Abstract:
A connection structure of an electrical component is provided wherein the first connection member consists of liquid crystalline polymer synthetic resin. A weld joint is formed in the sleeve of the first connection member during the molding process. This weld joint permits the second connection member to be press-fitted into the first connection member by permitting the first connection member to fracture along the weld joint, thereby resulting in a tight connection between the first and second connection members.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a connection structure of an electrical component such as a variable resistor. 
     2. Description of the Related Art 
     A connection structure of a conventional electrical component is described herein under with reference to FIG. 6 to FIG. 10 in which a variable resistor is exemplified. 
     A base plate  21  formed of a molded synthetic resin is flat and has a hole  21   a  at the center, and a U-shaped resistor (not shown in the drawing) and a circular collector (not shown in the drawing) are provided on the upper side of the base plate  21 . 
     Terminals  22  and  23  are embedded on the base plate  21 , the terminal  22  is connected to the collector and the terminals  23  are connected to the resistor. 
     A cover  24  formed of molded synthetic resin has a flat wall  24   a , a side wall  24   b  which extends from the periphery of the flat wall  24   a  downward, a plurality of snaps  24   c  which extend downward from the bottom end of the side wall  24   b , and a hole  24   d  formed at the center of the flat wall  24 . 
     The cover  24  covers the top side of the base plate  21  so as to cover the resistor and collector, and is fixed to the base plate  21  by snapping the snaps on the periphery of the base plate  21 . 
     The first connection member  25  consisting of polyacetal synthetic resin which constitutes a rotor has a sleeve  25   b  having a non-circular hole  25   a  and a plate  25   c  which extends radially from the sleeve  25   b , and a moving contact  26  having contacts  26   a  and  26   b  is embedded on the connection member  25 . 
     The connection member  25  is inserted supportingly to the hole  21   a  of the base plate  21  and the hole  24   d  of the cover  24 , and attached rotatably to the base plate  21  and the cover  24 . 
     When the connection member  25  is attached, the contact  26   a  is brought into contact with the collector slidably and the contact  26   b  is brought into contact with the resistor slidably. 
     The second connection member  27  which constitutes a shaft consists of metal material or synthetic resin material, and has a non-circular end  27   a.    
     Because the first connection member  25  is formed of polyacetal synthetic resin, if the clearance between the hole  25   a  of the first connection member  25  and the end  27   a  of the second connection member  27  is zero, the end  27   a  is not inserted into the hole  25   a , therefore a clearance K is provided between both members, and the end  27   a  is inserted into the hole  25   a  to connect the first connection member  25  to the second connection member  27 . 
     When the second member  27 , which is a shaft, is rotated, the first connection member  25 , which is a rotor, is rotated, and the contacts  26   a  and  26   b  of the moving contact  26  are slid on the collector and resistor respectively with the rotation to change the resistance value. 
     Next, a method for fabrication of the first connection member  25  is described with reference to FIG. 10. A metal mold  28  comprises an inner mold  28   a  provided at the center for forming the hole  25   a  of the first connection member  25 , and an outer mold  28   d  having a cavity  28   b  for forming the sleeve  25   b  and plate  25   c  and a gate  28   c  for injecting hot molten resin into the cavity  28   b . Next, when molten polyacetal synthetic resin is injected into the cavity  28   b  from the gate  28   c , polyacetal hot molten resin is jetted against the inner mold  28   a  and the stream is branched toward the arrow directions, the branched streams merge and are mixed at the position G located on the opposite side with the gate  28   c , and then polyacetal synthetic resin is solidified and thus the molding of the first connection member  25  is completed. 
     Because polymer molecules of the polyacetal synthetic resin are entangled each other in molten state and solid state, when streams are merged at the position G on the opposite side with the gate  28   c , the streams are mixed completely and form a molded product having no weld mark. Therefore, the sleeve  25   b  of the first connection member  25  exhibits little deformation, as the result, press fitting of the second connection member  27  into the sleeve  25   b  of the first connection member  25  having the structure as described above is difficult, and the first connection member  25  engages the second connection member with a play gap. 
