WO2007088560A1

WO2007088560A1 - An improved hybrid internal combustion engine with extended expansion

Info

Publication number: WO2007088560A1
Application number: PCT/IN2007/000036
Authority: WO
Inventors: P. Ravi
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-02-02
Filing date: 2007-02-01
Publication date: 2007-08-09
Anticipated expiration: 2008-08-02

Abstract

An engine is provided with two chambered cylinder bifurcated by a liner with such a ratio of volumes that the annular outer chamber to act as a compression chamber/zone while the suitably designed piston is moving towards Top Dead Center (TDC), and the inner chamber to act as an expansion zone with enough volume such that when the burnt gases are expanded during power stroke, the gases reaches pressure equivalent to atmospheric pressure and thus enabled to extract more power following Atkinson Cycle successfully. In particular, the volume ratio between the compression & expansion is provided by different effective cross sectional areas of compression chamber (encapsulated by the outer portion of cylinder (20), cylinder middle block (14), liner (23) and piston outer part (61) and the expansion chamber (encapsulated by liner (23) cylinder head (13) and piston inner part (60) ) for the same stroke length.

Description

An Improved Hybrid Internal Combustion Engine With Extended Expansion

Field of Invention

This invention relates to the field of Internal combustion engines particularly reciprocating type internal combustion engines. It relates to both spark ignition engines (petrol engines) as well as compression ignition engines(diesel engines). Back ground of Invention

The theoretical working cycle of a conventional four-stroke petrol engine is based on Otto-cycle. The engine output is usually being varied by means of a throttle which controls the amount of air fuel mixture inducted into the engine. One drawback of such an engine is that in the Otto-cycle, the suction and compression strokes are equal to the expansion ( power)and exhaust strokes which does not enable a complete expansion. Comparing with that of the Atkinson-cycle engine which uses longer strokes for expansion and exhaust than for suction and compression obtains more complete expansion and exhaust. The Otto-cycle engine is therefore not as efficient as the Atkinson-cycle engine.

Attempts has been made to adopt Atkinson-cycle in internal combustion engines (i.e., to provide sufficient expansion) to extract additional energy / work out put by limiting suction volume ( ie., by keeping the suction valve open beyond the piston after reaching BDC so that a part of already sucked air fuel mixture is returned to inlet manifold by reverse pumping ) by which the limited air fuel mixture will have enough expansion space during its power stroke.

In one such attempt (Vivian, U.S. Pat. No, 4,174,683), the suction valve of the working cylinder of the engine is kept open during part of the compression stroke and thereafter closing the valve and compressing only a fraction of the charge which is then ignited and expanded against the piston to the full volume of the cylinder. This process is very complex requiring means for both changing the point of axis of the crankshaft and for altering the intake valve timing according to load demands. Furthermore, no means of increasing compression or charge turbulence is provided. This concept continues to operate with the friction inherent in the four-stroke cycle engine. In addition, the operation of this engine at full load is the same as for a conventional engine so that it offers improved characteristics at part load only.

An internal combustion engine is described in US4138973; having a variable valve timing device controlling the timing of the intake-valve, and a coupling between the engine output control member (e.g. accelerator pedal) and the variable timing device for varying the timing of the intake- valve in response to the movement of the engine output control member, thereby controlling the quantity of the fuel-air mixture in the cylinder at the time of combustion. The engine also has an arrangement for maintaining a substantially constant compression ratio in the cylinder notwithstanding variations in the engine output, the latter means including a floating crown on the piston, a skirt coupled to the piston pin, and a spring connected at one end to the piston pin (directly, or indirectly via its skirt), and at the opposite end to the piston crown.

The lowering of the gas pressure acting on the floating crown upon an increase in the delay of the closing of the intake valve, permits the crown, by virtue of the inertia forces acting on it, to move further inwardly into the cylinder at the end of the compression stroke than when the delay is decreased. The further inward movement of the crown is directly proportional to the reduction of the original compression stroke resulting from the delay in the closing of the intake valve, thereby causing the engine operation to approximate a constant compression ratio operation notwithstanding variations in the valve closing delay and variations in the engine output. In addition, the spring acts to move the crown further inwardly into the cylinder at the end of a compression stroke, and to a greater extent at the end of the exhaust stroke, thereby maximizing the exhaust of the spent gases and the quantity of the fuel-air mixture that may be inducted.

