WO2004076831A2

WO2004076831A2 - Controlled auto-ignition engine

Info

Publication number: WO2004076831A2
Application number: PCT/US2004/004682
Authority: WO
Inventors: Edward Charles Mendler
Original assignee: Edward Charles Mendler
Priority date: 2003-02-24
Filing date: 2004-02-17
Publication date: 2004-09-10
Also published as: WO2004076831A3

Abstract

The problem of poor control of combustion timing in homogeneous charge compression (HCCI) engines is substantially eliminated by opening the exhaust valve (6) during the intake stroke, using the throttle (10) to precisely control large internal exhaust gas recirculation flow rates, and using adjustable intake valve control to establish the volume of the unburned combustion charge trapped within the firing cylinder (2). Two variable fluid flow control devices are used for controlling air intake, exhaust gas recirculation and engine power. Air intake is primarily controlled by variable intake valve control, freeing up the throttle for control of exhaust gas recirculation. Precise real-time control of large volumes of exhaust gas recirculation is used for controlling HCCI ignition timing. HCCI combustion provides large fuel economy benefits over spark ignition combustion.

Description

CONTROLLED AUTO-IGNITION ENGINE

PROVISIONAL APPLICATION REFERENCE

This application relates to United States

Provisional Application Ser. No. 60/449, 658 having a filing date of February 24, 2003, and

Provisional Application Ser. No. 60/472,366 having a filing date of May 20, 2003.

BAKGROUND OF THE INVENTION

Controlled auto-ignition (CAI) also referred to as homogeneous charge compression ignition (HCCI) is a new combustion process different from both gasoline spark-ignition (SI) combustion and Diesel combustion. During CAI combustion, a weak fuel/air mixture is raised to a high enough temperature to initiate auto ignition. The fuel/air mixture ratio is too weak for harsh detonation to occur, and cylinder pressure rises at an acceptable rate without detrimental engine knocking.

Attaining a high enough temperature for CAI combustion to occur in a weak fuel/air mixture has proven difficult to achieve. Charge temperature can be increased by recirculating exhaust gas back into the intake charge. In conventional engines exhaust gas recirculation (EGR) is increased by increasing the intake and exhaust valve overlap period, and/or modestly delaying exhaust valve closing and/or modestly delaying intake valve opening. The amount of valve overlap that can be used and the lateness of exhaust valve closing is limited, however, because the valves must be almost closed when the piston is near top-dead-center (TDC) in order to avoid piston to valve strike. Consequently, 4-stroke engines generally do not have enough EGR to provide a hot enough charge to trigger CAI combustion.

Another approach is to use so called external EGR, where exhaust gas is fed from the exhaust manifold into the intake manifold through a return duct and a flow rate control valve. A problem with this approach is that the exhaust gas cools down too much, and is not hot enough to support CAI combustion at low power levels. Additionally, the external EGR loop may not have a fast enough response for control of CAI combustion through rapidly changing power levels, such as those common to automobiles.

CAI has been achieved in a number of research engines, however the conditions that provide CAI are markedly dissimilar to the conditions found in SI and Diesel engines. SAE papers 2001-01-1030 and 2001- 01-3608 describe an engine that has achieved CAI over a relatively broad range of low power and low brake mean effective pressure (bmep) levels by using valve cams that provide an early closing exhaust valve and a late opening intake valve in order to trap exhaust gas in the cylinder, the exhaust gas being necessary for both increasing charge temperature sufficiently for CAI to occur and for diluting the charge sufficiently to slow combustion and prevent detonation. A problem with the engine is that high engine bmep and high power levels cannot be attained with the valve cams that provide CAI combustion, because the CAI cams provide relatively poor volumetric efficiency and relatively poor air flow rates into the engine. The problem of low power output is significant, firstly because the reduction in power would not be acceptable to prospective consumers of automobiles having these under powered engines, and secondly because very significant further improvement in fuel economy is achieved by reducing engine displacement and increasing engine power density, e.g., horsepower per liter (hp/L), to attain about the same power but from a smaller engine. This strategy is compromised if the valve cams do not support high hp L values from being attained. Supercharging could be used, however this would add expense and yield relatively poor engine efficiency during supercharged operation because the supercharging would have to overcome the airflow restriction of the CAI valve timing. Another problem with the engine is about a 10 percent loss of indicated efficiency due to the compression and expansion of the recycled exhaust gas when both intake and exhaust valves are closed.

SAE paper 2001-01-0549 describes another engine that has achieved CAI by opening the exhaust valve at a conventional time (just before piston bottom dead center, BDC), but holding the exliaust valve fully open well into the intake stroke, and in one case holding the exhaust valve open for more than one crankshaft rotation. With this strategy exhaust gas reenters the cylinder causing the following combustion charge to be hot enough for CAI to occur. It appears that the exhaust valve is also opened to only about one third of the valve lift height that provides maximum power, presumably to further retain exhaust gas in the cylinder. Opening the exhaust valve to about only one third of the maximum power value also permits the engine to be free revving with no possibility of piston to exhaust valve strike at the 10:1 compression ratio used in the research engine. Power is controlled by adjusting the opening and closing timing of the intake valve, and the traditional throttle is not used in order to eliminate throttling losses, also known as pumping losses. The valves are opened and closed by an electro-hydraulic servo instead of by a traditional camshaft, in order to provide adjustable valve opening and closing timing. A problem with this system is that the electro-hydraulic servo valve actuators are expensive and have a high power consumption, which partially offsets the fuel economy gains of CAI combustion. High power output can not be attained with the CAI exhaust valve lift profile because the late exhaust valve closing causes too much exhaust to reenters the cylinder. The exhaust valve opening during the intake stroke is shown to be large relative to the intake valve opening, and in one case the exhaust valve opening during the intake stroke is larger than the intake valve opening during the intake stroke, and consequently a high percentage of exhaust gas is drawn into the cylinder leading to a low maximum power output. The exhaust lift profile can be adjusted with the electro-hydraulic servo valves, however as just mentioned the electro-hydraulic servo valves are expensive.

Objectives of the present invention are to provide hot EGR as needed for robust CAI combustion while also providing valve cams for high power levels. Other objectives include a low cost, a fast response, and precise control of the EGR flow rate. Further objectives include improving the efficiency and lowering the emissions of spark ignition and Diesel engines.

SUMMARY OF THE INVENTION

According to the present invention an internal combustion engine has at least two variable fluid flow control devises for controlling air intake, exhaust gas recirculation and engine power. Air intake is primarily controlled by variable intake valve control, freeing up the throttle for control of exhaust gas recirculation. In the preferred embodiment of the present invention, the exhaust valve opens a second time during the intake stroke of the engine during selected engine operating conditions. With the exhaust valve open during the intake stroke, throttling draws exhaust gas from the exhaust manifold back into the firing cylinder. The throttle provides precise control of intake manifold pressure, and in turn precise control of exhaust gas recirculation. In the preferred embodiment of the present invention, the timing of intake valve closing is adjusted to control the intake volume trapped within the engine cylinder. Throttling establishes the ratio of exhaust gas to fresh air, and adjustable intake valve control establishes the volume or size of the mixture trapped within the cylinder.

Precise control of large volumes of exhaust gas recirculation are used according to the present invention for controlled auto ignition combustion. Controlled auto ignition combustion provides large fuel economy benefits over spark ignition combustion. According to the present invention, large volumes of exhaust gas reenter the firing cylinder as exhaust gas recirculation (EGR), with the throttle providing precise control of the EGR flow rate. The exhaust gas has a high temperature, sufficient to cause controlled auto ignition within the firing cylinder. Airflow is primarily controlled by variable intake valve means. During the controlled auto ignition mode of combustion, the fuel air mixture ratio is adjusted to provide a very lean mixture for attaining high efficiency and avoiding detrimental detonation or engine knock.

