Abstract:
A two cycle engine comprising an induction system to induct fuel and air into said two cycle engine, at least one cylinder arrangement to combust the fuel and air mixture of said two cycle engine, and a piston arrangement disposed in said at least one cylinder arrangement. The at least one cylinder arrangement is configured to combust the fuel and air mixture of the two cycle engine during each two cycle movement of said piston arrangement. The engine also has an ignition system disposed to combust the fuel and air mixture in the at least one cylinder during each two cycle movement of the piston arrangement and an exhaust system to exhaust gases from the at least one cylinder. The exhaust system comprises a reactor and a precombustion chamber, the precombustion chamber is disposed between the at least one cylinder and the reactor. The engine also includes a heat exchanger configured and disposed to transfer heat from exhaust gases from the reactor to the precombustion chamber.

Description:
This application is a continuation-in-part of PCT/SE98/00216 filed Feb. 8, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a two cycle or two stroke engine. The present invention also relates to a method of cleaning the exhaust gases emitted from a two-stroke engine. 
     2. Background Information 
     Two cycle or two stroke carbureted gasoline engines release an amount of non-combusted fuel through their exhaust pipe. The amount of non-combusted fuel thus emitted will depend on the engine speed. The exhaust system is normally adapted to generate a back pressure to counteract this emission, although the back pressure will only function effectively at a given engine speed. The amount of non-combusted fuel emitted through the exhaust system will thus vary with varying engine speeds. When fitting a conventional reactor burner in the exhaust system, there is a danger that the reactor will become too hot when large quantities of non-combusted fuel are emitted from the engine. 
     OBJECT OF THE INVENTION 
     An object of the present invention is to provide a reactor arrangement that will function effectively even on two-stroke engines and that will have a long useful life. 
     SUMMARY OF THE INVENTION 
     This object can be achieved in principle with the aid of a combustion chamber placed upstream of the reactor and also with the aid of a heat exchanger for transferring heat from the reactor exhaust gases to the combustion chamber. The inventive reactor arrangement can have a precombustion chamber upstream of the reactor, and a heat exchanger for transferring heat from the reactor exhaust gases to the precombustion chamber. The precombustion chamber can be comprised of an expansion chamber for tuning the resistance of engine exhaust gases. A second heat exchanger can be downstream in the reactor exhaust gases to transfer heat to the gas present in the conduit extending between the precombustion chamber and the reactor inlet. The heat exchanger can be comprised of a conduit means that extends transversely through the expansion chamber, the conduit means having an aerodynamic cross-sectional shape so as to have the least possible disturbing effect on the flow in the expansion chamber. The heat exchanger conduit means can have a cross-sectional shape essentially in the form of a symmetrical wing-profile, and can be provided with fins. 
     Additionally, there can be a method of cleansing the exhaust gases from a two-stroke engine by means of a reactor arrangement, characterized by initiating a precombustion upstream of the actual reactor combustion, with the aid of heat taken from the reactor exhaust gases. The method can also include initiating the precombustion process in an engine exhaust-gas expansion chamber and using the expansion chamber to tune the exhaust resistance of the engine. 
     The heat exchanger can be heated to such an extent by the exhaust gases from the reactor as to ignite non-combusted fuel in the combustion chamber when the amount of non-combusted fuel increases, therewith providing a self-regulating system. 
     The present invention relates to a reactor arrangement that is particularly suitable for use with two-stroke engines. The invention also relates to a method of cleaning the exhaust gases emitted from a two-stroke engine. 
     The above-discussed embodiments of the present invention will be further discussed hereinbelow with reference to the accompanying figures. When the word “invention” is used in this specification, the word “invention” includes “inventions”, that is, the plural of “invention”. By stating “invention”, the Applicant does not in any way admit that the present application does not include more than one patentably and non-obviously distinct invention, and maintains that this application may include more than one patentably and non-obviously distinct invention. The Applicant hereby asserts that the disclosure of this application may include more than one invention, and, in the event that there is more than one invention, that these inventions may be patentable and non-obvious one with respect to the other. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will now be described in more detail with reference to an exemplifying embodiment thereof and also with reference to the accompanying drawings, in which: 
     FIG. 1 shows a block diagram of an two cycle engine arrangement wherein the present invention may be utilized; 
     FIG. 2 shows a block diagram of another embodiment of an engine wherein the present invention may be utilized; 
     FIG. 3 is a schematic illustration of an inventive catalyst arrangement; and 
     FIG. 4 is a sectional view taken on the line  4 — 4  in FIG.  3 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 illustrates a two cycle carburetor gasoline engine in which the present invention may be utilized. FIG. 1 shows an injection system and an ignition system connected to a cylinder arrangement. The cylinder arrangement contains a piston arrangement. After the cylinder arrangement is an exhaust system, and the exhaust system includes a pre-combustion chamber, a reactor and a heat exchanger. 