A notable attempt was revealed in the Wishart engine, disclosed in U.S. Pat. No. 3,408,811 , in which a large piston compress the charge into a smaller cylinder which is further compressed, the charge then transferred into another small "firing" cylinder where the charge was ignited and expanded to the full volume of the smaller cylinder. It then passed the burned gases through ports uncovered by the piston into a larger cylinder where it was expanded further. This required four cylinders with pistons which made two working strokes for each power stroke, hence it is an eight-stroke cycle engine with all of the mechanical and fluid friction inherent in such a working cycle. The mechanical complexity of this engine makes it costly to manufacture.

Another method of deriving mechanical work from a combustion gas in an internal combustion engine and reciprocating internal combustion engines for carrying out the method are depicted in US4565167, wherein the reciprocating internal combustion engine comprising a compressor chamber for compressing an air charge, power chambers in which combustion gas is ignited and expanded, a piston operable in each chamber and connected to a crankshaft by connecting link means for rotating the crankshaft in response to reciprocation of each piston, a transfer manifold communicating said compressor chamber with said power chambers through which manifold the compressed charge is transferred to enter the power chambers, an admission valve controlling admission of air to said compressor chamber for compression therein, an outlet valve controlling admission of the compressed charge from the compressor chamber to the transfer manifold, an intake valve controlling admission of the compressed charge from the transfer manifold to said power chambers, and an exhaust valve controlling discharge of the exhaust gases from said power chambers, said valves being timed to operate such that the air charge is maintained within the transfer manifold and introduced into the power chamber so that ignition can commence at maximum compression, means being provided for causing fuel to be mixed with the air charge to produce a combustible gas, means being provided for ignition of the combustible gas, and said compressor chamber and the combustion chambers of said power chambers are sized with respect to the displaced volume of said power chamber such that the exploded combustion gas can be expanded beyond its initial volume.

Others have attempted to extract more shaft work from combustion gases using similar systems of conducting the burned gases into other cylinders after firing for additional expansion, also with similar results. Some have tried burning charges in one-half the cylinders of a multi-cylinder engine and then ducting the exhaust from the firing cylinders into the remaining half of the cylinders for the extraction of additional shaft work. To date none of these attempts has been successful and emissions were generally increased over conventional engines.

It can be observed that the basic aim to extract additional work(δω) through additional expansion till the burnt gases reaching atmospheric pressure by means of special mechanisms which helped to vary active stroke length different(i.e.,less) during suction stroke and different (i.e.,more) during expansion. Here the stroke length during expansion (I₆) is greater than stroke length during suction(l_s) and thus the required expansion volume (v_e) was achieved with required additional volume δv. The additional volume was observed as δv = v_e - v_s .

where v_e refers to expansion volume & v_s refers to suction volume

In this model the engine mechanism was complex and the size was abnormal. In addition, the increased frictional resistance due to the additional piston travel diluted the acquired additional / increased amount of work / energy (δω) . Thus the Atkinson engine went impracticable though the thermal efficiency was proved to be higher than Otto cycle. Object of Invention

The present invention aims to extract more energy from the expansion of burnt gases during its power stroke by suitably sizing the engine such that the expansion during power stroke is extended until the pressure inside the combustion chamber reduces to that of atmospheric pressure.

The another object of invention is to obtain / build an hybrid engine which has desirable qualities of four stroke engine as well as to produce power in every two stroke like a two stroke engine by suitably staging the cycle of operations in two compartment / cylinders with suitable piston arrangements.

Yet another object of present invention is to provide an internal combustion engine with least unburnt gases expulsion addressing to atmospheric pollution.

Yet another object of present invention is to provide an internal combustion engine with exhaust gases with least temperature by utilizing / converting more heat energy into useful work.

Yet another object of invention is to provide an internal combustion engine with improved fuel efficiency along with improved thermal efficiency addressing to fuel saving / conservation .

Yet another object of invention is to provide an internal combustion engine with reduced noise level of operation addressing to the reduction of noise pollution.

Statement of Invention

With the above said objectives, the need of increasing the expansion volume stands as main necessity. It is observed that volume is a function of / product of Area(!4*Iϊd²) and stroke length (1), where d is diameter of piston, i.e., V = (¹^IId²) * !

The required change in volume (δv) will vary linearly with change in stroke length as well as quadratically with change in diameter.

Instead of providing additional volume of expansion through mechanisms to provide additional stroke length (like Atkinson), it is providing different combustion chamber having calculated diameter suitable enough to expand the burnt gases up to atmospheric pressure.

