Patent Publication Number: US-10312011-B2

Title: Aluminum coil assembly having galvanic corrosion prevention structure for car electromagnetic clutch

Description:
BACKGROUND 
     The present invention relates to an aluminum coil assembly having a galvanic corrosion prevention structure for a car electromagnetic clutch, and more particularly, to an aluminum coil assembly having a galvanic corrosion prevention structure for a car electromagnetic clutch that is capable of preventing the occurrence of galvanic corrosion on a structure where an aluminum electromagnetic coil comes into electrical contact with a steel housing by means of a ground ring. 
     BACKGROUND OF THE RELATED ART 
     As well known, a car electromagnetic clutch is used as means for controlling power from a driving side to a driven side so as to perform power transmission or cut-off in an air conditioner compressor or full-time four wheel driving switching device. 
     When electricity is supplied or cut off to or from a coil assembly as a main part of such car electromagnetic clutch, a magnetic field is formed or disappears from the coil assembly wound onto a bobbin by means of electromagnetic induction, and according to the formation or disappearance of the magnetic field, the electromagnetic clutch operates to transmit or cut off the power from the driving side to the driven side. 
     A main part of the electromagnetic clutch coil assembly having the above-mentioned operation is the electromagnetic coil wound onto the bobbin, and the electromagnetic coil is made of a copper or aluminum coil adapted to allow the magnetic field to be formed or disappear by means of the electromagnetic induction. 
     If the electromagnetic coil constituting the electromagnetic clutch coil assembly is made of the copper coil, the copper coil comes into contact with a steel housing through a ground ring made of a brass material, and even if the coil assembly is exposed to a corrosion environment, accordingly, the copper coil has the highest electric potential to cause no corrosion, so that there is no danger of losing electrical functions of the electromagnetic coil. 
     However, the copper coil constituting the electromagnetic coil is heavy in weight and high in manufacturing cost, and so as to achieve the product lightness and the cost reduction of the coil assembly, accordingly, the copper coil has been recently changed into an aluminum coil. 
     By the way, the aluminum coil is a metal having a relatively low electric potential, and if exposed to a corrosion environment, the aluminum coil becomes under galvanic corrosion, so that it is oxidized upon the contact with air, which causes poor contact. Accordingly, the aluminum coil loses the electrical functions thereof to give serious defects to the electromagnetic clutch coil assembly. 
     The galvanic corrosion is an electrochemical reduction-oxidation process occurring if two dissimilar metals having different electric potentials are in electrical contact with each other, in the presence of an electrolyte, thereby accelerating the corrosion of the two dissimilar metals. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention has been made in view of the above-mentioned problems occurring in the prior art, and it is an object of the present invention to provide an aluminum coil assembly that is capable of removing the disadvantages of a copper coil, that is, heavy weight and high manufacturing cost, thereby achieving the lightness and cost reduction thereof. 
     It is another object of the present invention to provide an aluminum coil assembly that is capable of providing a self-contact type structure wherein galvanic corrosion of a car electromagnetic clutch is prevented even if an electromagnetic coil is made of an aluminum coil, thereby achieving the product lightness and cost reduction thereof. 
     To accomplish the above-mentioned objects, according to the present invention, there is provided an aluminum coil assembly having a galvanic corrosion prevention structure for a car electromagnetic clutch, the aluminum coil assembly including: a steel housing; an aluminum electromagnetic coil electrically connected to the steel housing and having an aluminum lead coil and a copper ground coil connected to the aluminum lead coil by means of soldering or a terminal; and a brass ground ring adapted to be press-fitted to a ring hole formed on the steel housing and having a ground hole formed on the center thereof in such a manner as to insert the copper ground coil connected to the aluminum lead coil thereinto, a cylindrical portion having a cut line adapted to be reduced when coupled to the ring hole of the steel housing to support the copper ground coil inserted into the ground hole, and an inclined portion formed on the underside of the cylindrical portion to allow easy press-fitting to the ring hole formed on the steel housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments of the invention in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a perspective view showing an aluminum coil assembly according to the present invention; 
         FIG. 2  is an exploded perspective view showing the aluminum coil assembly according to the present invention; 
         FIG. 3  is a perspective view showing a brass ground ring adapted to allow a copper ground coil to come into contact with a steel housing in the aluminum coil assembly according to the present invention; 
         FIG. 4  is a sectional view showing the state where the copper ground coil bonded to an aluminum lead coil comes into contact with the steel housing, together with the brass ground ring; and 
         FIG. 5  is a sectional view showing the state where the copper ground coil comes into contact with the steel housing, together with the brass ground ring. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, an explanation on an aluminum coil assembly having a galvanic corrosion prevention structure for a car electromagnetic clutch according to the present invention will be given in detail with reference to the attached drawings. 