     FIG. 2 illustrates another embodiment of an internal combustion engine wherein the present invention may be utilized. FIG. 2 shows an injection system connected to a cylinder arrangement. The cylinder arrangement contains a piston arrangement. After the cylinder arrangement is an exhaust system, and the exhaust system includes a pre-combustion chamber, a reactor and a heat exchanger. 
     FIG. 3 shows an engine  11  comprising an exhaust manifold  12  and an exhaust pipe which forms an expansion chamber  13 ,  14 ,  15 . The first part  13  of the expansion chamber widens in the principle of a curved cone, while the last part  15  of said chamber narrows in the principle of a cone having a closed end. The center part  14  of the expansion chamber has a generally constant cross-sectional area and includes a heat exchanger  17 . Mounted behind the heat exchanger  17  is an outlet pipe  18  that extends transversely to the expansion chamber and whose outlet orifice  19  is located close to the center of the expansion chamber. This outlet pipe  18  leads into an outer pipe  20  and extends along said outer pipe, whereby the two pipes function as a heat exchanger where heat is transferred from the outer pipe  20  to the inner pipe  18 . The pipe  18  leads into the last part  15  of the expansion chamber and exits from the expansion chamber  13 ,  14 ,  15  and into the inlet  21  of a conventional catalyst  22 . It is not necessary for the pipe  18  to pass back into the expansion chamber in the manner shown. The outlet of the catalyst  22  is coupled to the inlet  23  of the heat exchanger  17 , and the outlet of the heat exchanger is connected as an inlet to the pipe  20 . The pipe  20  is provided with two mufflers  24 , 25  and the pipe  18  is provided with one muffler  26 . The pipe  18  is provided with a by-pass valve  27  which is controlled by a device  28  connected to a sensor  29  for sensing the catalyst device  22  connected to a sensor  29  for sensing the catalyst outlet temperature. An air supply device  30  may be coupled to the front part  13  of the expansion chamber, as shown. Although the air supply device  30  is not normally required, it can, nevertheless, be of value in certain types of engines. 
     As will be seen from FIG. 4, the heat exchanger  17  has a streamline cross-sectional shape, and includes a number of fins  31 . Because of its streamline shape, the heat exchanger will not have any disturbing effect on the function of the expansion chamber  13 ,  14 ,  15 . The length of the expansion chamber shall be adapted to the type of engine concerned, and the center part  14  of the expansion chamber is therefore ideally produced in different lengths to suit different engines. The catalyst arrangement may be identical in other respects for a large number of different engines, with the exception that the inlet  19  of the pipe  18  can have different throttles for different engines. The pipe inlet or orifice  19  will preferably not be directed axially in the expansion chamber, but preferably transversely thereto, as shown. 
     The manner in which the illustrated catalyst arrangement operates will now be described. 
     When the engine  11  is started, the catalyst  22  will be heated-up and the catalytic combustion commences. When the engine reaches the optimum number of revolutions for which the expansion chamber  13 ,  14 ,  15  is dimensioned, the engine will release a minimum of non-combusted fuel to the expansion chamber and the catalyst will operate at a suitable temperature. When the engine is run at another speed, more non-combusted fuel is released from the engine and the catalyst exhaust gases will become hotter and thereby heat the heat exchanger  17  to a temperature at which fuel in the expansion chamber will be definitely ignited. As a result of this combustion, less fuel will be delivered to the catalyst  22  and overheating of the catalyst therewith prevented. There is thus obtained a self-regulating system and pulsating combustion of fuel taking place in the expansion chamber will be heard by the driver, for instance. When the engine exhaust gases contain a certain amount of non-combusted fuel, combustion will take place in the expansion chamber with each sixth revolution of the engine, for instance. The driver of a snow scooter or snowmobile, a motorcycle, a motorboat or some other engine-powered appliance, will therefore obtain information as to when the engine is most effective, for instance when it does not stutter or judder as a result of precombustion, and the driver is able to adapt the engine speed accordingly. 
