Abstract:
A partial forced induction system is provided that has one or more combustion engine cylinders with each engine cylinder having a first and a second intake valve with individual ports. A source of forced induction in fluid communication with the one or more combustion engine cylinders and urging air into the one or more combustion engine cylinders. A naturally aspirated intake manifold path connecting to each of the first intake valves at each of said one or more engine cylinders. A forced induction intake manifold path connects the source of forced induction to each of said second intake valves at each of the one or more engine cylinders.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority benefit of U.S. Provisional Application Ser. Nos. 61/921,272 filed 27 Dec. 2013; and 61/925,909 filed 14 Jan. 2014; the contents of which hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention generally relates to internal combustion engines; and in particular to partial forced induction system and methods for improved engine performance and efficiency. 
       BACKGROUND OF THE INVENTION 
       [0003]    Recent developments in internal combustion engine technology have simultaneously increased specific power, reduced fuel consumption, and reduced emissions. The performance improvements have been accomplished with the development of multi-valve engines, variable valve timing, direct fuel injection and application of forced induction (either supercharging, turbocharging, turbo-compounding, or a combination of supercharging and turbocharging). 
         [0004]    Forced induction is used to increase engine power and efficiency. A forced induction engine is essentially two compressors in series. The compression stroke of the engine is the main compression that every engine has, and an additional compressor feeding into the intake of the engine makes it a forced induction engine. A compressor supplying a pressurized induction charge into the engine greatly increases the total compression ratio of the entire system, and this additional intake pressure is commonly referred to in the industry as boost. 
         [0005]    A turbocharger relies on the volume and velocity of exhaust gases to spin (referred to herein synonymously as spool) a turbine wheel, which is connected to a compressor wheel via a common shaft. The boost pressure produced can be regulated by a system of release valves and electronic controllers. The chief benefit of a turbocharger is that it consumes less power from the engine than a supercharger; while the main drawback of a turbocharger is that engine response suffers greatly because it takes time for the turbocharger to come up to speed (referred to herein synonymously as spool up). The delay in power delivery from the turbocharger is referred to as turbo lag. Turbocharger design is inherently one of compromise in which a smaller turbocharger will spool quickly and deliver full boost pressure at low engine speeds, but boost efficiency will suffer at high engine revolutions per minute (RPM). It is appreciated that high and low values of RPM with respect to given engine are relative, with high RPM range typically being associated with acceleration of the vehicle. By way of example 3000 RPM is exemplary of a high RPM value for a conventional mid-size 6 cylinder sedan. A larger turbocharger, on the other hand, will provide improved high-RPM performance at the expense of lower RPM response. Other common design issues related to turbochargers include limited turbine lifespan, due to the high exhaust temperatures it must withstand, and the restrictive effect the turbine has upon exhaust flow. Superchargers, in contrast to turbochargers, have almost no lag time to build pressure because the compressor is always spinning proportionally to the engine speed. Superchargers are not as common as turbochargers because superchargers use the torque produced from the engine to operate; and, the torque utilized by the supercharger results in some loss in power and efficiency obtained from the engine. 
         [0006]    An electric forced induction system utilizes an electric motor driven compressor to pressurize the intake air. By pressurizing the air available to the engine intake system, the air becomes denser, and is matched with more fuel, thereby producing increased horsepower. However, the power requirements and costs associated with electrically powering a compressor have limited commercial application of electric forced induction to-date. 
         [0007]    Existing implementations of turbocharging, supercharging, and electric forced induction have met with growing acceptance but have limitations. For example, in turbocharging implementations, it is difficult to optimize compressor efficiency throughout the engine speed range, and that requires a compromise that accepts either lower efficiency and responsiveness at low RPMs to achieve higher efficiency at high rpm; or lower efficiency at high RPM to achieve better responsiveness and efficiency at low rpm. Turbocharging also suffers from turbo lag due to the inertial delay associated with accelerating the turbine wheels. The packaging of hot turbocharger components in the engine compartment is challenging, and there is heat transfer from the compressor to the intake charge under all operating conditions. There is also an undesirable back pressure associated with extracting exhaust heat energy with the turbocharger. In supercharging implementations the power required to drive the supercharger—even when boost is not required (assumes a typical internal compressor by-pass) is a drain on the engine, as well as the power required to overcome supercharger inertia upon acceleration. There is unwanted heat transfer from the supercharger housing to the intake charge under all operating conditions, and additional packaging requirements for the supercharger. In addition, supercharging efficiency decreases at higher engine speeds and airflow. Electric forced induction implementations suffer from high power requirements and high costs associated with electrically powering a forced induction compressor and have limited commercial application to date. 
