degrees. As illustrated in  FIG. 2 , the five linear grooves  111   g  are formed at an inner surface of the first fitting hole  115  of the outer housing  11 . Accordingly, the outer and inner housings  11  and  21  can be fit into each other when the three linear projections  212   c  of the inner housing  21  are aligned with three of the five linear grooves  111   g  of the outer housing  11 . 
     In  FIGS. 17 and 18 , the joint portion  2211  (of the first cylindrical terminal  22 ) is located close to one side (a left side in  FIG. 17 ) of the first contact terminal  12 , and the projections  1214   a  of the elastic contact piece  121  contact the contact surface  2212  of the first cylindrical terminal  22 . 
     The outer housing  11  is rotated in a counter-clockwise direction by 40 degrees, which is an angular interval between the adjacent linear grooves  111   g , relative to the condition illustrated in  FIG. 17 . Since the first contact terminal  12  is housed in the terminal space R 2  of the outer housing  11 , the first contact terminal  12  is rotated together with the outer housing  11 . 
     Alternatively, the inner housing  21  is rotated in a clockwise direction by 40 degrees. Since the first cylindrical terminal  22  is fixed to the inner housing  21 , the first cylindrical terminal  22  is rotated together with the inner housing  21 . 
     The rotated linear projection  212   c  is fit into one (the right one in  FIG. 17 ) of the linear grooves  111   g  (See,  FIGS. 19 and 20 .) located adjacent to another of the linear grooves  111   g  into which the linear projection  212   c  has been fit in  FIG. 17 . 
     Due to the rotation, the linear projection  212   c  moves between the one and the other of the linear grooves  111   g , and the joint portion  2211  of the first cylindrical terminal  22  moves over the projection  1214   a  of the first contact terminal  12 . 
     This is because an angular interval between the adjacent linear grooves  111   g  around the central axis L 1  (See,  FIG. 1 .) of the outer housing  11  is set greater than an angle covering the joint portion  2211  (See,  FIG. 12 .) of the first cylindrical terminal  22  around the central axis L 2  (See,  FIG. 10 .) of the inner housing  21 . 
     Since the joint portion  2211  is formed by joining the opposite ends  2211   a  and  2211   b  of the contact portion  221  to each other, a step in the joint portion  2211  may be formed. 
     However, since the linear projections  212   c  and the linear grooves  111   g  act as the positioning unit, even if the first electrical connector  10  is fit into the second electrical connector  20  at any peripheral position, the first contact terminals  12  do not contact the joint portion  2211  of the first cylindrical terminal  22  after the linear projections  212   c  has been fit into the linear grooves  111   g . Accordingly, it is possible to prevent the elastic contact piece  121  of the first contact terminal  12  from contacting the joint portion  2211  of the first cylindrical terminal  22  to thereby be damaged and/or worn out. Thus, the first and second electrical connectors  10  and  20  ensure high reliability to the connection therebetween. 
     Furthermore, since the linear projections  212   c  and the linear grooves  111   g  are arranged radially around the central axis L 2  of the outer and inner housings  11  and  21 , even if the outer and inner housings  11  and  21  are fit into each other with one of them being in rotation, they can be fit into each other such that the linear projections  212   c  and the linear grooves  111   g  align with each other. 
     How the contact terminal  12  contacts the first cylindrical terminal  22  is explained hereinbelow with reference to  FIGS. 21 and 22 . 
     As illustrated in  FIG. 21 , in a situation in which the first and second electrical connectors  10  and  20  are fit into each other, the contact terminal  12  of the first electrical connector  10  contacts the first cylindrical terminal  22  arranged on an inner surface of the second fixing hole  211  formed in the second electrical connector  20 . 
     The elastic contact piece  121  of the contact terminal  12  is arranged along an axial direction F 5  of the first cylindrical terminal  22 . In other words, the elastic contact piece  121  contacts the first cylindrical terminal  22  in a direction perpendicular to a peripheral direction of the arc contact surface  2212 . Accordingly, even if the contact surface  2212  does not have a uniform curvature, the elastic contact piece  121  can stably contact the contact surface  2212 . 
