Abstract:
Method and devices for controlling the combustion of a four-stroke engine. For each cylinder, in addition to the main combustion chamber, a smaller secondary combustion chamber is provided. The secondary combustion chamber is completely separate and independently supplied with a compressed fuel-air mixture such that, when the mixture is ignited, the explosion that takes place through a transfer channel into the main combustion chamber, igniting the mixture contained therein. The main combustion chamber is not supplied with fuel at low speeds. Application is also contemplated for four-stroke engines with spark or other ignition and with rotary or valve timing.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a method and devices for controlling the combustion of an internal combustion engine functioning according to a four-stroke cycle with spark or other ignition, with valve timing or equipped with a rotary intake and/or exhaust distributor. 
     2. Description of Background and Relevant Information 
     The thermodynamic efficiency of the combustion of internal combustion engines is directly proportional to the gas pressure at the end of the compression stroke and consequently to the load of the engine, itself a function of the opening of the accelerator valve. The specific consumption of the engine is related to the thermodynamic efficiency, which amounts to saying that for a given engine displacement the less torque and/or power required the more the specific consumption increases. This is extremely penalizing especially when the engine equips an automobile because the result is that at low speeds and low loads the fuel consumption is very substantial, and consequently so are the polluting exhaust emissions, but, especially in the city, the engine is always used at a low speed and at low loads. To clarify, an automobile engine that consumes at average or full load, approximately 200 to 250 grams of fuel per horsepower and per hour on the highway sees its consumption in the city increased to approximately 1000 or even 2000 grams of fuel per horsepower and per hour. 
     Conscious of this problem, motorists sought to improve the consumption at low loads in various manners: either by producing engines with poor or very poor mixtures (in the case of stratified load engines); or by trying to obtain variable compression ratio engines in order to try to increase the pressure at the end of compression; or even by &#34;disengaging&#34; one or more cylinders in order to increase the load on the cylinders that remain in operation, for equivalent power. 
     The solutions have the disadvantage of only very partially resolving the problem and are in addition in certain cases particularly difficult and onerous to implement. 
     SUMMARY OF THE INVENTION 
     The method according to the invention enables the engine to function at weak loads with combustion efficiencies equivalent to those obtained at average or full load. The invention also relates to devices for implementing this method. 
     During operation of the four-stroke engine, the intake gases, after having been drawn into the cylinder by the piston are compressed in the combustion chamber in order to be ignited therein by the spark plug, thereby increasing in volume and pushing the piston, thus obtaining the power stroke also called explosion or combustion. In practice, the volume of the combustion chamber substantially represents between 9 and 12% of the volume of the cylinder according to the chosen compression ratio. The method according to the invention is characterized by the joining to this assembly of a small secondary combustion chamber entirely separated from the principal chamber and supplied independently and separately with compressed intake gas. During average or full load operation, the gases compressed in this small secondary chamber are ignited by a spark plug, while shortly before or substantially after the start of this combustion, this small secondary combustion chamber is connected, by the opening of one (or several) linkage channel, the principal combustion chamber where the combustion of gases issuing from the secondary chamber will then ignite (instead of and in place of the spark plug) the intake gases compressed in the principal combustion chamber. The efficiency of this ignition by &#34;flame jet/burst of flames&#34; issued from the combustion of the secondary chamber also enables utilization in the principal chamber of very poor fuel-air mixtures as well as raised compression ratios ensuring a weak fuel consumption. 
     During the operation of the engine at low loads, the cylinder and the principal combustion chamber are no longer supplied with fuel, but only with air, and the piston is pushed in the principal cylinder only by the explosion of gases contained in the small secondary combustion chamber, through the linkage channel. One easily understands that the small secondary combustion chamber operates almost continuously at full load with a good thermodynamic efficiency, guaranteeing a low consumption of fuel. 
     During combustion stroke (or explosion) and exhaust stroke, the volume of the small secondary combustion chamber is maintained substantially constant at its small volume, so that all the efficiency of the explosion of gases during combustion serves to push the engine piston of the principal cylinder, as well as to better empty the small secondary combustion chamber during the exhaust stroke. 
     During low load operation when the principal cylinder and the principal chamber are no longer supplied with fuel, it is particularly interesting, during the intake and compression strokes, to open a valve in the principal combustion chamber, connecting the latter with the atmosphere, with the object of avoiding the pumping efforts during intake and the counter pressure on the piston during the compression stroke that would uselessly absorb the power. 
