Abstract:
An arrangement for a reciprocating internal combustion engines is provide that includes a reciprocating main piston and a smaller cell piston which works in cooperation with the main piston to vary the compression ratio of and igniting a fuel-air mixture in a homogenous compression ignition engine. An actuator controls movement of the smaller cell piston relative to movement of the main piston.

Description:
TECHNICAL FIELD  
       [0001]     The embodiment of the disclosed invention relates generally to reciprocating internal combustion engines. More particularly the present invention relates to an engine having a reciprocating main piston and a smaller cell piston which works in cooperation with the main piston to vary the compression ratio of and igniting a fuel-air mixture in a homogenous compression ignition engine.  
       BACKGROUND OF THE INVENTION  
       [0002]     Many forms of non-spark ignition systems are know for use in internal combustion engines. One of the oldest arrangements is the hot bulb ignition typically used with fuels such as crude oil, vegetable oil, and diesel fuel. An external heat source such as a flame is used to heat a protrusion on the engine head known as a bulb. Once the bulb is hot enough, the engine can be started by turning the flywheel. The compression of the air-fuel mixture and the heat in the bulb caused the fuel to ignite and, once working, the bulb would stay hot enough to keep the engine running.  
         [0003]     Another ignition system (the so-called “SmartPlug” system) consists of a pre-chamber containing a catalytic heating element. In this system cold starting requires up to 25 watts per igniter from an external power supply. Once the engine is warmed up under moderate load, the power supply is not required and the system is self-sustaining under load.  
         [0004]     In diesel systems, the fuel injection nozzle creates some turbulence as the fuel is injected into the combustion space. However, the so-called “Lanova” air or energy cell can be used to create the turbulence necessary for proper mixing of the fuel and compressed air in the cylinder of a diesel engine to obtain efficient combustion. A Lanova cell is an auxiliary chamber located in the cylinder head of a divided chamber type. The cell has two rounded spaces that are cast into the cylinder head opposite the fuel injector across the narrow section where the intake and exhaust valve lobes of the main combustion chamber join. Typically the cell volume is less than 20% of the main chamber volume.  
         [0005]     During the compression stroke, the piston forces air into the energy cell. Near the end of the stroke the nozzle sprays fuel across the main chamber where between a third and a half mixes with the hot air and burns at once. The remainder of the fuel enters the energy cell and starts to burn there. The pressure in the cell rises sharply, causing the combustion products to flow at a high velocity into the main combustion chamber and setting up a swirling movement of fuel and air in the lobes. This promotes final fuel-air mixing and ensures complete combustion. The restricted openings between the two cell spaces and the cell and the main chamber control the time and rate of expulsion of the turbulence-creating blast from the energy cell.  
         [0006]     In the Sonex® piston arrangement cavities called “micro-chambers” are formed around the circumference of the piston bowl. The micro-chambers form a segmented ring with each chamber positioned in line with a fuel injector spray. The micro-chambers are connected to the piston bowl by tunnel-like vents arranged so that a small fraction of the fuel can be trapped in the micro-chambers. The flame from the main chamber is quenched by the vent preventing complete combustion in the micro-chambers. Slow and incomplete combustion in the micro-chambers forms highly reactive radicals and intermediate species that exit at high velocity to reduce emissions in standard diesel engines.  
         [0007]     A variable compression ratio (“VCR”) piston typically involves variation in the compression height. A VCR piston requires a means to activate the height variation within a high speed reciprocating assembly. One method is to use hydraulics supplied from the engine lubricating oil to raise and lower an outer piston relative to an inner piston, but reliable control of the necessary oil flow is a problem. In some arrangements a Belville washer has been provided to spring the piston crown upwards against the combustion forces. This is intended to reduce the peak firing loads so that compression ratio variation becomes self-acting rather than externally controlled.  
         [0008]     While these modifications represent general improvements in the state of the art of engine systems providing variable compression ratios, there yet remains room for improvements in this technology.  
       SUMMARY OF THE INVENTION  
       [0009]     The present invention overcomes several problems known in the prior art and provides an advancement in internal combustion engine technology. The present invention provides an internal combustion engine having a cylinder block and a cylinder head. A cell cylinder is formed in the cylinder head. A cell piston is reciprocatingly provided in the cell cylinder. The cell piston is driven by an actuator. A main cylinder is formed in the cylinder block. A main piston is reciprocatingly provided in the main cylinder. A pepperpot having one or more orifices is formed between the cell cylinder and the main cylinder. The pepperpot is insulated from the surrounding cylinder head by an insulating material.  
         [0010]     The cell cylinder and the cell piston are provided to vary the volume of the cylinder and therefore the compression ratio of the complete cylinder system.  
         [0011]     The cell piston is movable between an intake position in which gas is drawn into the cell cylinder through the orifice(s) and a compression position in which gas is forced out of the cell cylinder through the orifice(s). The cell piston is moved to its intake position while the main piston is moving toward its top dead center position. Once the main piston achieves top dead center, the cell piston is moved to its compression position and the gas previously drawn into the cell cylinder is driven out and into the main cylinder. Once compression is effected, the cell piston remains generally in its compression position while the main piston is moved away from the pepperpot on its power stroke.  
         [0012]     The present invention provides the very precise feedback and quick response times absent from the prior art. The present invention provides for a rapid increase in compression pressure and temperature for more positive ignition.  
