Patent Publication Number: US-2011056449-A1

Title: Ignition coil for vehicle

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to vehicle ignition coils. 
     BACKGROUND OF THE INVENTION 
     Ignition coils are components that use the coupling between a primary winding and a secondary winding to transform relatively low voltages from the battery into high voltages that are supplied to the spark plugs in vehicle gasoline engines. The spark plugs start the internal combustion process that drives the rods and hence, crankshaft and axles. In older systems, a single ignition coil is provided, and a distributor sends the pulses from the coil through respective high voltage spark plug wires to the spark plugs in the cylinders in accordance with a timing that is established by the distributor. 
     In relatively modern engines, an engine can have several ignition coils, one for each cylinder or for each pair of cylinders, thereby advantageously eliminating the need for distributors and high voltage wires and also providing more precise control of the engine timing. One example of such an ignition coil system is set forth in U.S. Pat. No. 6,556,118, owned by the present assignee and incorporated herein by reference. 
     Ignition coils have been made in a cylindrical configuration with a small diameter (generally 22-27 mm) that is meant to fit into a spark plug well. These are commonly referred to as pencil coils. A pencil coil is relatively long. In applications with limited spark plug well height, a coil that resides above the spark plug well (known as a plug top coil or “PTC”) may be used. A PTC is shorter than a pencil coil and exploits room above the well, where the diameter of the space into which the coil must reside is less restricted than that of a spark plug well. 
     SUMMARY OF THE INVENTION 
     As understood herein, a disadvantage of a plug top coil is that the space within the well that would otherwise be occupied by a pencil coil remains unused. Another disadvantage of a PTC as recognized herein is that the silicone boot that is used to insulate the output of the coil from the well must be made longer than it would be for a pencil coil and, thus, and relatively more expensive. 
     Accordingly, an ignition coil assembly for an engine spark plug includes an axially lower secondary winding spool segment defining a first radius and an axially upper secondary winding spool segment defining a second radius larger than the first radius, with the segments being axially contiguous to each other. A secondary winding is on the segments and a primary winding core extends within the segments and bears a primary winding. 
     In an example embodiment the axially lower segment is disposable in a spark plug well and the axially upper segment is disposable above the well. The first radius is thus smaller than the radius of the well and the second radius can be larger than the radius of the well. If desired, the axially lower segment is longer than the axially upper segment, and the secondary winding can be progressively wound on the axially lower segment and wound in a segmented configuration on the axially upper segment. 
     The primary winding core may include an axially lower core segment disposed within the axially lower secondary winding spool segment and an axially upper core segment disposed within the axially upper secondary winding spool segment. The number of primary winding layers on the axially lower core segment can be different than the number of primary winding layers on the axially upper core segment. For example, the axially upper core segment can bear more primary winding layers than the axially lower core segment. 
     In another aspect, a method for providing voltage to an engine spark plug in a spark plug well includes disposing within the well an axially lower secondary winding spool segment defining a diameter less than the diameter of the well. A portion of a secondary coil winding is wound on the lower secondary winding spool segment. The method also includes disposing above the well an axially upper secondary winding spool segment defining a diameter greater than the diameter of the well. A portion of the secondary coil winding is wound on the upper secondary winding spool segment. Electrical communication between the spark plug and the secondary winding is established. 
     In another aspect, a method includes providing an ignition coil assembly, and mounting the ignition coil assembly within a spark well with a portion of the assembly disposed above the well in electrical communication with a spark plug in the well. 
     In another aspect, an apparatus includes an axially lower secondary winding spool segment defining a first radius, an axially upper secondary winding spool segment defining a second radius different from the first radius, and a secondary winding on both segments. A primary winding core extends within the segments and bears a primary winding. A different number of layers of the primary winding are on the core adjacent the lower secondary winding spool segment then are on the core adjacent the upper secondary winding spool segment. 
     The details of the present invention, both as to its structure and operation, can best be understood in reference to the accompanying drawings, in which like reference numerals refer to like parts, and in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a gasoline-powered engine with a spark plug and ignition coil; and 
         FIG. 2  is a side plan view of an example embodiment with an axially lower secondary winding spool segment defining a first radius and an axially upper secondary winding spool segment defining a second larger radius. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Beginning initially with  FIG. 1 , a gasoline-powered engine is shown. The engine  10  may have at least one spark plug well  12  which, in non-limiting embodiments, may be in either the engine block or an engine head. The well  12  is capable of receiving a spark plug  14 . Should the well  12  be made of a non-conductive material, a shield providing an outer magnetic return path is not required. 
