RELATED APPLICATIONS The present application claims the benefit of priority of U.S. provisional application No. 61/252,686, filed Oct. 18, 2009 entitled “INTEGRALLY CAST BLOCK AND GASEOUS FUEL INJECTED GENERATOR ENGINE, U.S. provisional application No. 61/538,935, filed Sep. 25, 2011 entitled “TWO-STROKE ENGINE AND LUBRICATION SYSTEM”, U.S. provisional application No. 61/541,027, filed Sep. 29, 2011 entitled “Engine”, U.S. provisional application No. 61/545,184, filed Oct. 9, 2011 entitled “Engine Lubrication”, U.S. provisional application No. 61/545,530, filed Oct. 10, 2011 entitled “Engine”, U.S. provisional application No. 61/545,588, filed Oct. 11, 2011 entitled “Half Crank Engine”, and U.S. provisional application No. 61/722,162, filed Nov. 3, 2012 entitled “Half Crank Engine”, filed the entirety of which is incorporated by reference herein for all purposes.
Prior arts: U.S. Pat. No. 6,216,651, U.S. Pat. No. 6,539,904, U.S. Pat. No. 4,930,462, U.S. Pat. Nos. 6,901,892, 4,253,433, and 6,273,037, U.S. Pat. No. 5,715,784, U.S. Pat. Nos. 6,901,892, 6,293,235, 5,918,574, 4,726,330, 6,216,651, 3,542,154, 6,427,672,
BACKGROUND Conventional gasoline fueled four-stroke engine used in hand-held applications as in a trimmer and a blower sold by Ryobi and MTD and gaseous fueled blower by LEHR are environmentally friendly. However, the drawback is that those engines are very heavy and cannot be operated upside down for extended time and the same design cannot be used in chainsaws. The two-stroke engines are advantageous, but are very high in emission levels. Gaseous fueled two-stroke trimmer engine as manufactured and sold by Mitsubishi is a conventional two-stroke engine, which has significantly higher pollutants in the exhaust. Some conventional two-stroke engines sold in US have catalysts to lower the emission levels.
It is known in the engine industry that there are gaseous fueled two-stroke engines with oil injection system. However, these engines are conventional type which has high emission levels and the cleaner stratified engines are gasoline fueled and typically have oil pre-mixed with the gasoline. Secondly, users have to always pre-mix oil for lubrication, which can harm the catalysts and as such emission levels may be bad toward the end of the life of the catalyst and or the engine. Thirdly, user may forget to mix oil with the gasoline which results in a scuffed engine. U.S. Pat. No. 4,930,462 describes an oil injection pump requiring an oil pump and a gear system. However, the drawback is that the oil pump cannot deliver oil at all attitude because the oil tank attached to bottom of the tank and when the engine is turned upside down, the oil pump may not receive oil from the tank. U.S. Pat. No. 6,216,651 describes an electronic oil injection system requiring expensive system, but does not guarantee that the oil system can deliver oil when the engine is turned upside down. U.S. Pat. No. 6,539,904 describes a very expensive four-stroke engine having a valve operating mechanism and an oil sump. But this engine requires camshaft, intake valve, and exhaust valve, where the overhead cam is driven by the crankshaft at half the engine speed. Secondly the construction of the four-stroke engine is so complex compared to the simple two-stroke engine disclosed in this embodiment. Also, the engine is not suitable where high power to weight ratio is important for chainsaw applications. The embodiment disclosed here does not require a camshaft, or valve train or any of the complexes of engine and drive mechanism to operate the valves. Also, the embodiment disclosed does not require the oil to return to the oil sump, but it is total loss oil system. The oil inducted into the engine is burnt in combustion chamber, unlike the four-stroke engine disclosed in the prior art.
The design described here has a gaseous fueled stratified two-stroke engine with a dual passage carburetor to lower the emissions and oil injection to lubricate the engine. The engine may further be fitted with catalysts to reduce the pollutants to even way below the legal limits. The gaseous fuel may be Butane, CNG, Methane, Hydrogen, or Propane or mixture of any gaseous fuels in any ratio. The engine can be used in many hand-held and lawn garden and mobile applications such as chainsaws, trimmers and scooters. Another advantage of the design disclosed here is that the oil need not be pre-mixed with fuel as it has a separate oil sump (reservoir) and lubricates the engine automatically. One significant advantage of the design disclosed is that the engine can operate in any attitude for extended period of time, as long as there is oil in the oil sump.
BRIEF SUMMARY The new invention describes the designs of the new two-stroke engine and the lubrication systems for use with portable engines, in particular that are operated in different attitudes, including upside down. The fuel used in such engines include gasoline, liquid fuel, gaseous fuel, like, H2, Methane, LPG, Pure propane, or Butane. The two-stroke engines described in the embodiments are especially best for lawn and garden tools such as chainsaws, trimmers, blowers, pumps, and scooters.
The new invention reduces the emissions significantly with LPG or Butane as fuel and just water vapor and N2 and NOx when H2 is used. It also reduces the oil consumption.