         [0008]    While there have been many advances in forced induction, further improvements in combustion engine performance and efficiency are needed to meet mileage and performance requirements, while mitigating the problems and design limitations of existing implementations of forced induction. Thus, there exists a need for improved forced induction systems for improving combustion engine performance and efficiency. 
       SUMMARY OF THE INVENTION 
       [0009]    A partial forced induction system is provided that has one or more combustion engine cylinders with each engine cylinder having a first and a second intake valve with individual ports. A source of forced induction in fluid communication with the one or more combustion engine cylinders and supplying air into the one or more combustion engine cylinders. A naturally aspirated intake manifold path connecting to each of the first intake valves at each of said one or more engine cylinders. A forced induction intake manifold path connects the source of forced induction to each of said second intake valves at each of the one or more engine cylinders. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The subject matter that is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and in which: 
           [0011]      FIGS. 1A and 1B  are schematic diagrams of conventional supercharger and turbocharger systems, respectively; 
           [0012]      FIGS. 2A and 2B  are schematic diagrams of a partial supercharging system according to embodiments of the invention; 
           [0013]      FIGS. 3A and 3B  are schematic diagrams of a partial turbocharging system according to embodiments of the invention; 
           [0014]      FIGS. 4A and 4B  are schematic diagrams of a switching valve in induction paths for naturally aspirated and under boost conditions according to embodiments of the invention; 
           [0015]      FIGS. 5A and 5B  are schematic diagrams of alternative check valve induction paths for naturally aspirated and under boost conditions according to embodiments of the invention; 
           [0016]      FIGS. 6A and 6B  are schematic diagrams of an electrical partial forced induction system according to embodiments of the invention; 
           [0017]      FIG. 7  is a valve timing schematic depicting the delayed forced induction intake valve (I) closing compared to the naturally aspirated intake valve (In) closing according to an embodiment of the invention; and 
           [0018]      FIG. 8  is a schematic of a partial turbocharging system with anti-reversion check valves, and a Detail B view of an anti-reversion check valve schematic according to an embodiment of the invention; and 
       
    
    
       [0019]    The detailed description explains the preferred embodiments of the invention 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    The present invention has utility as partial forced induction systems and methods for improved engine performance, responsiveness, and efficiency. Embodiments of the inventive partial forced induction systems also reduce implementation costs, weight, packaging requirements, and thermal loading of an engine. Embodiments of the inventive partial forced induction systems utilize separate induction ports in multi-valve engines, by applying forced induction to only one of each cylinder&#39;s intake valves according to an on demand basis. The fundamental advantage of this inventive approach is that the compressor need not be sized to handle the entire induction airflow. According to the present invention in some embodiments, the forced air induction is actuated under all operating conditions and as such, an inventive system is readily produced that that excludes and is therefore without a forced air induction stopping mechanism. Inventive embodiments of the partial forced induction system utilize direct fuel injection, and multiple intake valves with independently variable timing. Partial Forced Induction is particularly well suited to direct cylinder injection (gas, diesel, natural gas, etc.) because fuel is injected into the entire induction charge under all operating conditions. Independently variable valve timing can be used to optimize engine performance and efficiency under all operating conditions. With normal road load conditions (i.e., when boost is not required to meet vehicle road load demands), intake valve timing can be optimized as it would in a naturally aspirated engine. However, with increased power demand, the turbocharger, supercharger or compressor create a “forced induction” port to increase engine power. With variable valve timing, the intake valve timing is changed such that the naturally aspirated valve closing precedes the timing of the “forced induction” valve such that forced induction valve has a later closing, thus “capturing” the pressurized induction charge. In this manner, a portion of the induction charge by-passes the compressor (typically a turbocharger or supercharger), and the compressor needs only to supply enough pressurized air to “pack” the induction charge to the desired pressure level. 
