Title of Invention

"AN INTERNAL COMBUSTION ENGINE"

Abstract

The present invention relates to an internal combustion engine comprising : an engine cylinder; a piston moving freely in the said cylinder; a crank case connected to a fueling device supplying air and lube oil mixture to the said crank case; characterized in that: a crank shaft housed in the said crank case is provided with a sprocket driving air pump connected to the said fueling device; a cylindrical block mounted on the said crank case having a cylindrical bore for air pump assembly; said air pump having an inlet port connected to the said fueling device through a spacer and an outlet port connected to the said engine cylinder terminating at the desired location with respect to the main engine operation; a second sprocket provided in the said crank shaft for driving the chain from the engine crank shaft.

Full Text

The present invention relates to an improved internal combustion engine. The main embodiment of the present invention resides in the engine being capable of minimising the effect of dilution and of direct fuel and air mixture loss. The mechanical components and the system configuration of the engine of the present invention are simple and robust and eliminates the dynamic elements in the charging or discharge processes. BACKGROUND OF THE INVENTION The simple but inefficient mixture scavenged, spark ignition engines are used for a wide variety of utility engines, mopeds, motor cycles, for lawn and garden equipment such as chain saws, leaf blowers, trimmers and the like; smaller motorcycle engines used on dirt bikes, jet skis, small outboard motors as well as radio controlled model planes. These two stroke spark ignition engines find effective usage in two wheelers because of important advantages over four stroke engines viz., two stroke spark ignition engines do not have valves which simplifies their construction and they fire once every revolution while four stroke engines fire once every other revolution, giving two stroke spark ignition engines a significant power boost. These advantages make two stroke spark ignition engines lighter, simpler and less expensive. Besides being cost effective the two stroke spark ignition engines also have the potential to pack about twice the power into the same space because there are twice as many power strokes per revolution. The combination therefore gives two stroke spark ignition engines a greater power to weight ratio. The principal advantages of the spark ignition engines are higher specific power output, lower specific weight and volume, simpler construction, lower brake specific NOx emission and lower part load pumping losses. The spark ignition engines however suffer from major disadvantages as well. These disadvantages specifically relate to efficient usage of fuel. The spark ignition engines produce a lot of pollution which comes from two sources, insufficient combustion of oil and through leakage of fuel. The leakage of oil is due to that every time a charge of air/fuel is loaded in the combustion chamber, part of it leaks out through the exhaust port. The high specific hydrocarbon emission and the generally inferior fuel consumption of mixture scavenged spark ignition engines are attributed to the direct loss of air fuel mixture to the exhaust during the open cycle. This is further accentuated by impaired combustion due to high dilution. These emissions not only contribute to causing pollution hazard but also decreases fuel efficiency. Conventional two stroke engine has additional drawbacks consequent to the mode of replenishing the fresh charge in each cycle. In a four stroke internal combustion engine the burnt products are thrown out fully and only the requisite quantity of fresh charge is inducted, i.e., drawn into the engine cylinder. The charge in the four stroke is a clean charge and the charge in the two stroke engine is diluted by combination products left over in the cylinder from the previous cycle. The dilution effects even combustion of fuel. Dilution in a two stroke engine varies from 90% under idling to 50% under full throttle. Dilution requires rich mixture for stable operation of the engine. Dilution is also a contributing factor in increasing the fuel combustion. The main aim is to reduce the effect of dilution and elimination of direct loss. Therefore a need arises for fuel efficient engine which overcomes the drawbacks pertaining to fuel efficiency and pollution hazard. The lowest displacement capacity in the single cylinder version in the current scenario of spark ignition engine is about 35CC. These are crankcase mixture scavenged and are generally constant speed machines. In the 50-250cc capacity, in the single cylinder version they are used in the transport vehicle application and are generally crankcase mixture scavenged variable speed load machines. However, here direct loss of fuel air mixture during scavenging, high dilution of charge through out the range of engine operating conditions and in particular at low throttle operation, and petrol lubrication are principal factors responsible for high brake specific fuel consumption and emission.The 250CC and above capacity multicylinder engines are yet to be developed for automotive application. Here, however, the direct loss of fuel air mixture during scavenging is fully eliminated in systems employing in-cylinder injection in the closed part of the cycle and reduced substantially in those employing in-cylinder injection in the open part of the cycle. Independent lubrication system is employed to achieve more efficient lubrication system of the engine. However, these engines also suffer from the drawbacks of high