     As illustrated in  FIG. 22 , the contact portion  1214  of the elastic contact piece  121  is designed to have an arc surface extending in a cross-section perpendicular to the axial direction F 5  (See,  FIG. 21 .) of the first cylindrical terminal  22 , and along the arc contact surface  2212  of the contact portion  221 . Thus, the contact portion  1214  and the contact surface  2212  are both designed to be arc corresponding to each other, they can further stably contact each other. 
     A plurality of the projections  1214   a  is formed on an outer surface of the contact portion  1214  in a peripheral direction F 6  of the contact portion  221 . As illustrated in  FIG. 21 , each of the projections  1214   a  is designed to be elongate and to extend in the length-wise direction F 5  of the first cylindrical terminal  22 . 
     For instance, it is assumed that the elastic contact piece  121  is designed not to include the projections  1214   a  on an outer surface of the contact portion  1214 , and accordingly, the contact portion  1214  directly contacts at an outer surface thereof the arc contact surface  2212  of the first cylindrical terminal  22 . In such a case, the contact portion  1214  of the elastic contact piece  121  may be designed to have an arc outer surface along the arc contact surface  2212 , ensuring enlargement in an area at which the contact surface  2212  and the contact portion  1214  contact each other. 
     If the contact surface  2212  and the contact portion  1214  do not have a uniform curvature, they merely unstably contact each other. 
     However, since the contact portion  1214  is designed to possess a plurality of the projections  1214   a , even if the arc contact surface  2212  of the first cylindrical terminal  22  and the arc outer surface of the contact portion  1214  do not have a uniform curvature, the elastic contact piece  121  can contact the first cylindrical terminal  22  at two or more points. Thus, the first contact terminal  12  can stably contact the first cylindrical terminal  22 , ensuring high contact reliability. 
     Since the projections  1214   a  extend in the length-wise direction F 5  of the first cylindrical terminal  22 , that is, since the projections  1214   a  contacts the arc contact surface  2212  in a direction perpendicular to the peripheral direction of the arc contact surface  2212 , even if the arc contact surface  2212  does not have a uniform curvature, the non-uniform curvature of the arc contact surface  2212  does not exert harmful influence on the contact of the projections  1214   a  with the arc contact surface  2212 . 
     The projections  1214   a  are equally spaced away from one another in a peripheral direction thereof around a top  1214   b  (See,  FIG. 22 .) of the contact portion  1214 . Accordingly, each of the projections  1214   a  uniformly contacts the arc contact surface  2212  of the first cylindrical terminal  22 , ensuring that the projections  1214   a  can stably contact the contact surface  2212 . 
     Hereinbelow is explained how the contact terminal  12  acts when the contact terminal  12  is inserted into the terminal space R 2  of the outer housing  11 . 
     As illustrated in  FIGS. 4 and 5 , when the contact terminal  12  is not inserted into the terminal space R 2 , the folded portion  1212  projects out of the bottom wall  1221  of the first terminal body  122 . 
     The contact terminal  12  in such a condition as illustrated in  FIG. 14  is inserted into the terminal space R 2  through a rear end of the outer housing  11 . As illustrated in  FIG. 23A , being inserted into the terminal space R 2 , the folded portion  1212  of the elastic contact piece  121  is pushed up by a floor R 21  of the terminal space R 2 , and the folded portion  1212  slides on the floor R 21  of the terminal space R 2 . In the situation illustrated in  FIG. 23A , since the folded portion  1212  contacts the floor R 21  of the terminal space R 2 , the contact part  1214  of the elastic contact piece  121  is still located relatively low although it is slightly pushed up. Specifically, the contact part  1214  is partially exposed out of the opening  1222   a  (See,  FIG. 5 .), but not wholly exposed out of the opening  1222   a , that is, almost of the contact part  1214  is still housed in the first terminal body  122 . 
