Abstract:
An internal combustion engine includes a pre-chamber. In another aspect, pressure within a pre-chamber is equal to or greater than pressure within a main combustion chamber at least prior to ignition in the main combustion chamber. A further aspect provides a supplemental piston creating pressure and supplying a fuel-air mixture into a pre-chamber, and a spark or glow plug has an end located within the pre-chamber for ignition of the mixture therein. In yet another aspect, internal combustion engine control software automatically controls pressure within a turbulent jet ignition pre-chamber, controls a valve-actuator to admit a fuel-air charge into the pre-chamber, and causes an ignitor to initiate combustion in the pressurized pre-chamber.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application Ser. No. 61/730,184, filed on Nov. 27, 2012, which is incorporated by reference herein. 
     
    
     BACKGROUND AND SUMMARY 
       [0002]    The present application generally pertains to internal combustion engines and more particularly to an internal combustion engine including pre-chamber ignition. 
         [0003]    Various pre-chamber ignition systems have been experimented with in an effort to reduce engine emissions while simultaneously increasing fuel efficiency. Such traditional systems are discussed in E. Toulson, H. Schock and W. Attard, “A Review of Pre-Chamber Initiated Jet Ignition Combustion Systems,” SAE Technical Paper, 2010-01-2263 (Oct. 25, 2010). Further examples of conventional pre-chamber engines are U.S. Patent Publication No. 2012/0103302 entitled “Turbulent Jet Ignition Pre-Chamber Combustion System for Spark Ignition Engine” which published to Attard on May 3, 2012, U.S. Pat. No. 7,107,964 entitled “Control of Auto-Ignition Timing for Homogenous Combustion Jet Ignition Engines” which issued to Kojic et al. on Sep. 19, 2006, and U.S. Pat. No. 6,953,020 entitled “Control of Auto-Ignition Timing for Combustion in Piston Engines by PreChamber Compression Ignition” which issued to Kojic et al. on Oct. 11, 2005; all of which are incorporated by reference herein. It is noteworthy, however, that the Kojic pre-chamber piston is disadvantageously intended to solely compress the pre-chamber mixture to cause auto-ignition without a spark plug or the like. Differently, the Attard device only has fuel injected into the pre-chamber and the fuel-air mixture from the combustion chamber backfeeds into the pre-chamber thereby disadvantageously causing an unknown fuel and air ratio within the pre-chamber. Therefore, neither of the traditional Kojic nor Attard devices precisely control the pre-chamber fuel and air mixture nor do they precisely control the pressure within the pre-chamber. Accordingly, conventional pre-chamber ignition devices make it difficult to ignite lean fuel-air mixtures, especially at lower temperatures. 
         [0004]    In accordance with the present invention, an internal combustion engine includes a pre-chamber. In another aspect, pressure within a pre-chamber is equal to or greater than pressure within a main combustion chamber at least prior to ignition in the main combustion chamber. A further aspect provides a supplemental piston creating pressure and supplying a fuel-air mixture into a pre-chamber, and a spark or glow plug has an end located within the pre-chamber for ignition of the mixture therein. In yet another aspect, internal combustion engine control software automatically controls pressure within a turbulent jet ignition pre-chamber, controls a valve-actuator to admit a fuel-air charge into the pre-chamber, causes an ignitor to initiate combustion in the pressurized pre-chamber, receives a signal corresponding to pressure in the pre-chamber, and receives a signal corresponding to such pressure in a main combustion chamber of an engine block. A method of operating an internal combustion engine in an automotive vehicle is also provided. 