     Typically, the plug  14  is electrically connected to a coil  16 . It is to be understood that the coil  16  is capable of transforming relatively low voltages from a battery  18  into high voltages that are supplied to the plug  14  so that the plug  14  may create a spark. The plug  14  may thus initiate the internal combustion process of the engine  10 . It is to be further understood that the coil  16  and the coil to be referenced in  FIG. 2  may be waste spark (also known as a two-tower) ignition coil or a high energy coil per cylinder in non-limiting embodiments. 
     Proceeding to  FIG. 2 , an ignition coil assembly is shown, numbered  20 , it being understood that coil assembly  20  shown in  FIG. 2  can embody the coil  16  of  FIG. 1 . The ignition coil assembly  20  has an ignition coil  22 . The coil  22  may supply voltage from a battery (not shown) to a spark plug  24  through a coupling  26 , the coupling  26  potentially being a cup and spring coupling in non-limiting embodiments. 
     The coil  22  has an axially lower winding spool segment  28  defining a first radius and an axially upper winding spool segment  30  defining a second radius larger than the first radius, where both segments are axially contiguous to each other and bear a secondary winding discussed below. Both the lower segment  28  and upper segment  30  may be composed of a plastic in non-limiting embodiments. 
     Moreover, the lower segment  28  is configured for being disposed in a spark plug well  32  and the upper segment  30  is configured for being disposed above the well  32 . It is to be understood that the lower segment  28  may be longer than the upper segment  30 . It is to be further understood that the diameter of the well  32  is greater than the diameter of the lower segment  28  but less than the diameter of the upper segment  30 . 
     Sill referencing  FIG. 2 , the ignition coil assembly  20  has a primary winding core  34  which extends within both the lower segment  28  and upper segment  30 . Specifically, the core  34  may have an axially lower core segment  36  disposed within the axially lower secondary winding spool segment  28  and an axially upper core segment  38  disposed within the axially upper secondary winding spool segment  30 . The core  34  bears a primary winding  40  wound around the core  34  in accordance with ignition coil principles known in the art. It is to be understood that the primary winding  40  is electrically connected to an ignition system that selectively energizes the primary winding  40  from a source of voltage such as a vehicle battery in accordance with ignition coil principles known in the art, which in turn is inductively coupled to the secondary windings such that the coil  22  provides needed voltage to the plug  24  to create a spark. 
     Furthermore, in non-limiting embodiments the number of primary winding layers on the axially lower core segment  36  may be different than the number of primary winding layers on the axially upper core segment  38 . Thus, the axially upper core segment  38  may bear more primary winding layers than the axially lower core segment  36 . For example, in the specific non-limiting embodiment shown in  FIG. 2 , the upper core segment  38  may bear four winding layers whereas the lower core segment  36  may bear two winding layers. 
     Still remaining with  FIG. 2 , the assembly  20  having the lower secondary winding spool segment  28  and upper secondary winding spool segment  30  has a secondary winding  42 . In example non-limiting embodiments the secondary winding  42  may be progressively wound on the lower segment  28  and can be wound in a segmented configuration on the upper segment  30 . To maintain a segmented winding configuration on the upper segment  30 , disk-shaped ribs  44  are formed on the upper segment  30 . Further, in non-limiting embodiments a pole piece or flux director may be used to improve coupling between then upper core segment  38  and upper secondary segment  30 . 
     When the primary winding  40  is energized, the cooperation between the core  34 , primary winding  40 , and secondary winding  42  results in inductive coupling between the primary winding  40  and secondary winding  42 . Owing to this coupling and to the different number of layers between primary and secondary, the relatively low battery voltage in the primary winding  42  is transformed into relatively higher voltages in the secondary winding  42  for provision of the higher voltages to the spark plugs. 
     While the particular IGNITION COIL FOR VEHICLE is herein shown and described in detail, it is to be understood that the subject matter which is encompassed by the present invention is limited only by the claims.