     When the contact terminal  12  is further inserted into the terminal space R 2 , as illustrated in  FIG. 23B , the folded portion  1212  runs onto a raised portion  116  formed on the floor R 2  of the terminal space R 2 . 
     The raised portion  116  includes: a slope  1161  inclining ascending in a direction F 7  in which the contact terminal  12  is inserted into the terminal space R 2 ; and a horizontal portion  1162  continuous with a top of the slope  1161 . 
     Running onto the raised portion  116 , the folded portion  1212  is directed further upwardly. Thus, the contact part  1214  of the elastic contact piece  121  projects out of the opening  1212   a . As the folded portion  1212  stands up, the free second end  1213  of the elastic contact piece  121  lowers towards the bottom wall  1221  of the first terminal body  122 , and abuts on the bottom wall  1221 . Thus, the second end  1213  acts as a fulcrum to support the elastic contact piece  121 . 
     As a result that the second end  1213  and accordingly the second curved portion  1216  abuts on the bottom wall  1221 , the folded portion  1212  and the second end  1213  (or the second curved portion  1216 ) wholly support the elastic contact piece  121  therewith. Consequently, when the contact part  1214  contacts the first cylindrical terminal  22  to thereby be loaded, the load is divided by the folded portion  1212  and the second curved portion  1216 . Thus, it is possible to prevent the folded portion  1212  from being plastically deformed due to the load exerted onto the contact part  1214 , ensuring that a contact load with which the contact part  1214  contacts the first cylindrical terminal  22  can be increased. 
     Furthermore, since the free second end  1213  abuts on the bottom wall of the first terminal body  122 , a length of the elastic contact piece  121  between the contact part  1214  and the second end  1213  can be designed to be an allowable length within the first terminal body  122 . Accordingly, the elastic contact piece  121  can have a sufficiently long spring length, the elastic contact piece  121  can accomplish enhanced spring performance. In addition, the elastic contact piece  121  can be a spring shape difficult to be plastically deformed. 
     Since the second end  1213  is continuous to the second curved portion  1216 , the bottom wall  1221  is not hurt when the second end  1213  abuts on the bottom wall  1221 . Furthermore, since the second curved portion  1216  slides on the bottom wall  1221 , the second curved portion  1216  can smoothly move on the bottom wall  1221 . 
     As mentioned above, the contact part  1214  of the elastic contact piece  121  is kept not projected out of the opening  1222   a  until the elastic contact piece  121  runs onto the raised portion  116  after the first contact terminal  12  has been inserted into the terminal space R 2 . 
     When the folded portion  1212  runs onto the raised portion  116 , the contact part  1214  projects out of the opening  1222   a , and thus, is exposed out of the first terminal body  122 . 
     The first curved portion  1215  formed between the first end  1211  and the folded portion  1212  directs the folded portion  1212  towards the bottom wall  1211 . That is, the first curved portion  1215  acts as an angle changer changing an angle by which the elastic contact piece  121  is bent. A direction in which the elastic contact piece  121  extends between the first end  1211  and the angle changer  1215  is different from a direction in which the elastic contact piece  121  extends between the angle changer  1215  and the folded portion  1212 . When the folded portion  1212  runs onto the raised portion  116 , the first curved portion  1215  changes an angle by which the folded portion  1212  is bent relative to the first end  1211 , and hence, a portion of the elastic contact piece  121  between the first curved portion  1215  and the first end  1211  can be deformed. 
     A portion of the elastic contact piece  121  between the first curved portion  1215  and the first end  1211  obliquely ascend towards the opening  1222   a , and the first curved portion  1215  directs the folded portion  1212  downwardly towards the bottom wall  1221 . Thus, even if the folded portion  1212  is located at the same height as the raised portion  116 , the portion of the elastic contact piece  121  between the first curved portion  1215  and the first end  1211  can be deformed, and the first curved portion  1215  can be widened, resulting in that the first contact terminal  12  can be housed in the terminal space R 2  while the portion of the elastic contact piece  121  between the first curved portion  1215  and the folded portion  1212  is deformed. 