     Because the first connection member  25  is formed of acetal synthetic resin, press fitting of the second connection member  27  into the first connection member  25  is difficult in the conventional connection structure of an electrical component, both members are connected with play and engaged with play. 
     The rotation of the second connection member  27  is transmitted to the first connection member  25  with play, and the rotation transmission is not correct. 
     SUMMARY OF THE INVENTION 
     In a first embodiment for solving the above-mentioned problem, the structure comprises the first connection member having a sleeve provided with a hole and the second connection member to be press-fitted into the hole, the first connecting member being formed of synthetic resin consisting of liquid crystalline polymer. 
     In a second embodiment, the sleeve has a weld mark formed in the insertion direction of the second connection member. 
     In a third embodiment, the first connection member constitutes a rotor and the second connection member constitutes a shaft. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view for illustrating the connection structure of an electrical component of the present invention. 
     FIG. 2 is a cross sectional view for illustrating the connection structure of the electrical component of the present invention. 
     FIG. 3 is a plan view of the first connection member in accordance with the connection structure of the present invention. 
     FIG. 4 is a diagram for illustrating the relation between the first and second connection members in accordance with the connection structure of the electrical component of the present invention. 
     FIG. 5 is a diagram for illustrating a method for manufacturing the first connection member in accordance with the connection structure of the electrical component of the present invention. 
     FIG. 6 is a perspective view for illustrating the connection structure of a conventional electrical component. 
     FIG. 7 is a cross sectional view for illustrating the connection structure of the conventional electrical component. 
     FIG. 8 is a plan view for illustrating the first connection member in accordance with the connection structure of the conventional electrical component. 
     FIG. 9 is a diagram for illustrating the relation between the first and second connection members in accordance with the connection structure of the conventional electrical component. 
     FIG. 10 is a diagram for illustrating a method for manufacturing the first connection member in accordance with the connection structure of the conventional electrical component. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The connection structure of an electrical component of the present invention will be described below with reference to the exemplified variable resistor shown in FIG. 1 to FIG.  5 . FIG. 1 is a perspective view for illustrating the connection structure of an electrical component of the present invention, FIG. 2 is a cross sectional view for illustrating the connection structure of the electrical component of the present invention, FIG. 3 is a plan view of the first connection member in accordance with the connection structure of the electrical component of the present invention, FIG. 4 is a diagram for describing the relation between the first and second connection members in accordance with the connection structure of the electrical component of the present invention, and FIG. 5 is a diagram for describing a method for manufacturing the first connection member in accordance with the connection structure of the electrical component of the present invention. 
     The connection structure of the electrical component of the present invention is described with reference to the exemplified variable resistor shown in FIG. 1 to FIG.  5 . Abase plate  1  comprising a molded product consisting of synthetic resin is flat, and has a hole  1   a  at the center, and a U-shaped resistor (not shown in the drawing) and a circular collector (not shown in the drawing) are provided on the top side of the base plate  1 . 
     Terminals  2  and  3  are embedded on the base plate  1 , the terminal  2  is connected to the collector, and the terminal  3  is connected to the resister. 
     A cover  4  comprising a molded product consisting of synthetic resin has a flat wall  4   a , a side wall  4   b  which extends downward from the periphery of the flat wall  4   a , a plurality of snaps  4   c  which extend downward from the bottom end of the side wall  4   b , and a hole  4   d  provided at the center of the flat wall  4   a.    
     The cover  4  covers the top side of the base plate  1  so as to cover the resistor and collector, and is fixed to the base plate  1  by snapping the snaps  4   d  on the side edge of the base plate  1 . 
     The first connection member  5  which constitutes a rotor consists of liquid crystalline polymer synthetic resin, has a sleeve  5   b  having a non-circular hole  5   a , a plate  5   c  which extends radially from the sleeve  5   b , and a weld mark  5   d  formed in the axial direction on the sleeve  5   b . A moving contact  6  having contacts  6   a  and  6   b  are embedded on the connection member  5 . The connection member  5  is inserted supportingly into the hole  1   a  of the base plate  1  and the hole  4   d  of the cover  4 , and attached to the base plate  1  and cover  4  rotatably. When the connection member  5  is attached, the contact  6   a  is in contact with the collector slidably, and the contact  6   b  is in contact with the resistor slidably. 