The engine is provided with two stage cylinders bifurcated by a cylindrical liner with such a ratio of volumes that the annular outer chamber to act as a compression zone while a suitably designed piston is moving towards Top Dead Center(TDC), and the inner chamber to act as an expansion zone with enough volume. In general the volume ratio between the suction & expansion is provided by different effective cross sectional areas of compression chamber (encapsulated by the inner portion of cylinder(20), cylinder middle block(14), cylindrical liner(23) and piston outer part(61) ) and the expansion chamber (encapsulated by cylindrical liner(23) cylinder head (13) and piston inner part(60) ) for the same stroke length. Here l_β = l_s ; where l_e is expansion stroke length and l_s is suction stroke length.

Accordingly, air fuel mixture (charge) will be sucked in the annular chamber through suction valve(17) while the piston moves from Top Dead Center(TDC) to Bottom Dead Center(BDC). Then suction valve will be closed and the piston will move from BDC to TDC compressing the charge inside the compression chamber in a transient zone over the inner chamber encapsulated by a middle block, cylinder head, transfer valve ( at its lower position). Then, when piston is at 35° before TDC, the transfer valve is made to move up and transfer the above temporarily stored compressed charge downward and close the transfer ports. Simultaneously, the exhaust valve (15) starts closing the exhaust ports. As the piston still continues to move up to TDC, the charge is further compressed up to the required compression ratio ( when the piston reaches its TDC ). Spark is made to occur in the clearance volume/zone by a spark plug about 25° before TDC which initiates ignition and successively combustion. ( The spark timing is given as 25°as an example data. In actual performance the spark timing will vary according to relevant factors namely piston speed, rate of burning of mixture) Then combustion takes place and the burnt gases reaches its peak pressure (and temperature ) which pushes down the piston as power stroke until piston reaches its BDC. Simultaneously when the power stroke is performed in the inner chamber ; the outer annular chamber performs suction stroke for the next cycle and the cycles of operation continues. Then, the piston moves from BDC to TDC, exhaust valve opens & the burnt gases are expelled to atmosphere. It can be noted that suction & power strokes occur simultaneously in outer & inner chambers respectively when piston moves from TDC to BDC. Similarly compression & exhaust strokes occur simultaneously in outer & inner chambers respectively when piston moves from BDC to TDC. Power is produced for each rotation (i.e. every two strokes of crank shaft / 360° rotation of crank shaft) attaining the second object of invention. However, scavenging (expulsion of burnt gases) is maintained without carry over of fresh charge to atmosphere as like a four stroke engine by a suitable valve arrangement& attains the third object of invention.

This invention also attains its fourth object by expanding the burnt gases to atmospheric pressure by utilizing more thermal energy into crank shaft movement for useful work, which in turn improves fuel efficiency along with improved thermal efficiency & fuel saving. Thus the fifth object of invention is also attained. As the burnt gases are expanded to atmospheric pressure & then pushed out by piston to exhaust, the high sound intensity during exhausting is reduced, which helps to attenuates noise level & attains its sixth object of invention. The invention provides a method of deriving mechanical work from combustion gas in an internal combustion engine having two chambers such as outer annular chamber (28) in which suction & compression take place and the inner main chamber(29) in which combustion / expansion & exhaust strokes take place and a grooved piston operable in each chamber simultaneously comprising the steps of: (i) sucking air fuel mixture in annular outer chamber(28) while the piston (21) moves down from TDC to BDC as a result of expansion of burnt gases in inner main chamber, (ii) compressing air fuel mixture in annular outer chamber (28) while the piston(21) moves upward from BDC to TDC simultaneously exhausting the expanded burnt gases from inner main chamber through the opened exhaust valve, (iii) actuating transfer valve (25) to its extended position to form a transient zone and storing compressed air fuel mixture in transient zone, (iv) de-actuating transfer valve (25) to its normal retracted position and transferring the temporarily stored compressed air fuel mixture from the transient zone to the inner main chamber(29), (v) producing spark from a spark plug and allowing the combustion of air fuel mixture in inner main chamber, (vi) allowing burnt gases to expand up to pressure equivalent to atmospheric pressure and thereby extracting additional mechanical work from combustion gas, (vii) actuating the exhaust valve into its open position and allowing the burnt gases to be exhausted from the inner main chamber through the exhaust valve.