     Accordingly, it is possible to prevent the elastic contact piece  121  from being damaged and/or deformed while the first contact terminal  12  is being inserted into the outer housing  11 , and further, the first contact terminal  12  can keep a sufficient contact pressure after having been inserted into the outer housing  11 . 
     When the first contact terminal  12  is not inserted into the terminal space R 2 , the first curved portion  1215  has a curvature to direct the folded portion  1212  towards the bottom wall  1221 . The elastic contact piece  121  possesses an area S 1  (See,  FIG. 23B .) in which the folded portion  1212  lies on the horizontal portion  1162  (a top face  116   a ) of the raised portion  116  when the folded portion  1212  runs onto the raised portion  116 . The top face  116   a  of the raised portion  116  is formed to be flat, and the area S 1  of the elastic contact piece  121  is formed in a shape of a plate. Thus, the elastic contact piece  121  can closely contact at the area S 1  with the top face  116   a  of the raised portion  116 , because the area S 1  is in parallel with the top face  116   a  when the folded portion  1212  runs onto the raised portion  116 . 
     Since the folded portion  1212  lies on the top face  116   a  of the raised portion  116  through the flat area S 1 , when the contact part  1214  of the elastic contact piece  121  contacts the first cylindrical terminal  22  (See,  FIG. 21 .), the folded portion  1212  is supported on the horizontal portion  1612  with the contact pressure between the contact part  1214  and the first cylindrical terminal  22  being received uniformly and wholly by the area S 1  of the folded portion  1212 . Thus, it is possible to uniformly compress the contact part  1214  onto the first cylindrical terminal  22 . 
     In this embodiment, the elastic contact piece  121  includes the first curved portion  1215  acting as an elasticity changer. Thus, a curved degree of the elastic contact piece  121  is reduced at a position where the first curved portion  1215  is formed. On the contrary, the curved degree of the elastic contact piece  121  may be increased instead. An elastic contact piece  121   x  shown in  FIGS. 24 and 25  includes a constricted portion  1217  acting as an elasticity changer. The constricted portion  1217  is formed by constricting both side edges of an area S 2  (in a direction from the first end  1211  of the elastic contact piece  121   x  to the folded part  1212 ) in a shape of a rectangle. By forming the constricted portion  1217 , the constricted portion  1217  reduces a curved degree of the elastic contact piece  121  when the folded portion  1212  is lifted up by the raised portion  116  (See,  FIG. 23B .). Thus, the elastic contact piece  121  can be deformed at a position where the constricted portion  1217  is formed. 
     Thus, even if the folded portion  1212  is located at the same height as the raised portion  116 , since the elastic contact piece  121  is deformed, the first contact terminal  12  can be housed in the terminal space R 2  while keeping the shape of the folded portion  1212 . 
     Hereinbelow is explained how the lance  1224  acts when the first cylindrical terminal  12  is inserted into the terminal space R 2 . 
     The first contact terminal  12  is housed in the terminal space R 2 . As illustrated in  FIGS. 23A and 23B , a first fitting hole R 2 A and a second fixing hole R 2 B are formed in the terminal space R 2 . The first fitting hole R 2 A is formed including: a floor R 21  facing the bottom wall  1221  of the first terminal body  122 ; a ceiling R 22  facing the top wall  1222 ; and sidewalls R 23  in  FIGS. 26 and 27  facing the sidewalls  1223 . The second fixing hole R 2 B is located deeper than the first fitting hole R 2 A in a direction F 7  in which the first contact terminal  12  is inserted into the terminal space R 2 . The second fixing hole R 2 B is vertically longer than the first fitting hole R 2 A, and is horizontally longer than the first fitting hole R 2 A. 
     The first contact terminal  12  first enters the first fitting hole R 2 A. The lance  1224  standing up from the sidewalls  1223  of the first terminal body  122  are compressed by a pair of the sidewalls R 23  of the first fitting hole R 2 A facing each other, and thus, are kept deformed while the first contact terminal  12  is forwarding. 
