SEQUENTIAL INTERNAL EXHAUST GAS RECIRCULATION SYSTEM FOR INTERNAL COMBUSTION ENGINES
Field of Invention:
The present invention relates to four stroke internal combustion engines and more particularly to those engines with exhaust gas recirculation systems operated by changing the engine valve timing, for controlling nitric-oxide emissions in internal combustion engines.
Background of the invention:
The major problem with internal combustion engines arises due to the formation of various compounds of gaseous nitrogen oxides (NOx), such as nitric oxide (NO), nitrous oxide (N02), etc., during the combustion process. As is well-known, the presence of such compounds in the exhaust gases contributes significantly to the unhealthful emissions that add to the environmental pollution and thereby global warming. One method for reducing the amount of gaseous nitrogen oxides in the exhaust gas is to recirculate a portion of the exhaust gases through an EGR cooler into the combustion chamber.
The recirculated exhaust gas mixes with the intake air charge passing to the combustion chamber, and thereby reducing its total oxygen concentration, which, of course, means that less oxygen is available during combustion to form nitrogen oxides. These exhaust gas recirculation (EGR) systems have proven to be very effective when used with the four-stroke internal combustion engines. In off-road vehicle applications the usage of these exhaust gas recirculation (EGR) with EGR cooler is deterrent due to failures owing to bad quality of the fuel, in particular the high sulfur concentration in the fuel. Such exhaust gas recirculation systems have

complex electronic control circuits and require high initial cost and excessive level of maintenance costs. Moreover, most EGR systems used on diesel engines tend to require frequent cleaning, or worse, may shorten the life of the engine.
The increase in the cost of engines adopting the exhaust gas recirculation technique demands simple and cost effective technologies, in particular those without the use of electronics. While it is theoretically possible to lower the nitrogen oxide emissions (NOx) of diesel engines by using EGR systems, it has proven considerably more difficult to design an EGR system that is simple and effective.
Therefore it is desirable to provide an EGR system that can be effectively used on diesel engines, and resulting in a significant reduction in nitrogen oxide emissions, yet without requiring expensive maintenance or frequent cleaning of various components of the EGR system, thus extending the life of the engine.
Objective of the invention:
The main object of the present invention is to provide an EGR system that can be effectively used on diesel engines, without requiring expensive components for the EGR system.
Another object of the present invention is to provide improved valve timing with internal exhaust gas recirculation for internal combustion engines.
Another object of the present invention is to provide an EGR system resulting in a significant reduction in nitrogen oxide emissions.

Summary of invention:
The present invention which achieves the objectives relates to an exhaust gas recirculation system provided with the internal combustion engine. Unlike a control system connected to the EGR valve that selectively opens and closes the valve to direct cooled/uncooled and filtered/unfiltered exhaust gases into the intake manifold of the engine, the present invention involves new cam lobe design for providing valve timing such that there is secondary opening of exhaust valve during intake stroke and secondary opening of intake valve during exhaust stroke causing uncooled, unfiltered exhaust gases in to the intake manifold and/or into the combustion chamber.
The EGR system has a valve train mechanism constructed to control the operation of the valves through a cam in the cam shaft. The intake valve and exhaust valves are placed at the intake port and exhaust ports of the engine. The intake and exhaust valve cams have a secondary lobe arranged for opening of intake valve and exhaust valve twice in a thermodynamic cycle. The secondary lobe in the intake and exhaust valve cams is constructed to have a secondary opening of exhaust valve during intake stroke and secondary opening of intake valve during exhaust stroke, such that the exhaust gases are trapped for recirculation. The secondary opening of the exhaust valve causes exhaust gases flow into the combustion chamber when the exhaust manifold pressure is higher than combustion chamber pressure. The secondary openings of intake valve causes exhaust gases flow into the intake manifold pressure as the intake manifold pressures are lesser than the combustion chamber pressure.
During secondary intake valve opening in exhaust stroke, exhaust gases are pushed by the piston into the intake manifold to form a mixture with fresh charge that is later drawn into the cylinder during suction stroke. During the secondary exhaust