Further, the inventions provide a new lubricating system where in the oil injection pump is driven by the crankshaft or belt or gear drive off of the crankshaft. Alternatively the oil pump may be a diaphragm pump with or without a plunger. The oil may be injected into the intake, particularly into the air-fuel mixture passage, or into the crankcase, and may also be injected into the transfer passage, particularly at the bottom of the passage in a stratified engine where air is drawn into the crankcase through the transfer passage. The oil in the form of mist or fine droplets may also inducted in to the engine, particularly into the crankcase chamber through the intake system (ports) or directly into the crankcase chamber for lubrication of the internal moving parts. The gaseous fuel tank is attached to the bottom of the crankcase or at the top of the engine above the cylinder. In the embodiment described here, the oil pump is driven off a out-board shaft 222 which may not be concentric with the inboard shaft 22, such that it becomes economical to build such engines. In another embodiment, the oil sump is on the outboard side having a common wall with the crankcase chamber (or separate wall to reduce heating up of oil). Yet, in another embodiment the oil in the form of mist and oil small oil droplet is automatically inducted into the engine. The outboard shaft has slinger inside the oil sump to generate oil vapors and or fine droplets of oil for induction into the engine for lubricating the engine. The starter assembly is adjacent to the oil sump. The oil splashing slinger and the starter pulley (cup) are on the same shaft. The shaft for splashing the oil may be run at different speed than the crankshaft through intermediate gears or belt or friction couplings. Also, it is possible that the drive may be perpendicular or any other angle to the crankshaft.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional diagram of a special gaseous fuel carburetor and the engine 100 with the charge tube.
FIG. 2 is a sectional diagram of a dual passage gaseous fuel carburetor and the air-head stratified engine 200.
FIG. 3 is a cross sectional diagram of the engine shown in FIG. 2 having an oil pump.
FIG. 4 is a cross sectional diagram of a two-stroke engine 250 having an oil sump.
FIG. 5 is a cross sectional diagram of a two-stroke engine 350 having an oil sump and a starter.
FIG. 6 is a cross sectional diagram of a two-stroke engine 255 having oil sump and oil level sensor.
FIG. 7 is side view of the oil sump cover showing the oil level sensor for the engine 255.
FIG. 7b is a side view of the oil sump showing oil level indicater.
FIG. 8 is cross sectional view of a half crank two-stroke engine 450 showing oil sump in the front of the engine block.
FIG. 9 shows the ignition and safety switch control logic.
FIG. 10 is cross sectional view of an engine 600 having oil sump between the flywheel and the crankcase chamber.
FIG. 11 is a cross sectional view of an engine having oil sump on outboard side of the starter assembly.
FIG. 12 is a cross sectional view of a half crank engine having integral oil sump and housing.
DETAILED DESCRIPTION FIGS. 1, through 11 show new two-stroke oil injected engines with special gaseous fueled carburetors having built in pressure regulator and metering chambers and lubrication system. The two-stroke engine shown are of stratified type having either a rich charge tube or air-head scavenging as described in U.S. Pat. Nos. 6,901,892, 4,253,433, and 6,273,037. However, the embodiments disclosed are applicable to many types of engines, including gasoline two-stroke fuel injected engine. The draw back in the prior arts are that the engines employ gasoline as fuel and oil has to be pre-mixed. The gaseous fuel two-stroke engine made by Mitsubishi as described in U.S. Pat. No. 5,918,574 has an oil injection system, but is not a stratified engine, hence has significantly higher emission levels. Secondly the engine has a separate oil tank, but it cannot supply oil to the oil pump all attitudes of the engine. Thus has a limitation how the equipment or the engine can be operated and for how long the engine can be operated at other than normal attitude. The most commonly used gaseous fueled carburetors are not suitable for stratified engines. There are, however, gasoline fueled stratified carburetors, but they are not made to handle gaseous fuels. Secondly gaseous fueled engine are typically oil injected type having a separate oil tank and an oil pump for injecting oil into the engine. The oil injected engines have a limitation on attitude in which they can be operated and for how long they can be operated upside down. Therefore, it is believed by the inventors that the inventions disclosed here would be beneficial to the environment and particularly the hand-held engines can now be operated in any attitude for any length of time. The embodiment also describes that the amount of oil consumed by the engine at different speeds can be varied according to the speed and throttle position.
U.S. Pat. No. 6,901,892 for example describes a charge stratified engine similar to the one in FIG. 1. The operating principle of the innovative engine 100 disclosed in this invention is similar to the engine 10 in the above reference. As such it will be understood by the person who has knowledge of engine will be in a position to execute the disclosed design. Engine 100 in FIG. 1 consists of a cylinder 12 inside which is a reciprocating piston 16 connected to the crankshaft 22 through a connecting rod 18, a crankpin 20 and a piston pin 114. The crankshaft 22 has crank weight 21 and the crankshaft is supported by main bearings either on both ends of a full crank engine or just on one side in a half crank engine. The lower side of the piston has crankcase chamber 26 in the crank case 28. The cylinder 12 has cylinder bore 14 having combustion chamber 30 on the upper side of the piston 16. The crankcase chamber and combustion chamber are interconnected periodically through transfer passage 11. The cylinder has at least one intake port 84, exhaust port 50, at least one transfer port 33 and an injection port 40. The injection port 40 is connected intermittently to the crankcase chamber 26. The lubricating system consists of an oil pump 802 driven by the crankshaft, typically mounted to the side of the crankcase wall. Oil pump 802 has an inlet oil line 806 and receives oil from oil tank 808 and has outlet pipe 803 injecting oil into the intake passage 310 downstream of the lean valve 80 and possibly into the heat dam 902.
