Abstract:
A connector for a vehicular AC generator includes a resin connector case having an element-accommodating chamber in which a leaded circuit element having a pair of leads at opposite ends is received. The leads are bent at right angles and soldered at respective tip end portions to element connecting terminals of wiring metal pieces embedded in the connector case. The element-accommodating chamber is filled with an elastic sealing resin. The right-angled leads take up or absorb the difference in thermal expansion between the connector case and the circuit element including the leads. The elastic sealing resin prevents a crack from occurring at an interface boundary between the circuit element and the leads and offers an improved environmental resistance.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    The present application is based on and claims priority from Japanese Patent Application No. 2006-276522, filed Oct. 10, 2006, the content of which is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates generally to connectors, and more particularly to a connector having a circuit element built therein. 
         [0004]    2. Description of the Related Art 
         [0005]    Vehicular AC (alternating current) generators have a connector for communication of signals with external electronic control units (ECUs). Typical examples of such vehicular AC generators are disclosed in Japanese Patent Laid-open Publications (JP-A) Nos. 2001-016829 (corresponding to U.S. Pat. No. 6,291,913 B1) and 2002-033438 (corresponding to U.S. Pat. No. 6,390,854 B2). It has been a conventional practice that a circuit element such as surge absorber is incorporated or built in the connector. Such connector having a circuit element built therein will be hereinafter referred to as “connector with a built-in circuit element”. The circuit element to be built in the connector may include capacitors, resistance elements, varistors, various passive or active elements, and ICs. For these circuit elements, leaded circuit elements, which do not need a circuit board, are employed. The leaded circuit elements each have leads extending in a longitudinal direction from opposite ends thereof. 
         [0006]    One example of such conventional connectors with a built-in circuit, which is employed in a vehicular AC generator, will be described with reference to  FIGS. 7 to 9 .  FIG. 7  is a front elevational view of the connector,  FIG. 8  is a rear elevational view of the connector, and  FIG. 9  is a vertical cross-sectional view of the connector with sealing resin filled therein. 
         [0007]    In  FIGS. 7-9 , reference numeral  100  denotes a connector case as a resin molded article,  102  to  105 , wiring metal pieces fixed or embedded in the connector case  100  by insert molding or resin molding; and  106 , a leaded circuit element. The connector case  100  includes a body portion  112  of rectangular block-like configuration having laterally-elongated element accommodating chambers  111   a  and  111   b,  and a tubular connector portion  113  projecting from the body portion  112  in an upward direction in  FIGS. 7-9  The leaded circuit element  106  has an element body  160  and a pair of leads  161  and  162  extending from opposite ends of the element body  160  in a longitudinal direction thereof The leaded circuit element  106  solely or in combination with another circuit element offers the function of a surge absorbing circuit such as snubber circuit. A tip of the lead  161  is soldered to an element-connecting terminal  132  of the wiring metal piece  103 , and a tip of the lead  162  is soldered to an element-connecting terminal  152  of the wiring metal piece  105 . Numeral  200  shown in  FIG. 9  denotes a partition wall provided in the connector case  100  to isolate the element accommodating chamber  111   a  on the front side from the element accommodating chamber  111   b  on the rear side. 
         [0008]    The conventional connector with a built-in circuit element shown in  FIGS. 7-9  has a problem, however, that the leads  161  and  162  may be damaged or otherwise broken when the connector is used in a high-temperature environment. This problem will be discussed below in greater detail with reference to  FIG. 7 . 
         [0009]    In a high-temperature environment, the resin connector case  100  undergoes thermal expansion. In this instance, a temperature-dependent dimensional change occurring at the lateral distance L between the element-connecting terminals  132  and  152  fixed to the connector case  100  is approximately equal to the product of a coefficient of thermal expansion of the connector case  100  and the lateral distance L. On the other hand, the leads  161  and  162  are made of metal and have a smaller coefficient of thermal expansion than the resin connector case  100 . Thus, due to the difference in thermal expansion, the metal leads  161 ,  162  soldered to the element-connecting terminals  132 ,  52  are subjected to a tensile force and, hence, a lateral stress is developed in each of the soldered joint portions between the leads  161 ,  162  and the element-connecting terminals  132 ,  152 . In the event that the lateral stress occurs repeatedly, the soldered joint portions will cause a fatigue breakdown. Since the vehicle engine room temperature shows a tendency to increase, the connector with a built-in circuit element for use in a vehicular AC generator installed in the engine room is required to solve the foregoing problem. 