Transition from the spark ignition mod of combustion to the controlled auto ignition mode of combustion is accomplished according to the present invention, by using the two variable fluid flow control devises for presetting the intake manifold pressure needed for controlled auto ignition combustion, and controlling air intake with the variable intake valve control means prior to transition to the controlled auto ignition mode of combustion. The manifold pressure is set in advance (during the spark ignition mode of combustion) so that when the exhaust valve is activated to open during the intake stroke, the ideal amount of EGR will be immediately provided for the controlled auto ignition mode of combustion. After the controlled auto ignition mode of combustion has been activated, according to the present invention, the fuel to air mixture ratio is adjusted, and the air intake flow rate is adjusted primarily with the variable intake valve means, to provide the desired torque or brake mean effective pressure (bmep).

Transition from the controlled auto ignition mode of combustion to the spark ignition mode of combustion is preferably accomplished largely in the reveres order. One method for changing from the controlled auto ignition mode of combustion to the spark ignition mode of combustion includes the steps of first operating the engine in the controlled auto ignition mode with the exhaust valve opening during the exhaust stroke and also during the intake stroke with throttling to bring EGR into the cylinder; second discontinuing opening of the exhaust valve a second time during the intake stroke to stop drawing large volumes of EGR from flowing into the cylinder; and third adjusting the throttle and/or fuel flow rate to maintain approximately the same bmep or torque as during the controlled auto ignition mode of combustion. Alternatively, the intake valve timing may be adjusted to maintain approximately the same bmep, torque, and engine power.

Significant benefits of the present invention include precision control of large flow rates of EGR beneficial for spark ignition, controlled auto ignition and Diesel modes of combustion; a method of transitioning from the spark ignition mode of combustion to the controlled auto ignition mode of combustion and back again; and control of power output during the controlled auto ignition mode of combustion. Further benefits of the present invention include improved efficiency and lower emissions of spark ignition and Diesel engines. Other significant benefits of the present invention include a fast response and a low cost.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is intended to illustrate the gas flow system of an engine according to the present invention having means for controlling large internal exhaust gas recirculation flow rates.

Fig. 2 is intended to illustrate the valve control systems for the engine shown in Fig. 1.

Fig. 3 is intended to illustrate an adjustable exhaust valve mechanism.

Fig. 4 illustrates intake and exhaust valve lift curves relative to crankshaft rotational degrees.

Fig. 5 is intended to illustrate the timing of valve opening events according to the present invention.

Fig. 6 illustrates an optional exhaust valve lift profile.

Fig. 7 is similar to Fig. 4, but shows phase shifted intake and exhaust valves.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Fig. 1 is intended to illustrate an engine according to the present invention having means for precisely controlling large internal exhaust gas recirculation flow rates and engine power. The reciprocating piston four stroke engine 1 has a first cylinder 2 having a compression ratio CR, one or more intake valves 4, one or more exhaust valves 6, and an intake manifold 8 having an intake manifold pressure 9 and a throttle 10 for controlling the intake manifold pressure. Air 12 flows into intake manifold 8 during operation of engine 1. Engine 1 further has an exhaust manifold 14 and optionally a catalytic converter 16. Exhaust gas 18 from the firing cylinders is eventually exhausted to the atmosphere.

Engine 1 may include one or more fuel injectors 20 or other fuel delivery means such as a carburetor or direct in-cylinder fuel injector for gasoline, Diesel, or another type of fuel (not shown). Engine 1 may include one or more spark plugs 22. The engine may operate as a Diesel engine according to the present invention, and in such case a spark plug is generally not employed. Engine 1 further has a trapped residuals ratio, the trapped residuals ratio is equal to the ratio of fresh intake air to exhaust gasses trapped in the first cylinder just prior to the combustion period. The trapped exhaust gasses may contain significant amounts of unburned oxygen, and in particular if the engine is operating with a lean fuel to air mixture ratio. The engine will generally have only trace amounts of unburned oxygen in the exhaust gas when the engine is operating with a stoichiometric or rich fuel to air mixture ratio.

Referring now to Figs. 1 and 2, preferably engine 1 has adjustable intake valve means for controlling the amount of air trapped in the first cylinder. The preferred method of adjustable intake valve means 24 is shown in Fig. 2, although other functional methods of adjustable intake valve means may be used according to the present invention. Preferably, according to the present invention engine 1 has at least two intake valves 4a and 4b per cylinder (illustrated with dashed lines) and means for adjusting the closing timing of at least one of the two intake valves, such as a phase shifter 26. Specifically, according to the present invention, the closing timing of the first intake valve 4a is adjusted relative to the closing timing of the second intake valve 4b to control engine power and/or to control the amount of intake air 12 trapped in the first cylinder 2. Adjustable intake valve means 24 includes a first camshaft 28 for opening the first intake valve 4a, and a second camshaft 30 for opening the second intake valve 4b acting through a rocker 32. Rocker cam 33 activates rocker 32, and intake cam 5a opens intake valve 4a. Camshaft 30 may be driven by a sprocket or pulley 34, and camshaft 28 is preferably driven by camshaft 30 acting through phase shifter 26. The camshafts having bearings 31. Adjustable intake valve means 24 preferably provides a contiguous range of trapped intake volumes, thereby providing continuous control of the amount of air intake, and engine power.

Referring now to Figs. 2 and 3, one or more exhaust valves 6 may have adjustable exhaust valve means. The preferred method of adjustable exhaust valve means 36 is shown in Figs. 2 and 3, although other functional methods of adjustable exhaust valve means may be used according to the present invention. Fig. 3 show an exhaust tappet 38 actuated by either primary cams 40 or a secondary exhaust cam 42. Tappet 38 in turn opens valve 6. Spring 44 is used to close valve 6. Referring now to Figs. 1 and 3, engine 1 has a controller 46 for controlling engine operational settings. Engine 1 includes a switch or hydraulic valve 48 or other means for switching cam lob profiles used to open exhaust valve 6, valve 48 preferably being controlled by controller 46.

Referring now to Fig. 4, exhaust curve 50 is intended to illustrate the preferred lift profile of exhaust valve 6 generated by primary cams 40. Fig. 4 schematically illustrates valve lift on the vertical axis and crankshaft rotation in degrees on the horizontal axis. BDC indicates the "bottom dead center" location of the piston, which is furthest from the cylinder head and occurs approximately 180 crank angle degrees before the piston "top dead center location" indicated as TDC in Fig. 4. Minor differences in crank angle timing may occur in engines where the crankshaft is slightly offset from the cylinder axis, however such small differences are not significant to the scope of the present invention. Fig. 5 is a polar diagram that also shows the timing of valve opening. Referring now to Figs. 3, 4 and 5, EGR curve 52 is intended to illustrate the preferred lift profile of exhaust valve 6 generated by secondary exhaust cam 42. "EGR" refers generally to exhaust gas recirculation. Referring now to Figs. 2, 4 and 5, intake curve 54 is intended to illustrate the lift profile of intake valve 4b generated by intake rocker 32. Referring now to Figs. 1 , 4 and 5, the first cylinder 2 has an intake or first stroke 56 for drawing air into cylinder 2 through the one or more intake valves 4a and 4b, a compression or second stroke 58 for compressing the air in cylinder 2, a fuel to air mixture ratio 60 and means for adjusting the fuel to air mixture ratio 20, a combustion period 62 for combustion of the compressed fuel and air mixture 60, a power or third stroke 64 for expanding the high pressure combustion products for producing useful power, and an exhaust or forth stroke 66 for exhausting the combustion products through one or more exhaust valves 6.