The special gaseous carburetor 400 shown in FIGS. 1 has at least two passages; a rich charge passage 300 and a lean charge passage 310. The gaseous fuel carburetor has at least one pressure regulating chamber and a metering chamber.
The gaseous carburetor 400 has a rich charge passage 300 supplying rich charge (rich fuel-air mixture) into the injection tube 38, through a one way valve 36 in the intake heat dam 902. As described in prior art, U.S. Pat. Nos. 6,901,892 and 6,293,235. The lean passage 310 supplies lean charge (lean fuel-air mixture) with oil into the crankcase chamber 26. The intake and scavenging process is explained in detail in the prior arts U.S. Pat. No. 6,901,892 and others. It is to be known that person skilled in the art understands the operating principle by reading the prior arts U.S. Pat. Nos. 6,901,892 and 6,293,235 in its entirety. However, in this invention, the oil is injected into lean charge in the lean passage 310, preferably at the intake heat dam 902. The flow of rich and the lean charge into the engine are regulated by the respective control valves 81 and 80. Both the valves 81 and 80 are mounted on to a common throttle shaft 479. However, they may be mounted on separate throttle shafts linked to each other and may be at phase with each other. Also, in the disclosure, the undercut (or a through hole) in the throttle shaft 479 in the rich charge passage may act as a throttle valve 81 and not have a separate valve. It must be understood that the dual valves may be of any type; butterfly valve, rotary valve also known as barrel valves, or slide valve, which are commonly known to the person skilled in the art.
Further the invention discloses a dual passage carburetor 8400 for air-head stratified engines. Prior arts U.S. Pat. Nos. 6,901,892 and 6,112,708 describe in detail the operating principle of a air-head stratified engine. Engine 200 in FIG. 2 consists of a cylinder 2012 inside which is a reciprocating piston 2016 connected to the crankshaft 22 through a connecting rod 18, a crankpin 20 and a piston pin 114. The crankshaft 22 has crank weight 21 and the crankshaft is supported by main bearings either on both ends of a full crank engine or just on one side in a half crank engine. An outboard shaft 222 loosely connected to the connected to the crankpin 20 through a yoke 1450 is shown in FIG. 3, which is a sectional view of the half crank engine 200. An oil pump 802 may be driven by the outboard shaft 222. As shown the axis 2927a of the crankshaft 22 and the axis 2927b of the outboard shaft 222 may not be in line and is not critical to be in line, because the yoke 1450 has a slot and accounts for any misalignment between the shafts. However, it must be understood that the outboard shaft 222 may be similar to a conventional crankshaft rigidly attached to the crankpin 20. The lower side of the piston has crankcase chamber 26 in the crank case 28. The cylinder 2012 has cylinder bore 14 having combustion chamber 30 on the upper side of the piston 2016. The crankcase chamber 26 and combustion chamber 30 are interconnected periodically through transfer passage 11 and transfer port 33. The cylinder 2012 has at least one intake port 84 for air-fuel mixture, at least one air inlet port, exhaust port 50, and at least one transfer port 33. The engine operates like a conventional two-stroke engine. First and second piston ports 99 and 101 are disposed on the skirt 2113 of the piston 2016 and are connected to each other in gaseous communication by air channel 96. The complete description of the air-head engine is described in entirety in the U.S. Pat. No. 6,901,892. The lubricating system consists of a oil pump 802 driven by the crankshaft, typically mounted to the side of the crankcase wall. Oil pump 802 has an inlet oil line 806 and receives oil from oil tank 808 and has an outlet pipe 803 injecting oil into the intake passage 310 downstream of the lean valve 80 and possibly into the heat dam 904. The engine 200 described is referred to as a piston ported air-head engine. It must be understood that the air-head stratified engine may also be a reed valve air-head stratified engine, where in the air is inducted into the transfer passage 11 through a reed valve) also known as one-way valve) as described in U.S. Pat. No. 6,901,892 in FIG. 31. However, it is optional to have rotary valve open and close the opening of the transfer passage in the crankcase chamber. An outboard shaft (222) driven oil pump is also described in FIG. 25 in the U.S. provisional application 61/252,695 filed on Oct. 18, 2009 and in the U.S. provisional application 61/277,476 filed Sep. 26, 2009. It must be understood that the air-head engine can also use reed valve in the air passage as described in prior arts.
It is also possible for rich fuel to be inducted into the injection tube 38 and the opening into the crankcase chamber 26 be periodically opened and closed by the cut out on the counter weight 21, as described in the prior art U.S. Pat. No. 6,901,892. Also, it is possible that the pure air with or without oil injected into the air be inducted into the crankcase chamber 26 through transfer ports 33 as in the air-head engine described in U.S. Pat. No. 6,901,892, where as the air inlet is through a one way valve or through the air channel in the piston as described in U.S. Pat. No. 6,901,892.