         [0021]    Alternatively, in other embodiments of the inventive partial forced induction system variable valve timing is not required. An engine with a fixed valve timing configuration can take advantage of the time/transport lag associated with intake gas dynamics. Partial Forced Induction will work with intake valves that have identical timing, but will be limited at the point where the forced intake charge escapes through the naturally aspirated intake valve. One solution to this “reversion” of the forced induction incorporates check valves in the naturally aspirated ports or intake manifold runners to capture the pressurized charge, thus preventing reversion. Alternatively, a single anti-reversion check valve can be incorporated upstream of the individual naturally aspirated intake manifold runners. In either configuration, the improvements to engine performance will be comparable to the embodiments that utilize variable valve timing. Additionally, these configurations with fixed valve timing can still be used in combination with the “cam phasing” utilized on many modern engines. 
         [0022]    In embodiments of the invention, the issue of reversion with fixed valve timing may be addressed by providing intake valves with a fixed timing differential, such that the naturally aspirated valve always closes before the “forced induction” valve. One way in which this fixed timing differential can be accomplished is by splitting the cam lobes that actuate the intake valves so that the naturally aspirated intake valve closing can precede the closing of the “forced induction” valve. This approach can still incorporate “cam phasing”, as utilized on many modern engines. Note also that researchers have experimented with staggered intake valve timing in naturally aspirated engines to increase turbulence in the combustion chamber, through tumble or swirl motions, to create a “fast burn” and further improve engine efficiency. Hence, there is potential for an additional benefit using staggered intake valve timing. 
         [0023]    Embodiments of the inventive partial forced induction systems can also incorporate a switching mechanism that is generically depicted in the accompanying drawings with respect to reference numeral  50  and illustratively includes devices such as a switching valve, a check valve or a combination thereof, such that under normal road load conditions (i.e., when boost is not required to meet vehicle road load demands), the entire induction charge by-passes the turbocharger, supercharger or compressor. However, with increased power demand, a portion of the intake charge is routed from the forced induction device. Incorporation of such a switching mechanism avoids restriction and heat transfer from the forced induction device under road load conditions; improving efficiency and responsiveness. 
         [0024]    Embodiments of the inventive partial forced induction systems provide the following efficiency and implementation advantages for turbocharging, supercharging, and electric forced induction as follows: 
         [0025]    In turbocharging implementations with embodiments of the inventive system there are lower parasitic losses, since the turbocharger compressor only needs to handle 70-75% of the intake charge versus a conventional turbocharging implementation. This 25-30% lower range of airflow requirements for partial turbocharging allows selection of turbocharger aspect ratio dimensions that better optimize low/high speed trade-offs. The 25-30% reduced airflow requirements with partial turbocharging yield smaller, less expensive and lighter turbochargers. In some applications, a twin-turbocharger or twin-scroll system can be replaced with a simpler single turbocharger and still provide equivalent responsiveness and performance. There is a potential for proportionately reduced intercooler size and cost due to the 25-30% lower quantities of air that pass through the turbocharger. The lower rotating inertia of a smaller turbocharger reduces turbocharger “lag”, and the fact that the 100% of the exhaust flow is used to power only 70-75% of the induction flow also makes for a more responsive turbocharger. This smaller turbocharger is easier to package, and reduces thermal loads in the engine compartment. A reduction in intake air charge temperatures can be expected when a switching mechanism is incorporated, since heat transfer from the compressor only occurs under boost, and when it does, only to a portion of the intake charge. 
         [0026]    In supercharging implementations with embodiments of the inventive system there are 25-30% lower compressed airflow requirements associated with partial forced induction that allow for a smaller, less expensive, and lighter supercharger, requiring proportionally less engine power to drive the smaller supercharger, thus reducing parasitic losses. Furthermore, a smaller supercharger has lower rotating masses and inertia, making the system even more responsive. Partial supercharging utilizing a switching mechanism reduces heat transfer to the intake charge, since heat transfer only occurs under boosted conditions, and when it does, heat is transferred to only a portion of the intake charge; consequently the intercooler size and cost may be reduced, as well as reducing packaging requirements. The proportionately smaller superchargers is made to be more efficient throughout the speed range by the present invention. The lower rotating mass of partial supercharging in some inventive embodiments allows for replacement of a by-pass system, with a clutched system, further reducing engine parasitic losses when no boost is required. 