The first intake valve curve or lift profile 54 is functionally open for a portion of the intake or first stroke 56, and the first exhaust valve curve or lift profile 50 is functionally open for a portion of the exhaust or forth stroke 66. According to the present invention, the EGR curve or second exhaust valve lift profile 52 for at least one of exhaust valves 6 is functionally open during a portion of the intake or first stroke 56 during selected periods of engine operation. As described earlier, the first cylinder 2 including activation means 48 for activating the EGR curve or second exhaust valve lift profile 52 during the intake or first stroke 56 during selected periods of engine operation, the activation means further being capable of both activating and deactivating the EGR curve or second exhaust valve lift profile 52.

The present invention provides both a method and apparatus for precisely controlling large internal exhaust gas recirculation levels an engine power. The large internal exhaust gas recirculation levels are used for controlled auto ignition combustion and/or for improving spark ignition and/or Diesel modes of combustion.

According to the present invention, the method of controlling large internal exhaust gas recirculation flow rates and engine power has the steps of, opening exhaust valve 6 during the intake or first stroke 56 with the adjustable exhaust valve means 36, adjusting the manifold pressure 9 with the throttle 10 to provide a large and controlled the internal exhaust gas flow rate from exhaust manifold 14 into the first cylinder 2, and adjusting the amount of intake air 12 trapped in first cylinder 2 with the adjustable intake valve means 24 to control engine power.

Preferably manifold pressure 9 is reduced to provide a trapped residuals ratio greater than 40 percent to support stable controlled auto ignition and high engine efficiency. Preferably EGR curve or second exhaust valve lift profile 52 is made large enough so that a large trapped residuals ratio can be attained with only a modest reduction in manifold pressure 9. Reduced manifold pressure causes engine pumping losses and a subsequent reduction in efficiency. Consequently it is valuable to attain the desired amount of trapped residuals with the minimum reduction in manifold pressure 9. According to the present invention, preferably a trapped residuals ratio greater than 40 percent is attained with a manifold pressure greater than one half of atmospheric pressure, and ideally with a manifold pressure closer to 10% below atmospheric pressure. According to the present invention, the EGR flow rate is quickly and precisely controlled by the throttle for CAI combustion over varying and transient engine power levels. A relatively small manifold vacuum draws a large amount of exhaust gas into the cylinder, and therefore high EGR flow rates can be achieved with minimal throttling or pumping losses. It should be noted that at light engine loads less fresh air enters the engine, and therefore less throttling is needed to provide the desired amount of EGR.

During the controlled auto ignition mode of combustion, the trapped residual ratio may be adjusted for establishing optimum ignition timing and/or timing of the combustion period and/or to ensure stable and robust combustion and/or to reduce emission levels. The fuel to air ratio may also be adjusted to further control engine power and/or combustion stability and/or to provide low emission levels. The trapped residual ratio and the fuel to air ratio and the trapped amount of fresh intake air are preferably concurrently adjusted to provide the desired amount of power, optimum efficiency, minimum emissions, and combustion stability.

Low cost is a significant benefit of the present invention. The trapped residuals ratio is adjusted by adjusting manifold pressure 9 with throttle 10. Preferably expensive adjustable exhaust valve control system are not used, such as systems that have the capability of changing the shape of EGR curve 52 in order to control the trapped residuals ratio. While these systems may be used in some embodiments of the present invention, in the preferred embodiment of the present invention a constant shape EGR curve or second exhaust valve lift profile 52 is used to minimize cost and also to avoid power lost to driving the adjustable exhaust valve systems.

Referring now to Fig. 4 and 5, engine 1 has a valve overlap duration 68 during selected periods of engine operation in some embodiments of the present invention. The valve overlap duration is the crank angle duration where an intake valve 4 and an exhaust valve 6 in the first cylinder 2 are both open, measured with 1.27 millimeter valve lift off from the valve seats. The valve overlap duration has a first minimum valve overlap duration during the engine operating conditions when the EGR curve or second exhaust valve lift profile 52 is inactive, and/or during periods of engine operation when controlled auto ignition is not being used. The valve overlap duration has a second minimum valve overlap duration during the engine operation conditions when the EGR curve or second exhaust valve lift profile 52 is active, and/or during periods of engine operation when controlled auto ignition is being used. Cost can also be minimized in some embodiments of the present invention by attaining controlled auto ignition according to the present invention without using adjustable valve systems that change the valve overlap duration 68, for example when intake and exhaust valves are opened by the same camshaft. It should also be noted that the valve overlap period or duration can have a value of zero in some embodiments of the present invention. Preferably, manifold pressure 9 is adjusted to provide a trapped residuals ratio greater than 40 percent, and the first minimum valve overlap duration is equal to the second minimum valve overlap duration, to provide a lower cost than systems having an adjustable overlap duration. According to the present invention, the first intake valve lift profile 54 preferably overlaps the first exhaust valve lift profile 50 during the controlled auto ignition mode of operation, thereby providing a simple and low cost valvetrain. In some embodiments of the present invention, valve overlap may not be present during the controlled auto ignition mode of combustion.

According to the preferred embodiment of the present invention, adjustable intake valve means 24 has means for providing a contiguous range of air trapped in first cylinder 2 for a given throttle position and manifold pressure 9. In more detail, preferably adjustable intake valve means 24 is used to continuously adjust the air flow rate for airflow and/or varying power needs.

According to the present invention, the adjustable valve means preferably controls the volume of gas trapped in first cylinder 2 without causing a reduction in the pressure within the first cylinder 2 as the volume trapped within the cylinder is reduced. Objectively, when a small volume is trapped within the cylinder, cylinder pressure is no smaller than when a large volume is trapped within the cylinder. For comparative purposes, cylinder pressure should be measured at a crank angle as close to BDC as possible with one or more of the intake valves being open in first cylinder 2 in the two cases being compared. The valve is considered open when the valve has lifted 1.27 millimeters or more off of the valve seat.

Intake valve means 24 controls the amount of volume trapped in the cylinder by closing one of two intake valves late, and has almost no "throttling at the valve." Throttling at the valve adjustable valve systems use small intake valve opening to effectively throttle the airflow at the intake valve. Throttling at the valve systems are non-ideal for the present invention, as they interfere with performance of two independent fluid flow control systems. According to the preferred embodiment of the present invention, cylinder pressure is preferably higher at idle and small bmep levels (measured at or near BDC with at least one intake valve open, as described earlier) during the controlled auto ignition mode of combustion than at higher bmep levels also operating under the controlled auto ignition mode of combustion. In general terms, cylinder pressure is preferably higher at small bmep levels when exhaust valve lift profile 52 is active than at higher bmep levels when exhaust valve lift profile 52 is active.

To reduce the amount of intake air trapped in first cylinder 2 using intake valve means 24, intake valve 4a is phase shifted to close late. When intake valve 4a is closed late, some of the air inside of first cylinder 2 is pushed back out of the cylinder and into the intake manifold during compression stroke 58 (see Fig. 5) that first entered cylinder 2 during intake stroke 56. The later intake valve 4a is closed, the more intalce air will be pushed back out of the first cylinder and into the intake manifold, resulting in a smaller amount of trapped air and typically a smaller engine power level.

When intake airflow through the engine is reduced (preferably with adjustable intake valve means 24) during idle and light power level conditions, internal EGR needs to be reduced proportionately if the ratio of EGR to intake air is to remain constant or near constant. To reduce EGR flow rates, throttling is reduced, resulting in higher intake manifold pressures at light load than at higher loads when exhaust lift profile 52 is being used. Adjustable intalce valve means 24 does not have throttling at the valve, and enables cylinder pressure (measured at BDC with the intake valve open) to be higher at light loads than at higher loads. Preferably, according to the present invention, manifold pressure 9 is greater at a setting between idle and 1 bar bmep engine load at 2000 rpm than at a setting at or higher than 3 bar bmep engine load at 2000 rpm during the controlled auto ignition mode of combustion and/or when exhaust valve lift profile 52 is active. It should be noted that this embodiment of the present invention performs in generally an opposite manner relative to current practice throttling for load control, in that throttling is preferably increased with increased engine power in the present invention.