Further FIG. 4 shows the oil sump 1250 on the outboard side. The outboard shaft 222 driven by the crankpin 20 through the arm 1450 is either solidly attached to the crank pin 20 or loosely attached. The outboard shaft 222 has slinger 1234b attached to it and the slinger has fingers (1234c) extended outwardly at the extreme ends and one set (1234d) at the center. The purpose of the slinger with the fingers is to splash the oil 1340 as the engine runs and create oil vapors and or small oil droplets. This oil vapor and or droplets are inducted into the crankcase chamber 26 directly through the passage 808b in the shaft 222 or into the intake port 84 through a throttle valve or directly through the intake passage (preferably entering the intake downstream of the throttle valve) to lubricate the internal parts. Since the engine is a two-stroke engine, oil indicted into the crankcase chamber 26 eventually transferred into the combustion chamber 30 through the transfer passage 11. The oil inducted into the engine is burnt and unlike four-stroke engines it is not re-circulated. However, there are designs that allow for at least partial recovery of the oil.
In the case where the oil is inducted into the crankcase chamber 26 directly through the central passage 808b in the shaft 222, there can be a check valve or one way valve 914 to induct oil when the piston 2016 (16) is moving upward, particularly from about BDC to until about before the intake port 84 or air port (or reed valve opens as in air-head engine) opens. The oil sump 1250 may have a breather (1250b) having a one-way check valve to allow for ambient air to enter into the oil sump 1250, which eventually mixes with oil droplets and or oil vapors and is inducted into the crankcase chamber 26. The oil sump cover 28c may be of translucent material so the level of the oil is visible to the operator. Or there can be a window 28d on the cover 28c to indicate the oil level. There can be oil level sensor to shut off ignition if the oil level is below certain level. Alternately a temperature sensor may be used to shut off ignition (or fuel). The oil sump and slingers with fingers are designed such that the engine can be operated in any attitude without the raw oil getting into the inlet of the passage 808b or 803c. In the case the oil is inducted through the central passage 808b, then the opening and closing of the oil passage into the crankcase chamber may be timed by the opening and closing of the opening 809 at the end of the radial passage 809a, by a circumferentially but partial cut out section on the bearing sleeve 222b. The design of having oil sump on outboard side and oil passage in the crankshaft is also described in the prior application Ser. No. 12/890,627, which has a similar design, but for a four-stroke engine. The oil passage 808b may also have a centrifugal valve (as described in the application Ser. No. 12/890,627) to prevent the oil from getting into the crankcase chamber when the engine is not running. Secondly the opening of the passage 808b (and 803c) in the oil sump 1250 is such that the oil never gets into the opening when the engine is stored or operated in any attitude. The maximum oil level filled by the user is below the level of inlet to the oil passage 808b (and 803c). In the case the oil passage 808b opens straight into the crankcase chamber 26, the passage can have a check valve 914 such the positive pressure, as the piston moves downward (or or due to blow-by) in the crankcase chamber does not get into the oil sump. As the piston moves upward, the sub-atmospheric pressure in the crankcase chamber causes the oil vapor/droplets to be drawn into the crankcase chamber 26 and the amount of suction may be regulated by a self regulating valve such that when the engine is running at part throttle or at idle less oil is supplied and when the engine is running at wider throttle position more oil is supplied or through a separate throttle valve. Self regulating may be through a centrifugal valve that varies the flow areas as per engine speed. The oil is periodically filled to marked level through an oil filler and may have an oil level indicator (28d) as in any engine. The oil passage may have a centrifugal valve 808b to shut off the passage when the engine is not running and opens as the engine RPM increases. The self regulation may be due to combined effects of the governing weight, spring, RPM, and suction in the passage. As the sub-atmospheric pressure is lower at part throttle, the opening of the valve may be restricted, even though the centrifugal force tries to open the valve. Alternatively a tapered plunger (not shown) in the central oil passage 808b attached to the centrifugal valve may vary the oil getting into the crankcase chamber 26 depending on the engine RPM. In which case, it may also work as a shut off valve when the engine is not running. Therefore the amount of oil vapor/droplets entering the crankcase chamber may be self regulating. The end point of the oil tube 803b may be upstream or downstream side of the carburetor throttle valve and the amount of vapor may be regulated by the throttle valve common to the controlling the air-fuel or just oil vapor. As explained, the oil induction into the crankcase chamber 26 may be directly through the oil passage in the shaft 222 having a check valve, or through the passage in the shaft and a radial passage 809 in the shaft which may be opened and closed periodically the cut out in the bearing sleeve 222b. The oil may be inducted through an oil line 803b (or 803b′) having inlet 803c at the center of the oil sump as shown in FIG. 4 and FIG. 5 and the outlet of the oil line 803b (or 803b′) may in the passage leading into intake port 84. Alternately, the outlet may have a separate inlet port on the cylinder 2012 (12) periodically opened and closed by the piston 2016 (16). The port is opened as the piston moves upward and closed as the piston moves downward. The oil when fed into the intake passage downstream of the carburetor, the opening into the intake passage may be at the intake manifold called heat dam 904. There may be a check valve in the oil line 803b to prevent any back flow of pressure signal into the oil line, particularly when the piston closes the intake port 84.