The invention also provides an improved internal combustion engine comprising : a cylinder(20); a cylinder middle block(14) being fixed over the said cylinder, a liner(23) extending from the said middle block to form an annular outer chamber(28) and an inner main chamber(29); a cylinder head(13) being fixed over the middle block(14) housing a spark plug(12) and a transfer valve(25) operably placed such that the transfer valve forms a transient zone when it is actuated; a piston(21) connected to a crank shaft (22) which is operable in each chamber simultaneously such that when the piston moves from TDC to BDC air fuel mixture is sucked in outer annular chamber (28) and simultaneously burnt gases are expanded as power stroke in the inner main chamber(29) and when the piston moves from BDC to TDC, air fuel mixture is compressed in outer annular chamber(28) until 35° Before Top Dead Center(BTDC) and stored in transient zone and then the compressed charge is transferred and furthermore compressed to required compression ratio in the main chamber by deactivating the transfer valve, around 25° BTDC the charge ignited and is burnt by producing a spark from spark plug (12) while the piston reaching TDC, and the inner main chamber is suitably sized such that when the burnt gases are expanded in inner main chamber the gases are expanded until it reaches atmospheric pressure which is beyond the initial volume and the energy is extracted by the piston and converted into useful work. Brief Description Of The Drawings

The embodiment of the invention will be described , by way of example, with reference to the accompanying drawings. . Fig Ia is general representation of PV diagram of Otto Cycle. Fig Ib represents PV diagram of Atkinson Cycle

Fig 2 is an illustrative cut sectional view of first embodiment of present invention.( when engine just commence its suction /power stroke)

Fig 3 is an illustrative cut sectional view of first embodiment of present invention when the engine is at the initial starting stage of compression / exhaust stroke. Fig 4 is an illustrative cut sectional view of fist embodiment of present invention when the engine is at the stage of transferring of pre-compressed air fuel mixture in the inner main chamber / combustion space.

Fig 5a is general representative PV diagram of conventional dual cycle. Fig 5b represents PV diagram of dual cycle for a diesel engine with extended expansion and according to our invention.

Fig 6a is a top view of the piston according to the first embodiment of invention. Fig 6b is a cross sectional view taken along line AA of the piston depicted in fig 6a. Fig 7a is a cut section view of liner according to first embodiment of invention. . Fig 7b is a cut section view of piston according to first embodiment of invention. Fig 8 is three dimensional view of transfer valve according to the first embodiment of invention. Fig 9 is an illustrative cut sectional view of second embodiment of present invention. ( when engine just commence its suction /power stroke)

Fig 10 is an illustrative cut sectional view of second embodiment of present invention when the engine is at the initial starting stage of compression/exhaust stroke. Detailed Description Of The Invention

Figure Ia Shows P - V diagram of Otto cycle in which volume v is plotted in x axis & absolute pressure p is plotted in Y axis . The point 1 refers to a stage when an internal combustion engine is at the end of suction stroke having sucked to its full swept volume V_s at atmospheric pressure Pa . The process of adiabatic compression is represented by linel to 2, where the pressure inside the combustion chamber increases with decreasing volume and thereby reaches point 2 which in turn refers to the stage of end of compression stroke. Then the spark is generated and combustion takes place which results in sudden raise in pressure with heat supply (Q_s ) from combustion denoted by line 2 to 3. From point 3 the air expands adiabatically to point 4 as power stroke. Then, due to exhaust stroke heat (Q_R) is rejected to atmosphere and the process reaches its original point 1 by sucking air fuel mixture as a starting of next cycle.

It can be observed that, when piston descends to BDC (ie., point 4), the piston's further linear motion is restrained as the crank has to reverse its direction from BDC to TDC . Even though the piston reaches its BDC the pressure inside the combustion chamber does not expand fully to the level of atmospheric pressure. If the burnt air fuel mixture is expanded up to atmospheric level, as proposed by Atkinson Cycle and as Shown with similar notations in fig Ib, further energy / work (δω) can be extracted which is denoted by line 4 to 4' . The additional work (δω) extracted will be equivalent to the area covered by 4-4 -1- 4 as shown with hatched portion when the Otto cycle's work output is denoted with W which will be equivalent to the area covered by 1-2-3-4-1. Whereas, the proposed engine produces /extracts a total work out put (w+δω) following Atkinson cycle as principle, but with different engine construction which makes it possible with out the drawbacks of previous models.

As described in statement of invention, this invention provides separate annular chamber to compress the air fuel mixture to sufficient compression ratio and the compressed air fuel mixture is transferred to a transient zone with in the main inner chamber with a transfer valve positioned at lower position. When piston reaches 35⁰BTDC, the transfer valve moves up and transfers the air fuel mixture into the main inner chamber. The inner chamber is suitably sized that it expands the burnt gases up to atmospheric pressure after the combustion process which is started 25⁰BTDC by a spark from a spark plug ( The spark timing is given as 25°as an example data. In actual performance the spark timing will vary according to relevant factors namely piston speed, rate of burning of mixture) . Then after the end of power stroke, the burnt gases will be expelled through a exhaust valve to atmosphere during the return upward stroke of piston, and after which the next cycle follows. According to invention , suction & expansion are performed simultaneously at annular chamber and inner main chamber respectively. Similarly, compression & exhaust are performed simultaneously at annular chamber and inner main chamber respectively. Thus the invention produces power for every two strokes ( ie., for every rotation of crank shaft) like a two stroke engine. However, all the four functions are carried out with out any over lap and without any escapement of fresh charges during scavenging operation along with complete burning of fuel air mixture with necessary arrangements equivalent to four stroke engine.