     One thus notes that in the method according to the invention, one distinguishes two modes of operation: average/full load operation, low load operation. The operation cycles of an engine cylinder according to the combustion control method according to the invention are thus the following: 
     1. When the engine is at average or full loads 
     induction: of air and fuel into the principal cylinder of air and fuel for supplying the small secondary combustion chamber 
     compression: of the mixtures in the two combustion chambers 
     ignition: lighting of the mixture in the small chamber by a spark plug 
     opening: of the linkage channel(s) between the small combustion chamber and the principal combustion chamber, lighting of the mixture in the principal combustion chamber 
     explosion: of the set of combustions (power stroke) during this cycle the volume of the secondary combustion chamber is maintained at its minimum value 
     exhaust: of the gases burned in the engine cylinder and in the small secondary combustion chamber. During this cycle the volume of the secondary combustion chamber is also conserved at its minimum value. 
     2. When the engine is at low loads: 
     induction: of air alone into the principal cylinder of air and fuel intended to supply the secondary chamber 
     compression: of the fuel-air mixture in the secondary chamber, opening of the aeration valve of the principal chamber to avoid counter pressure on the piston 
     lighting: of the fuel-air mixture in the secondary chamber, closure of the aeration valve of the principal chamber, opening of the linkage channel between the secondary chamber and the principal chamber. 
     explosion: of the gases contained in the secondary chamber in the principal cylinder through the linkage channel, during this stroke the volume of the secondary chamber is maintained at its minimum value. 
     exhaust: of the combustion gases, during this cycle, the volume of the secondary chamber is also maintained at its minimum value. 
     The arrangement of the small secondary combustion chamber, the opening mode of the linkage channel(s) between the small secondary combustion chamber and the principal combustion chamber, the methods for supplying and pressurizing the gases in the small secondary combustion chamber, the opening and the closing of the aeration valve can use any appropriate means to obtain the required functions without at all changing the principle of the method of the invention. The volume of the small combustion chamber will be chosen as a function of the characteristics sought during operation at low loads and can vary by several percent from that of the principal combustion chamber until possibly equalling it, without at all changing the principle of the method of the invention. 
     The method according to the invention applies to internal four-stroke combustion engines with spark or other ignition with one or several cylinders, with cam shaft or valve timing or otherwise, nonetheless it appears that the method according to the invention finds an application more particularly easy to obtain in the case of a rotary timing engine in which the timing rotor will also serve to ensure in its rotation the cycled linkage between the principal combustion chamber and the secondary combustion chamber. 
     The invention also relates to several devices which can be implemented for the application of the method according to the invention, especially in the case of an engine equipped with rotary timing with a unique lateral transfer port assuring successively the exhaust then the intake, while the body of the distributor obstructs the combustion chamber during the compression stroke and the explosion stroke, characterized by the joining, in another transverse plane, of a small secondary combustion chamber, opening up on the rotary distributor, and supplied, by an independent intake circuit, with a compressed fuel-air mixture by a small piston itself controlled by a cam, enabling during the operation of the engine, induction by the intake circuit independent of that of the principal cylinder, of a fuel-air mixture, compressing it in the small volume of the secondary combustion chamber, and maintaining substantially constant the small volume of this combustion chamber while in the cycle, and after having ignited by means of a spark plug, the mixture in the secondary combustion chamber, the rotary distributor in which is (are) cut one (several) linkage channel(s), goes into its rotation, through this (these) linkage channel(s) connects the two chambers so that on the one hand, during operation at low loads, the gases burned in the secondary chamber explode in the principal chamber which in this case of operation is only supplied with air (without fuel) thus pushing the piston that assures the power stroke, and that, on the other hand, during average or full load operation, the gases burned in the secondary chamber come to ignite the mixture contained in the principal chamber, which, in this case of operation is supplied with a fuel-air mixture and, enables the combustion and the explosion of the gases contained both in the principal chamber and in the secondary chamber pushing the piston and thus assuring the power stroke. 
     During low load operation, while the cylinder and the principal combustion chamber are only supplied with fresh air without fuel, an electrovalve will open during the induction stroke and compression stroke to connect the principal chamber with the atmosphere, in order to avoid the pumping efforts during induction, and the counter pressure on the piston during the compression stroke, and closes during the explosion stroke and exhaust stroke. 
     During average or full load operation, this electrovalve always stays closed to enable the normal operation of the cylinder. 