         [0010]    Japanese Patent Laid-open Publication (JP-A) No. 10-318403 (corresponding to U.S. Pat. No. 6,033,189) shows a prior proposal for preventing a fatigue breakdown from occurring, wherein the leads of a leaded circuit element have a bent portion to absorb a displacement caused due to temperature variations. The prior proposal is, however, directed to a control valve for compressors, which has a resin molded structure in its entirety with a circuit element integrally molded with a body of the resin molded control valve. If this structure is employed in a vehicular AC generator, since the vehicular AC generator per se forms a high-temperature heat source as compared to the compressor, the circuit element and its peripheral portion will be subjected to a great thermal stress, tending to form a crack at interface boundary between the molded resin and the circuit element or between the molded resin and the leads of the circuit element. Additionally, since the vehicular AC generator is placed in a use environment with high risk of getting wet with water, water entering the crack may cause an insulation failure or short between the leads of the circuit element or the circuit element itself, resulting in malfunction of the AC generator. 
       SUMMARY OF THE INVENTION 
       [0011]    With the foregoing difficulties in view, the present invention seeks to provide a connector with a built-in circuit element for a vehicular AC generator, which has highly reliable heat-resisting properties. 
         [0012]    According to the invention, there is provided a connector for a vehicular AC generator, comprising: a resin connector case having a sealed element accommodating chamber for receiving therein a circuit element; a leaded circuit element received in the element accommodating chamber and having a pair of leads protruding from opposite longitudinal ends thereof; and a plurality of wiring metal pieces embedded in the resin connector case, each of the wiring metal pieces having an external connecting terminal projecting from an outer wall of the connector case for external connection, and an element connecting terminal projecting into the element accommodating chamber and soldered to a tip end portion of each of the leads of the leaded circuit element. Each of the leads has a bent portion, which is bent at an angle of 45 degrees or greater within the element-accommodating chamber, and the element-accommodating chamber is filled with an elastic sealing resin. 
         [0013]    With this arrangement, since the leads at the opposite ends of the leaded circuit element are soldered to the element connecting terminals of the wiring metal pieces with the respective bent portions disposed intermediately between the element connecting terminals and a body portion of the leaded circuit element, the difference in thermal expansion between that portion of the connector case extending between the element connecting terminals and the leaded circuit element soldered to the element connecting terminals can be readily taken up or absorbed via elastic deformation of the respective bent portions of the pair of leads of the leaded circuit element. The connector can thus offer a good resistance to thermal stress. Furthermore, since the leads having the bent portions can reduce or shorten the overall length of the leaded circuit element, the length of the connector case portion extending between the soldered joint portions is reduced correspondingly. Thus, the aforesaid difference in thermal expansion can be reduced with the result that a further improvement in the thermal stress resisting properties can be attained. 
         [0014]    Additionally, since the element-accommodating chamber of the connector case is filled with the elastic sealing resin, this structure provides the connector with an improved degree of heat resisting properties and a high environmental stress cracking resistance. In general, due to the bent portions formed on the leads, the leaded circuit element is likely to displace in the longitudinal direction thereof when the connector is subjected to external vibrations. However, this problem does not take place for the connector of the present invention because the leaded circuit element is stably held in position against displacement within the element-accommodating chamber by means of the elastic sealing resin filled in the element-accommodating chamber. As compared to a molding resin, which seals the element-accommodating chamber at the same time it forms the connector case, the elastic sealing resin is able to prevent a crack from occurring at an interface boundary between the sealing resin and the circuit element even when subjected to repeated thermal stresses. In the absence of a crack, the connector does not allow for the entry of water, which may otherwise lead to an insulation failure. 
         [0015]    The bent portions of the leads may have a bent angle much larger than 45 degrees. For instance, each of the leads may be bent at approximately 180 degrees (or folded on itself about the bent portion). In this case, since the distance between the tip end portions of the leads joined by soldering to the element connecting terminals is greatly reduced, the aforesaid difference in thermal expansion can be greatly reduced correspondingly. The bent portions of the leads may have a corrugated or wavy shape. 