valve opening in suction stroke, the exhaust gases flow into the cylinder from the exhaust port and mix with exhaust gas-air mixture already formed followed by compression, fuel injection and combustion processes.
Further a method for recirculation of exhaust gases in an internal combustion engine that comprises the steps such that during intake stroke there is a secondary opening of exhaust valve and during exhaust stroke there is a secondary opening of intake valve is executed. The method involves providing cam with a secondary lobe in the valve train mechanism for both intake and exhaust such that the valves open and close twice in a thermodynamic cycle.
The exhaust valve opens for the second time during intake stroke and the intake valve opens for the second time during exhaust stroke, such that the exhaust gases are trapped inside the combustion chamber for reducing nitric oxide emissions. The secondary opening of the exhaust valve causes EGR when the exhaust manifold pressure is higher than combustion chamber pressure, and the secondary opening of intake valve causes EGR when the intake manifold pressure is lesser than the combustion chamber pressure. This gas exchange between the intake and exhaust gases occur based on the pressure differential between the intake manifold and cylinder/combustion chamber and that between exhaust manifolds and the cylinder/combustion chamber.
The EGR according to the present invention overcomes the ailing effects of conventional methods of exhaust gas recirculation particularly for off-road applications where fuel quality is not guaranteed with respect to sulfur concentration. The present invention reduces the nitric oxide emissions in all four stroke internal combustion engines working on diesel, CNG or any other alternate fuel under On-road or off-road applications.

The present invention also avoided the use of expensive and complex CRS technology which is otherwise required to meet the stringent emission norms as external EGR technology had profound durability concerns for the aforesaid applications. Moreover, with internal EGR there is a significant cost reduction in the engine with respect to the existing external EGR engine as some of the components that are otherwise required for external EGR are eliminated.
Further there is practically no impact on manufacturing including camshaft machining line except for the change in forging. The present invention is a cost effective technology, meeting stringent off-road engine emission norms without any degradation in fuel consumption or performance thereby offering a competitive edge in the market.
Brief description of drawings:
Referring now to the drawings wherein the showings are for the purpose of illustration only, and not for the purpose of limiting the same.
Fig. 1 shows the suction and exhaust process in the internal combustion engine, in accordance to the exemplary embodiment of the present invention.
Fig. 2 shows the valve train mechanism and cam shaft actuating the intake and exhaust valve in accordance to the exemplary embodiment of the present invention.
Fig. 3 shows the cam lobes of the exhaust and intake valve in accordance to the present invention.
Fig. 4 shows the valve timing of the engine in accordance to the present invention.

Fig. 5 shows a table detailing the mass emissions at two power ranges of the internal combustion engine in accordance to the present invention.
Detailed description:
The present invention relates to four stroke internal combustion engines and more particularly to exhaust gas recirculation systems operated by changing the valve timing, for controlling nitric-oxide emissions. In a four stroke internal combustion engine, the thermodynamic processes, (suction, compression, power, exhaust), are exemplified by the piston and valve positions. Exhaust gas recirculation (EGR) is adopted such that some portion of exhaust gas is metered from the exhaust system and then provided back into the engine. Internal exhaust gas recirculation is achieved through the valve timing optimization such that the exhaust gases are either retained within the combustion chamber or directed from exhaust manifold/intake manifold into combustion chamber. There is change in valve timing during suction and exhaust processes while there is no change in compression and power generation processes.
Fig. 1 shows the suction and exhaust process in the internal combustion engine, in accordance to the exemplary embodiment of the present invention. The internal combustion engine (1) has exhaust gas recirculation (EGR) system with a valve train mechanism constructed to control the operation of intake valve (2) and exhaust valve (3) through a cam (11) in the cam shaft (12). The intake valve and exhaust valve are placed at the intake port (4) and exhaust ports (5) of the engine. These ports are generally a part of cylinder head of the engine. The intake valve (2) and exhaust valve (3) are driven by an inlet cam and exhaust cam to open and close the inlet and exhaust port passage respectively by the rotation of the cams which in turn are operated by the crankshaft through a gear train.

In the current invention of internal Exhaust Gas Recirculation system, the cam (11) has a secondary lobe (14) arranged for opening of intake valve (2) and exhaust valve (3) twice in a thermodynamic cycle. The secondary lobe (14) in the cam is constructed to secondary opening of exhaust valve (3) during intake stroke and secondary opening of intake valve (2) during exhaust stroke, such that the exhaust gases are trapped for recirculation.
In thermodynamic processes of a four-stroke IC engine, suction, compression, power, exhaust strokes are characterized by the intake valve (2) and exhaust valve (3) and piston (15) positions. The valve position is defined by engine valve timing indicated with respect to piston top dead center (TDC) and bottom dead center (BDC). The key change associated with this innovation is the valve cam lobe (14), which causes change in the valve timing to facilitate gas exchange and thereby obtaining internal EGR. The exhaust and suction strokes are divided into two stages each with one stage involving gas exchange. In stage-1 of exhaust stroke both the intake valve (2) and the exhaust valve (3) are made open with a portion of exhaust gases entering into the intake manifold while in the stage-2, a regular exhaust stroke, intake valve (2) is closed expelling all the gases outside cylinder through the exhaust port(5). The gases that are trapped in the intake manifold (2) begin to mix with fresh air.
In stage-1 of suction stroke only intake valve (2) is open and the exhaust gas-air mixture is inducted from the intake manifold into the combustion chamber while in stage-2 exhaust valve also opens allowing additional amount of exhaust gases from the exhaust port into the cylinder based on the pressure difference. This flow from exhaust manifold happens predominantly during high speed or low load operation. Certain amount of EGR is obtained during the exhaust stroke while certain amount is obtained during the suction stroke. The EGR trapping mechanism is sequential with respect to the operation of processes within the internal combustion engine.