     As an additional safety measure against overheating of the catalyst  19 , the arrangement may include a by-pass valve  27  that opens when the temperature sensor  29  registers a dangerously high catalyst exhaust gas temperature. The by-pass valve  27  may ideally be designed to require the valve to be re-set in a workshop, or garage, since the valve shall not normally be opened. Because the by-pass valve is coupled upstream of the mufflers  24 ,  25 , it will be clearly heard when the valve opens. 
     It is advantageous that the pipe  18  extends within the pipe  20  so that the pipe  18  will be heated by the catalyst exhaust gases, i.e. so that the catalyst exhaust gases heat the catalyst inlet gas. 
     In a simpler embodiment of the invention, the pipe  18  and its orifice  19  may, for example, extend directly from the expansion chamber to the inlet  21  of the catalyst  22 , i.e. without the pipe  18  extending within the pipe  20  and without the pipe  18  reentering into the expansion chamber. This results in a considerably simplified construction of the inventive arrangement. 
     Naturally, one or more of the mufflers  24 - 26  may be excluded, if considered suitable to do so. 
     It will also be noted that the connection of the catalyst outlet to the inlet  23  of the heat exchanger  17  may be affected through the medium of a first outer chamber (not shown) to the expansion chamber, while the connection of the pipe  20  to the outlet of the heat exchanger may be effected through the medium of a second outer chamber (not shown) to the expansion chamber. 
     It will be understood that the invention is not restricted to two-stroke carburetor engines, but can be applied to two-stroke engines/internal combustion engines in general. 
     It will also be understood that the invention is not limited to the illustrated and described embodiment, and that changes and modifications can be made within the scope of the following features and claims. 
     Two-stroke carburetor engines release an amount of non-combusted fuel through their exhaust pipe. The amount of non-combusted fuel thus emitted will depend on the engine speed. The exhaust system is normally adapted to generate a back pressure to counteract this emission, although the back pressure will only function effectively at a given engine speed. The amount of non-combusted fuel emitted through the exhaust system will thus vary with varying engine speeds. When fitting a conventional catalyst burner in the exhaust system, there is a danger that the catalyst will become too hot and therewith destroyed when large quantities of non-combusted fuel are emitted from the engine. The noble metal coating of the catalyst is liable to be burned off and the ceramic material to be cracked. 
     An object of the present invention is to provide a reactor arrangement that will function effectively even on two-stroke engines and that will have a long useful life. 
     This object can be achieved in principle with the aid of a combustion chamber placed upstream of the catalyst and also with the aid of a heat exchanger for transferring heat from the catalyst exhaust gases to the combustion chamber. The inventive catalyst arrangement can have a precombustion chamber upstream of the catalyst, and a heat exchanger for transferring heat from the catalyst exhaust gases to the precombustion chamber. The precombustion chamber can be comprised of an expansion chamber for tuning the resistance of engine exhaust gases. A second heat exchanger can be downstream in the catalyst exhaust gases to transfer heat to the gas present in the conduit extending between the precombustion chamber and the catalyst inlet. The heat exchanger can be comprised of a conduit means that extends transversely through the expansion chamber, said conduit means having an aerodynamic cross-sectional shape so as to have the least possible disturbing effect on the flow in the expansion chamber. The heat exchanger conduit means can have a cross-sectional shape essentially in the form of a symmetrical wing-profile, and can be provided with fins. 
     Additionally, there can be a method of cleansing the exhaust gases from a two-stroke engine by means of a catalyst arrangement, characterized by initiating a precombustion upstream of the actual catalyst combustion, with the aid of heat taken from the catalyst exhaust gases. The method can also include initiating the precombustion process in an engine exhaust-gas expansion chamber and using said expansion chamber to tune the exhaust resistance of the engine. 
     It is also possible that embodiments of the present invention can be utilized in, for example, four-stroke or other engines. 
     The present invention may be used, for example, in engines such as snowmobile engines, lawn mower or lawn tractor engines, moped or motorcycle engines, outboard motors for boats or other similar engines. 
     One feature of the present invention resides broadly in a catalyst arrangement, particularly for two-stroke engines, characterized by a precombustion chamber ( 13 ,  14 ,  15 ) upstream of the catalyst ( 22 ), and a heat exchanger ( 17 ) for transferring heat from the catalyst exhaust gases to the precombustion chamber. 
     Another feature of the present invention resides broadly in that the precombustion chamber is comprised of an expansion chamber ( 13 ,  14 ,  15 ) for tuning the resistance of engine exhaust gases. 