The present invention may be used in Diesel engines, and in more detail the internal exhaust gas recirculation flow rate is used to control emission levels. According to the present invention, the trapped residuals rate and the fuel to air mixture ratio are adjusted to control engine power and minimize emissions, while returning a high engine efficiency.

Stable combustion at idle and small power levels is difficult to attain during the controlled auto ignition mode of combustion, because the mixture is week and exhaust gas temperatures are relatively low. According to the present invention, stable combustion is attained at idle and small power levels by raising the mechanical compression ratio to a value greater than 13.5 to 1 in engines having a variable compression ratio capability, and ideally to a compression ratio value greater than 14.0 to 1, and providing a trapped residuals ratio greater than 40 percent.

Additionally, according to the present invention, the timing of the first intake valve may be phase shifted relative to the second intake valve to trap a smaller charge volume in first cylinder 2, thereby attaining a small engine power without overly leaning or diluting the combustion charge at lighter loads.

Controlled auto ignition combustion has a relatively low exhaust temperature. During extended periods of low power output, such as idle and other low power conditions, the exhaust temperature may become too low to support controlled auto ignition combustion. According to an embodiment of the present invention, the engine is operated using SI combustion intermittently with CAI combustion in order to maintain a high enough exhaust temperature for controlled auto ignition combustion during at least a portion of the operational time. In more detail, the engine first operates using the controlled auto ignition mode of combustion. When temperatures fall below a threshold value, the engine is adjusted to operate using the spark ignition mode of combustion. Once exhaust temperature has been restored to a value above the threshold value, the engine is operated using the controlled auto ignition mode of combustion. Optionally, the engine is modulated between the two combustion regimes at a predetermined frequency to provide steadier engine operation.

Cylinders may be transitioned from spark ignition combustion to controlled auto ignition combustion one at a time or in groups. According to the present invention the engine may optionally be operated with some cylinders having controlled auto ignition combustion and some having spark ignition combustion, thereby providing sufficient exhaust heat for controlled auto ignition combustion and/or for effective operation of the catalytic converter and/or to provide more reliable engine operation. Preferably the power and torque produced by a cylinder remains almost constant during transition from spark ignition combustion to controlled auto ignition combustion, and from controlled auto ignition combustion to spark ignition combustion. According to the present invention, the fuel to air ratio and/or exhaust dilution levels are adjusted concurrently with deactivation of one of the exhaust valves (and optionally one of the intake valves) thereby providing almost constant power and torque during transition from spark ignition to controlled auto ignition combustion, and vise versa during transition from controlled auto ignition to spark ignition combustion. Alternatively, the overall power output of the engine is held generally constant or steady, and the change in power for the controlled auto ignition cylinders is compensated for by a generally equal and opposite change in power for the spark ignition cylinders.

The swept displacement of first cylinder 2 is the cross section area of first cylinder 2 times the full stroke of the piston from BDC to TDC as shown in Figs. 4 and 5. First cylinder 2 has a minimum combustion chamber volume 3, shown in Fig. 1. Minimum combustion chamber volume is the trapped volume within first cylinder 2 when the piston is at TDC. The mechanical compression ratio is equal to the sum of the swept displacement and combustion chamber volume divided by the minimum combustion chamber volume. Mechanical compression ratio, CR is equal to

CR = (D + d)/d

Where D is the swept displacement and d is the combustion chamber volume. Stable combustion during idle and light power conditions may also be attained by of reducing the volume of intake air trapped in the first cylinder 2 with the adjustable intake valve means 24, and maintaining the fuel air mixture ratio above the stable combustion threshold. Ideally the compression ratio is also raised, however some engines may not have a variable compression ratio capability.

According to the present invention, during controlled auto ignition combustion valve timing is typically adjusted to provide the maximum amount of trapped mixture and the maximum cylinder pressure, as this generally provides best efficiency. Concurrently, throttling is used to attain the optimum amount of EGR. Fuel flow is first reduced to reduce power, while cam timing is set to provide maximum pressure. EGR may also be adjusted concurrently with change of power.

At a certain point, further reduction in fuel flow will cause a large increase in emission of pollutants such as hydrocarbons (HC) and carbon monoxide (CO) and/or unstable combustion. According to the present invention, the fuel/air ratio is largely maintained above the value resulting in excessive emissions and/or unstable combustion, and intake valve timing is adjusted to further reduce power by trapping a smaller amount of mixture in the cylinder. Throttling may optionally be adjusted to adjust EGR flow rate for minimizing emissions and providing optimum ignition timing and optimum engine efficiency, and/or providing a hotter exhaust gas and a hotter catalytic converter for improved catalytic reduction of emissions. In general compression ratio will already be at a maximum value or be non-adjustable, however, in some embodiments compression ratio may be further increased. Preferably, to reduce power to very small levels and to idle the engine, intake valve timing is adjusted to reduce the amount of trapped charge while maintaining conditions for controlled auto ignition combustion with relatively low emissions and a low coefficient of variance (COV). In general terms, controlled auto ignition combustion is combined with the Atkinson cycle at very light loads and during idle in order to attain the efficiency advantages of controlled auto ignition combustion, while reducing power with valve timing, and not further reducing, or reducing to a lesser extent, the fuel/air mixture strength, in order to prevent a large increase HC and CO emission levels, as well as to provide a stable idle with a small COV.

Alternatively, very light loads and engine idling may be attained using a stratified charge established with fuel injection directly into the cylinder. In this embodiment of the present invention, a fuel to air mixture ratio providing low emissions levels is established locally preferably in a small plume, and the size of the plume is reduced to reduce power. Optionally, air may be injected with the fuel to provide localized conditions ideal for ignition and combustion.

Referring now to Figs. 1 through 5, according to the present invention, engine 1 has multiple variable fluid flow control devises for controlling exhaust gas recirculation and engine power, including a first cylinder 2 having one or more intake valves 4, one or more exliaust valves 6, and an intalce manifold 8 having an intake manifold pressure 9. First cylinder 2 has a first stroke 56 for drawing air into the cylinder through the one or more intake valves 4, a second stroke 58 for compressing the air in first cylinder 2, a fuel to air mixture ratio 60 and means for adjusting the fuel to air mixture ratio such as fuel injectors 20, a combustion period 62 for combustion of the compressed fuel and air mixture, a third stroke 64 for expanding the high pressure combustion products and providing useful power, and a forth stroke 66 for exhausting the combustion products through the one or more exhaust valves 6. First cylinder 2 includes multiple variable fluid flow control devises including a first fluid flow control devise primarily for controlling the volume of gas trapped within the first cylinder and a second fluid flow control devise primarily for controlling the ratio of exliaust gas to intake air within the first cylinder. Preferably the first fluid flow control devise including variable intake valve control means such as adjustable intake valve control means 24. Preferably the second fluid flow control devise including a variable exhaust valve means such as adjustable exliaust valve means 36 and a throttle 10 for controlling manifold pressure 9. The variable exhaust valve means provides a first exhaust valve lift profile 50 and a second exhaust valve lift profile 52, where the second exhaust valve lift profile 52 is functionally open during first stroke 56 during selected periods of engine operation, and the first exhaust valve lift profile 50 is functionally open during the fourth stroke 66. Engine 1 further includes activation means for activating the second exhaust valve lift profile 52, such as valve 48 and adjustable exhaust valve means 36 during selected periods of engine operation, the activation means further being capable of both activating and deactivating second exhaust valve lift profile 52.