dilution which has a negative impact on the engine performance. The air breathing capacity of crankcase scavenged two-stroke engine is known to be limited by the volumetric efficiency (delivery ratio) characteristic of the crankcase. At full throttle the best figure achieved is around 60 percent in a predetermined (3000-3500 RPM) speed range of engine operation. With the inevitable through-put loss of a substantial part of this during scavenging (upto 30-35% at full throttle and 15-20% under idling), a considerable part of the combustion product of the previous cycle is carried forward and dilutes the fresh mixture of the operating cycle. The proportion of the residual products could be as high as 80% under low throttle condition and almost around 50% even under full throttle operation. The high dilution in spark ignition crankcase mixture scavenged spark ignition engines is the fundamental factor contributing to high emission under low speeds and the torque trough at low speeds. The problem of high dilution persists in conventional stroke engines, single or multicylinder, constant or variable speed type. This loss due to high dilution is at least 20% in the existing conventional design. The present invention aims to eliminate the problem pertaining to dilution of charge. In a mixture scavenged spark ignition engine, the scavenging of the residual combustion products at the end of each cycle of engine processes is carried out by a pre mixed charge of fuel and air. This necessarily involves loss of fuel and air, referred to as "short circuiting" of fresh charge. Besides, dilution and short circuiting, another problem encountered in the conventional engines relates to direct mixture loss. Cause of such direct mixture loss is scavenging of the combustion products at the end of the blow down after the expansion phase of the cycle by fuel air mixture. The present invention aims to overcome the disadvantages inherent to the conventional spark ignition engines, especially pertaining to high dilution, short circuiting and direct mixture loss. In-cylinder fueling necessarily involves meeting three related aspects-regulation of fuel quantity with respect to speed and load, disintegration of the metered quantity to the requisite degree of fineness to help rapid vaporisation of the fuel in the limited time available during compression, injection of the disintegrated fuel over the appropriate phase of the engine cycle and dispersing it in the desired domain of the cylinder space. The mixture scavenged ignition engine of the present invention is designed as a low pressure pump to achieve efficient scavenging. As a consequence of this, the maximum volume of air-fuel mixture delivered by the crankcase in relation to engine displacement capacity, referred to as "Delivery ratio" is about 0.75 (maximum) at full throttle in well designed constant speed engines. In variable speed engines it is about 0.65 (maximum) in a predetermined range of engine speed and much lower outside the range. At part throttle it is even lower and is about 0.15 under near closed throttle engine idling. Coupled with the 'short circuited' loss, the volume of fresh charge retained in the cylinder as a ratio of engine displacement volume varies from 0.1 to a maximum ofO.5. The production of residual combustion products in relation to the fresh charge, referred to as 'Dilution' is therefore always high in this class of engines. The extreme mechanical design simplicity and the low cost thereof are the principal advantages of the mixture scavenged spark ignition engine of the present invention. The embodiment of the invention consists of two parts-an air pump working in conjunction with the fueling device. The new improved two stroke spark ignition engine of the present invention ensures that an additional quantity of air charge is provided during the compression phase of the cycle. Regulation and timing of this additional quantity of fresh air to be provided can in principle be achieved by several means - through an air compressor and mechanical or electronic control. The present invention defines mechanical means to regulate the timing of this additional quantity of fresh air. An in-built timing and duration control is provided to the present system. By an appropriate choice of the system design parameters, the quantity of additional air to be provided can be optimised. In the present invention a cavity type piston with a corresponding static core working in a cylinder with transfer ports communicating with the engine cylinder, driven off the engine through a one-one drive with provision for phasing of the engine and air pump cycles, a robust and simple mechanical system to address the issue of dilution in two stroke spark ignition engines have been described. To mitigate the through-put loss, in-cylinder injection during the open phase of the cycle is carried out and to completely eliminate such loss fueling is carried out in the closed part of the cycle. In-cylinder fueling necessarily involves meeting three related aspects-regulation of fuel quantity with respect to speed and load, disintegration of the metered quantity to the requisite degree of fineness to help rapid vaporisation of the fuel in the limited time available during compression, and injection of the disintegrated fuel over the appropriate phase of the engine cycle and dispersing it in the desired domain of the cylinder space. This novel fueling device for in-cylinder fuel injected spark ignition engine forms subject matter of a copending Indian patent application where this has been achieved in experimental engines using fuel injectors controller electronically with or without air assistance. In