Patent Publication Number: US-8113164-B2

Title: Ignition source adapted for positioning within a combustion chamber

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. application Ser. No. 11/589,118, filed on Oct. 30, 2006 now U.S. Pat. No. 7,448,352, which claims the benefit of U.S. Provisional Application No. 60/731,266 filed on Oct. 31, 2005. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to spark ignition systems for use in combustion devices, e.g., reciprocating engines, furnaces, etc., and more particularly, to an ignition source having one or more elements adapted for adjustable positioning within the combustion device. 
     SUMMARY OF THE INVENTION 
     In one aspect of embodiments of the present invention, an ignition source for initiating combustion is provided. The ignition source includes an electrical delivery conductor mounted in a delivery conductor mounting structure. An electrical ground conductor is mounted in a ground conductor mounting structure and extends from the ground conductor mounting structure to a point proximate the delivery conductor to define an ignition spark gap between the delivery conductor and the ground conductor. At least one of the delivery conductor and the ground conductor are mounted in a respective one of the delivery conductor mounting structure and the ground conductor mounting structure so as to be selectively positionable with respect to the other one of the delivery conductor and the ground conductor to selectively adjust a width of the ignition spark gap. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of an internal combustion engine incorporating an ignition source in accordance with an embodiment of the present invention. 
         FIG. 2  is a schematic view of an internal combustion engine incorporating an ignition source in accordance with another embodiment of the present invention. 
         FIG. 3  is a partial cross-sectional view of an ignition source in accordance with the embodiment of  FIG. 1  extending into a combustion chamber of an engine. 
         FIG. 4  is a partial cross-sectional view of an ignition source in accordance with the embodiment of  FIG. 2  extending into a combustion chamber of an engine. 
         FIG. 5  is a partial cross-sectional view of an ignition source in accordance with yet another embodiment of the present invention extending into a combustion chamber of an engine. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a portion of an internal combustion engine  12  including an ignition source, generally designated  10 , positioned within a combustion chamber  36 , in accordance with embodiments of the present invention. Various embodiments of a mechanism for providing an ignition spark to the interior of the combustion chamber are described herein. 
     As shown in  FIG. 1 , the engine  12  has a cylinder head  14 , plurality of cylinder chambers  18  (one shown) defined in an engine body or cylinder block  16 , and a plurality of pistons  20  (one shown) axially displaceably disposed in the cylinder chamber  18 . When the piston  20  is displaced in its stroke, it changes the effective volume of the combustion chamber  36  to cause the engine  12  to operate in intake, compression, power, and exhaust strokes, in a manner known in the art. The displacement of the piston  20  is output as drive power from the engine  12 , from the piston  20  through a connecting rod  22  and a crankshaft  24 . 
     The engine body  16  has an intake port  26  and an exhaust port  28  defined therein, which open into each of the cylinder chambers  18 . An intake valve  30  is operatively disposed in the intake port  26 , and an exhaust valve  32  is operatively disposed in the exhaust port  28 . 
     Embodiments of the ignition source described herein include conductors  38 ,  46  (described in greater detail below) mounted to a wall of the cylinder, to cylinder head  14 , to the cylinder block or engine body  16 , or to another mounting structure suitable for mounting of the ignition source components described herein. 
     As used herein, the term “mounting structure” is understood to mean any portion of the device into which ignition source  10  is incorporated that is suitable for mounting of either of delivery conductor  38  or ground conductor  46  therein, so as to enable the ignition source to perform the functions described herein. For example, in the embodiment shown in  FIGS. 1 and 3 , conductors  38 ,  46  are mounted in cylinder head  14  and extend into a combustion chamber  36  defined by the cylinder head  14 , the cylinder wall(s), and the piston  20 . In the embodiment shown in  FIGS. 2 and 4 , conductors  38  and  46  are mounted in the cylinder block  16  and extend across at least a portion of the width or diameter of the cylinder. The delivery conductor mounting structure and the ground conductor mounting structure may comprise the same element of the device into which the ignition source is incorporated. For example, in  FIG. 1 , both of the delivery and ground conductors are mounted in the cylinder head. Alternatively, each of the conductors  38  and  46  could be mounted in different elements of the device (i.e., the delivery conductor could be mounted in the cylinder head, while the ground conductor is mounted in the cylinder wall). Thus, the mounting of the conductors can be adjusted to meet the requirements of a particular device geometry or functional application. 