         [0027]    Electric forced induction implementations with embodiments of the inventive system can make electrification of the compressor commercially viable, since a 25-30% smaller compressor is required, with corresponding reduction of the electric motor sizing. The smaller compressor and electric motor translate into a reduced system cost and weight. Furthermore, the 25-30% lower range of airflow requirements for partial forced induction allow for improved optimization of the compressor sizing. Electrification using partial forced induction can further reduce parasitic losses from the engine output thereby making the system more efficient. Due to the 25-30% lower quantities of air, there is also potential for reduced intercooler size and cost. Through electrification, turbo lag can be virtually eliminated, as the electric motor driving the compressor can be switched on in anticipation of boost requirements. The smaller electrified compressor allows for package flexibility and eliminates the engine compartment thermal loads associated with turbochargers. These proportionately lower power requirements for the electrically driven compressor makes it easier to integrate the system with other electrical power systems, such as electrified stop/start, or hybrid vehicle systems. 
         [0028]    While implementations of embodiments of the present invention are applicable to a whole range of internal combustion engines, it is exemplified herein in the following figures as applied to a conventional 4-cylinder, 4-valve (2 intake (I), 2 exhaust (E)) engine. All other configurations (3-cylinder, 4-cylinder, I6, V6, V8, etc.) are made up of the essential building blocks described herein. In this example, direct gas or diesel injection is assumed, although embodiments of partial supercharging can be applied to carbureted, or port injected engines as well. 
         [0029]    Referring now to the figures,  FIGS. 1A and 1B  show conventional prior art implementations of supercharging system  10  and turbocharging system  30 , respectively for comparison to the inventive embodiments of  FIGS. 2A-9 . As shown in  FIG. 1A , filtered air from air filter  18  is fed via line  20  into supercharger  22  which is driven by the engine  12  via drive mechanism  28 . The charged air output from the supercharger  22  is supplied to the intercooler  26  via line  24 . It is appreciated that in numerous embodiments of the present invention, an intercooler is not present. The cooled supercharged air is then supplied via the intake manifold  16  to both of the intake valves (I) of each of the cylinders  14  of engine  12 . In a similar manner in  FIG. 1B , filtered air from air filter  18  is fed via line  20  into turbocharger  32  which utilizes heated exhaust gas from the exhaust valves (E) via exhaust manifold  34 . The charged air output from the turbocharger  32  is supplied to the intercooler  26  via line  24 . The cooled supercharged air is then supplied via the intake manifold  16  to both of the intake valves of each of the cylinders  14  of engine  12 . 
         [0030]      FIGS. 2A and 2B  are schematic diagrams of a partial supercharging system  40  according to embodiments of the invention both without ( FIG. 2A ) and with a switching mechanism  50  ( FIG. 2B ). The intake manifold using partial forced induction splits the induction flow into two paths: ( 1 ) a naturally aspirated intake manifold path  54  connected to the naturally aspirated ports and intake valves (In), and ( 2 ) a “forced induction” intake manifold path  48  connected to the forced induction intake ports and valves (I). Note that the supercharger  42  and intercooler  46  with partial supercharging are schematically depicted as smaller in size than their conventional counterparts in  FIG. 1A , since they handle reduced air flow. In  FIG. 2A  an engine driven supercharger  42  receives air from the air filter  18  and supplies compressed air through the intercooler  46  to the forced induction intake manifold path  48 . In  FIG. 2B  a switching mechanism  50  as used herein illustratively includes a switching valve, or alternatively a check valve detailed with respect to reference numeral  52 , located upstream of the force induction intake manifold path, can alternatively connect to uncompressed air from the air filter  18 , or direct compressed air from the engine driven supercharger  42 , through the intercooler  46  to the forced induction intake manifold path  48 . It is appreciated that in some inventive embodiments the switching mechanism is located within the forced induction portion of the engine and mounted therein. It is further appreciated that the switching mechanism  50  in other inventive embodiments is positioned upstream of the supercharger  42  relative to air flow to yield an operative inventive device that retains the benefits of the present invention (not shown). 