liquid fuel injection system high pressure is employed to achieve disintegration and dispersion of fuel. In air assisted systems, disintegration and dispersion is achieved by a relatively low pressure air blast. Low pressure in cylinder fuel injection system utilise air flow into the cylinder through the transfer passage for assisting disintegration and dispersion of the fuel air mixture. An electronically controlled continuous fueling of spark ignition engines with in cylinder injection forms subject matter of another copending Indian patent application. In the prior art reported information on in-cylinder two stroke spark ignition engines is mostly in the capacity range of around 250CC for the high cost automotive application. No information is reported so far for engines below 100CC. In principle, the methodology should be feasible independent of engine size. The only issue has been of cost and complexity. Air assist system described earlier to address the issues of dilution and "torque trough" reveals that it can also be used to eliminate direct loss of mixture and accomplish in-cylinder injection of fuel vapour mixture in conjunction with an appropriate fueling device. This air assisting system defining an air pump forms subject matter of a copending Indian application. The crank case of the two stroke spark ignition engine performs two functions 1. Inducts the requisite quantity of air into the crankcase depending on engine capacity. The size of the crankcase is therefore a function of the engine size. 2. Inducts into the crankcase along with the air a regulated quantity of fuel in a finely disintegrated form. The low pressure created in the crankcase is the forcing function acting on the fueling device. This forcing function is independent of crankcase size. In two stroke crankcase scavenged engines, compressive/expansion employed in the crankcase is determined by factors related to achieving efficient scavenging. The compression/expansion ratio is generally around two in all crankcase scavenged engines. Therefore a reciprocating air pump of a size much smaller than the crank pump but with the requisite compression/expansion ratio provides the requisite forcing function for achieving regulates fueling from a continuous fueling device akin to the one used in current practice. Alternatively, it is equally feasible to have continuous fueling into the inlet of the air pump controlled by electronic means. Therefore as can be seen from the description the prior art systems call for sophisticated electronic control for regulating timing, duration of injection , quantity of air required for disintegration and quantity of fuel required under variable speed load conditions. These prior art low pressure ignition systems employing electronic control are susceptible to through-put loss of the charge during the scavenge phase, as in conventional two stroke spark ignition engines. The prior art systems have been developed generally for engine placement in the range of 250CC and above, for the high cost automotive application. In the range below, engine displacement of 100CC there is no reported information on in cylinder injection. An improved two stroke spark ignition engine of the present invention aims to eliminate the drawbacks of the prior art two stroke spark ignition engines. The mechanical components and the system configuration of the present invention are simple and robust. The use of flash ports in the improved engine of the present invention eliminates dynamic elements in the charging/discharge processes. The charge injected into the system of the present invention is a mixture of fuel vapour and air which eliminates the need for vaporisation of the fuels and the engine cycle time involved thereof. Further the injection cut off is achieved by the engine piston provided into the improved system. The improved engine of the present invention provides flexibility in the choice of the pump capacity to meet an important engine performance characteristic. It also permits to address the "Torque trough" issue in the low speed domain of engine operation. Elimination of through-put loss of the charge during the scavenge phase is feasible as the injection of the fuel vapour air mixture can be fully achieved in the closed cycle period of the engine. Timing and duration control are shared by the engine and the air pump systems of the present invention. The injected fuel vapor air mixture is located at a desired part of the engine cylinder space to facilitate stratification. The system is applicable to two stroke spark ignition engine of any capacity from 20-250CC and above in single and multicylinder configurations. The novel concept of the present invention is applicable to four stroke spark ignition engine also to improve maximum power and minimum fuel consumption. It also improves the smoke limited power output and minimum fuel consumption and also achieve phased injection to suppress opacity of exhaust and achieve smooth engine operation. The air pump used of the present invention help attain electronic control in two stroke spark ignition engines. Novel lubrication systems can also be employed in the present invention which forms a subject matter of copending Indian patent application. In the solution, putting extra air (5-10%) helps in fuel injection. Inducting fuel from continual fueling device vapourises fuel on combustion and introduces rich fuel-air mixture to achieve satisfaction in the engine cylinder on one hand and adding into air charged to the cylinder reduces the dilution. Reduction of dilution is of the order of 15-20%. There is a change to the extent of from 20-25% to a higher torque, higher power, lower