         [0016]    In one preferred form of the present invention, the connector case further has a lead support wall disposed between the tip end portion and the bent portion of each of the pair of leads and supporting thereon a portion of each respective lead. The lead support wall extends perpendicularly to each respective lead and has a recess in which the lead is received. The lead support wall thus provided keeps the tip end portion (soldered portion) of the each lead away from the influence of a thermal deformation of the bent portion caused due to temperature variations. Furthermore, the lead support wall is also able to effectively suppress a vibration-induced problem, which may occur at the soldered tip end portion of the lead when vibrations of the leaded circuit element caused due to vibrations of the vehicle enlarge the deformation of the bent portion of the lead. 
         [0017]    Preferably, the leads of the leaded circuit element are bent parallel to each other at right angles in the same direction. By thus arranging the leads o the leaded circuit element, it is possible to reduce the overall size of the element-accommodating chamber. 
         [0018]    In one preferred form of the invention, the connector case has a rectangular block-like configuration having a flat first wall, a flat second wall extending perpendicularly from one end of the first wall, and a flat third wall extending perpendicularly from the other end of the first wall and parallel to the second wall. The element-accommodating chamber includes an element receiving portion extending substantially parallel to and along the first wall of the connector case and receiving therein a body portion of the leaded circuit element in substantially parallel spaced relation to the first wall, a first lead receiving portion extending substantially parallel to and along the second wall of the connector case and receiving therein one of the pair of the leads in substantially parallel spaced relation to the second wall, and a second lead receiving portion extending substantially parallel to and along the third wall of the connector case and receiving therein the other lead in substantially parallel spaced relation to the third wall. With this arrangement, since the leads having the bent portions of the leaded circuit element are arranged to extend along three surfaces of the rectangular block-like connector case, it is possible to reduce the overall size of the connector case while the leads of the leaded circuit element are kept out of interference with another leaded circuit element received in the element-accommodating chamber. 
         [0019]    Preferably, the connector case further has a pair of lead support walls extending perpendicularly to each other and supporting each of the leads at portions located on opposite sides of the bent portion of each respective lead. By thus arranging the pair of lead support walls thus arranged, it is possible to prevent displacement of a body portion of the leaded circuit element caused due to vibrations of the vehicle and deformation of the bent portion of the lead resulting from the displacement of the circuit element body portion. Thus, the vibration-induced fatigue of the lead can be avoided. Furthermore, the pair of lead support walls extending in two mutually perpendicular directions are able to support each lead while controlling deformation of the lead, which may otherwise occur in various directions under the effect of external vibrations. 
         [0020]    In one preferred embodiment of the invention, the element connecting terminal has a joint end portion completely separated from the connector case and soldered to the tip end portion of each lead, a base portion opposite to the joint end portion and fully embedded in the connector case, and a contact exposure portion disposed between the joint end portion and the base portion, the contact exposure portion being in close contact with an inner wall surface of the connector case only at a surface thereof which is hidden when viewed from an open side of the element-accommodating chamber. With this arrangement, the element connecting portion of the wiring metal piece is relatively long and, hence, the difference in thermal expansion between the connector case and the leaded circuit element is partially accommodated by thermal deformation of the element connecting terminal. This is particularly effective to improve the thermal stress resisting performance of the connector. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  is a front elevational view of a connector for vehicular AC generators according to one preferred embodiment of the present invention; 
           [0022]      FIG. 2  is a rear elevational view of the connector shown in  FIG. 1 ; 
           [0023]      FIG. 3  is a vertical cross-sectional view of the connector shown in  FIG. 1 ; 
           [0024]      FIG. 4  is an enlarged view of a portion of  FIG. 1 ; 
           [0025]      FIG. 5  is an enlarged cross-sectional taken along line A-A of  FIG. 2 ; 
           [0026]      FIG. 6  is an enlarged cross-sectional view taken along line B-B of  FIG. 4 ; 
           [0027]      FIG. 7  is a front elevational view of a conventional connector for vehicular AC generator; 
           [0028]      FIG. 8  is a rear elevational view of the connector shown in  FIG. 7 ; and 
           [0029]      FIG. 9  is a vertical cross-sectional view of the connector shown in FIG.  7 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0030]    One preferred structural embodiment of the present invention will be described in detail in conjunction with a connector for vehicular AC generator shown in  FIGS. 1 to 6 . As shown in these figures, the connector generally comprises a connector case  1  as a resin molded article, a plurality of wiring metal pieces  2 - 5  fixed or embedded in the connector case  1  by inert molding or resin molding, and a leaded circuit element  6 . The connector case  1  includes a body portion  12  of rectangular block-like configuration having an element-accommodating chamber of horizontally elongated U shape, and a tubular connector portion  13  projecting from the body portion  12  in an upward direction shown in  FIG. 1 . The leaded circuit element  6  includes an elongated element body  60  and a pair of leads  61  and  62  projecting from opposite longitudinal ends of the element body  60 . The leaded element  6  in the illustrated embodiment is constituted by a passive circuit element such as a resistive element, varistors or the like. 