According to the present invention, throttle 10 provides a reduced intake manifold pressure 9 causing back flow of exhaust gas 18 through the second exhaust valve lift profile 52 of one or more exhaust valves 6 when the second exhaust valve lift profile 52 is active during the first stroke 56. In more detail, the back flow of exhaust gas 18 is controlled by intake manifold pressure 9, and throttle 10 provides full variability of manifold pressure 9 and thereby the exhaust gas back flow. The first fluid flow control device substantially controls the volume of air plus exhaust gas trapped in the first cylinder, and the second fluid flow devise substantially controls the ratio of exhaust gas to intake air trapped within the cylinder when the second exhaust valve lift profile is active. Preferably the trapped residuals ratio is greater than 40 percent during selected engine operating conditions, one of those modes of operation being controlled auto ignition. The trapped residuals ratio and internal exhaust gas recirculation flow rate may be adjusted to control combustion charge temperature, and/or crank angle timing of the combustion period 62. Preferably during the controlled auto ignition mode of combustion the fuel air mixture ratio has more than twice the stoichiometric amount of air to provide high efficiency and low emissions.

In some embodiments of the present invention, low cost is attained operating the engine without adjustable intake valve control. According to an embodiment of the present invention, engine power and large internal exhaust gas recirculation flow rates are controlled by opening one or more exhaust valves 6 during the intake or first stroke 56 with adjustable exhaust valve means 36 or other functional means, adjusting manifold pressure 9 with throttle 10 to provide a large and controlled amount of internal exhaust gas recirculation, and adjusting the fuel to air mixture ratio with fuel injectors 20 or other functional fuel to air mixture adjustment means to thereby control engine power. Other functional means for controlling engine power may include direct injection of gasoline into first cylinder 2 or direct injection of diesel fuel into first cylinder 2. With direct fuel injection, very lean fuel to air mixtures can be combusted. Preferably the manifold pressure is reduced to provide a trapped residuals ratio greater than 40 percent, thereby providing high efficiency and low emissions. Objectively, the manifold pressure is reduced to provide a trapped residuals ratio greater than 40 percent and controlled auto ignition, thereby providing both control of engine power and high efficiency.

Preferably, to minimize cost the second exhaust valve lift profile 52 has a fixed lift profile shape (illustrated in Fig. 4). The fixed profile may be provided by a metal cam lob, to provide low cost and low frictional power loss. In more detail it is preferable to avoid electrically actuated valve systems, and hydraulic systems that employ a high pressure oil pump and/or that hydraulically adjust valve lift, although these systems may be used in some embodiments of the present invention. Preferably the second exhaust valve lift profile 52 has a fixed profile provided by a direct acting cam lobe to avoid the cost of a hydraulically or electrically adjusted valve lift profile and also to avoid the power consumption that would be lost to the valve actuation system. A direct acting cam lobe is preferable, and defined as a cam lobe that mechanically opens the valve following the lift profile formed on the cam lobe. With a direct acting cam lobe, the valve is not opened by displacement of an electric servo valve or a small hydraulic piston that is activated each time the valve opens. A hydraulic switch may be used to activate or deactivate a hydraulic system for extended periods of operation (e.g., to initiate general use of the system), but the switch need not be fired on a cycle by cycle basis. Hydraulic fluid may be used in direct acting cam lobe systems to take up lash and or hold substantially fixed clearances.

EGR flow rate could be controlled during the controlled auto ignition mode of combustion by realtime fine-tuning adjustment of the exhaust valve lift and timing during the intake stroke with an electromagnetic valve actuation system, a hydraulic or electro-hydraulic valve actuation system, or other real time actuation system(instead of a direct acting cam lobe system), however such systems are generally expensive, complex and consume power, which off-sets efficiency gains.

Fig. 6 is similar to Fig. 4, but shows an optional exhaust valve lift profile 53H during intake stroke 56. Optional exhaust valve lift profile 53H provides a continuously open exhaust valve 6 through TCD, so that the valve does not seat twice as often as in a conventional engine. Additionally, with the valve not closing during TDC, the opening ramp for optional exhaust valve lift profile 53H can be shortened in some embodiments of the present invention. The optional exhaust valve lift profile may have a high lift, indicated by dashed curve 53H, or a low lift indicated by dashed curve 53L.

Of note, the present invention may be practiced in Diesel engines as well as in spark ignition engines. In Diesel engines the exhaust gas recirculation flow rate may be used to control emission levels.

Referring now to Fig. 1, an external EGR line or exliaust gas recirculation line 70 may be used in some embodiments of the present invention. Preferably flow control valve 72 connected to controller 46 is used to open and close EGR line 70. The present invention having multiple variable fluid flow control devises for controlling exhaust gas recirculation and the volume of intalce air trapped in the first cylinder 2 may be practiced with external EGR line 70, or with adjustable exhaust valve means 36 and EGR curve 52 (or 53H or 53L), or both EGR line 70 and EGR curve 52 (or 53H or 53L). Exhaust gas recirculation through EGR line 70 is generally cooler than exhaust gas recirculation through exhaust valves 6 when EGR curve 52 has been activated. The hotter exhaust gas recirculation, through exhaust valves 6 when EGR curve 52 has been activated, is preferable for the controlled auto ignition mode of combustion. The cooler exhaust gas recirculation, through external EGR line 70, can provide higher efficiency and lower nitrous oxide emissions in spark ignition and Diesel modes of combustion under some load or bmep conditions. Optionally, exhaust gas recirculation may be provided by both external EGR line 70 and by adjustable exhaust valve means 36 and EGR curve 52. As described earlier, preferably the first fluid flow control devise including variable intake valve control means such as adjustable intake valve control means 24. According to the present invention, engine power and large exhaust gas recirculation flow rates may be controlled in a reciprocating piston four stroke diesel engines by opening external EGR line 70 with valve 72, adjusting the manifold pressure with throttle 10 to provide a large and controlled exhaust gas flow rate, and adjusting the fuel to air mixture ratio with fuel injectors that preferably inject fuel directly into the firing engine cylinders (not shown) to control engine power. Variable intake valve control may also be used to control engine power as described earlier.

Referring now to Figs. 1 and 2, preferably phase shifter 26 is controlled by a position means, servo or valve 27, and valve 27 is controlled by controller 46.

Preferably, according to the present invention, first cylinder 2 has a trapping ratio, the trapping ratio being the maximum trapped intake volume to the minimum frapped volume provided for by adjustable intake valve means 24, and the trapping ratio is at least 1.2. The maximum trapped volume is no greater than the swept displacement of the first cylinder, and in more detail the cross section area of first cylinder 2 times the stroke of the piston. The minimum trapped volume provided for by adjustable intake valve means is the cross section area of first cylinder 2 times the portion of the stroke length occurring between closing of intake valve lift profile 54 and the following TDC piston location.

Optimum conditions for controlled auto ignition combustion generally include fuel and oxygen densities within the combustion chamber that are too week for supporting spark ignited combustion flame fronts. The present invention provides a method for transitioning from the spark ignition mode of combustion to the controlled auto ignition mode of combustion, and from the controlled auto ignition mode of combustion back to the spark ignition mode of combustion. In detail, intake manifold 8 has An intake manifold pressure 9 having a first manifold transition pressure 9T for transitioning from the spark ignition mode of combustion to the controlled auto ignition mode of combustion. It should be noted that in some embodiments of the present invention there are more than one manifold transition pressure values, and/or a range of values suitable for transition to the controlled auto ignition mode of combustion.