     An engine equipped according to the method and device according to the invention operate in fact as a small cubic capacity engine when one requires little power (thus at actual full load with good efficiency and little specific consumption) and like a large cubic capacity engine when one needs more power (thus at average or full load with good efficiency and little specific consumption). 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects, advantages and characteristics of the invention will appear upon reading the non-limiting description of several embodiments of the invention applied to controlling the combustion of a four-stroke engine, made in reference to the attached drawings wherein: 
     FIG. 1 schematically represents, seen in a transverse section, a four-stroke engine with spark ignition, with rotary timing, with top dead center ignition, equipped with a device for controlling the combustion according to the method of the invention, in a low load mode of operation. 
     FIG. 2 represents the same engine at the same moment in the cycle, in the average/full load mode of operation. 
     FIG. 3 represents this engine during the exhaust stroke. 
     FIG. 4 represents this engine during the induction stroke in the mode of operation at low loads. 
     FIG. 5 represents the engine during the induction stroke in the average/full load mode of operation. 
     FIG. 6 represents the engine during the compression stroke in the low load mode of operation. 
     FIG. 7 represents the engine during the compression stroke in the average/full load mode of operation. 
     FIG. 8 schematically represents, seen in a transverse section, a four-stroke rotary distribution engine, equipped with a device for controlling the combustion according to the method of the invention, where the principal combustion chamber operates with heterogeneous mixtures like a diesel engine. 
     FIG. 9 represents the same engine whereas the principal combustion chamber and the small secondary combustion chamber operate on heterogeneous mixtures. 
     FIG. 10 represents a device according to the method according to the invention applied to a valve engine. 
     FIG. 11 represents an inter-chamber blocking device with a rotary slide valve/oscillating cylindrical valve. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The engine schematically represented in FIGS. 1 through 7 comprises elements that are well known in rotary distribution engines, operating according to the four-stroke cycle. A piston 1, sliding in a cylinder liner 2 is covered by a cylinder head 3 in which is driven, at half speed of the engine, a rotary distributor 4, with a unique transfer port 5, which during its rotation (in the direction of the arrow) will successively connect the exhaust conduit 6 and the combustion chamber 7 in order to assure the exhaust stroke, then the combustion chamber 7 with the induction 8 thus assuring the induction stroke, the body of the rotary distributor 4 blocking the combustion chamber 7 during the compression stroke and the combustion or power stroke, the impermeability of the chamber being assured by the sliding element 9. Supplying the cylinder with fuel is assured by the injector 10, and the air flow controlling the fuel-air load of the cylinder by the throttle 11. 
     FIGS. 1-9 show the engine at different phases of its operation, where, to simplify understanding of the drawings, the transverse section is offset at the level of the combustion chambers 7 and 12, gasket rings 9 and 12B, and pistons 1 and 17, and shows these elements on the same plane whereas in reality they are not on the same transverse plane, while the induction conduit 8, the transfer port 5 and the exhaust conduit 6 represented by dashed lines are substantially on the same plane as the principal combustion chamber 7 and its gasket ring 9. 
     FIG. 1 represents at top dead center ignition a rotary distribution engine such as described above and equipped with a device enabling application of the method according to the invention, in a low load mode of operation, seen in a transverse section (offset at the level of the cylinders) where the compressed fuel-air mixture contained in the small secondary combustion chamber 12, has just been ignited by the spark plug 13 while the transfer port 14 arranged in the rotary distributor 4 connects the principal or primary combustion chamber 7 with the secondary combustion chamber 12 and the fuel-air mixture ignited in the latter expands through the transfer port 14 into the principal chamber 7 pushing the piston 1 and thus assuring the power stroke at low loads; the gas throttle supplying the principal combustion chamber 7 is closed as well as the aeration electrovalve 15. 
     FIG. 2 represents the same engine similarly equipped at the same moment in the cycle but whereas it operates in average/full load mode, the gas throttle 11 is then opened and the injector 10 supplied the chamber during the induction stroke, the &#34;flame jet&#34; from the combustion of the secondary chamber ignites in turn the fuel-air mixture of the principal chamber and the gases contained in the two chambers expand pushing the piston thus assuring the power stroke. 
     One consequently understands all the advantages of the method as well as of the device above. 
     The exhaust is carried out normally, FIG. 3 by the exhaust conduit 6 and empties the cylinder, the combustion chamber 7 as well as the secondary combustion chamber 12 through an orifice 16 arranged for that purpose, the secondary piston 17 controlled by a double acting cam 18 (or positive drive control) is maintained substantially at its top dead center to reduce to the maximum the volume to be emptied during this cycle: this cycle is common to the two modes of operation, at low loads, and at average/full loads. 
