Title of Invention

"AN AIR ASSIST DEVICE FOR AN INTERNAL COMBUSTION ENGINE"

Abstract

An air assist device for an internal combustion engine comprising: an air pump assembly having a cylindrical block; a hollow static core of conical configuration provided in the said cylindrical block; a piston body conforming to the said conical configuration of the static core to enable vertical movement of the said piston within the said static core having an outlet port, said piston being provided with piston rings, characterized in that; an ambient inlet port is provided within the said cylindrical block and a transfer port for communicating with the engine cylinder provided within the said air pump assembly; and crank and crank case connected within the air pump assembly by a connecting rod; wherein the said piston assembly and static core are conical in configuration having a cavity depth and tapered configuration proportional to the desired pump stroke of the engine.

Full Text

The present invention relates to an air assist system for an internal combustion engine. The air assist system of the present invention eliminates the problems associated with dilution and direct mixture loss in a spark ignition engine. 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. 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. 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. SUMMARY OF THE INVENTION The present invention provides an air assist system for a spark ignition internal combustion engine which overcomes all problems relating to fuel loss and inefficient combustion of oil. The air assist system of the present invention comprises an air pump assembly, which addresses the problem of high dilution through appropriate means to provide an additional quantity of air charge during the compression phase of the cycle. Further the air assist system of the present invention overcomes problems related to short circuiting as well as mixture scavenged loss. DETAILED DESCRIPTION OF THE INVENTION The present invention provides an air assist system for use in spark ignition internal combustion engine. The air assist system of the present invention comprises an air pump assembly which provides a solution to the problems related to short circuiting, dilution and direct mixture loss. Solution to the problem of direct mixture loss requires that scavenging of the residual combustion products should be carried out with only air, and fuel should be introduced in the appropriate phase of the cycle separately. Through-put loss is mitigated to a substantial extent by in-cylinder injection during the open phase of the cycle and is completely eliminated if fueling is 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, 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 air pump 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 of 0.5. 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 new improved air assist system of the present invention for spark ignition engine 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 in principle is achievable 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 is optimised. The air pump assembly of the present invention, which is a robust and a simple mechanical system, provides an air pump having 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. The crank case of the 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 spark ignition 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 regulated 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. The air assist system of the present invention therefore provides an air pump of a much smaller size than the crank pump with the requisite compression/expansion ratio. 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. The air assist system of the present invention helps overcome the problem of dilution and "torque trough" and also finds application to eliminate direct loss of mixture and accomplish in-cylinder injection of fuel vapour mixture in conjunction with an appropriate fueling device. The air assist system of the present invention comprises an air pump cylindrical block, wherein a static core and piston assembly is provided within the cylindrical block. The static core and the air pump are conical in shape. The parameters of the air pump piston, i.e., the depth and the width, are in conformity with that of the static core so as to enable a vertical movement of the piston within the static core. The tapering and the depth of the conical static core and the pump piston assembly, i.e., the pump capacity is chosen by an appropriate choice of pump bore and stroke. The core cavity configuration is designed to ensure that the annulus area is unrestricted from the piston top to cavity bottom. The taper of the core/cavity are adjusted to achieve a continual reduction of annulus area. Cavity depth is more than pump stroke by a few millimeters to separate the domain of inflow and outflow. Outlet port in the pump sleeve and the outlet port in the piston and their location decide the timing of the beginning of injection with respect to engine cylinder operation. The beginning of the injection in an engine is controlled by the air pump of the present invention. There are provided piston rings which provide a sliding seal between the outer edge of the piston and the inner edge of the cylinder. The piston rings prevents any leakage of the air/fuel mixture and exhaust in the combustion chamber. These piston rings therefore play a vital role in prevention of the loss of fuel and air. The piston rings are selected from standard cast iron piston rings of PTFE rings with glass metal fillings or any other conventional rings. According to the present invention there is provided an air assist device for an internal combustion engine comprising: an air pump assembly having a cylindrical block; a hollow static core of conical configuration provided in the said cylindrical block; a piston body conforming to the said conical configuration of the static core to enable vertical movement of the said piston within the said static core having an outlet port, said piston being provided with piston rings, characterized in that; an ambient inlet port is provided within the said cylindrical block and a transfer port for communicating with the engine cylinder provided within the said air pump assembly; and crank and crank case connected within the air pump assembly by a connecting rod; wherein the said piston assembly and static core are conical in configuration haying a cavity depth and tapered configuration proportional to the desired pump