According to the present invention, the method of transitioning from a spark ignition mode of combustion to a controlled auto ignition mode of combustion including the steps of, operating the first cylinder 2 in engine 1 under the spark ignition mode of combustion with the EGR curve or second exhaust valve lift profile 52 deactivated to provide stable combustion and a hot exhaust, adjusting manifold pressure 9 with throttle 10 to the first manifold transition pressure 9T in preparation for transition to controlled auto ignition, and controlling air flow into the first cylinder 2 with adjustable intake valve means 24 to control engine power during the spark ignition mode of engine operation. The EGR curve or second exhaust valve lift profile 52 is then activated with adjustable exhaust valve means 36 to increase exhaust flow into first cylinder 2 responsive to the first manifold transition pressure 9T, thereby providing a hot exhaust for initiating controlled auto ignition. According to the present invention, manifold pressure is preferably established for controlled auto ignition during the spark ignition mode of combustion, and air flow is controlled during the spark ignition mode of combustion with the adjustable intalce valve means to provide the target power level given the transition manifold pressure. After initiating transition to the controlled auto ignition mode of combustion, the fuel air mixture ratio 60 is adjusted with fuel injectors 20 or other means, and the air flow rate into engine 1 and the first cylinder 2 is adjusted with the adjustable intake valve means 24 to control the brake mean effective pressure of first cylinder 2 and engine 1 operating under the controlled auto ignition mode of combustion. A near stoichiometric fuel to air mixture ratio may be used during the spark ignition mode of combustion to provide a hot exhaust in preparation for transition to the controlled auto ignition mode of Ϊ combustion. The high temperature of the exhaust gas is beneficial for initiating controlled auto ignition combustion. Optionally, according to the present invention a lean fuel to air mixture ratio may be used during the spark ignition mode of combustion prior to transitioning to the controlled auto ignition mode of combustion, and a fuel to air mixture closer to stoichiometric used at the start of the controlled auto ignition mode of combustion, thereby providing a near constant engine torque during the transition period.

Fig. 7 is similar to Fig. 4, but shows exhaust valve lift profile 50 phase shifted to a phase shifted exhaust valve position 50P, and shows intake valve lift profile 54 phase shifted to a phase shifted intake valve position 54P. According to the present invention, the intake and exhaust valves may be phase shifted to provide functional opening of the exhaust valve during the first stroke or intake stroke of the engine, and in more detail as an alternative to opening the exhaust valve a second time during the intake stroke as illustrated by curve 52 in Fig. 4. The amount of phase shifting is limited in practice in order to avoid piston to valve clash. Phase shifting is therefore not the preferred method of practicing the present invention, but may provide cost advantages in some embodiments of the present invention. According to the present invention, the method of transitioning from a spark ignition mode of combustion to a controlled auto ignition mode of combustion including the steps of operating the first cylinder 2 in engine 1 under the spark ignition mode of combustion with the second exhaust valve lift setting deactivated to provide stable combustion and a hot exhaust. According to the present invention, the second exhaust valve lift setting can be either second exhaust valve lift profile 52 or phase shifted exhaust valve position 50P. The next step includes adjusting manifold pressure 9 with throttle 10 to the first manifold transition pressure 9T and/or a value less than atmospheric pressure to control air intake during the spark ignition mode of combustion. The next step includes activating the second exhaust valve lift setting to increase exhaust flow into first cylinder 2 responsive to the manifold pressure 9, thereby providing a hot exhaust for initiating controlled auto ignition. The next step includes adjusting the fuel to air mixture ratio with the fuel to air mixture ratio adjustment means, and adjusting the trapping ratio with the throttle to provide the controlled auto ignition mode of combustion and the desired power level. According to this embodiment of the present invention, adjustable intake valve control is not required for transitioning from the spark ignition mode of combustion to the controlled auto ignition mode of combustion.

During the controlled auto ignition mode of combustion, the combustion period 62 and timing at which 50 percent of the combustion charge is burned is preferably controlled according to the present invention, by adjusting the temperature of the gas entering the combustion chamber, which is preferably controlled by throttling the engine to increase internal EGR flow rate. The recirculating exhaust gas is very hot, and increasing its proportion within the intake air flow stream increases the temperature of the gas trapped within the combustion cylinder, in turn causing the combustion period 62 and 50 percent burn point to occur earlier. Optionally, the compression ratio and/or other variables of the engine may be varied to adjust the combustion period 62. Optionally the intake air is pre heated by a hot surface of the engine such as the radiator, intake manifold, engine block, exhaust system, or other heating surface. According to the present invention, during the controlled auto ignition mode of combustion the fuel/air ratio and the combustion period 62 are adjusted to provide a high efficiency, low emission levels, and robust combustion. The timing of the combustion period 62 (or 50 percent burn point) is detected by a sensor 74 similar in design to a knock sensor (or other functional sensor), but tuned to detect the rapid pressure rise of controlled auto ignition combustion (shown in Fig. 1). Sensor 74 preferably detects knock as well as controlled auto ignition combustion. Optionally a separate sensor may be used to detect harmful detonation or knock. Optionally, the timing of the combustion period 62 (or 50 percent burn point) is detected by a torque sensor 76 which detects fluctuations in the rotational speed of the crankshaft or a sensor wheel mounted on the crankshaft 78. Engine 1 may further include a cam timing sensor 80, a first oxygen sensor upstream of the catalytic converter 82 and a second oxygen sensor down stream of the catalytic converter 84. The intake may include a mass flow sensor 86, and manifold 8 may include a manifold pressure sensor 88 and a manifold temperature sensor 90. Readings from sensor 74, 76, 80, 82, 84, 86, 88, and/or 90 are routed into controller 46 for controlling operation of the engine.

Preferably the engine includes a drive by wire system where, according to the present invention controlled auto ignition combustion is controlled by determining the combustion period 62 either directly through sensor readings and/or calculated from engine readings and data accessed by the controller 46, and outputting control commands to the fuel injector(s) 20 and/or throttle position drive for controlling exhaust gas recirculation and/or by adjusting other variables to control the combustion period 62 and engine power output.

Those skilled in the art will appreciate that alternative embodiments of the present invention may be practiced within the spirit and scope of the claims.

Claims

1. A reciprocating piston engine having multiple variable fluid flow control devises for controlling exhaust gas recirculation and engine power, including one or more firing cylinders and a first cylinder having one or more intake valves, one or more exhaust valves, and an intake manifold having an intake manifold pressure, the first cylinder further having a first stroke for drawing air into the cylinder through the one or more intake valves, a second stroke for compressing the air in the cylinder, a fuel to air mixture ratio and means for adjusting the fuel to air mixture ratio, a combustion period for combustion of the compressed fuel and air mixture, a third stroke for expanding the high pressure combustion products, and a forth stroke for exhausting the combustion products through the one or more exhaust valves, wherein said first cylinder includes multiple variable fluid flow control devises including a first fluid flow control devise primarily for controlling the volume of gas trapped within the first cylinder, and a second fluid flow control devise primarily for controlling the ratio of exliaust gas to intake air within the first cylinder, said first fluid flow control devise including variable intake valve control, said second fluid flow control devise including a variable exhaust valve and a throttle for controlling manifold pressure, said variable exhaust valve having a first exliaust valve lift profile and a second exhaust valve lift profile, said second exhaust valve lift profile being functionally open during said first stroke during selected periods of engine operation, and said first exhaust valve lift profile being functionally open during said fourth stroke, and activation means for activating said second exhaust valve lift profile during selected periods of engine operation, said activation means being capable of both activating and deactivating said second exhaust valve lift profile, wherein said throttle provides a reduced intake manifold pressure causing back flow of exliaust gas through the second exhaust valve when the second exhaust valve lift profile is active, said back flow of exhaust gas being controlled by said intake manifold pressure, said throttle providing full variability of said manifold pressure and exhaust gas back flow. wherein said first fluid flow control device substantially controls the volume of air plus exhaust gas trapped in the first cylinder, and said second fluid flow devise substantially controls the ratio of exhaust gas to intake air trapped within the cylinder when the second exhaust valve lift profile is active.

2. The reciprocating piston engine having multiple variable fluid flow control devises for controlling exhaust gas recirculation and engine power of claim 1, wherein the first cylinder has a trapped residuals ratio, the trapped residuals ratio being equal to the ratio of fresh intake air to exhaust gases trapped in the first cylinder prior to the combustion period, wherein the engine has a trapped residuals ratio greater than 40 percent during selected engine operating conditions.