General arrangement of an improved hybrid internal combustion engine(l l l) as first embodiment of invention is depicted in fig 2. The engine comprises a cylinder block(20) , a middle block (14) with an integrated cylindrical liner(23) , a cylinder head (13), and a piston(21) suitably shaped to co-operate with the cylinder & liner in such a manner to reciprocate and perform all the functions viz., suction, compression, power/expansion, exhaust strokes.The cylinder block has water jacket (19) / fins (18) to cool & maintain the engine temperature within its operation temperature limits. The cylinder block has suction valve arrangement (17) at the top side enabling suction of fuel air mixture during suction stroke. An exhaust valve (15) is provided in middle block(14) to be able to cooperate with the engine to expel the burnt gases during exhaust stroke. Thfαniddle block also has transfer port first part to transfer the compressed air fuel mixture from the annular outer chamber (28) encapsulated between the cylinder(20) , liner (23) , piston (21), and the middle block (14) through transfer port second part provided in cylinder head(13). The cylinder head houses a transfer valve (25) suitably made to co-operate with middle block(14) and with transfer port second part to perform transfer function of compressed air fuel mixture from the annular outer chamber. The transfer valve is made to toggle between two position; one is its top position at which it closes transfer port second part as shown in fig 2 and the other position is its actuated position (ie., extended position) as shown in fig 3 during which it opens the transfer port second part and at the same time it rests on its seat (30) provided in the inner wall curved surface of middle block. Transfer valve comprises a valve plate (50) , at least two valve actuating stems(52) and a guide sleeve (51) as shown in fig 8. The piston (21) comprises two portions namely piston outer part (61) & piston inner part (60), which are all spaced apart by liner pass through groove (62) and connected by inter connecting ribs (66). The liner (23) pass through groove (62). The groove extends from the top end of piston to a distance which is slightly more than stroke length such that piston is guided always by liner (23) as liner pass through groove (62). Suitable piston ring grooves are provided at piston outer surface ( ie., piston ring outer groove(64) ) and at the region where liner pass through groove ( ie., piston ring inner grooves ( 65) ). The remaining arrangements like lubrication, crank shaft , connecting rod, fuel supply system etc., are made suitably such that they co-operate with each other along with above mentioned parts to form an internal combustion engine.

The operation of the engine is as follows :

Referring fig 2, the suction valve (17) opens as the piston starts moving downward from 0°/TDC and air fuel mixture is inducted from inlet manifold into the annular outer chamber(28) (indicated in fig 3) until the piston reaches BDC/180°. After the end of above suction stroke(from 0° to 180°),the suction valve closes at 180°. During the suction stroke, transfer valve(25) is in its top position closing the transfer port second part as shown in fig 2. On further upward movement of piston to TDC, the suction valve (17) remains closed and the transfer valve is actuated & moved downward to its extended position. When the transfer valve is in its extended position ( as shown in fig 3) it sits on its seat (30)(shown in fig 2) provided in the inner wall curved surface of middle block & opens the transfer port(27). As the piston moves further from BDC towards TDC from 180° to 325°, the transfer valve will remain in its extended / actuated position and the above inducted charge is compressed over the transfer valve space encapsulated by transfer valve(25), middle block(14) & cylinder head (13) (simultaneously the previous cycle's burnt gases are expelled via exhaust valve as exhaust valve(15) has been kept open from 180° to 325° of crank reference angle). When the crank angle is 325°, the transfer valve is made to move up and revert back to its top / normal position; during which the above compressed charge is transferred to inner main chamber (29). The transferring operation is shown in fig 4. During above transferring operation, the exhaust valve(15) closes simultaneously.