         [0005]    The internal combustion engine of the present invention is advantageous over traditional devices. For example, the present device and method precisely control a pre-chamber fuel and air mixture while also precisely controlling and causing the pre-chamber pressure to be the same as or greater than that of the main combustion chamber during at least one operating condition. This reduces if not entirely prevents backfeeding from the main chamber to the pre-chamber. Furthermore, the present device is expected to significantly improve combustion of a lean fuel-air mixture or one that is heavily diluted with exhaust gas recirculation, in the main combustion chamber, even at lower operating temperatures, which should greatly reduce undesirable NOx emissions while also significantly increasing fuel efficiency. Additional advantages and features of the present invention will become apparent when considering the following description and appended claims as well as the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a cross-sectional view showing an internal combustion engine of the present invention; 
           [0007]      FIG. 2  is a perspective view showing a portion of the internal combustion engine; 
           [0008]      FIG. 3  is an enlarged and fragmentary cross-sectional view, like that of  FIG. 1 , showing a turbulent jet ignition system for the internal combustion engine; 
           [0009]      FIG. 4  is a schemmatic view showing an electrical control system for the turbulent jet ignition system of the internal combustion engine; and 
           [0010]      FIG. 5  is a chart showing expected ignition results in different operating conditions for the internal combustion engine. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    Referring to  FIG. 1 , an internal combustion engine  11  of an automotive vehicle includes an engine block  13  and a cylinder head  15  mounted thereto. A main driving piston  17  operably advances and retracts within a cylinder cavity  19  in order to drive a connecting rod  21  spanning between a pin  23  of piston  17  and a crank shaft  25 . Furthermore, cylinder head  15  includes an intake manifold  31 , an exhaust manifold  33 , a direct (not shown) or port fuel injector  35  and a turbulent jet ignition system  41 . A main combustion chamber  43  is located above main piston  17  partially within cylinder cavity  19  and cylinder head  15 , directly below turbulent jet ignition system  41 . 
         [0012]    Referring now to  FIGS. 2 and 3 , turbulent jet ignition system  41  includes a cup-shaped housing  51  which internally defines the pre-chamber  53  therein. Housing  51  is secured to cylinder head  15  and a cap is in threaded engagement with an upper section of the housing. At least one and more preferably three to ten aperatures  55  are always open and connect pre-chamber  53  to main combustion chamber  43 . Each aperature is approximately  1  mm in diameter. Turbulent jet ignition system  41  further includes an ignitor  61 , such as a spark plug, glow plug or the like, which has an end  63  located within pre-chamber  53  for providing a spark or other heat ignition source for a fuel-rich, fuel-air mixture within pre-chamber  53 . As used herein, “rich” means the actual fuel to air ratio is greater than stoicheometric, and “lean” is less than the stoicheometric fuel to air ratio. 
         [0013]    Additionally, turbulent jet ignition system  41  includes a supplemental piston  65  which moves within a piston housing  67  in response to hydraulic or pneumatic fluid flowing into an inlet port  69  and exiting an outlet port  71 . A biasing compression spring  73  is employed to retract piston  65  when the fluid actuating pressure is removed. Furthermore, a supply valve  75  is connected to a passageway  77  adjacent a bottom of piston housing  67  to operably allow the rich fuel-air mixture into a supplemental piston cavity for subsequent pushing of piston  65  outwardly through a conduit  77 . Conduit  77  connects a bottom of supplemental piston housing  67  to an intermediate portion of a poppet valve passageway  79  via a connecting conduit  81  in the cap. A poppet valve  83  retracts to a nominal position by way of a compression spring  85  and advances when an electro-magnetically operated solenoid  87  is energized. When energized, solenoid  87  causes poppet valve  83  to open which thereby allows the piston-pressurized and rich fuel-air charge to flow from supplemental piston housing  67  into pre-chamber  53  for ignition therein. 
         [0014]    A first pressure transducer  91  is partially located within or is otherwise accessible to pre-chamber  53  for sensing internal pressure therein and a second pressure transducer  93  is partially located within or is otherwise accessible to main combustion chamber  43  for sensing an internal pressure therein. Transducers  91  and  93  are electrically connected to an electronic controller  95 , such as a programmable engine computer having a micro-processor, and non-transient computer ROM or RAM memory, capable of storing and running software including various programmed instructions. 