     According to the present invention, an aluminum coil assembly having a galvanic corrosion prevention structure for a car electromagnetic clutch includes an electromagnetic coil  1  for generating an electromagnetic force, a steel housing  30  for forming an outer shape of the electromagnetic coil  1  in such a manner as to be electrically grounded, a copper ground coil  15  connected to an aluminum lead coil  11  of an aluminum electromagnetic coil  10  by means of soldering or a terminal  16 , a brass ground ring  20  adapted to allow the copper ground coil  15  to come into contact with the steel housing  30 , and an epoxy molding material  40  for fixing the aluminum electromagnetic coil  10  to the steel housing  30 . 
     So as to electrically connect the aluminum electromagnetic coil  10  to the steel housing  30 , the aluminum lead coil  11  of the aluminum electromagnetic coil  10  is connected to the copper ground coil  15  by means of soldering or the terminal  16 . 
     So as to allow the copper ground coil  15  connected to the aluminum lead coil  11  by means of the soldering or terminal  16  to come into contact with the steel housing  30 , the steel housing  30  has a ring hole  31  formed thereon to couple the brass ground ring  20  thereto and at the same time to contactedly insert the copper ground coil  15  connected to the aluminum lead coil  11  by means of the soldering or terminal  16  into a ground hole  21  formed on the brass ground ring  20 . 
     The brass ground ring  20  includes the ground hole  21  formed on the center thereof in such a manner as to come into contact with the copper ground coil  15  connected to the aluminum lead coil  11  by means of the soldering or terminal  16  if coupled to the ring hole  31  of the steel housing  30 , a cylindrical portion  23  having a cut line  25  adapted to be reduced if coupled to the ring hole  31  of the steel housing  30  to support the copper ground coil  15  inserted into the ground hole  21 , and an inclined portion  24  formed on the underside of the cylindrical portion  23  to allow the coupling to the ring hole  31  of the steel housing  30  to be easily performed. 
     A reference numeral  50  not explained yet indicates a screw for fixing the aluminum coil assembly,  51  indicates a grommet, and  52  indicates a power lead coil. 
     Under the above-mentioned structure, now, an explanation on the operation of the aluminum coil assembly having the galvanic corrosion prevention structure for the car electromagnetic clutch according to the present invention will be given in detail. 
     According to the present invention, the aluminum lead coil  11  of the aluminum electromagnetic coil  10  and the copper ground coil  15  are connected to each other by means of soldering or the terminal  16  and buried by the epoxy molding material  40 , so that through complete sealing, ionic paths (electrolyte, moisture and so on) can be blocked from the outside to completely prevent the galvanic corrosion from occurring on the aluminum lead coil  11 . 
     The brass ground ring  20 , which is adapted to allow the copper ground coil  15  connected to the aluminum lead coil  11  to be grounded to the steel housing  30 , is configured to insert the copper ground coil  15  into the ground hole  21  formed on the center thereof, so that as the brass ground ring  20  is press-fitted to the ring hole  31  of the steel housing  30 , a space formed by the cut line  25  of the cylindrical portion  23  becomes reduced to support and firmly fix the copper ground coil  15  inserted into the ground hole  21 . 
     When the brass ground ring  20  is coupled to the ring hole  31  of the steel housing  30  in such a manner as to be press-fitted to the ring hole  31  of the steel housing  30  to support the copper ground coil  15  inserted into the ground hole  21 , easy coupling of the brass ground ring  20  to the ring hole  31  of the steel housing  30  is achieved by the inclined portion  24  formed on the underside of the cylindrical portion  23 . 
     After the aluminum lead coil  11  of the aluminum electromagnetic coil  10  is electrically connected to the copper ground coil  15  by means of the soldering or terminal  16 , without coming into direct contact with the steel housing  30 , the copper ground coil  15  is compressed by means of the brass ground ring  20  and thus comes into contact with the aluminum lead coil  11  to perfectly block ionic paths from the outside, so that the occurrence of the galvanic corrosion on the connected portion of the copper ground coil  15  to the aluminum lead coil  11  can be completely prevented. 
     As described above, the aluminum coil assembly according to the present invention can block the ionic paths (electrolyte, moisture and so on) from the outside even if the aluminum coil and the copper coil come into direct electrical contact with each other, so that the galvanic corrosion of the aluminum electromagnetic coil is prevented to keep the electrical functions from being lost due to contact resistance defects. 
     In addition, the aluminum coil assembly according to the present invention can provide the car electromagnetic clutch having the aluminum electromagnetic coil, thereby achieving the lightness and cost reduction of the car electromagnetic clutch and improving the quality and reliability thereof. 
     While the present invention has been described with reference to the particular illustrative embodiments, it is not to be restricted by the embodiments but only by the appended claims. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present invention.