As the piston continues to move further towards TDC , the pre-compressed & transferred charge is further compressed in a clearance volume V₀ to a required compression ratio in the main chamber. When piston is at 25° before TDC, spark is generated and the compressed air fuel mixture is ignited and combustion takes place resulting in pressure raise and the piston moves up to TDC and completes one revolution( i.e 360°). (The pressure further raises to its peak after TDC)

The pressure exerted on piston forces the piston to move forcefully from TDC to BDC as a power stroke (during which suction takes place simultaneously in outer annular chamber by keeping the suction valve open and transfer valve closed ). As the piston moves from TDC to BDC, the burnt gases under goes expansion by exerting pressure over the piston. The engine is designed such that circular cross sectional area of the piston in the inner part of piston (60) (fig 6a) is more than the annular cross sectional area at outer part of piston (61). Because of the common stroke length,the expansion volume is more than the suction volume and this size suitably designed so that the products of expansion expand till the pressure drops to atmospheric pressure and hence additional work is extracted. Thus the engine is made to follow Atkinson Cycle successfully with out the drawbacks of prior art. Then with the power taken from the power stroke, crank is made to rotate further rotations & the work output is drawn for all intended /designed purposes. As the crank further moves the engine continues to repeat the cycle of operation ( 0° to 180°; 180° to 325°, 325° to 360°) as explained above. The General arrangement of an improved hybrid internal combustion engine(112) as second embodiment of invention is depicted in fig 9. The engine comprises a stepped cylinder block(71), a cylinder head (78), and a stepped piston(73) suitably shaped to co-operate with the cylinder in such a manner to reciprocate and perform all the functions viz., suction, compression, power/expansion, exhaust strokes. The cylinder block has water jacket (75) / fins (72) to cool & maintain the engine temperature within its operation temperature limits. The cylinder block has one number ring shaped shuttle valve arrangement (74) at the top side of cylinder block bottom part(89) enabling suction of fuel air mixture during suction stroke. An exhaust valve (76) is provided in the top side of cylinder block top part(88) to be able to co-operate with the engine to expel the burnt gases during exhaust stroke. The transfer port first part(90) is connected with transfer port second part(91) by a transfer manifold to transfer the compressed air fuel mixture from the outer compression chamber(82) which is encapsulated between the cylinder block bottom part(89) and piston outer skirt(86). The cylinder head houses a transfer valve (77) suitably made to co-operate with cylinder block top part(88) and with transfer port second part(91) to perform transfer function of compressed air fuel mixture from the outer compression chamber to a transient zone(83). The transfer valve is made to toggle between two position; one is its top position at which it closes transfer port second part as shown in fig 9 and the other position is its actuated position (ie., extended position) as shown in fig 10 during which it opens the transfer port second part and at the same time it rests on its seat (92) provided in the inner wall curved surface of cylinder block top part. Transfer valve comprises a valve plate (50) , at least two valve actuating stems and a guide sleeve as shown in fig 8.

The stepped piston (73) comprises two portions namely piston outer skirt(86) & piston main part (87), which are all connected by piston shoulder(93). The piston main part(87) is sized enough relative to the stroke length as well as to cylinder block top part(88) which is slightly more than stroke length such that piston main part(87) is guided always by cylinder block top part(88) and at the same time the piston outer skirt part(86) is guided always by cylinder block bottom part(89). Suitably piston ring grooves are provided at piston outer surfaces. The remaining arrangements like lubrication, crank shaft , connecting rod, etc., are made suitably such that they co-operate with each other along with above mentioned parts to form an internal combustion engine. The operation of the engine according to second embodiment is as follows :

Referring fig 9, as the piston starts moving from TDC/O⁰, the air fuel mixture is inducted into the outer compression chamber(82) ( fig 10)through the shuttle valve (74) which opens to connect the outer compression chamber(82) with inlet manifold passage (94), until the piston reaches BDC. During this period transfer valve (77) is in its top position closing the transfer port second part (91) as shown in fig 9. The shuttle valve(74) closes the connecting passage with inlet manifold when the piston reaches its BDC as an end of suction stroke (0° to 180°), simultaneously opens the passage(90) connecting with transfer port. On further movement, piston starts to move from BDC to TDC during which the transfer valve is actuated & moved to its extended position. When the transfer valve is in its extended position as shown in fig 10 it sits on its seat (92) provided in the inner wall curved surface of cylinder block top part & opens the transfer port. As the piston moves from BDC towards TDC & until 180° to 325°, the transfer valve will remain in its extended / actuated position and the inducted charge is compressed over the space encapsulated by transfer valve(77), cylinder block top part(88) & cylinder head (78). (simultaneously the previous cycle's burnt gases are expelled via exhaust valve(76) as exhaust valve has been kept open from 180° to 325° of crank reference angle). When the crank angle is 325°, the transfer valve is made to move up and revert back to its top / normal position; during which the compressed charge is transferred to inner main chamber (84). During the above transferring operation , the exhaust valve (76) is closed.