     The second connection member  7  which constitutes a shaft consists of metal material or synthetic resin material, and the end  7   a  of the second connection member  7  is non-circular. 
     Because the first connection member consists of liquid crystalline polymer synthetic resin, as shown in FIG.  3  and FIG. 4, the weld mark  5   d  is formed in the axial direction of the sleeve  5   b  namely in the insertion direction of the second connection member  7 , and when the end  7   a  is press-fitted into the hole  5   a  with zero clearance between the hole  5   a  of the first connection member  5  and the end  7   a  of the second connection member  7 , the sleeve  5   b  cracks widened and the cracked sleeve  5   b  holds the end  7   a  elastically, thus the first and second connection members  5  and  7  are connected. 
     When the second connection member  7 , which is a shaft, is rotated, the first connection member  5 , which is a rotor, is rotated, and the contacts  6   a  and  6   b  of the moving contact  6  slide on the collector and the resistor respectively with the rotation to vary the resistance value. 
     Next, a method for manufacturing the first connection member  5  is described with reference to FIG. 5. A metal mold  8  comprises an inner mold  8   a  provided at the center for forming the hole  5   a  of the first connection member  5 , and an outer mold  8   d  having a cavity  8   b  for forming the sleeve  5   b  and the plate  5   c  and a gate  8   c  for injecting molten synthetic resin into the cavity  8   b.    
     Next, when molten liquid crystalline polymer synthetic resin is injected into the cavity  8   b  from the gate  8   c , the molten synthetic resin is jetted against the inner mold  8   a  and flows into branched passages along the arrows, branched streams merge at the position G on the opposite side with the gate  8   c , the streams are mixed partially, and when liquid crystalline polymer synthetic resin is solidified the manufacturing of the first connection member  5  is completed. 
     Polymer molecules in the molten liquid crystalline polymer synthetic resin are oriented in the flow direction of the resin, and when the streams merge at the position G on the opposite side with the gate  8   c , the first connection member having a weld mark  5   d  marked in the axial direction of the sleeve  5   b  is formed, the weld strength of this portion is very low. As the result, when the second connection member  7  is press-fitted into the sleeve  5   b  of the first connection member  5  having the structure as described herein above, the sleeve  5   b  cracks at the position of the weld mark  5   d , and the crack brings about tight connection between the first and second connection members  5  and  7 . 
     Because the first connection member  5  of the connection structure of an electrical component of the present invention consists of liquid crystalline polymer synthetic resin, a weld mark  5   d  is formed in molding, as the result, the second connection member  7  is press-fitted into the first connection member  5 , when press-fitted the first connection member  5  cracks along the weld mark  5   d , and the crack brings about tight connection between the first and second connection members, and thus the present invention provides a connection structure of an electrical component which realizes tight connection. 
     Furthermore, because the connection structure having no play between the first and second connection members  5  and  7  is realized, there is no play between the first and second connection members  5  and  7  in rotation transmission, as the result the present invention provides the connection structure of an electrical component which transmits rotation correctly. 
     Furthermore, because the sleeve  5   b  of the first connection member  5  is provided with the weld mark  5   d  in the insertion direction of the second connection member  7  to thereby form a crack on the sleeve  5   b  in the insertion direction of the second connection member  7 . Therefore, the second connection member  7  is press-fitted into the first connection member  5  easily, and as the result the present invention provides the connection structure of an electrical component which is excellent in connection between the first and second connection members  5  and  7 . 
     Furthermore, the first connection member  5  constitutes a rotor and the second connection member  7  constitutes a shaft, and particularly these members are used for an electrical component such as variable resistor in which rotation of the shaft is transmitted to the rotor used for electrical controlling. Accordingly, the present invention can provide the connection structure of an electrical component which is used for controlling consistently by means of rotation of a shaft without play.