         [0031]      FIGS. 3A and 3B  are schematic diagrams of a comparison of a partial turbocharging system  60 , where the partial forced induction is applied in a similar manner to the partial supercharging described in  FIGS. 2A and 2B . The intake manifold using partial forced induction splits the induction flow into two paths: (1) a naturally aspirated intake manifold path  54  connected to the naturally aspirated ports and intake valves (In), and (2) a “forced induction” intake manifold path  48  connected to the forced induction intake ports and valves (I). Note that the turbocharger  62  and intercooler  46  with partial forced induction are schematically depicted as smaller in size than their conventional counterparts of  FIG. 1B  since they handle reduced airflow. In  FIG. 3A  the turbocharger  62  receives air from the air filter  18  and supplies compressed air through the intercooler to the forced induction manifold path  48 . In  FIG. 3B , a switching mechanism  50  as used herein illustratively includes a switching valve, or alternatively a check valve  52 , located upstream of the force induction intake manifold path  48 , can alternatively connect to uncompressed air from the air filter  18 , or direct compressed air from the turbocharger  62 , through the intercooler  46  to the forced induction intake manifold path  48 . It is appreciated that in some inventive embodiments the switching mechanism is located within the forced induction portion of the engine and mounted therein. It is further appreciated that the switching mechanism  50  in other inventive embodiments is positioned upstream of the turbocharger  42  relative to air flow to yield an operative inventive device that retains the benefits of the present invention (not shown). 
         [0032]      FIGS. 4A and 4B  are schematic diagrams of a switching valve  50  in induction paths for naturally aspirated and under boost conditions according to embodiments of the invention. The switching valve  50  incorporates a valve gate  56 . In the naturally aspirated mode, as shown in  FIG. 4A , the valve gate  56  closes off the intake path from the supercharger and intercooler, and simultaneously opens the path from the air filter to the forced induction manifold. Under boost, as shown in  FIG. 4B , the valve gate  56  is switched to close the path from the air cleaner, and opens the path from the supercharger and intercooler to the forced induction manifold. Note that the switching valve  50  can be either passively or actively operated. For passive operation, the valve gate  56  is spring loaded to close the path from the supercharger and intercooler in the naturally aspirated mode. Under boost, pressure from the supercharger overcomes the spring bias pressure on the valve gate  56 , opening the connection to the forced induction manifold, while simultaneously closing the path from the air filter. For an actively operated switching valve  50 , the valve gate  56  is moved from the normally closed naturally aspirated position to the boost position by a signal from the electronic engine controller, where the signal is predominantly derived by power demand deduced from manifold pressure. 
         [0033]      FIGS. 5A and 5B  are schematic diagrams of alternative check valve  52  for induction paths for naturally aspirated and under boost conditions according to embodiments of the invention. The check valve  52  is an alternative to the switching valve  50  described in  FIGS. 4A and 4B , where check valve  52  is incorporated within a “T” or “Y” shaped connector  58  between the air filter  18 , intercooler  46 , and forced induction intake manifold path  48 . The check valve  52  is located within the connector  58  such that it freely allows induction air to pass from the air filter  18  to the forced induction intake manifold port  48  when in the naturally aspirated mode. When the compressor (e.g., supercharger  42 ) provides boost, however, the check valve  52  prevents the boosted induction charge from reverting to the air filter  18 , thus directing it to the forced induction intake manifold path  48 . Typical check valves that can be employed include flapper valves and reed valves. 