As the piston continues to move further towards TDC, the pre-compressed & transferred charge is further compressed to a clearance volume V₀ to get the required compression ratio. When piston is at 25° before TDC, spark is generated and the compressed air fuel mixture is ignited and combustion takes place resulting in pressure raise while piston still moves up to TDC and complete one revolution. ( i.e. 360° ). (The pressure reaches to its peak after TDC)

The pressure exerted on piston forces the piston to move forcefully from TDC to BDC as a power stroke (during which suction takes place in outer compression chamber by keeping the shuttle valve open with inlet manifold and transfer port in closed condition). As the piston moves from TDC to BDC, the burnt gases under goes expansion by exerting pressure over the piston. The engine is designed such that circular cross sectional area of the piston main part (87) is more than the annular cross sectional area at piston outer skirt(86). Because of the common stroke length,the expansion volume is more than the suction volume and this size is suitably designed so that the products of expansion expand till the pressure drops to atmospheric pressure and hence additional work is extracted. It can be noted that the engine is designed such that the burnt gases are allowed to expand that they reach atmospheric pressure and thus the engine is made to follow Atkinson Cycle successfully with out the drawbacks of prior art. Then with the power taken from the power stroke, crank is made to rotate further rotations & the work output is drawn for all intended /designed purposes. As the crank further moves the engine continues to repeat the cycles ( 0° to 180°; 180° to 325°; 325° to 335°;335° to 360°) as explained above.

In addition, if the engine operates in a poor load conditions / idling, the end of expansion may reach sub-atmospheric pressure (ie., vacuum) inside the inner main chamber(84). During such period a vacuum suppression valve(81) will automatically open and the outside atmospheric air will enter into the inner main chamber(84) collapsing the vacuum.

For the purpose of explanation, specific nomenclature is set forth to provide a through understanding of the present invention. The invention has been described with reference to the specific embodiments, as well as alternate embodiments of the invention, will become apparent to the person skilled in the art upon reference to the description of the invention.

For clarity, this description has been depicted keeping petrol engine as reference. However, the invention, obviously applicable to diesel engine with suitable air and fuel system arrangements & which are all with in the scope of present invention.

Therefore the present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest possible scope consistent with the principles & features disclosed herein.

Claims

I Claim,

1. A method of deriving mechanical work in an internal combustion engine having at least two chambers such as outer annular chamber(28) in which suction & compression take place and inner main chamber(29) in which combustion / expansion & exhaust strokes take place and a stepped / grooved piston operable in each chamber simultaneously comprising the steps of :

i. sucking air fuel mixture in annular outer chamber(28) while the piston (21) moves down from Top Dead Center(TDC) to Bottom Dead Center (BDC) as a result of expansion of burnt gases in inner main chamber(29),

ii. compressing air fuel mixture in annular outer chamber (28) while the piston(21) moves upward from BDC to TDC simultaneously exhausting out the expanded burnt gases to atmosphere from inner main chamber through the opened exhaust valve(15),

iii. actuating transfer valve(25) to its extended position to form a transient zone and storing compressed air fuel mixture in the transient zone,

iv. deactivating transfer valve(25) to its normal position and transferring the stored compressed air fuel mixture from the transient zone into inner main chamber(29),

v. producing spark from a spark plug for the combustion of air fuel mixture in inner main chamber,

vi. allowing burnt gases to expand upto a pressure equivalent to atmospheric pressure and thereby extracting mechanical work from combustion gases,

vii. actuating the exhaust valve into its open position and allowing the burnt gases to be exhausted out from the inner main chamber to atmosphere through the exhaust valve.

2.The method according to claim 1 wherein the suction of air fuel mixture in annular outer chamber (28) and expansion of burnt gases in inner main chamber(29) are simultaneously performed.

3. The method according to any one of claims 1 to 2 wherein , the compression of air fuel mixture in annular outer chamber(28) and exhaust of burnt gases in inner main chamber(29) are simultaneously performed.

4.The method according to any one of claims 1 to 3 wherein, suction of air fuel mixture at annular outer chamber & expansion of burnt gases at inner main chamber are taking place from 0° to 180° of crank reference angles; compression of air fuel mixture at outer annular chamber and exhaust of burnt gases from inner main chamber are taking place from 180° to 325° of crank reference angles; transferring of compressed air fuel mixture from a transient zone to inner main chamber takes place from 325° to 335° of crank reference angles; combustion of air fuel mixture takes place at inner main chamber from 335° of crank reference angles.