     Yet another feature of the present invention resides broadly in that a second heat exchanger ( 18 ,  20 ) downstream in the catalyst ( 22 ) exhaust gases to transfer heat to the gas present in the conduit extending between the precombustion chamber ( 13 ,  14 ,  15 ) and the catalyst inlet ( 21 ). 
     Still another feature of the present invention resides broadly in that the heat exchanger ( 17 ) is comprised of a conduit means that extends transversely through the expansion chamber ( 13 ,  14 ,  15 ), said conduit means having an aerodynamic cross-sectional shape so as to have the least possible disturbing effect on the flow in the expansion chamber. 
     Another feature of the present invention resides broadly in that the heat exchanger conduit means ( 17 ) has a cross-sectional shape essentially in the form of a symmetrical wing-profile, and is provided with fins ( 31 ). 
     Still another feature of the present invention resides broadly in a method of cleansing the exhaust gases from a two-stroke engine by means of a catalyst arrangement, characterized by initiating a precombustion upstream of the actual catalyst combustion, with the aid of heat taken from the catalyst exhaust gases. 
     Another feature of the present invention resides broadly in initiating the precombustion process in an engine exhaust-gas expansion chamber ( 13 ,  14 ,  15 ) and using said expansion chamber to tune the exhaust resistance of the engine. 
     The following U.S. patents, which may contain two cycle motors, or components thereof, which may be used in embodiments of the present invention, are hereby incorporated by reference as if set forth in their entirety herein: U.S. Pat. No. 5,857,435, issued Jan. 12, 1999; U.S. Pat. No. 5,823,150, issued Oct. 20, 1998; U.S. Pat. No. 5,769,041, issued Jun. 23, 1998; U.S. Pat. No. 5,769,040, issued Jun. 23, 1998; U.S. Pat. No. 5,724,938, issued Mar. 10, 1998; U.S. Pat. No. 5,611,302, issued Mar. 18, 1997; U.S. Pat. No. 5,370,088, issued Jan. 3, 1995; U.S. Pat. No. 5,361,732, issued Nov. 8, 1994; U.S. Pat. No. 5,251,583, issued Oct. 12, 1993; and U.S. Pat. No. 5,245,824, issued Sep. 21, 1993. 
     Examples of snowmobiles, and components thereof, in which the present invention may be utilized, may be found in the following U.S. patents: U.S. Pat. No. 5,904,217, issued May 18, 1999; U.S. Pat. No. 5,902,021, issued May 11, 1999; U.S. Pat. No. 5,853,061, issued Dec. 29, 1998; U.S. Pat. No. 5,730,510, issued Mar. 24, 1998; U.S. Pat. No. 5,727,643, issued Mar. 17, 1998; U.S. Pat. No. 5,713,645, issued Feb. 3, 1998; U.S. Pat. No. 5,700,020, issued Dec. 23, 1997; U.S. Pat. No. 5,692,579, issued Dec. 2, 1997; U.S. Pat. No. 5,685,387, issued Nov. 4, 1997; U.S. Pat. No. 5,673,772, issued Oct. 7, 1997; U.S. Pat. No. 5,660,245, issued Aug. 26, 1997; U.S. Pat. No. 5,472,215, issued Dec. 13, 1994; U.S. Pat. No. 5,152,255, issued Oct. 6, 1992; U.S. Pat. No. 5,060,745, issued Dec. 29, 1991; U.S. Pat. No. 4,917,207, issued Apr. 17, 1990; U.S. Pat. No. 4,237,997, issued Dec. 9, 1980; U.S. Pat. No. 4,186,291, issued Jan. 29, 1980; U.S. Pat. No. 3,776,354, issued Dec. 4, 1973; and U.S. Pat. No. 3,773,127, issued Nov. 20, 1973. 
     Examples of lawn mowers in which the present invention may be utilized, may be found in the following U.S. patents: U.S. Pat. No. 5,921,072, issued Jul. 13, 1999; U.S. Pat. No. 5,915,496, issued Jun. 29, 1999; U.S. Pat. No. 5,913,802, issued Jun. 22, 1999; U.S. Pat. No. 5,901,536, issued May 11, 1999; U.S. Pat. No. 5,893,817, issued Apr. 13, 1999; U.S. Pat. No. 5,890,354, issued Apr. 6, 1999; U.S. Pat. No. 5,887,484, issued Mar. 30, 1999; U.S. Pat. No. 5,878,730, issued Mar. 9, 1999; U.S. Pat. No. 5,873,287, issued Feb. 23, 1999; U.S. Pat. No. 5,832,708, issued Nov. 10, 1998; U.S. Pat. No. 5,822,961, issued Oct. 20, 1998; U.S. Pat. No. 5,809,756, issued Sep. 22, 1998; U.S. Pat. No. 5,797,251, issued Aug. 25, 1998; and U.S. Pat. No. 5,775,078, issued Jul. 7, 1998. 