Fig. 2 shows the valve train mechanism and a cam shaft actuating the intake and exhaust valve in accordance to the exemplary embodiment of the present invention. The valve train mechanism controls the operation of the intake and exhaust valves (2, 3) with a series of components transmitting motion from one end to the other to control air and fuel flow into and out of the cylinders, thereby facilitating combustion and useful power generation. The valve train adopted in this invention is a push rod type mechanism that transmits the cam profile to the valve through the tappet (10), push rod (9), and rocker arm (8).
In the present invention there are secondary lobes (14) on both the intake and exhaust cams (11) that are additionally introduced for operating both the valves (2, 3) to facilitate opening of both the valves twice in a thermodynamic cycle. The variants provided in the valve timing mechanisms include different valve lifts, valve durations and valve timings. During the secondary exhaust valve opening, exhaust gases are drawn into the cylinder from the exhaust port and during secondary intake valve opening exhaust gases are trapped in the intake manifold which are then sucked into the cylinder during the suction stroke.
Fig. 3 shows the cam lobe of the exhaust and intake valve in accordance to the present invention. The cam (11) has a primary lobe (13) and a secondary lobe (14), wherein the primary lobe leads to primary opening of the intake valve and the exhaust valves and the secondary lobes accounts for lifting of the secondary intake valve and exhaust valve. The secondary cam lobe height is from 0.5 mm to 1.5 mm for the test case. The secondary lobe (14) is constructed to lift the intake valve (2) and exhaust valve (3) such that, secondary intake valve opening in exhaust stroke, exhaust gases are pushed by the piston into the intake manifold to form a mixture with fresh charge that is later drawn into the cylinder during suction stroke and secondary exhaust valve opening occurs in suction stroke, during which exhaust gases flow into the

cylinder from the exhaust port and mix with Air-Exhaust gas mixture forming a richer EGR mixture before participating in the combustion of fresh fuel injected after compression stroke followed by combustion. The amount of EGR depends on the secondary cam lobe (14) height and opening duration in addition to the magnitude of the pressure difference between manifold and cylinder.
Fig. 4 shows the valve timing for secondary opening and closing of the exhaust and intake valve in accordance to the present invention. The cams can have several combinations of primary and secondary lobe height to meet EGR rate targets. The secondary opening of the exhaust valve (3) causes EGR when the exhaust manifold (5) pressure is higher than combustion chamber pressure. The secondary opening of intake valve (2) causes EGR when the intake manifold pressure is lower than the combustion chamber pressure. The duration of the secondary exhaust valve opening, where there is positive pressure difference between exhaust manifold and cylinder, can be narrow and limits the amount of EGR. On the other hand, secondary intake valve opening results in heating of the intake manifold which affects the volumetric efficiency and air-fuel ratio of the engine thereby setting limitation on the amount of internal EGR. Opening both intake and exhaust valves twice in a thermodynamic cycle can be a solution to the aforesaid concerns.
The EGR flow to the combustion chamber is based on the pressure difference and it involves secondary opening of exhaust valve during the intake stroke or secondary opening of intake valve during the exhaust stroke. The present invention involves new valve timing such that both the secondary opening of the exhaust valve during the intake stroke and secondary opening of intake valve during the exhaust stroke takes place. The present invention provides a sequential internal exhaust gas recirculation, which is a unique internal EGR mechanism achieved by a combination of intake valve opening twice (2IVO) and exhaust valve opening twice (2EVO) in a

thermodynamic cycle. With this new technique the ailing effects of conventional methods are overcome in the entire speed range as EGR rates are distributed between the above two flow paths (intake and exhaust) eliminating loss in volumetric efficiency, fuel economy and also reducing smoke emissions.
Fig. 5 shows a table detailing the mass emissions at two power ranges of the internal combustion engine in accordance to the present invention. The emission results reveal that the present invention has met stringent norms such as NOx level in 3.6 -3.7 g/kWh, with the internal exhaust gas recirculation. As has been described heretofore, according to the engine equipped with the internal EGR system, decrease in NOx reduction is achieved. Further the CO emission and the HC emission level are also improved with the internal exhaust gas recirculation system.
The present invention involves new mechanism to provide valve timing such that there is secondary opening of exhaust valve during intake stroke and secondary opening of intake valve during exhaust stroke.
The EGR according to the present invention overcome the ailing effects of conventional methods of exhaust gas recirculation. The present invention can reduce the nitric oxide emissions in all four stroke internal combustion engines working on diesel, CNG or any other alternate fuel under On-road or off-road applications.
The present invention also avoided the use of expensive and complex CRS technology which is otherwise required to meet the above emission norms as external EGR technology had profound durability concerns for the aforesaid applications. Moreover, with internal EGR there is a significant cost reduction in the engine with respect to the existing external EGR engine as the external EGR circuit is eliminated.