Further, the crankshaft 222 may be extended through the oil sump cover 28c as shown in FIG. 4 of the application Ser. No. 12/890,627 to have a provision for a starter, either conventional or electrically driven type. Further, the excess oil in the crankcase chamber may return to the oil sump, as described in the application Ser. No. 12/890,627. The embodiments described can be used in any type of two-stroke engines, not limited to; carbureted, gaseous fueled two-stroke, liquid fueled two-stroke, fuel injected two-stroke engine, stratified engines, etc. However, it would be beneficial more in a gaseous fueled two-stroke engine, particularly hand held applications, where the product will likely to be operated in many attitudes, including up-side down. Since the oil passage is located in the oil sump such that the raw oil never reaches the opening no matter which attitude the engine is operated or stored.
Further the FIG. 4 shows different embodiments for oil passages and valves for lubricating the two-stroke engine. However, it must be known that any one type is used. Different types are shown in FIG. 4 for illustration only. The oil is injected into the air-fuel passage 8300 at downstream of the air-fuel valve 881 through an oil injector. The oil may also be injected directly into the crankcase chamber 26 through the side wall of the crankcase 28 or may also be injected through a central hole in the crankshaft 222 (or 22) and through a radial hole in the counter weight (not shown). When inducted directly into crankcase chamber or through crankshaft, it eliminates the need for oil feed line 803b (or 803 in FIGS. 1 and 2). Also, the oil sump may be attached to the side of the crankcase on the outside between the starter housing and the crankcase outer wall. It must be understood that the carburetors 400 and 8400 may be combined to form a three-way carburetor as described in U.S. Pat. No. 6,901,892, however, it will be a gaseous fuel with oil injection into lean charge passage. Also, the control valves may be of any type; butterfly valve, barrel or rotary valve, or slide valve.
FIG. 5 shows an engine 350 having a starter assembly on the outboard side. The starter assembly consisting of a starter cup 1852, which can be part of the slinger 1234b, having starter pawls 1855, which are centrifugally disengaged above certain engine RPM and engaged to the starter gear at the end of the starter reel 1850. The starter reel rotates when the starter rope 1851 is pulled for starting the engine. The reel 1850 rotates on the starter shaft 1823, which can be an integral part of the oil sump cover 28c. The starter mechanism and the assembly can be of any type commonly used in similar engines. The oil in the oil sump 1250 is separated from the starter cavity 1850 through a member 1848, which can be a conventional oil seal or any flexible element. FIG. 5 shows that oil sump cover 28c also has starter cavity 1858 separated from the oil sump 1250 by the oil seal 1848. Oil sump cover 28c also has an integral starter shaft 1823. Alternately the two; oil sump and the starter cavity 1858 and the starter shaft 1823 can all be separate parts assembled together. The oil sump cover 28c has a oil refilling cap 1250d having a breather 1250b. The starter assembly, however, can also be on the inboard side (on the side of crankshaft 22), as in many half crankshaft engines. Similarly, the oil sump with oil slinger and oil passages in the crankshaft may be on the inboard side as shown in FIGS. 10 and 12 in the US publication number 2011/0088650. It must be understood that the shaft 222 may not be running at the same speed as the crankshaft 22, because shaft 222 may be driven through coupling (gear, belt, or flexible coupling such as spring etc., between the crankshaft and shaft 222.
The oil tube 803b may be connected to the crankcase chamber 26 through a separate port (not shown) in the cylinder intermittently opened and closed by the piston 2016 (16).
Also, the amount of oil inducted into the crankcase chamber may be regulated by means of a throttle valve and the throttle valve may be operated by the fuel and air regulating carburetor or throttle body and by the same shaft 479 (shown in FIG. 1) as used to control the charge or air-fuel mixture or the air only, as it is dependent on type of carburetor used. The amount oil mist inducted may also be automatically regulated by the governor (either mechanical or electrical). It is also possible that up to 15 to 25 of the total air inducted by the engine is inducted through the oil sump and pre-mixed with the oil (in the form mist and or small oil droplets). This ensures that the engine receives adequate oil for lubrication at all conditions. It is also possible that this fraction of air pre-mixed with oil by virtue of air passing through the oil sump is inducted through a dedicated port similar to the piston ported air-head engine, or conventional port or even through reed valves. It is also possible to combine the oil induction system with main intake system by means of the rotary valve system as described above and illustrated in FIG. 5 where the radial passage 809a is timed by the cut section in the sleeve 222b. That is, as the piston moves upward and after the exhaust port and transfer ports are closed, the oil passage is opened to the crankcase chamber through dedicated port followed by the opening of the main intake (or air port as in air-head) port. When the piston begins to move downward, the radial port can be closed by virtue of asymmetric port timing in a rotary valve system. Alternately, the radial passage 809c, shown in FIG. 4C having an outlet port 809d may be opened and closed according to the desired timing by the cast feature on the inside wall 29 of the crankcase 28. As the piston moves upward, after the exhaust port sis closed and just before the intake port opens, the oil port 809d is opened and it closes as desired either before the TDC or any time after the exhaust port 50 is closed and a few angles after TDC. Thus a guaranteed supply of oil from oil sump is ensured in the embodiment disclosed here. The oil consumption may range from 1.5% to 6% of the fuel consumption and it can at the lower end when idling and can be as high as 6% at wide open throttle. Therefore the percentage of oil in the up to 25% of air inducted through the oil sump will be higher than the total air inducted into the engine. Additionally, the air mixed with oil may be regulated by the throttle valve in the carburetor and also be mixed with fuel along with