         [0015]    Controller  95  has programmed instructions automatically controlling pressure within turbulent jet ignition pre-chamber  53  by causing movement of supplemental piston  65  and energization of solenoid  87  to open or close poppet valve  83 . Furthermore, controller has programmed instructions which cause ignitor  61  to create a spark for igniting the rich fuel-air charge in pressurized pre-chamber  53 . Moreover, controller  95  has programmed instructions receiving signals indicative of the sensed pressure in pre-chamber  53  via transducer  91  and main combustion chamber  43  via transducer  93 . The controller thereafter automatically adjusts the pressure in pre-chamber  53 , through piston  65  and valve  83  actuation, in a closed-loop manner for a subsequent cycle based at least on part on the sensed pressure signals. Moreover, the controller has additional programming instructions causing a fuel-air charge to be emitted into the pre-chamber at 0.9          or richer, and the fuel-lean main fuel-air mixture to be injected into the main combustion chamber at a ratio of 1.8          or leaner. The controller will automatically calculate and vary pre-chamber pressure, fuel quantity and ignition timing based on the sensed pressure signals, but also at least partly based on throttle positioning/signals, engine temperature, air temperature and the like. 
         [0016]    The fuel-air mixture is mixed prior to entry into piston housing  67  which supplies pre-chamber  53 . It is noteworthy that piston  65  controls the fuel-air charge pressure in pre-chamber  53  so that the pre-chamber internal pressure matches that of the main combustion chamber to reduce if not eliminate gas flow or backfeeding between the two chambers during compression of driving piston  17  in order to maintain the desired fuel-air ratio in the pre-chamber prior to spark ignition therein. Piston  65  pressurizes pre-chamber  53  on a continuous basis during the driving piston stroke of the engine. It is preferred that the internal pre-chamber pressure be the same as or up to 5% greater than that of the main combustion chamber, at least prior to ignition in the main combustion chamber. This pre-chamber pressurization methodology prevents uneven burning in the pre-chamber due to the added piston-supplied air since supplemental piston  65  is supplying a mixed fuel-air charge and not simply only air or only fuel. The pre-chamber ionization signal, along with the pre-chamber pressure signal, during the pre-chamber combustion period, is used to achieve the desired intensity level of the turbulent jet ignition system  41  by adjusting the dwell current of spark plug ignitor  61 , and the pressure of the trapped fuel-air mixture in pre-chamber  53 . Accordingly, solenoid  87  actuates valve  83  to an open position for emitting the rich fuel-air charge into pre-chamber  53  timed between 50-110° before TDC, and in one configuration it is preferred that the timing be approximately 90° before TDC. 
         [0017]    The air charge in the engine main chamber is regulated using the engine throttle and intake belt timing. The fuel is also injected into the main combustion chamber  43  either through port fuel injection or direct injection. No spark plug is required for main combustion chamber since the lean fuel-air mixture in main combustion chamber  43  is ignited by the previously ignited fuel-air charge pushed through aperatures  55  from the higher pressure pre-chamber  53 . 
         [0018]    The present internal combustion engine and turbulent jet ignition system can use a variety of fuels such as gasoline, syngas, propane, natural gas and the like. The present turbulent jet ignition system has a reduced and slightly retarded ignition delay which advantageously reduces burn variability resulting from the pre-chamber ignition process and permits a wider range of operating conditions as the distributed ignition sites enable relatively small flame travel distances which promote higher burning rates. While the fuel-air mixture in the main combustion chamber can be stoichiometric, it is more advantageous to employ a leaner mixture up to 2          or even 2.5          (for propane and gasoline depending on the engine) thereby burning faster, improving flame propogation in lean mixtures, improving fuel efficiency, and reducing NOx emissions.  FIG. 5  illustrates the expected combustion propogation of spark ignition and jet ignition at different crank angles (“° CA”) and different fuel-air ratios, in an exemplary 1500 revolutions/minute and 3.3 bar IMEPn, operating condition. More complete lean fuel-air combustion is expected in the main combustion chamber using turbulent jet ignition of the present system. 
         [0019]    While various features of the present invention have been disclosed, it should be appreciated that other variations may be employed. For example, supplemental piston  65  is illustrated above and aligned with driving piston  17 , however, alternate supplemental and driving piston configurations and positions can be employed, although various advantages of the present system may not be realized. Additionally, alternate fuel-air passageways, conduits, and ports may be provided, although some advantages may not be achieved. Additionally, it is envisioned that different types of valves, sensors and actuators may be used, but certain benefits may not be achieved. Alternately, variations in the fuel-air mixture can be used, but performance may suffer. Variations are not to be regarded as a departure from the present disclosure, and all such modifications are intended to be included within the scope and spirit of the present invention.