3. The reciprocating piston engine having multiple variable fluid flow control devises for controlling exhaust gas recirculation and engine power of claim 2, wherein the engine has a controlled auto ignition mode of operation, wherein the internal exhaust gas recirculation flow rate is adjusted to control combustion charge temperature.

4. The reciprocating piston engine having multiple variable fluid flow control devises for controlling exhaust gas recirculation and engine power of claim 3, wherein the fuel air mixture ratio has more than twice the stoichiometric amount of air.

5. The reciprocating piston engine having multiple variable fluid flow control devises for controlling exhaust gas recirculation and engine power of claim 1, wherein the second exhaust valve lift profile has a fixed lift profile, for provide low cost and low frictional power loss.

6. The reciprocating piston engine having multiple variable fluid flow control devises for controlling exhaust gas recirculation and engine power of claim 5, wherein the engine has a controlled auto ignition mode of operation and a spark ignition mode of operation, wherein the first intake valve lift profile overlaps the first exhaust valve lift profile during the controlled auto ignition mode of operation, thereby providing a simple and low cost valvetrain.

7. The reciprocating piston engine having multiple variable fluid flow control devises for controlling exhaust gas recirculation and engine power of claim 1, wherein the engine has a diesel mode of operation, the internal exhaust gas recirculation flow rate being used to control emission levels.

8. The reciprocating piston engine having multiple variable fluid flow control devises for controlling exhaust gas recirculation and engine power of claim 1, wherein the first cylinder has at least two intake valves and means for adjusting the closing timing of at least one of the two intake valves relative to the other intake valve in the first cylinder for controlling air flow into the first cylinder.

9. The reciprocating piston engine having multiple variable fluid flow control devises for controlling exhaust gas recirculation and engine power of claim 1, wherein the adjustable intake valve means includes contiguous range means for trapping a contiguous range of intake volumes, thereby providing continuous control of engine power.

10. The reciprocating piston engine having multiple variable fluid flow control devises for controlling exhaust gas recirculation and engine power of claim 1, wherein the first cylinder has a trapping ratio, said trapping ratio being the maximum trapped intake volume to the minimum trapped volume provided for by said adjustable intake valve means, said trapping ratio being at least 1.2, said maximum trapped volume being the swept displacement of said first cylinder.

11. A method of precisely controlling large internal exhaust gas recirculation flow rates and engine power in a reciprocating piston four stroke engine, the engine having a first cylinder having a compression ratio, one or more intake valves and a first intake valve lift profile for at least one of said intake valves, one or more exhaust valves and a first exhaust valve lift profile for at least one of said exhaust valves, and an intake manifold having an intake manifold pressure and a throttle for controlling the intake manifold pressure, the first cylinder further having a first stroke for drawing air into the cylinder through the one or more intake valves, a second stroke for compressing the air in the cylinder, a fuel to air mixture ratio and means for adjusting the fuel to air mixture ratio, a combustion period for combustion of the compressed fuel and air mixture, a third stroke for expanding the high pressure combustion products, and a forth stroke for exhausting the combustion products through the one or more exhaust valves, the first intake valve lift profile being functionally open for a portion of the first sfroke, and the first exhaust valve lift profile being functionally open for a portion of the forth stroke, a second exhaust valve lift profile for at least one of said exhaust valves, said second exhaust valve lift profile being functionally open during said first stroke during selected periods of engine operation, the first cylinder further including activation means for activating the second exhaust valve lift profile during the first stroke during selected periods of engine operation, said activation means being capable of both activating and deactivating said second exhaust valve lift profile, a trapped residuals ratio, the trapped residuals ratio being equal to the ratio of fresh intake air to exhaust gasses trapped in the first cylinder just prior to the combustion period, and a valve overlap duration, said valve overlap duration being the crank angle duration where an intake valve and an exhaust valve in the first cylinder are both open, said valve overlap duration having a first minimum valve overlap duration during the engine operating conditions when the second exhaust valve lift profile is inactive, and a second minimum valve overlap duration during the engine operation conditions when the second exhaust valve lift profile is active, adjustable intake valve means for controlling the amount of air trapped in the first cylinder, the method of controlling large internal exhaust gas recirculation flow rates and engine power having the steps of, opening the exhaust valve during the first stroke with the actuation means, adjusting the manifold pressure with the throttle to provide a large and controlled the internal exhaust gas flow rate, and adjusting the amount of air trapped in the cylinder with the adjustable intake valve means to control engine power.

12. The method of precisely controlling large internal exhaust gas recirculation flow rates and engine power of claim 11 further including the steps of reducing the manifold pressure to provide a trapped residuals ratio greater than 40 percent and controlled auto ignition, thereby providing both control of engine power and high efficiency.

13. The method of precisely controlling large internal exhaust gas recirculation flow rates and engine power of claim 12 further including the step of adjusting the fuel to air ratio to further control engine power and combustion stability of the controlled auto ignition mode of combustion.

14. The method of precisely controlling large internal exhaust gas recirculation flow rates and engine power of claim 11 further including the step of maintaining a constant second exhaust valve lift profile for varying load conditions to avoid frictional power and efficiency loss present with adjustable exhaust valve systems.

15. The method of precisely controlling large internal exhaust gas recirculation flow rates and engine power of claim 11 further including the steps of reducing the manifold pressure to provide a trapped residuals ratio greater than 40 percent and controlled auto ignition, and providing first minimum valve overlap duration equal to the second minimum valve overlap duration to provide a lower cost than systems having an adjustable overlap duration.

16. The method of precisely controlling large internal exhaust gas recirculation flow rates and engine power of claim 11 where the engine has at least two intake valves and means for adjusting the closing timing of at least one of the two intake valves, further including the step of adjusting the closing timing of one of the two intake valves to control engine power.

17. The method of precisely controlling large internal exhaust gas recirculation flow rates and engine power of claim 11 where the adjustable intake valve means has means for providing a contiguous range of air trapped in the first cylinder for a given throttle position, further including the step of continuously adjusting the air flow rate with the adjustable intake valve means to provide for varying power needs.

18. The method of precisely controlling large internal exhaust gas recirculation flow rates and engine power of claim 11 where the engine has a diesel mode of operation, and where the internal exhaust gas recirculation flow rate controls emission levels, further including the step of adjusting the fuel to air mixture ratio to control engine power.

19. The method of precisely controlling large internal exhaust gas recirculation flow rates and engine power of claim 11, further including the step of raising the compression ratio, thereby providing stable combustion at very low power levels, the stable combustion being required for engine idling.

20. The method of precisely controlling large internal exhaust gas recirculation flow rates and engine power of claim 11, further including the step of reducing the volume of intake air trapped in the first cylinder, and maintaining the fuel air mixture ratio above the stable combustion threshold, thereby providing stable combustion at very low power levels, the stable combustion being required for engine idling.

21. The method of precisely controlling large internal exhaust gas recirculation flow rates and engine power of claim 20, further including the step of raising the compression ratio, thereby providing stable combustion at very low power levels, the stable combustion being required for engine idling.