     As illustrated in  FIG. 27 , when the first contact terminal  12  passes over the sidewalls R 23  by which the lance  1224  is compressed, and arrives at the second fixing hole R 2 B, the lance  1224  is no longer compressed by the sidewalls R 23 , and hence, returns to an original form thereof. Thus, the lance  1224  gets wider than a gap between the first terminal body  122  and the sidewalls R 23 . Accordingly, even if the first contact terminal  12  is tried to be pulled out of the terminal space R 2 , the lance  1224  is caught by the sidewalls R 23 , and hence, the first contact terminal  12  is prevented from being pulled out of the terminal space R 2 . 
     The lance  1224  includes a projected portion  1224   c . Between the sidewalls R 23  of the terminal space R 2  and the lance  1224  is formed gaps S 0  through which the second portions  1224   n  can pass. 
     For instance, when the first contact terminal  12  is inserted into the terminal space R 2 , if the lance  1224  is compressed at proximal ends thereof by the sidewalls R 23  of the terminal space R 2 , the lance  1224  is plastically deformed with the proximal ends thereof being closed, and accordingly, the lance  1224  cannot get wide. In such a condition, the first contact terminal  12  can be readily pulled out of the terminal space R 2 , if the cable C 1  is strongly pulled. 
     However, since the gaps S 0  through which the projected portions  1224   c  of the second slope portion  1224   n  can pass are formed between the sidewalls R 23  of the terminal space R 2  and the lance  1224 , there can be ensured a sufficient gap between the first terminal body  122  and the sidewalls R 23 . 
     The gaps S 0  causes the lance  1224  to contact the sidewalls R 23  at a point P 1  closer to an open end  1224   b  than a proximal end  1224   a  of the second slope portion  1224   n . The gaps S 0  formed between the first contact terminal  12  and the sidewalls R 23  are designed to allow the sidewalls R 23  to contact the lance  1224  at a point closer to the open end  1224   b  than a center of a full length of the lance  1224 . 
     Accordingly, it is possible to maintain an elastic force by which the compressed lance  1224  wants to return to an original form thereof to thereby prevent the open ends  1224   a  of the lance  1224  from being plastically deformed. Thus, the lance  1224  can be engaged to the sidewalls R 23  of the terminal space R 2  by a sufficient length, ensuring it possible to prevent the first contact terminal  12  from being pulled out of the terminal space R 2 , even if the first contact terminal  12  is pulled backwardly. 
     Thus, the first contact terminal  12  can be kept inserted in the terminal space R 2  of the outer housing  11 , ensuring high reliability to electrical connection between the first contact terminal  12  and the first cylindrical terminal  22 . 
     For instance, it is assumed that the lance  1224  is designed not to include the projected portion  1224   c , and hence, the second slope portion  1224   n  inclines by a constant angle. If the lance  1224  is designed to be longer than the present one, the lance  1224  contacts the sidewalls R 23  of the terminal space R 23  at a location remoter from the first terminal body  122  when the sidewalls R 23  contact the proximal end of the lance  1224 . Thus, since a gap to be formed between the sidewalls R 23  of the terminal space R 2  and the first terminal body  122  can be wide, it is possible to prevent the sidewalls R 23  from abutting on the proximal end of the lance  1224 . 
     However, if the lance  1224  is designed to be longer, since the lance  1224  is housed in the second fixing hole R 2 B while contacting the sidewalls R 23  in the first fitting hole R 2 A, it is necessary to forward the first contact terminal  12  by a distance by which the lance  1224  is made longer. Thus, it is necessary to fabricate the second fixing hole R 2 B to be longer. 