the remainder of the air passing through the carburetor, in a conventional two-stroke engine. However, the percentage of air mixed with fuel will be about 20 to 35% less in the case of an air-head scavenged engine. Also, the oil mixed air may be inducted directly into the charge injection tube 39, particularly when large percent of charge in allowed to go into the crankcase chamber 26. The oil mixed air may be inducted through a port at the bottom on the transfer passage 11, but may be timed by the rotary valve, as described above, where the opening 809 in the radial passage 809a is opened and closed according the preferred timing by the cut out on the sleeve 222b (9041 in FIG. 4). A separate window 2018 in the piston 2016 aligning periodically with the port 86 dedicated for oil induction may also be employed. The window 2018 on the piston skirt allows for the induction of oil only for a short time, while the intake port 84 is opened for a longer time. Electromagnetic valve may also be employed to regulate the amount and timing for induction of oil into the crankcase chamber 26. It must be noted that in FIGS. 4 and 5, the outboard shaft 222 terminates inside the oil sump 1250. A shorter shaft helps reduce the weight and cost. Secondly, the centrifugal valve at the end of the shaft 222 is easily serviceable and is well lubricated. Also, if the starter assembly is on the inboard side (driving the shaft 22) as in many half crank engines (Homelite, MTD companies make such engines), the centrifugal valve or a tapered control valve may be actuated from the outboard side to regulate the flow of oil mist into the crankcase chamber, particularly when the oil passage is in the shaft 222. It is also possible to keep the centrifugal valve closed when the engine is being cranked for starting, such that all the suction in the crankcase chamber is now through the carburetor that helps easy starting. As the starter rope is pulled, a lever or a pin may act against the centrifugal valve or simply shut the central oil passage and the pin is pulled away once the starter rope is released.
FIG. 6 discloses an oil level indicating system 60, having a floating ball or equivalent float or liquid level sensor 62 attached at the end of an arm 63. The arm has a hinge on the oil sump cover 28c so that the position of the ball/sensor varies depending on the oil level. The hinge may have a needle to show the level of the oil or the arm itself may indicate the oil level through the window 28d. The arm may also actuate a switch to turn the ignition off when the level of the oil 1340 in the oil sump 1250 is below a certain level. This prevents the user from starting the engine if the level of oil is below the predetermined level. A potentiometer 69 or any equivalent position sensor 69 may be used to turn of the ignition If the oil level is below certain minimum level. However, it must be note that the ignition switch is turned off only if the engine RPM is below certain RPM, such as 200 or so. An ECM 72 can measure the engine RPM and oil level to determine if the ignition switch is to be turned off. This is required as the arm may return to the minimum oil level position when the engine is running and as the oil level drops due to splashing of the oil and also due to attitude of the running engine. A baffle plate 78 with small holes in it may be provided such that the oil does not drain away from the float area as soon as the engine is cranked. This may allow certain time for the ECM to be powered as the engine is cranked and before the oil level sensor position is changed due to drainage of oil near the float. An intelligent ECM 72 may also predict how long the engine could be operated once the initial oil level is determined and automatically turn off the ignition or fuel to prevent the engine from running without oil. A warning light may be displayed to warn the user of low engine oil. A simple float in ball within a tube may also be used to indicate the oil level, without having any warning or safety switch. The power supply to the ECM 72 may come from the ignition coil 9404 or battery or even solar cells. The cranking speed may be good enough to generate the power to power the sensor and operate the ECM 72. The ECM 72 may be part of the ignition coil 9404 assembly. The window to see the oil level may also be on side of the oil sump cover 28c, which would be toward the user for easy inspection. A dip stick may also be used to check the oil level in the oil sump 1250. It may be desirable to have a red light visible to the user to indicate that oil level is below the minimum. The light may turn on momentarily when the engine is initially cranked, because the power to the ECU may come from the generator, which requires the engine to be running to generate power. But at this time, the ECM may be programmed to either turn the ignition off (or fuel) or run only momentarily just enough to generate power for the ECM to perform other operation as necessary. One such operation may be an audio signal or voice warning the user to check oil. If a mechanical oil level indicating system is used, system may ground the kill switch only when the engine is cranked to start the engine, when the RPM (RPM=X) is well below the idle RPM (RPM Y). When a position sensor is used to check the oil level, then it may be possible to estimate the run time before the oil level is at minimum.
FIG. 6 also discloses an radial oil passage 809c in the counter weight or yoke 1450 having a oil outlet port 809d. As the outboard shaft 222 is rotating the oil outlet port periodically opens and closes into the crankcase chamber by virtue of its angular position with respect to the inner surface 29 of the oil sump cover 28b (or crankcase 28, if outboard shaft is a crankshaft) 28b if the outboard shaft is a short shaft driven by a yoke 1450, which may be slightly off-centered to the crankshaft 22. Alternately the inner surface may have a circumferentially cut out area to time the port 809d, as in a rotary valve.
It is possible for the upper crankcase 28b and cylinder block 2012 to be cast as single piece, while the lower crankcase 28b is a separate piece. In that case, the upper section of the oil sump cover 28c may be integral with the upper block, while the lower section of the oil sump cover is integral part of the lower section of the crankcase 28.The split line is along the center line 2927a of the crankshaft 22. This type of casting is feasible, particularly when the outboard shaft 222 is a crankshaft as in a full crank engine.