22. A method for transitioning from a spark ignition mode of combustion to a controlled auto ignition mode of combustion in a reciprocating piston four stroke engine, the engine having a first cylinder, one or more intake valves and a first intake valve lift profile for at least one of said intake valves, one or more exhaust valves and a first exhaust valve lift profile for at least one of said exhaust valves, and an intake manifold having an intake manifold pressure and a throttle for controlling the intake manifold pressure,

A spark ignition mode of combustion and a confrolled auto ignition mode of combustion, and a first manifold transition pressure for transitioning from the spark ignition mode of combustion to the controlled auto ignition mode of combustion, the first cylinder further having a first stroke for drawing air into the cylinder through the one or more intake valves, a second stroke for compressing the air in the cylinder, a fuel to air mixture ratio and means for adjusting the fuel to air mixture ratio, a combustion period for combustion of the compressed fuel and air mixture, a third sfroke for expanding the high pressure combustion products, and a forth stroke for exhausting the combustion products through the one or more exhaust valves, the first intake valve lift profile being functionally open for a portion of the first stroke, and the first exhaust valve lift profile being functionally open for a portion of the forth stroke, a second exhaust valve lift profile for at least one of said exhaust valves, said second exhaust valve lift profile being functionally open during said first stroke during selected periods of engine operation, the first cylinder further including activation means for activating the second exhaust valve lift profile during the first stroke during selected periods of engine operation, said activation means being capable of both activating and deactivating said second exhaust valve lift profile, a trapped residuals ratio, the trapped residuals ratio being equal to the ratio of fresh intake air to exhaust gasses trapped in the first cylinder just prior to the combustion period, and adjustable intake valve means for controlling the amount of air frapped in the first cylinder, the method of transitioning from a spark ignition mode of combustion to a confrolled auto ignition mode of combustion including the steps of, operate the first cylinder in the engine under the spark ignition mode of combustion and the second exhaust valve lift profile deactivated to provide stable combustion and a hot exhaust, adjusting manifold pressure with the throttle to the first manifold transition pressure in preparation for transition to controlled auto ignition, and control air flow into the first cylinder with the adjustable intake valve means to control engine power during the spark ignition mode of engine operation, activate the second exhaust valve lift profile with the activation means to increase exhaust flow into the first cylinder responsive to the first manifold transition pressure, thereby providing a hot exhaust for initiating controlled auto ignition, and adjust the fuel air mixture ratio and the air flow rate into the engine with the adjustable intake valve means to control the brake mean effective pressure of the first cylinder operating under the controlled auto ignition mode of combustion.

23. The method for transitioning from a spark ignition mode of combustion to a confrolled auto ignition mode of combustion in a reciprocating piston four stroke engine of claim 22, further including the step of using a near stoichiometric fuel to air mixture ratio during the spark ignition mode of combustion to provide a hot exhaust in preparation for transition to the controlled auto ignition mode of combustion.

24. The method for transitioning from a spark ignition mode of combustion to a confrolled auto ignition mode of combustion in a reciprocating piston four stroke engine of claim 23, further including the step of using a lean fuel to air mixture ratio during the spark ignition mode of combustion prior to transitioning to the controlled auto ignition mode of combustion, and using a fuel to air mixture closer to stoichiometric at the start of the controlled auto ignition mode of combustion, thereby providing a near constant engine torque during the transition period.

25. A method of precisely controlling large internal exhaust gas recirculation flow rates and engine power in a reciprocating piston four stroke engine, the engine having a first cylinder having a compression ratio, one or more intake valves and a first intake valve lift profile for at least one of said intalce valves, one or more exhaust valves and a first exhaust valve lift profile for at least one of said exhaust valves, and an intake manifold having an intake manifold pressure and a throttle for controlling the intake manifold pressure, the first cylinder further having a first stroke for drawing air into the cylinder through the one or more intalce valves, a second stroke for compressing the air in the cylinder, a fuel to air mixture ratio and means for adjusting the fuel to air mixture ratio, a combustion period for combustion of the compressed fuel and air mixture, a third stroke for expanding the high pressure combustion products, and a forth stroke for exhausting the combustion products through the one or more exhaust valves, the first intake valve lift profile being functionally open for a portion of the first stroke, and the first exliaust valve lift profile being functionally open for a portion of the forth stroke, a second exhaust valve lift profile for at least one of said exhaust valves, said second exhaust valve lift profile being functionally open during said first stroke during selected periods of engine operation, the first cylinder further including activation means for activating the second exhaust valve lift profile during the first stroke during selected periods of engine operation, said activation means being capable of both activating and deactivating said second exhaust valve lift profile, a frapped residuals ratio, the frapped residuals ratio being equal to the ratio of fresh intake air to exhaust gasses frapped in the first cylinder just prior to the combustion period, and the method of controlling engine power and large internal exhaust gas recirculation flow rates having the steps of, opening the exhaust valve during the first sfroke with the actuation means, adjusting the manifold pressure with the throttle to provide a large and confrolled the internal exhaust gas flow rate, and adjusting the fuel to air mixture ratio with the fuel to air mixture adjustment means to control engine power.

26. The method of precisely controlling large internal exhaust gas recirculation flow rates and engine power of claim 25 further including the steps of reducing the manifold pressure to provide a trapped residuals ratio greater than 40 percent, thereby providing high efficiency and low emissions.

27. The method of precisely controlling large internal exhaust gas recirculation flow rates and engine power of claim 25 further including the steps of reducing the manifold pressure to provide a trapped residuals ratio greater than 40 percent and controlled auto ignition, thereby providing both control of engine power and high efficiency.

28. A method for transitioning from a spark ignition mode of combustion to a confrolled auto ignition mode of combustion in a reciprocating piston four stroke engine, the engine having a first cylinder, one or more intake valves and a first intake valve lift profile for at least one of said intake valves, one or more exliaust valves and a first exhaust valve lift profile for at least one of said exhaust valves, and an intake manifold having an intake manifold pressure and a throttle for controlling the intake manifold pressure,

A spark ignition mode of combustion and a controlled auto ignition mode of combustion, and a first manifold transition pressure for transitioning from the spark ignition mode of combustion to the controlled auto ignition mode of combustion, the first cylinder further having a first stroke for drawing air into the cylinder through the one or more intake valves, a second stroke for compressing the air in the cylinder, a fuel to air mixture ratio and means for adjusting the fuel to air mixture ratio, a combustion period for combustion of the compressed fuel and air mixture, a third stroke for expanding the high pressure combustion products, and a forth stroke for exhausting the combustion products through the one or more exhaust valves, the first intake valve lift profile being functionally open for a portion of the first stroke, and the first exhaust valve lift profile being functionally open for a portion of the forth stroke, a second exhaust valve lift setting for at least one of said exhaust valves, said second exhaust valve lift setting being functionally open during said first stroke during selected periods of engine operation, the first cylinder further including activation means for activating the second exhaust valve lift setting during the first stroke during selected periods of engine operation, said activation means being capable of both activating and deactivating said second exhaust valve lift setting, said second exhaust valve lift setting having a fixed lift profile provided by a direct acting cam lobe, a frapped residuals ratio, the trapped residuals ratio being equal to the ratio of fresh intake air to exhaust gasses frapped in the first cylinder just prior to the combustion period, the method of transitioning from a spark ignition mode of combustion to a confrolled auto ignition mode of combustion including the steps of, operating the first cylinder in the engine under the spark ignition mode of combustion and the second exliaust valve lift setting deactivated to provide stable combustion and a hot exhaust, adjusting manifold pressure with the throttle to a value less than atmospheric pressure to control air intake during the spark ignition mode of combustion, activating the second exhaust valve lift setting with the activation means to increase exhaust flow into the first cylinder responsive to the reduced manifold pressure, thereby providing a hot exhaust for initiating controlled auto ignition, and adjusting the fuel to air mixture ratio with the fuel to air mixture ratio adjustment means, and adjusting the trapping ratio with the throttle to provide the controlled auto ignition mode of combustion and the desired power level.

29. The method for transitioning from a spark ignition mode of combustion to a confrolled auto ignition mode of combustion in a reciprocating piston four stroke engine of claim 28, further including the step of activating a second exhaust valve lift profile during the first stroke with the activation means to increase exhaust flow into the first cylinder responsive to the reduced manifold pressure, thereby providing a hot exhaust for initiating controlled auto ignition.

30. The method for transitioning from a spark ignition mode of combustion to a controlled auto ignition mode of combustion in a reciprocating piston four stroke engine of claim 28, further including the step of phase shifting the exhaust valve lift profile with the activation means to provide a functionally open period for the exhaust valve during the first stroke to increase exhaust flow into the first cylinder responsive to the reduced manifold pressure, thereby providing a hot exhaust for initiating controlled auto ignition.