     FIG. 4 represents the engine during the induction stroke in a low load mode of operation, the gas throttle 11 is closed, injector 10 is not activated, the aeration valve 15 is open to avoid a pumping brake during the descent of the piston 1; the secondary piston 17 returned by the cam 18 uncovers the secondary induction circuit 19 to admit the fuel-air mixture dosed by the injector 21, the fine steering/control of the engine is carried out by means of the secondary gas throttle 20. 
     FIG. 5 represents the engine during the induction stroke at a average/full load mode of operation, the gas throttle 11 is open, the injector 10 activated, and the fuel-air mixture is admitted into the cylinder through the transfer port 5 arranged in the rotary distributor 4; the secondary piston 17 returned by the cam 18 uncovers the secondary admission circuit 19 to admit the fuel-air mixture dosed by the injector 21, the secondary gas throttle 20 is open, and the aeration electrovalve 15 of the principal combustion chamber 7 is closed. 
     FIG. 6 represents the engine during the compression stroke in a low load mode of operation, the principal piston 1 carries out its ascendant path whereas the aeration electrovalve 15 is open in order to avoid counter pressures on the piston 1; the cam 18 pushes the secondary piston 17 to compress the fuel-air mixture in the secondary chamber 12 blocked by the body of the rotary distributor 4, the impermeability being assured by the sliding ring 12B. At the end of compression air without fuel is thus found in the principal chamber 7 and a compressed fuel-air mixture in the secondary combustion chamber 12. 
     FIG. 7 represents the engine during the compression stroke in the average/full load mode of operation, the principal piston 1 carries out its ascendant course whereas the aeration electrovalve 15 is closed, and compresses the fuel-air mixture in the principal combustion chamber 7, the impermeability of the chamber is assured by the sliding ring 9; the cam 18 pushes the secondary piston 17 to compress the fuel-air mixture in the secondary chamber 12 blocked by the body of the rotary distributor 4, the impermeability being assured by the sliding ring 12B. At the end of compression, fuel-air mixtures are found in the principal chamber 1 and in the secondary chamber 12. 
     The cycle in the low load mode of operation starts again by ignition and explosion such as described in FIG. 1. 
     The cycle in the average/full mode of operation starts again by ignition and explosion such as described in FIG. 2. 
     The method and the devices according to the invention also apply in the case of engines operating with heterogeneous mixtures, with self ignition more commonly called &#34;diesel&#34; engine, operating with gas oil or other heavy fuels, two cases can be obtained, either a mixed method where the small combustion chamber operates with an ignition controlled by spark plug, whereas the principal cylinder is supplied with gas oil and operates on a heterogeneous mixture, the start of combustion being controlled by the opening of the linkage channel 14. FIG. 8 shows an engine thus equipped, seen in a transverse section (offset) where a direct fuel injector 22 has been installed in the principal combustion chamber 7. 
     In addition, the method and devices according to the invention also apply in the case of engines entirely using a heterogeneous mixture where the small secondary combustion chamber also operates like a diesel engine; FIG. 9 shows an engine thus equipped, seen in a transverse section where a fuel injector 23 has been installed in the secondary combustion chamber 12. 
     FIG. 10 represents a device according to the method as per the invention applied to a valve timing engine, a transfer or linkage port 24 is arranged in the upper portion of the principal combustion chamber that it connects to a small secondary combustion chamber 12, supplied with a compressed fuel-air mixture by a piston 17, and a secondary induction circuit comprised of a conduit 19, an injector 21 and a gas throttle 20; the secondary piston is controlled by a double acting cam 18. A shutter/plug 25 is positioned in the transfer port 24 and connects, during its cycled opening, the small secondary combustion chamber 12 and the principal combustion chamber 7. The low load and average/full load modes of operation and the course of the cycles are the same as previously described. 
     FIG. 11 represents, in a valve engine equipped according to the method of the invention a shutter/plug device of the transfer port 24 using a rotary distributor 26 comprising a transfer conduit 27 traversing it, while the impermeability of the principal combustion chamber 7 is assured by a sliding ring 9 and while the impermeability of the small secondary combustion chamber 12 is assured by a sliding ring 12B. This rotary distributor 26 is driven at one-fourth of the speed of the crankshaft if the gasket rings 9 and 12B are on the same transverse plane or at half speed if the rings 9 and 12B are on a different plane and will connect the two combustion chambers substantially at top dead center ignition to enable the operation according to the method as per the invention. 
     Of course, the present invention is not at all limited to the embodiments described and represented; it is capable of numerous variations accessible to one with ordinary skill in the art, according to the applications envisioned and without departing from the scope of the invention.