Further there will practically no impact on manufacturing line other than the CNC programming for milling and grinding machines. Forging should have enough material build to take the additional lobe or a new forging can be used. The present invention is a cost effective technology, meeting stringent off-road engine emission norms without any degradation in fuel consumption or performance thereby offering a competitive edge in the market.
The foregoing description is a specific embodiment of the present invention. It should be appreciated that this embodiment is described for purpose of illustration only, and that numerous alterations and modifications may be practiced by those skilled in the art without departing from the spirit and scope of the invention. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention as claimed or the equivalents thereof.

We Claim:
1. A sequential internal exhaust gas recirculation (EGR) system for
internal combustion engine (1), said system comprises,
a valve train mechanism constructed to control the operation of intake valve (2) and exhaust valve (3) through intake and exhaust valve cams (11) in the cam shaft (12), wherein said cams has a secondary lobes (14) arranged for secondary opening of intake valve (2) and exhaust valve (3) twice in a thermodynamic cycle;
wherein said secondary opening (7) of the exhaust valve (3) cause EGR when the pressure in the exhaust manifold (5) is higher than combustion chamber pressure, and said secondary opening (6) of intake valve (2) causes EGR when the pressure in the intake manifold (4) is lesser than combustion chamber pressure.
2. The exhaust gas recirculation system as claimed in claim 1, wherein said secondary lobes (14) in the cams (11) is constructed to secondary opening (7) of exhaust valve (3) during intake stroke and secondary opening (6) of intake valve (2) during exhaust stroke.
3. The exhaust gas recirculation system as claimed in claim 1, wherein exhaust gases are trapped inside the combustion chamber or directed into intake manifold (4) for participation in combustion during next thermodynamic cycle.
4. The exhaust gas recirculation system as claimed in claim 1, wherein said system cams has several combinations of primary and secondary lobe height for varying the valve opening height and duration.

5. The exhaust gas recirculation system as claimed in claim 1, wherein said secondary cam lobe height is from 0.5 mm to 1.5 mm.
6. The exhaust gas recirculation system as claimed in claim 1, wherein the gas exchange takes place with respect to the pressure differential between the intake manifold (4) and cylinder in the engine and differential between exhaust manifold (5) and the cylinder in the engine.
7. The exhaust gas recirculation system as claimed in claim 1, wherein the exhaust gas trapping is sequential with the operation of the engine where a portion of EGR happens in exhaust stroke and remaining portion happens in subsequent suction stroke.
8. The exhaust gas recirculation system as claimed in claim 1, wherein the amount of exhaust gas recirculated is with respect to the height of the secondary cam lobe (14) and opening duration and the magnitude of the pressure differential of the manifolds (4, 5) with the cylinder of the engine.
9. A method of internal exhaust gas recirculation for internal combustion engines, said method comprising the steps of:
providing cam with a secondary lobe (14) in the exhaust and intake cams (11) placed in the valve train mechanism for opening of intake valve (2) and exhaust valve (4) more than once in a thermodynamic cycle;
with secondary opening (7) of the exhaust valve (3) during intake stroke and secondary opening (6) of the intake valve (2) during exhaust stroke, such that the exhaust gases are trapped inside the combustion chamber for recirculation, wherein said secondary opening of the exhaust valve (3) causes

EGR when the pressure in the exhaust manifold (5) is higher than pressure in the combustion chamber, and said secondary opening of intake valve (2) causes EGR when the pressure in the intake manifold (4) is lesser than the pressure in the combustion chamber.
10. The method as claimed in claim 9, wherein during secondary exhaust valve opening in suction stroke, exhaust gases flow into the combustion chamber from the exhaust manifold (5) and add to the already existing EGR mixture forming a EGR richer mixture that participates in combustion of fresh fuel injected after compression stroke and thereby reduce nitric oxide emissions.
11. The method as claimed in claim 9, wherein the gas exchange between the intake and exhaust gas occurs based on the pressure difference between the intake manifold (4) and exhaust manifold (5) and the combustion chamber.
12. The method as claimed in claim 9, wherein the gas exchange between the intake and exhaust gas occurs in exhaust and suction strokes sequentially wherein a portion of EGR occurring in exhaust stroke while an additional amount of EGR is happening in the subsequent suction stroke.