stroke of the engine. , BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS The air assist system of the present invention is precisely described with reference to the accompanying drawings without restricting the broad scope of the invention. Figure 1 shows air pump cylindrical block and the integrated engine which employs the air assist system of the present invention. Figure 2 shows air pump piston. Figure 3 shows the static core. Figure 4 shows air pump of the present invention, connecting rod and crank assembly. Figure 5 shows air pump assembly of the present invention. Figure 6 shows the engine with air pump at the beginning of induction working in conjunction with an internal combustion two stroke engine. Figure 7 defines the engine with the air pump assembly at the beginning of injection The air assist system of the present invention stands alone or integral with engine cylindrical block of a spark ignition engine. The air assist system has an air pump assembly. As evident from the drawings enclosed, the air pump of the present invention is provided with inlet and outlet ports for communicating with the engine cylinder. The pump bore has been shown in figure 1 while figure 2 defines the air pump piston and clearly shows the conical cavity which is supported by a corresponding static core, conical in shape (figure 3). This distinctive shape of the core and the cavity help regulate the timing and duration of injection. The air pump of the present invention connection with the connecting rod and crank mechanism is depicted clearly in figure 4. Figure 5 shows the air pump assembly of the present invention clearly showing the core and the cavity of the piston, along with pump cylindrical block, crank, crank case, connecting rod and the ports of the pump assembly. At the top of the piston stroke, a predetermined bumping clearance is provided between the piston cavity and the static core. The pump is driven at engine speed, in a two stroke configuration, or at half engine speed in a four stroke configuration. Therefore the air pump of the present invention can be used both in two stroke and four stroke ignition engines. The pump capacity is achieved by an appropriate choice of pump bore and stroke. The inlet and the outlet port depth and width, determine the area vis-a-vis an induction into the air pump, injection into the engine cylinder and pump compression/expansion ratio. Whenever used in an engine, the air pump piston of the air assist system of the present invention and the engine piston are phased to ensure that the opening of the air pump outlet, as shown in figure 7, corresponds with the closure of the exhaust port of the engine cylinder. As the two pistons move in phase, the high pressure contents of the air pump, i.e., fuel vapour and air are transferred into the engine cylinder. The cut off injection is achieved by closure of air pump outlet port in the engine cylinder by the engine piston as clearly shown in figure 8. 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 depicted in figure 6, which represents the beginning of induction into the air pump. The air pump assembly has a cavity type piston with a corresponding static core, in a cylinder which also has a plurality of ports for communicating with the engine cylinder (1)(1), and the ambient inlet ports (1)(2) and a split crankcase (1)(3). Engine transfer port is shown as (1)(4), pump bore is shown as (1)(5), exhaust port is shown as (1) (6) and engine bore as (1)(7). The air pump piston has a cavity (2)(4) and a port (2)(5). The air pump has a static core corresponding to the cavity in the piston. The air pump is connected to a connecting rod and crank mechanism(4)(7) and (4)(8). Figure 5(1) represents the core, 5(2) shows the pump cylindrical block, (5)(3) shows the crank, (5)(4) shows the connecting rod, 5(5) shows the crank case and (5)(6) shows the piston. In the pneumatic pump bore the cavity depth and/or taper configuration is proportional to the pump stroke. The timing and the duration control are controlled by the air pump systems. With the new air pump system of the present invention, continuous injection with electronic control can be achieved in spark ignition engines. Therefore the present invention defines an air pump system for spark ignition fuel injection engines which overcomes the disadvantages of the prior art relating to direct mixture loss, short-circuiting and dilution. We claim: 1. An air assist device for an internal combustion engine comprising: an air pump assembly having a cylindrical block; a hollow static core of conical configuration provided in the said cylindrical block; a piston body conforming to the said conical configuration of the static core to enable vertical movement of the said piston within the said static core having an outlet port, said piston being provided with piston rings, characterized in that; an ambient inlet port is provided within the said cylindrical block and a transfer port for communicating with the engine cylinder provided within the said air pump assembly; and crank and crank case connected within the air pump assembly by a connecting rod; wherein the said piston assembly and static core are conical in configuration having a cavity depth and tapered configuration proportional to the desired pump stroke of the engine. An air assist device for an internal combustion engine as claimed in claim 1, wherein piston rings are between the outer edge of the piston and inner edge of the cylinder to provide a sliding seal. 2. An air assist device as claimed in claim 1, wherein the said cylindrical block comprises inlet and outlet ports on its alternate sides. 3. An air assist device as claimed in claim 1, wherein the said inlet port is provided near the middle of the said static core. 4. An air assist device as claimed in claim 1, wherein the said transfer port is provided near the bottom end of the said static core. 5. An air assist device as claimed in claim 1, wherein the said cavity depth is more than the pump stroke by a few millimeters. 6. An air assist device substantially as hereinbefore described with reference to the accompanying drawings.

Documents:

832-del-1998-abstract.pdf

832-del-1998-claims.pdf

832-del-1998-correspondence-others.pdf

832-del-1998-correspondence-po.pdf

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

832-del-1998-drawings.pdf

832-del-1998-form-1.pdf

832-del-1998-form-19.pdf

832-del-1998-form-2.pdf

832-del-1998-form-4.pdf

832-del-1998-form-5.pdf

832-del-1998-form-6.pdf

832-del-1998-gpa.pdf

832-del-1998-petition-others.pdf