         [0031]    The element-accommodating chamber  11  has an element receiving portion  11   a  extending parallel along a flat first wall  12   a  of the body portion  12 , a first lead receiving portion  11   b  extending parallel along a second wall  12   b  extending from one end of the first wall  12   a  in a direction perpendicular to the first wall  12   a , and a second lead receiving portion  11   c  extending parallel along a third wall  12   c  extending from the other end of the first wall  12   a  in a direction perpendicular to the first wall  12   a . The element body  60  of the leaded circuit element  6  is received in the element receiving portion  11   a , the first lead  61  of the leaded circuit element  6  is received in the first element receiving portion  11   b , and the second lead  62  of the leaded circuit element  6  is received in the second element receiving portion  11   c.    
         [0032]    As shown in  FIG. 1 , the leads  61  and  62  are bent or curved upward at a right angle so as to form bent portions  61   a  and  62   a  having a predetermined curvature (in the illustrated embodiment, the radius of curvature of the bent portions is 2.5 mm). Stated more specifically, the lead  61  extends from one end of the element body  60  in a common longitudinal direction (leftward in  FIG. 1 ) of the element body  60  and the element receiving portion  11   a , then bends or curves upward at a right angle toward the connector portion  13  so as to form a bent portion  61   a , further extends from the bent portion  61   a  in an upward direction perpendicular to the longitudinal direction of the element receiving portion  11   a , and finally terminates in a tip end portion  61   a . Similarly, the lead  62  extends from the other end of the element body  60  in a common longitudinal direction (rightward in  FIG. 1 ) of the element body  60  and the element receiving portion  11   a , then bends or curves curved upward at a right angle toward the connector portion  13  so as to form a bent portion  62   a , further extends from the bent portion  62   a  in an upward direction perpendicular to the longitudinal direction of the element receiving portion  11   a , and finally terminates in a tip end portion  62   b.    
         [0033]    The wiring metal piece  2  has two external connecting terminals  21  and  22  projecting outward from an outer surface of the body portion  12  of the connector case  1  in two mutually perpendicular directions. The wiring metal piece  3  has a connector terminal  31  projecting into the tubular connector portion  13  as an external connecting terminal, and an element connecting terminal  32  projecting into the element-accommodating chamber  11 . The wiring metal piece  4  has an external connecting terminal  41  projecting outward from the outer surface of the body portion  12  of the connector case  1  in a direction parallel to the external connecting terminal  22 , and a connector terminal (not shown) projecting into the tubular connector portion  13  as an external connecting terminal. The wiring metal piece  5  has an external connecting terminal  51  projecting outward from the outer surface of the body portion  12  of the connector case  1  in a direction diametrically opposite to the projecting direction of the external connecting terminal  21 , and an element connecting terminal  52  projecting into the element-accommodating chamber  11 . The external connecting terminals  22 ,  41  project from a lower side surface of the body portion  12  of the connector case  1  in a direction opposite to the projecting direction of the connector portion  13 . The element connecting terminal  32  of the wiring metal piece  3  has a tip end portion (joint end portion) soldered to the tip end portion  61   b  of the lead  61 . Similarly, the element connecting terminal  52  of the wiring metal piece  5  has a tip end portion point end portion) soldered to the tip end portion  62   b  of the lead  62 . The element connecting terminal  32  of the wiring metal piece  3  and the element connecting terminal  52  of the wiring metal piece  5  project from the body portion  12  of the connector case  1  in a lateral leftward direction as shown in  FIG. 1 . 