5.An Improved Internal Combustion Engine comprising a cylinder(20); a cylinder middle block(14) being fixed over the said cylinder, a liner(23) extending from the said middle block to form an annular outer chamber(28) and an inner main chamber(29);a cylinder head(13) being fixed over the middle block(14) housing a spark plug(12) and a transfer valve(25) operably placed such that the transfer valve forms a transient zone when it is actuated; a piston(21) connected to a crank shaft (22) which is operable in each chamber simultaneously such that when the piston moves from TDC to BDC air fuel mixture is sucked in outer annular chamber (28) and simultaneously burnt gases are expanded as power stroke in the inner main chamber(29) and when the piston moves from BDC to TDC, air fuel mixture is compressed in outer annular chamber(28) until 35° BTDC and stored in transient zone then the compressed charge is transferred to main chamber by deactivating the transfer valve, around 25° BTDC the charge is burnt by producing a spark from spark plug (12) and the inner main chamber is suitably sized such that when the burnt gases are expanded in inner main chamber the gases are expanded until the pressure reduces to that of atmospheric pressure which is beyond the initial swept volume and the energy is extracted by the piston and converted into useful work. β.The improved internal combustion engine as claimed in claim 5 wherein, suction valve (17)is operably provided in cylinder(20) which is connected to annular outer chamber(28) and an exhaust valve(15) is operably provided in middle block(14) which is connected with inner main chamber(29) such that it expels the burnt gases to atmosphere during exhaust stroke in its open position.

7.The improved internal combustion engine as claimed in any one of claims 5 or 6 wherein the piston (21) comprises a piston outer part (61) to act in annular outer chamber (28) and a piston inner part (60) to act in inner main chamber (29) which are integrally joined with each other by inter connecting ribs(66) but being separated at its top portion by liner pass through groove(62) such that the piston reciprocates in the liner pass through groove during the pistons reciprocatory motion and the piston has atleast two piston ring inner grooves (65) and atleast two piston ring outer grooves(64) to house piston rings.

8. The improved internal combustion engine as claimed in any one of claims 5 to 7 wherein, the middle block (14) has a transfer port first part(26) extending from the annular outer chamber (28) to the transfer port second part (27) provided in the cylinder head, and the transfer port second part extends from the said transfer port first part to main inner chamber (29) through the transfer valve(25) operably connected such that it transfers the compressed air fuel charge from annular outer chamber to the inner main chamber during transfer operation.

9.The improved internal combustion engine as claimed in any one of claims 5 to 8 wherein, the engine is cooled either by water jackets (19) or fins (18). 10. An Improved Internal Combustion Engine comprising:

a stepped cylinder(71) including a cylinder block bottom part (89) and a cylinder block top part(88);a cylinder head(78) being fixed over the cylinder block top part(88) housing a spark plug(80) and a transfer valve(77) operably placed such that the transfer valve forms a transient zone when it is actuated and closes the transfer port second part(91) when it is deactuated; a stepped piston(73) including a piston main part(87) and a piston outer skirt(86), the stepped piston being connected to a crank shaft through a connecting rod(85) the piston being operable in each chamber simultaneously such that when the piston moves from TDC to BDC air fuel mixture is sucked in outer compression chamber(82) and simultaneously burnt gases are expanded as power stroke in the inner main chamber(84) and when the piston moves from BDC to TDC, air fuel mixture is compressed in outer compression chamber(82) until 35° BTDC and stored in transient zone(83) by keeping transfer valve in actuated position, and in furtherance the compressed charge is transferred to main chamber(84) by deactivating the transfer valve, around 25° BTDC the charge is burnt by producing a spark from spark plug (80) such that when the burnt gases are expanded in inner main chamber the gases are expanded until it reaches atmospheric pressure which is beyond the initial volume as the inner main chamber(84) is suitably sized as relatively larger than the outer compression chamber(82) such that the burnt gases are expanded until the pressure inside the inner main chamber (84) reduces to that of atmospheric pressure and the energy is extracted by the piston and converted into useful work.

11. The improved internal combustion engine as claimed in claim 10 wherein, shuttle valve(74) is operably provided in cylinder(71) which connects outer compression chamber(82) with inlet manifold in one position and with transfer port first part(90) according to its actuation.

12. The improved internal combustion engine as claimed in any one of claims 10 or 11 wherein an exhaust valve(76) is operably provided and is connected with inner main chamber(84) such that it expels the burnt gases during exhaust stroke in its actuated open position.

13. The improved internal combustion engine as claimed in any one of claims 10 to 12 wherein, the engine is cooled either by water jackets (75) or fins (72).

14. The method of deriving mechanical work from combustion of gases in an internal combustion engine substantially as herein described with reference to the accompanying drawing.

15.The improved internal combustion engine substantially as herein described with reference to the accompanying drawing.

Dated this 29 th of January 2007.