fuel consumption and lower dilution. The reduction of emission is greater than 50% by the engine of the present invention with respect to the conventional internal combustion engines. The direct loss of fuel is directly eliminated. The engine of the present invention consists of a crank case connected to a fueling device supplying air and lube oil mixture to the crank case unlike the conventional engine where the crank case is charged by air and fuel vapour and lube oil mixture. The crank shaft housed in the crank case has a sprocket to drive by a chain the air pump. The drive is 1:1, i.e., the air pump and engine operate at the same speed. The cylinder block mounted on the crank case has the cylinder bore for the main engine piston and an auxiliary bore for the air pump system. The air pump part of the cylinder block has provision for a crank shaft and connecting rod to drive, the air pump piston. The crank shaft carries the second sprocket for getting the chain drive from the main engine crank shaft. The air pump has ports for inlet and outlet, the inlet is connected to the novel fueling device which forms subject matter of a copending application, through a spacer ensuring smooth change in transfer passage configuration from rectangular at the pump end to circular at the new fueling device end. The outlet port is connected to the engine cylinder which terminates at the desired location with respect to main engine operation. The air pump piston has a transfer port located at the base of the piston cavity. The air pump piston and the main engine piston motion are set in appropriate phase by fixing the location of sprockets on the main engine shaft and the pump shaft. The phasing, i.e., the two piston movement is adjusted such that the discharge from the air pump into the engine cylinder is achieved, only on the open cycle and only in the closed cycle or partially in both. The cut off of injection is achieved as the engine piston on its outward stroke closes the injection outlet port. The injection outlet port of the air pump is directed into the engine cylinder in such a way that fuel air mixture injected into the cylinder such that rich fuel air charge is located in the clean air domaining the engine cylinder. As compression proceeds after fuel vapour air injection; (the mixture segregated combines with fresh air coming from the side) mixing of clean air provided from the crank case and rich mixture provided from injection takes place. The cylinder head has the combustion chamber and provision for mounting the spark plug as in a conventional engine. A chain tension for adjusting the stack ensures smooth functioning of the drive system. The accompanying graphs, i.e., graph 1-6 show the various comparative datas. Graph 1 shows the maximum torque at full throttle over the engine speed range of 1500-5500 rpm for the engine of the present invention as against its conventional counterpart. The new engine has a higher torque, more than 15% throughout the range. At low speed it is even higher. The engine is able to hold on to more than 50% of the maximum even at the lowest operating speed unlike the conventional counterpart. In graph 2 the advantage of a higher torque is confirmed by higher pressure. Graph 3 highlights the advantage of eliminating throughput loss and stratification by injection of a rich fuel-vapour air mixture in a preferred domain of the working space, i.e., the engine cylinder is reflected by a reduction of more than 20% in fuel consumption. The advantage is again more in the low speed range. Graphs 3-6 relate to emission characteristics of the new engine vis-a-vis its conventional counterpart are compared. Reduction in hydrocarbon consequent to elimination of short circuited loss is significant and is on an average more than 50%. Similar improvement in CO reduction is also observed. According to the present invention there is provided an internal combustion engine comprising: an engine cylinder; a piston moving freely in the said cylinder; a crank case connected to a fueling device supplying air and lube oil mixture to the said crank case; characterized in that: a crank shaft housed in the said crank case is provided with a sprocket driving air pump connected to the said fueling device; 6 fwowct-ed voitf^ 0- ty(if> a cylindrical block/mounted on the said crank case having a cylindrical bore for air pump assembly; said air pump having an inlet port connected to the said fueling device through a spacer and an outlet port connected to the said engine cylinder terminating at the desired location with respect to the main engine operation; a second sprocket provided in the said crank shaft for driving the chain from the engine crank shaft. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS The present invention is better understood with reference to the accompanying drawings which do not restrict the scope of the invention and only illustrate what the invention relates to, wherein Figure 1 shows an elevational view of conventional two stroke engine. Figure 2 shows integrated engine and air pump cylinder block. Figure 3 shows air pump piston. Figure 4 shows the static core. Figure 5 shows pump, connecting rod and crank assembly. Figure 6 shows air pump assembly. Figure 7 shows fueling device. Figure 8 shows engine with air pump at the beginning of injection. Figure 9 shows engine with air pump at the end of the injection and Figure 10 shows engine with air pump at the beginning of induction. Figure 11 and 12 depicts the engine assembly of the present invention. Figure 13 and 14 shows the sectional view of the pneumatic pump assembly. In figure 1, the combustion chamber is indicated as (1) while (2) defines the transfer port, (3) shows the crank case, (4 and 5) show the inlet port and exhaust port respectively. Further in figure 2, the air pump cylinder has ports, i.e. outlet ports, communicating with the engine cylinder (2)(1), and the ambient inlet ports (2)(2) and a split crankcase (2)(3). Engine transfer port is shown as (2)(4), pump bore is shown as (2)(5), exhaust port is shown as (2) (6) and engine bore as (2)(7). The air pump piston has a cavity (3)(4) and ports (3)(5). The air pump piston (5)(6) is connected to a connecting rod and crank mechanism (5)(7) and (5)(8). Figure 6(1) represents the core, 6(2) shows the pump cylinder block, (6)(3) shows the crank, (6)(4) shows the connecting rod, (6)(5) shows the crank case and (6)(6) shows the piston. Figure 7 shows the fueling device comprising of an inlet chamber also working as an air filter 7(6), a control element 7(7) and the fuel control needle 7(2) working in the fueling chamber 7(3). The fuel control needle 7(2) has special features for starting/acceleration, i.e. high speed operation, low speed operation and idling. These special features are in the form of tapering of the fuel control needle which provides charged annulus area where the extent of tapering is decided by the quantity of fuel required to be injected in the engine. The quantity of fuel required to be injected is in turn dependent on the load features of the engine. The fueling chamber is connected to the inlet of the air pump. Figure 8 shows the engine with air pump at the beginning of the injection while figure 9 brings out the engine and air pump configuration at the end of injection. The outlet port and the engine port location is clearly visible from these two figures both at the beginning of the injection and at the end of injection. Similarly figure 10 brings out the position of engine port and the port of the air pump at the beginning of induction. Figure 11 and 12 show the engine assembly where 11(1) shows the air pump, 11(2) shows the fueling device needle control; 11(3) shows the fueling device, 11(4) shows the crank case inlet, 11(5) shoes the chain tensioner, 11(6) shows the magneto; while 11(7) and 11(8) show the crank case and chain drive respectively. 11(9) show the integrated cylinder block. Figure 13(1) shows the transfer port, 13(2) is the injection port, 13(3) is the port in pump bore, 13(4) is the port in piston, 13(5) is the piston core, 13(6) is the injection port in engine bore and 13(7) is the exhaust port. Figure 14(1) shows the engine bore, figure 14(2) shows the pump bore, 14(3) shows the crank pin, figure 14(4) shows the pump crankshaft and 14(5) shows the crank shaft bearing. In the spark ignition engine of the present invention, the air pump piston and engine piston are phased to ensure that the opening of the air pump outlet corresponds with the closure of the exhaust port in the engine cylinder. As the two pistons move in phase, the high pressure contents of the air pump, viz., fuel vapour and air is transferred into the engine cylinder. Cut-off of injection is achieved by the closure of air pump outlet port in the engine cylinder by the engine piston. On the downward stroke of the air pump piston, the position corresponding to the registry of the air pump piston top with the inlet port is shown in figure 10. This represents the beginning of induction into the air pump. During injection, the air pump is charged through the fueling device. The air flows through the air filter, the control element and the fueling chamber. The filling of the air pump creates a depression in the fueling chamber and results in fueling, regulating an improved fuel control needle, volume of the fueling chamber, the design of the control element and air filter. WE CLAIM;- 1. An internal combustion engine comprising: an engine cylinder; a piston moving freely in the said cylinder; a crank case connected to a fueling device supplying air and lube oil mixture to the said crank case; characterized in that: a crank shaft housed in the said crank case is provided with a sprocket driving air pump connected to the said fueling device,- a cylindrical block provided with cylinder head mounted on the said crank case having a cylindrical bore for air pump assembly; said air pump having an inlet port connected to the said fueling device through a spacer and an outlet port connected to the said engine cylinder terminating at the desired location with respect to the main engine operation; a second sprocket provided in the said crank shaft for driving the chain from the engine crank shaft. 2. An internal combustion engine as claimed in claim 1, wherein the said air pump has a transfer port located at the base of the piston cavity. 3. An internal combustion engine as claimed in claim 1, wherein zhe said air pump is prrivide with r;-i=ron :r:Gvabl.~ r;- -,-ir: chs sa.id piston being set in phase with the piston in said cylinder by fixing the location of said sprockets on the main enqine shaft arid the pump shaft. 4. An internal combustion engine as claimed in claim 1, wherein the said cylinder head has a combustion chamber and a provision for mounting the - spark plug. 5. An internal combustion engine substantially as herein before described with reference to the accompanying examples.

Documents:

835-del-1998-abstract.pdf

835-del-1998-claims.pdf

835-del-1998-correspondence-others.pdf

835-del-1998-correspondence-po.pdf

835-del-1998-description (complete).pdf

835-del-1998-drawings.pdf

835-del-1998-form-1.pdf

835-del-1998-form-19.pdf

835-del-1998-form-2.pdf

835-del-1998-form-4.pdf

835-del-1998-form-5.pdf

835-del-1998-form-6.pdf

835-del-1998-gpa.pdf

835-del-1998-petition-others.pdf