         [0034]    The connector case  1  has a plurality of lead support walls  14  to  17  each for supporting thereon one of the leads  61  and  62 . The lead supporting wall  14  is disposed in the first lead receiving portion  11   b  of the element accommodating chamber  11  and extends in a direction transversely across the first read receiving portion  11   b  at a position located between the tip end portion  61   a  of the lead  61  and the bent portion  61   a  of the lead  61 . The lead support wall  15  is disposed in the element receiving portion  11   a  of the element-accommodating chamber  11  and extends in a direction transversely across the element receiving portion  11   a  at a position between a base portion (proximal end portion not designated) of the lead  61  and the bent portion  61   a  of the lead  61 . Similarly, the lead support wall  16  is disposed in the element receiving portion  11   a  of the element-accommodating chamber  11  and extends in a direction transversely across the element receiving portion  11   a  at a position between a base portion (proximal end portion not designated) of the lead  62  and the bent portion  62   a  of the lead  62 . The lead supporting wall  17  is disposed in the second lead receiving portion  11   c  of the element accommodating chamber  11  and extends in a direction transversely across the second read receiving portion  11   c  at a position located between the tip end portion  62   a  of the lead  62  and the bent portion  62   a  of the lead  62 . 
         [0035]    The lead support walls  14  and  15  are in contact with a back side of the lead  61  and extend perpendicularly to the lead  61 . Similarly, the lead support walls  16  and  17  are in contact with a back side of the lead  62  and extend perpendicularly to the lead  62 . Each of the lead support walls  14 - 17  has on its front surface an arcuate recess in which a portion of the lead  61 ,  62  is received and held therein via a frictional forced acting between the back side of the lead  61 ,  62  and the recessed front surface of each respective lead support wall  14 - 17 .  FIG. 6  shows one such arcuate recess  14   a  formed in the lead support wall  14 . Though not shown, other lead support walls  15 ,  16 ,  17  have the same arcuate recesses. 
         [0036]    As shown in  FIG. 3 , the element-accommodating chamber  11  is filled with an elastic sealing resin  7 . The element-accommodating chamber  11  has a front-side opening  11   d  and a rear-side opening  11   e , which are sealingly closed by a front lid  11   f  and a rear lid  11   g , respectively. The element-accommodating chamber  11  is enlarged on its rear side in an upward direction toward the connector portion  13  so as to receive therein a capacitor  8 . Thus, the leaded circuit element  6  is received in a front-side portion of the element-accommodating chamber  11 , and the capacitor  8  is received in an enlarged rear-side portion of the element-accommodating chamber  11 . The capacitor  8  is not shown in  FIG. 2  for clarity. 
         [0037]    As shown in  FIG. 4 , the element connecting terminal  52  of the wiring metal piece  5  has the joint end portion (tip end portion)  52   a  soldered to the tip end portion  62   b  of the lead  62 , and a contact exposure portion  52   b  located closer to a base of the element connecting terminal  52  than the joint end portion  52   a.    
         [0038]    The contact exposure portion  52   b  of the element connecting terminal  52  is in close contact with a wall portion  1 V of the connector case  1 , which is located on the front side of the element connecting terminal  52 , as shown in  FIG. 5 . The wall portion  1 V of the connector case  1  is formed as a result of formation of a cutout recess  1 X of an inverted U-shape in cross-section of a wall part  1 W extending along an inner surface of the connector case  1 . The wall portion  1 V corresponds in position to the contact exposure portion  52   b  of the element connecting terminal  52  and projects to some extent from the bottom of the inverted U-shaped cutout recess  1 X toward the rear side of the connector case  1 . In other words, the contact exposure portion  52   b  of the element connecting terminal  52  has a four-sided or rectangular cross-sectional shape and is in contact with the wall portion  1 V of the connector case  1  only at its one flat surface facing toward the front side of the connector case  1 . Remaining three flat surfaces of the contact exposure portion  52   b  are separated from the connector case  1  by virtue of the presence of the inverted U-shaped cutout recess  1 X. With this arrangement, it is possible to improve the elastic deformation of the element connecting terminal  52  in other directions than the direction facing toward the wall portion  1 V of the connector case  1 . 
         [0039]    Using five samples, the conventional connector with a built-in circuit element shown in  FIGS. 7-9  and the inventive connector with a built-in circuit element shown in  FIGS. 1-6  were subjected to a heat cycle test effected in a temperature range −30° C to 150° C. The results show that breaking of lead occurred at 500 cycles on average for the conventional connector samples and no breaking of lead was found for the inventive connector samples even after 2,000 cycles. 
         [0040]    Obviously, various minor changes and modifications are possible in the light of the above teaching. It is to be understood that within the scope of the appended claims the present invention may be practiced otherwise than as specifically described.