     However, the projected portions  1224   c  of the lance  1224  is formed such that an inclination angle between the first terminal body  122  and the open ends  1224   b  is greater than an inclination angle between the first terminal body  122  and the proximal end  1224   a  in the first contact terminal  12 . Accordingly, even if gaps formed between the first terminal body  122  and the sidewalls R 23  are wide, it is possible for the projected portion  1224   c  of the lance  1224  to engage with the sidewalls R 23 , and hence, it is not necessary to design the second fixing hole R 2 B to be long. 
     The projected portion  1224   c  of the non-compressed lance  1224  slide on and are compressed by the sidewalls R 23  at an entrance to the terminal space R 23 . Each of the projected portions  1224   c  is formed such that a gap between each of the projection portions  1224   c  and each of the sidewalls  1223  is greater at a location closer to each of the open ends  1224   b . Accordingly, as a location at which each of the sidewalls R 23  contacts the lance  1224  transfers towards each of the open ends  1224   b  as the first contact terminal  12  forwards into the terminal space R 2 , the lance  1224  can be gradually closed along the above-mentioned gap between each of the projections portion  1224   c  and each of the sidewalls  1223 . Thus, the first contact terminal  12  can be smoothly inserted into the terminal space R 2  without the lance  1224  being interfered with the sidewalls R 23   
     Furthermore, since each of the projected portions  1224   c  is formed such that a gap between each of the projections portion  1224   c  and each of the sidewalls  1223  is greater at a location closer to each of the open ends  1224   b , it is possible for the open ends  1224   b  of the projected portions  1224   c  to have an enhanced resistance against being compressed and/or collapsed. Accordingly, it is possible to prevent the projected portions  1224   c  from being deformed due to a compressive force increasing as the first contact terminal  12  forwards into the terminal space R 2 , exerted onto the lance  1224  by the sidewalls R 23 . 
     Furthermore, since the lance  1224  is formed by forming a cutting line around a part of the sidewall  1223  of the first terminal body  122 , and causing the part to outwardly stand, it is not necessary to attach any separate part to the first terminal body  122  for forming the lance  1224 . Thus, the lance  1224  can be readily fabricated. 
     The lance  1224  illustrated in  FIGS. 27 and 28  is designed to include the projected portions  1224   c . Instead of the projected portions  1224   c , the lance  1224  may be designed to include folded portions formed by folding open end of the lance  1224 . 
       FIGS. 28 and 29  illustrate a lance  1224   x  including a folded portion formed by folding an open end of the lance, according to a first variant. 
     As illustrated in  FIGS. 28 and 29 , the lance  1224   x  includes: a first slope portion  1224   m  extending at the proximal end  1224   a  from the first terminal body  122 ; and a second slope portion  1224   n  constituted of a folded portion  1224   d  or a folded portion  1224   d  formed by outwardly folding a open end of the first portion  1224   n  into two layers stacking one on another. The lance  1224   x  is fabricated by forming a cut line around a portion of the sidewall  1223  of the first terminal body  122 , and causing the portion to stand relative to the sidewall  1223 . 
     Each of the folded portions  1224   d  is located outside of the first portions  1224   m  inclining relative to the sidewalls  1223  of the first terminal body  122 . Accordingly, it is possible to form such a gap S 0  between the first terminal body  122  of the first contact terminal  12   x  and each of the sidewalls R 23  that the sidewalls R 23  do not contact the proximal end  1224   a  of the lance  1224   x  when the first contact terminal  12   x  is inserted into the second fixing hole R 2 A. 
     In the first variant, the sidewalls R 23  contact the lance  1224   x  at locations closer to the open ends  1224   b  than a center of the lance  1224   x  when the first contact terminal  12   x  is inserted into the terminal space R 2 . In  FIG. 28 , the sidewalls R 23  contact the second portions  1224   n  of the lance  1224   x . Accordingly, it is possible to maintain an elastic force by which the compressed lance  1224   x  wants to return to the original form thereof to thereby prevent the first contact terminal  12   x  from being pulled out of the terminal space R 2 , even if the first contact terminal  12   x  is pulled backwardly. 