FIG. 7 shows the side view of the oil sump with an oil level sensor 62 where the center of the arm 63 is below the center line of the oil sump or the center line of the shaft 222. FIG. 7b shows where the center of the arm 63 is substantially in line with the center line of the shaft 222, and it also has an arm extending outward to show the levels at FULL and EMPTY and the scale is on the top side of the sump 1250 and is visible to the operator.
FIG. 8 shows a half crank two-stroke engine 350 having the oil sump 1250 between the inner bearing 22b and the outer bearing 32b. A flywheel 9429 is mounted on the crankshaft 22. The bearings 22b and 32b may have built in oil seals. The oil slinger assembly 1234b may be press fit on to the crankshaft 22. FIG. 8 shows the oil passage 88b in the crankshaft 22 and has a radial passage to connect the crankcase chamber 26 to the oil sump 1250. A sleeve may be pressed in to the journal 32a or 32b to time the induction of oil into the crankcase chamber 26, as described earlier. The sleeve with a circumferentially cut out slot to open the port at the end of the radial passage may be integral with the separate detachable lower block 48 of the oil sump. In FIG. 8, the cylinder block 2012 and the crankcase block 25 consisting of the full journal 32b for the inner bearing 22b and top half of the outer bearing journal 32c may be a single cast piece. And the lower half of the oil sump and the lower journal 32a of the outer bearing 32b may be a separate detachable part. Alternatively, the lower crankcase block for the lower half of the outer bearing journal and lower half of the inner bearing journal 32b and lower crankcase 28 can be a single part attached to the upper cylinder block 2012. Also, the crank web 21 may have a radial passage as shown in FIG. 6. FIG. 8 shows a check valve 818 which act as one way valve to induct oil into the crankcase chamber 26 and prevent the blow back of gases when the pressure crankcase chamber 26 exceeds the pressure in the oil sump 1250. Secondly, the check valve may not be necessary when the oil passage 88b is intermittently connected to the crankcase chamber 26 when there is a radial oil passage 809c by virtue crank web 21 acting as a rotary valve in conjunction with the circumferentially cut out section in the inner wall (29) of the crankcase 28, as described for FIG. 6.
FIG. 8 also shows a centrifugal valve assembly 812, having a weight 810 and a pair of oil ports 814; one on the valve assembly and one on the crankshaft 22. As the RPM increases, the area of opening of the port on the crankshaft is increased due to mechanism controlled by the centrifugal valve and thus volume of oil getting into the crankcase chamber is higher. At rest the port may be completely closed until certain RPM is reached.
FIG. 9 shows a very simple control logic to protect the engine from running without lubricating oil. It consists of logic where the ignition is ON when there is minimum level of oil in the sump. However, when the engine is running, due to attitude and or vibration or when oil level drops because the slinger is splashing oil, it is possible for the float to indicate oil level to be lower than minimum and thus ground the kill switch. Without the intelligent ECM 72, the ignition would be turned off, which is not desirable. However, once the engine is running above certain RPM (say X), the ECM overrides the mechanical grounding of the kill wire by the oil float or sensor assembly an keeps the engine running. Additionally, if the oil level sensor is a position sensor, in the sense that it indicates how much oil is there in the sump, then it is possible to estimate the run time before the oil reaches minimum oil level and automatically turns of the ignition to save the engine from being destroyed.
FIG. 10 discloses the engine 600 and another embodiment in which the oil sump 1250 and the oil slinger 1234c are located between the flywheel 9429 and the crankcase chamber 26. The advantage with this arrangement is that the engine is more compact and the starter pulley can be similar to most half crank engine similar to the one made by Homelite Company. Secondly, it can have just one bearing 22b on the flywheel side and the starter assembly can be outboard side of the flywheel similar to most commonly used systems in chainsaws. The operating principle of the lubrication system and the individual parts are same as the ones described for other type of arrangements disclosed in this application. The oil passage in the FIG. 10 also shows a passage 88c integral with the slinger 1234c. However, alternatively, the oil line 803b may be used for inducting the oil through the intake port 84.
FIG. 11 discloses the engine 650 and another embodiment in which the oil sump 1250 is adjacent to the starter assembly 1900, having a separate shaft 333 coupled to the outboard crankshaft 322 through a flexible coupling 336 running through the starter housing 328c. Alternatively, the crankshaft 322 may be extended through the starter assembly such that the shaft 333 is not required. The slinger 1234c is directly mounted on to the shaft 322 (or 333). The starter housing 328c has bearing (either sleeve type or roller type) with an oil seal to support the shaft 333 (or 322). The starter assembly 1900 consists of a starter pulley 1850, and the starter handle 1853. The starter assembly 1900 can be of any one of many designs disclosed in many different prior arts, including U.S. Pat. No. 5,715,783. Secondly the starter cup 1852 may be replaced with a flywheel 9429, while maintaining the operating principle of the new lubrication system. The oil sump 1250 now has sump cover 348, which may have translucent window and oil level sensors, oil breather, oil cap, as explained for other embodiments. The advantage with the engine 650 having a oil sump on outboard side as disclosed in the embodiment is that only the starter housing 328c has to be slightly modified while entire engine assembly can be maintained as is produced today.