     The engine block  12 , cylinder head  14 , cylinders  18 , and other engine components may each be formed conventionally, e.g., cast as a single, monolithic unit, or manufactured as separate components and mechanically assembled together, as desired. 
       FIGS. 1 and 3  illustrate ignition source  10  extending into a combustion chamber  36  formed within cylinder  18  of the engine, in accordance with one embodiment of the present invention. In this embodiment, the ignition source includes a two-piece spark rod having an electrical delivery conductor  38  with a base end  40  that is secured to a wall of a cylinder, a portion of a cylinder head, or any other structure suitable for mounting the conductor therein. While the conductor  38  is mounted to the cylinder wall or other mounting structure, the conductor may be electrically insulated from the wall and the structure in which the conductor is mounted, to prevent premature grounding. A known insulating material (for example, a polymer or ceramic material)  39  may be positioned between conductor  38  and the structure in which the conductor is mounted. 
     The conductor  38  extends from the cylinder head  14  into the combustion chamber  36 , and terminates in an electrode end  44 . In a particular embodiment, the electrode end  44  is positioned within the generally central area or volume of the combustion chamber  36  as defined by the cylinder wall, cylinder head, and piston at approximately the moment at which ignition of the fuel/air mixture is designed to occur. In other embodiments, conductor  38  is configured so that electrode end  44  resides at a desired position which is spaced apart from the theoretical center of the combustion chamber  36 , according to the needs of a particular application. Accordingly, conductor  38  may be straight, curved (as shown in  FIG. 3 ), or may include any combination of straight or curved portions or have any shape necessary for positioning electrode end  44  in the desired position within the combustion chamber. 
     Referring again to  FIGS. 1 and 3 , a second spark rod component comprises an electrical ground conductor  46  having an electrically grounded end  48  which is mechanically and electrically connected to a wall of the cylinder, a portion of the cylinder head  14 , or to any other structure suitable for mounting the ground conductor therein. The structure in which ground conductor  46  is mounted may be the same structure or a different structure from that in which delivery conductor  38  is mounted. 
     Grounded end  48  may be secured to any desired portion of the mounting structure, either proximate (and suitably electrically isolated from) delivery conductor  38  (as shown in  FIG. 3 ), or spaced apart from the delivery conductor. The ground conductor  46  further includes an electrode end  52  extending into the combustion chamber  36  adjacent the electrode end  44  of the delivery conductor  38 . Accordingly, ground conductor  46  may be straight (as shown in  FIG. 3 ), curved, or may include any combination of straight or curved portions or have any shape necessary for positioning electrode end  52  in the desired position adjacent electrode end  44  within the combustion chamber. 
     The respective electrode ends  44  and  52  of the two conductors  38  and  46  define an ignition spark gap  54  therebetween, with a spark jumping the gap  54  when sufficient electrical potential is applied to the delivery conductor  38 . In an embodiment where electrode end  44  (and, therefore, spark gap  54 ) is positioned at or proximate the theoretical center of the combustion chamber volume, substantially optimum ignition of the fuel/air mixture within the combustion chamber may be facilitated, with the combustion propagation spreading essentially uniformly in all directions from such a centrally located ignition source. 
     In the embodiments shown herein, the dimension of the spark gap  54  may be adjusted by providing a threaded base end for one or more of the two conductors, inserting the base end of the conductor into its associated mounting structure, and threading it inwardly or outwardly in its attachment to the mounting structure. For example, delivery conductor  38  could be mounted in a threaded sleeve  39  ( FIG. 3 ) formed from a non-conductive material or otherwise insulated from the device in which the conductor is mounted. This sleeve  39  would also provide a conduit enabling electrical connection of the delivery conductor  38  to the voltage supply line (described below). Ground conductor  46  could be mounted in a threaded hole (as shown in  FIG. 3 ) formed in an element of the device that is electrically connected to ground. Other modes of controlling the positioning of the conductors are also contemplated. 
       FIGS. 1-5  illustrate various embodiments of the present ignition source. In all cases the spark gap  54  is located a sufficient distance from the peripheral wall of combustion chamber  36  to prevent premature grounding of delivery conductor  36 . 