     The folded portions  1224   d  make it possible for the lance  1224   x  to contact the sidewalls R 23  at a location outside than an inclination angle of the first portions  1224   m . Thus, even if the gaps S 0  are formed wide, the lance  1224   x  can be engaged to the sidewalls R 23  while the second fixing hole R 2 B is not fabricated longer. 
     Since the open end  1224   b  of the lance  1224   x  is outwardly folded to form the folded portions  1224   d , end surfaces  1224   e  of the folded portions  1224   d  face end surfaces R 23   a  of the sidewalls R 23  to each other. On each of the end surfaces R 23   a , an inclined surface R 23   b  for enlarging open ends of the sidewalls R 23  is formed. Accordingly, it is possible to insert the lance  1224   x  into the first fitting hole R 2 A having a gradually reducing space therebetween while the folded portions  1224   d  slides on the inclined surfaces R 23   b.    
     In  FIGS. 28 and 29 , the inclines surfaces R 23   b  are formed on the sidewalls R 23 . Alternatively, the inclines surfaces R 23   b  may be formed on the end surfaces  1224   e  instead. 
       FIGS. 30 and 31  illustrate a lance  1224   y  according to a second variant. In the second variant, an inclining portion is formed by folding an open end of a lance of a contact terminal. 
     As illustrated in  FIGS. 30 and 31 , the lance  1224   y  includes: a first slope portion  1224   m  extending from the proximal end  1224   a ; and a second slope portion  1224   n  possessing an slope  1224   f  formed by outwardly bending the open end  1224   b.    
     The slope  1224   f  formed by outwardly bending the open end  1224   b  is located outside than an inclination angle of the first portion  122   m . Accordingly, it is possible to form such a gap S 0  between the first terminal body  122  of the first contact terminal  12   y  and each of the sidewalls R 23  that the sidewalls R 23  do not contact the proximal end  1224   a  of the lance  1224   y  when the first contact terminal  12   y  is inserted into the second fixing hole R 2 A. 
     In the second variant, similarly to the first variant, the sidewalls R 23  contact the lance  1224   y  at locations closer to the open ends  1224   b  than a center of the lance  1224   y  when the first contact terminal  12   y  is inserted into the terminal space R 2 . In  FIG. 30 , the sidewalls R 23  contact the second portions  1224   n  of the lance  1224   y . Accordingly, it is possible to maintain an elastic force by which the compressed lance  1224   y  wants to return to an original form thereof to thereby prevent the first contact terminal  12   y  from being pulled out of the terminal space R 2 , even if the first contact terminal  12   y  is pulled backwardly. 
     Furthermore, the slopes  1224   f  make it possible for the lance  1224   y  to contact the sidewalls R 23  at a location outside than an inclination angle of the first portions  1224   m . Thus, even if the gaps S 0  are formed wide, the lance  1224   y  can be engaged to the sidewalls R 23  while the second fixing hole R 2 B is not fabricated longer. 
     In the present embodiment, the first and second housings are defined as the outer and inner housing  11  and  21 , respectively. Alternatively, the first and second housings are defined as the inner and outer housing  21  and  11 , respectively. 
     INDUSTRIAL APPLICABILITY 
     The electrical connector according to the present invention can be used as a connector equipped in a glow plug, a connector for connecting a combustion pressure sensor and a wire harness to each other, a connector for connecting cables to each other, a connector equipped in various electric/electronic devices, and a connector equipped in an automobile. The electrical connector according to the present invention can be employed broadly in fields such as an electric/electronic industry and an automobile industry. 
     While the present invention has been described in connection with certain preferred embodiments, it is to be understood that the subject matter encompassed by way of the present invention is not to be limited to those specific embodiments. On the contrary, it is intended for the subject matter of the invention to include all alternatives, modifications and equivalents as can be included within the spirit and scope of the following claims. 
     The entire disclosures of Japanese Patent Applications No. 2014-252494 filed on Dec. 12, 2014 including specification, claims, drawings and summary are incorporated herein by reference in its entirety.