FIG. 12 shows a half crank engine, which are commonly used in trimmer applications. The oil sump in the half crank engine may be located between the starter housing 330 and the clutch assembly 352. The engine housing 330 now also forms the clutch housing, as commonly known in the industry. The crankshaft 322 extends through starter assembly 1900, the oil sump 1250, and has a clutch assembly 352 at the outer end of the shaft. The clutch assembly 352 consists of a clutch and a drum as commonly used in many such applications, such as trimmer, chainsaw, etc. The oil sump can be an integral part of the engine housing and the oil sump surrounds the crankshaft 322, as shown in FIG. 12. The oil sump is substantially circular like a disk in shape, having a drive shaft for the slinger 1234c in the center of the oil sump. The translucent window may be provided on the side clearly visible to the operator. The oil level sensor may also be incorporated. Similar assembly may be used in blower applications as well, where the blower fan is assembled on the inboard crankshaft 22.
The following are embodiments, not claims:
A. A two-stroke engine 350 having:
-
- a piston 2016, transfer passage 11, exhaust port 50, intake port 84;
- an oil sump 1250
- at least one slinger 1234b
- oil vapor passage 808b in the crankshaft
- crankcase chamber 26
- combustion chamber 30
- check valve 914
- a centrifugal valve 808d
- a oil breather 1250b
- oil tube 802
- oil injector 702
- dual passage gaseous fuel carburetor 8400.
- oil refilling cap 1250d oil
- oil line 803b′
- oil line 803b
- starter cavity 1858
- starter shaft 1823
- starter cup 1852
- starter pawl 1855
- oil seal 1848
- oil level sensor 60
- outboard shaft 222 of centered from crankshaft 22
Various embodiments include a carburetor that advantageously has a built-in pressure regulating chamber, because fuel supplied to carburetor is already under pressure. Various embodiments utilize a fuel compressing liquefied petroleum gas. In some embodiments, the fuel could be natural gas, hydrogen gas, or any type of fuel essentially free of oil. The fuel may also be injected using an electronic fuel injection system.
PARTS LIST
- 100 Engine
- 11 transfer passage
- 12 Cylinder
- 14 cylinder wall
- 16 Piston
- 18 connecting rod
- 20 crank pin
- 22 crankshaft
- 22b Inner bearing
- 25 Crankcase block
- 26 crankcase chamber
- 28 crankcase
- 28b Side wall (crankcase—outboard side)
- 28c Oil sump cover
- 28d Oil level indicator
- 28d Window
- 30 Combustion chamber
- 32a Outer bearing journal
- 32b Inner bearing journal
- 32c Upper journal for outer bearing
- 33 transfer port
- 36 One way valve
- 38 Injection tube
- 40 charge injection port
- 48 Lower block
- 50 Exhaust port
- 60 Oil level sensor
- 62 Float
- 63 Float arm
- 64 Oil level indicator
- 65 Ground terminal
- 68 Kill wire
- 69 Potentiometer/position sensor
- 72 ECM
- 74 Power supply
- 78 Baffle plate
- 80 Lean valve
- 81 Rich valve
- 84 Intake port
- 88b Oil passage
- 94 Air valve
- 95 Air-filter box
- 96 Air channel
- 98 Air inlet port
- 99 First piston port
- 101 Piston pin
- 101 Second piston port
- 200 Engine
- 220 Rich fuel passage
- 222 Outboard shaft
- 222b Sleeve
- 300 Rich charge passage
- 310 Lean passage
- 328c Starter housing
- 322 Outboard crankshaft
- 336 Flexible coupling
- 348 Oil sump cover
- 406 Air passage
- 479 Throttle shaft
- 620 Fuel inlet
- 702 Oil injector
- 802 Oil outlet tube
- 803b Oil line
- 803b′ Oil line
- 804 Oil pump
- 806 Oil inlet tube
- 808 Oil tank
- 808b Oil passage in crank shaft
- 808d Centrifugal valve
- 809a Radial passage
- 809d Port in the radial oil passage
- 809 Orifice (opening)
- 810 Centrifugal weight
- 812 Assembly of centrifugal valve
- 814 Oil ports
- 818 Check valve
- 850 Gaseous fuel tank
- 881 Air-fuel valve
- 902 Heat dam
- 904 Heat dam
- 914 Check valve
- 1250 Oil sump
- 1340 Oil
- 1900 Starter assembly
- 2012 Cylinder
- 2016 Piston
- 2113 piston skirt
- 8300 Air-fuel passage
- 8310 Air passage
- 8320 Fuel passage
- 8400 Dual passage gaseous Carburetor
- 9041 Sleeve
- 9041 Sleeve bearing
- 9404 Ignition coil (power coil)
- 1250b Breather
- 1250d Oil cap with filter
- 9429 Flywheel
- 352 Clutch assembly
- 330 Engine housing
- 1852 Starter cup
It is to be understood that other modifications of the invention shall be apparent to those skilled in the art from the teachings herein and, it is, therefore, desired to be secured in the appended claims all such modifications as fall within the true spirit and scope of the invention.