     An electrical supply line  56  extends through the cylinder wall, cylinder head  14 , or other mounting structure into which delivery conductor  38  is mounted. Supply line  56  electrically communicates with delivery conductor  38 . A controller  50  is coupled to a voltage source (not shown) and/or to the supply line for regulating application of a voltage to delivery conductor  38 . Supply line  56  provides electrical power to the delivery conductor  38  responsive to a command from the controller. 
     The controller may be set or programmed to periodically activate the voltage source, to permit periodic electrical communication between the voltage source and the delivery conductor, or otherwise to regulate application of a voltage to delivery conductor  38  so as to generate a spark at spark gap  54 , in a manner timed to substantially coincide with maximum compression of the fuel/air mixture during the engine cycle (for example, when the piston is at or near top dead center). In other applications (for example, in a furnace) (not shown), application of the voltage to the delivery conductor may be regulated based on feedback received from a thermostat or other control device, in a manner known in the art. The controller  50  may be a micro-processor based controller or any other controller suitable for regulating the timing of voltage application to the delivery conductor in accordance with the requirements of the desired engine cycle. 
     While electrical insulation along the entire lengths of the delivery and ground conductors  38  and  46  is generally not required due to the spacing between the delivery conductor  38  and any electrically grounding structure, such insulation can provide additional physical or mechanical strengthening for the ignition rod assembly comprising the two conductors  38  and  46 . 
     Referring to  FIGS. 2 and 4 , in one embodiment, an electrical insulator is in the form of a continuous tube  66  surrounding the two conductors  38  and  46 . Tube  66  may be formed from any suitable insulating material (for example, a polymer or ceramic material) or combination of materials, and may be either relatively rigid or relatively flexible, according to the requirements of a particular application. In the embodiment shown in  FIGS. 2 and 4 , the insulator tube  66  includes at least one spark exposure aperture or passage  68  adjacent the spark gap  54 , to allow the air/fuel mixture to circulate and flow therethrough in the vicinity of the spark gap  54  in order for an ignition spark to ignite the air/fuel mixture when the spark occurs. In an alternative embodiment (not shown), a series of spark exposure passages  68  are formed along tube  66  in the vicinity of spark gap  54 . 
     In one embodiment, tube  66  is relatively rigid and provides additional physical or mechanical strengthening for the ignition rod assembly. In another particular embodiment (shown in  FIG. 5 ), tube  66  is formed from a relatively flexible or malleable material) or combination of materials) which permits the configuration of the spark rod assembly to be adjusted according to the needs of a particular application, while maintaining the desired spatial relationship between the electrode ends of conductors  38  and  46 . 
     In another particular embodiment (shown in  FIG. 5 ), the insulation tube covers only a portion of each of conductors  38  and  46 , or only the electrode ends of each of conductors  38  and  46 . Thus, the insulator serves to maintain the spatial relationship between the electrode ends of conductors  38  and  46  and includes openings  68  providing fluid communication between spark gap  54  and the fuel/air mixture in the combustion chamber. 
     The range of electrode configurations described herein provides the ability to position the spark gap  54  at essentially any desired point within the combustion chamber. This flexibility in positioning of the spark gap enables optimization of the combustion reaction to be facilitated within a wide variety of combustion chamber shapes and sizes, by facilitating positioning of the spark gap at or near the theoretical center of the combustion chamber or at any other desired location within the combustion chamber, for any given combustion chamber configuration. In addition, the electrodes may be configured as needed so as lie within the combustion chamber, yet outside the path of motion of a piston mounted in the chamber. Thus, the benefits of positioning the spark source within the combustion chamber are retained. 
     It should be noted that although the embodiments disclosed herein are described as they may be applied to an internal combustion engine, embodiments of the present invention may be applied to other devices than engines, such as furnace combustors and the like. 
     It will be understood that the foregoing description of the present invention is for illustrative purposes only, and that the various structural and operational features herein disclosed are susceptible to a number of modifications, none of which departs from the spirit and scope of the present invention. The preceding description, therefore, is not meant to limit the scope of the invention. Rather, the scope of the invention is to be determined only by the appended claims and their equivalents.