     Examples of outboard motors which may be used in embodiments of the present invention may be found in the following U.S. Patents: U.S. Pat. No. 5,921,829, issued Jul. 13, 1999; U.S. Pat. No. 5,921,827, issued Jul. 13, 1999; U.S. Pat. No. 5,915,363, issued Jun. 29, 1999; U.S. Pat. No. 5,913,294, issued Jun. 22, 1999; U.S. Pat. No. 5,911,610, issued Jun. 15, 1999; U.S. Pat. No. 5,911,608, issued Jun. 15, 1999; U.S. Pat. No. 5,910,191, issued Jun. 8, 1999; U.S. Pat. No. 5,908,338, issued Jun. 1, 1999; U.S. Pat. No. 5,904,605, issued May 18, 1999; U.S. Pat. No. 5,899,778, issued May 4, 1999; U.S. Pat. No. 5,893,783, issued Apr. 13, 1999, U.S. Pat. No. 5,873,347, issued Feb. 23, 1999; U.S. Pat. No. 5,822,985, issued Oct. 20, 1998; U.S. Pat. No. 5,803,036, issued Sep. 8, 1998; U.S. Pat. No. 5,778,848, issued Jul. 14, 1998; and U.S. Pat. No. 5,778,847, issued Jul. 14, 1998. 
     Examples of catalysts, or catalytic systems, which may be used in embodiments of the present invention, may be found in the following U.S. patents: U.S. Pat. No. 5,836,152, issued Nov. 17, 1998; U.S. Pat. No. 5,345,762, issued Sep. 13, 1984; U.S. Pat. No. 3,885,539, issued May 27, 1975; U.S. Pat. No. 5,921,080, issued Jul. 13, 1999; U.S. Pat. No. 5,911,961, issued Jun. 15, 1999; U.S. Pat. No. 5,897,846, issued Apr. 27, 1999; U.S. Pat. No. 5,887,421, issued Mar. 30, 1999; U.S. Pat. No. 5,884,474, issued Mar. 23, 1999; U.S. Pat. No. 5,867,983, issued Feb. 9, 1999; U.S. Pat. No. 5,822,982, issued Oct. 20, 1998; U.S. Pat. No. 5,839,276, issued Nov. 24, 1998; U.S. Pat. No. 5,839,273, issued Nov. 24, 1998; U.S. Pat. No. 5,791,139, issued Aug. 11, 1998; and U.S. Pat. No. 5,744,104, issued Apr. 28, 1998. 
     The components disclosed in the various publications, disclosed or incorporated by reference herein, may be used in the embodiments of the present invention, as well as, equivalents thereof. 
     The appended drawings in their entirety, including all dimensions, proportions and/or shapes in at least one embodiment of the invention, are accurate and to scale and are hereby included by reference into this specification. 
     All, or substantially all, of the components and methods of the various embodiments may be used with at least one embodiment or all of the embodiments, if more than one embodiment is described herein. 
     All of the patents, patent applications and publications recited herein, and in the Declaration attached hereto, are hereby incorporated by reference as if set forth in their entirety herein. 
     The corresponding foreign and international patent publication applications, namely, Swedish Patent Application No. 9700459-2, filed on Feb. 10, 1997, having the inventor Mats Tikka, and published Swedish Patent Application No. 9700459-2, and Swedish Patent No. 9700459-2, and International Application No. PCT/SE98/00216, filed on Feb. 8, 1998, and publication No. WO 98/35142, having the inventor Mats Tikka, as well as their published equivalents, and other equivalents or corresponding applications, if any, in corresponding cases in Sweden and elsewhere, and the references cited in any of the documents cited herein, are hereby incorporated by reference as if set forth in their entirety herein. 
     The details in the patents, patent applications and publications may be considered to be incorporable, at applicant&#39;s option, into the claims during prosecution as further limitations in the claims to patentably distinguish any amended claims from any applied prior art. 
     Although only a few exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims. In the claims, means-plus-function clause are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. 
     The invention as described hereinabove in the context of the preferred embodiments is not to be taken as limited to all of the provided details thereof, since modifications and variations thereof may be made without departing from the spirit and scope of the invention.