         [0013]     Other features of the various embodiments of the invention will become apparent when viewed in light of the detailed description of the preferred embodiments when taken in conjunction with the attached drawings and the appended claims.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     For a more complete understanding of this invention, reference should now be made to the embodiments illustrated in greater detail in the accompanying drawings and described below by way of examples of the invention wherein:  
         [0015]      FIG. 1  illustrates a fragmentary, schematic cross-sectional view of an engine provided with the variable compression ratio of the present invention showing the main piston moving toward compression and the small piston moving to allow the gas to move into the air cell;  
         [0016]      FIG. 2  is a view similar to that of  FIG. 1  but showing the main piston at top dead center and the small piston moving toward the main piston to compress the charge in the main cylinder; and  
         [0017]      FIG. 3  is a view similar to that of  FIG. 3  but showing the main piston moving away from top dead center after ignition. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0018]     In the following figures, the same reference numerals will be used to refer to the same components. In the following description, various operating parameters and components are described for plural constructed embodiments. These specific parameters and components are included as examples and are not meant to be limiting.  
         [0019]     With reference to  FIG. 1 , an engine block  10  is illustrated. The configuration of the engine block  10  is shown only for illustrative purposes and is not intended as being limiting. The engine block  10  may find utility in any one of a variety of applications, including automotive vehicles and trucks.  
         [0020]     The engine block  10  has a main cylinder  12  formed therein. A main piston  14  is reciprocatingly provided in the main cylinder  12  in a known manner. The open upper end of the main cylinder  12  is closed by a cylinder head  16 . Conventional engine elements such as intake valves, exhaust valves, a connecting rod and a crankshaft are not illustrated as these components, their arrangement and configurations, are well known to those skilled in the art.  
         [0021]     An air cell  18  is formed in the cylinder head  16 . It is to be noted that while the air cell  18  is shown as being formed in the cylinder head  16 , it may be that the air cell  18  may be alternatively formed in the cylinder block or in the piston. However, in the illustrated embodiment which is intended as being non-limiting the air cell  18  is formed in the cylinder head  16  and is defined by a cell cylinder  20 . A multi-holed pepperpot  22  is formed at the lower end of the cell cylinder  20 . The pepperpot  22  includes at least one orifice and may include two or more orifices, as illustrated in the figures as a pair of orifices  24 ,  24 ′ although it is to be understood that the configuration of the pepperpot  22  is based on appropriately tailored thermal conductivity. An insulating material  25  is provided between the pepperpot  22  and the wall of the cell cylinder  20 .  
         [0022]     The air cell  18  further includes a reciprocating cell piston  26 . Movement of the cell piston  26  between a first or raised position and a second or lowered position varies the volume of the cell cylinder  20  and therefore the compression ratio of the cell cylinder  20  and the main cylinder  12 . An actuator  28  of a known design is provided to selectively move the reciprocating cell piston  26  between the first or raised position and the second or lowered position. The actuator  28  may be part of a mechanical system, such as a camshaft, or may be an electronic or hydraulic system. As a further alternative arrangement a crank-driven piston may be provided having a variable phase angle to allow control over the compression ratio.  
         [0023]     In operation, and referring to  FIG. 1 , as the main piston  14  moves toward the top of the main cylinder  12 , the cell piston  26  moves away from the pepperpot  22  and gas is drawn into the cell cylinder  20 . The effective compression ratio of the combination is lower than that of just the main cylinder  12  and the main piston  14  assembly. This lower compression ratio avoids ignition of the homogenous charge on the upward stroke of the main piston  14 .  
         [0024]     Referring to  FIG. 2 , the main piston  14  has moved to a point around top dead center (“TDC”). At or about this point the actuator  28  drives the cell piston  26  toward the pepperpot  22  thus compressing the charge in the cell cylinder  20 . This forces the hot gas (or the air-fuel mixture) out of the cell cylinder  20  through the orifices  24 ,  24 ′ and into the main cylinder chamber  12 . The hot gas exiting the cell cylinder  26  through the orifices  24 ,  24 ′ formed in the pepperpot  22  provides a higher pressure and temperature in the main cylinder  12  that will ignite the homogeneous charge in the main cylinder  12 , provided that the main charge is rich enough for ignition.  
         [0025]     With the cell piston  26  in its compression position as illustrated in  FIG. 2 , ignition occurs and the main piston  14  is driven in a direction away from the pepperpot  22  as illustrated in  FIG. 3 . The cell piston  26  remains generally in this position until the powerstroke of the main piston  14  is completed and the main piston  14  begins its movement again toward the pepperpot  22 , whereupon the cell piston  26  again begins to move as shown in  FIG. 1 .  
         [0026]     It should be understood that for certain operating conditions the cell piston  26  may be maintained in a fixed position and the pepperpot  22  may, on its own, provide ignition to the charge. With the cell piston  26  in a fixed position, the gas in the main cylinder  12  will enter the cell cylinder  20  on the upstroke of the main piston  14  and will exist the cell cylinder  20  on the downstroke of the main piston  14 . The charge will be heated on both entry and exit to the cell cylinder  20  and will provide an ignition function on exiting the cell cylinder.  
         [0027]     Advantages over existing technology are that controlling the ignition point of the homogeneous charge and high load operation is difficult with today&#39;s indirect methods of adjusting cylinder pressure via variable valve timing or inlet manifold temperature. These methods require very precise feedback and quick response times that are difficult to achieve. The proposed device according to the present invention provides for a rapid increase in compression pressure and temperature for more positive ignition.  
         [0028]     The foregoing discussion discloses and describes exemplary embodiments of the present invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the true spirit and fair scope of the invention as defined by the following claims.