         [0034]      FIGS. 6A and 6B  are schematic diagrams of an electrical partial forced induction system  70  according to embodiments of the invention that operates in a similar manner to the partial supercharging described in  FIGS. 2A and 2B , respectively. As shown in  FIG. 6A , the intake manifold using partial forced induction splits the induction flow into two paths: (1) a naturally aspirated intake manifold path  54  connected to the naturally aspirated ports and intake valves (In), and (2) a “forced induction” intake manifold path  48  connected to the forced induction intake ports and valves (I). The compressor  74 , driven by an electric motor  72 , receives air from the air filter  18  and provides compressed air through the intercooler  46  to the forced induction intake manifold path  48 . As with the supercharger and turbocharger applications, the compressor  74  and intercooler  46  are smaller than that required for a conventional application due to the reduced airflow requirements. The compressor  74  can be either positive displacement, or centrifugal, although centrifugal is probably more efficient in most cases. The smaller compressor  74  allows sizing of a less powerful motor  72 , making such an application more commercially viable. In  FIG. 6B , a switching mechanism  50  as used herein illustratively includes a switching valve, or alternatively a check valve  52 , located upstream of the force induction intake manifold path, can alternatively connect to uncompressed air from the air filter  18 , or direct compressed air from the compressor  74  driven by an electric motor  72 , through the intercooler  46  to the forced induction intake manifold path  48 . As with the supercharger and turbocharger applications, the compressor  74  and intercooler  46  are smaller than that required for a conventional application due to the reduced airflow requirements. It is appreciated that in some inventive embodiments the switching mechanism is located within the forced induction portion of the engine and mounted therein. In certain embodiments the electric motor is connected to an electric power supply system of other regenerative engine systems, such as electrified stop/start, or hybrid powertrains. It is further appreciated that the switching mechanism  50  in other inventive embodiments is positioned upstream of the compressor  74  relative to the airflow to yield an operative device that retains the benefits of the present invention (not shown). 
         [0035]    In an embodiment of this invention that utilizes direct fuel injection, and multiple intake valves with independently variable timing, intake and exhaust valve timing can be optimized in the same manner as conventional engines under normally aspirated operating conditions. Under boost, however, the timing of the intake valves is split according to whether the intake valve is connected to the naturally aspirated intake manifold, or forced induction intake manifold. As depicted in  FIG. 7 , both intake valves open at the same time (nominally Top Dead Center (TDC), however, under boost, intake valve timing is changed so that the naturally aspirated valve closing (nominally Bottom Dead Center (BDC)) precedes the timing of the “forced induction” valve; such that the forced induction valve has a later closing  91 —“capturing” the pressurized induction charge. 
         [0036]    Partial Forced Induction can be applied to internal combustion engines without fully independently variable valve timing. Such an approach takes advantage of the transport time lag associated with the intake gas dynamics. Partial forced induction will work with intake valves that have identical timing, but the amount of boost achieved may be limited by the transport time between the boosted intake valve and naturally aspirated intake valve. Boost pressures are limited by the time it takes for the boosted intake charge to escape through the open naturally aspirated intake valve, in a condition called reversion. 
         [0037]    Referring to  FIG. 8 , this reversion of pressurized air through the naturally aspirated intake vale can be minimized by the incorporation of anti-reversion check valves  90  located in the naturally aspirated intake valve ports (In) or individual naturally aspirated intake manifold runners. In  FIG. 8 , partial forced induction of a turbocharger application is depicted. Check valves  90  (for example, flapper or reed valves) are used to prevent backflow of the pressurized intake charge into the naturally aspirated intake manifold, thus capturing the boosted intake charge within the combustion chamber. Alternatively, a manifold anti-reversion check valve  92  can be incorporated in the naturally aspirated intake manifold upstream of the individual runners, as shown. Note that “cam phasing” used on many of today&#39;s engines can still be incorporated with either approach. 
         [0038]    Another method of applying forced induction valve timing is to incorporate intake cams with split lobes that actuate the valves. As depicted in  FIG. 7 , both intake valves open at the same time (nominally Top Dead Center (TDC), however, intake valve timing is changed so that the naturally aspirated valve closing (nominally Bottom Dead Center (BDC)) precedes the timing of the “forced induction” valve; such that the forced induction valve has a later closing  91 —“capturing” the pressurized induction charge. Traditional cam phasing can still be employed with this approach. This split lobe cam approach can also be used in concert with the anti-reversion check valves. 
         [0039]    The foregoing description is illustrative of particular embodiments of the invention, but is not meant to be a limitation upon the practice thereof. The following claims, including all equivalents thereof, are intended to define the scope of the invention.