Abstract:
This invention relates to an improvement of two stroke engine in which a sleeve piston is employed to move up and down in the cylinder and to control alternatively the opening and closing of the intake guide and exhaust guide and to prevent the lubricant from exuding out of the crank case in an effort to ensure an environmental-friendly clean exhaust.

Description:
FIELD OF THE INVENTION 
     This invention relates to the two stroke engine, mainly an improvement to reduce the high pollution contained in the exhaust, a dominant weakness the traditional two stroke engine has ever embraced. Particularly, it requires no mixing of engine oil to be added during the refilling with gasoline. 
     BACKGROUND OF THE INVENTION 
     Please refer to FIGS. 1 and 2. They are schematic diagrams showing the general two stroke engine where the cylinder  10  provides an intake way  11  and an exhaust way  12  at the opposed direction. A piston  13  has a piston ring  131  installed on the piston crown to choke the gasoline mixture with the cylinder  10 . A connecting rod  14  has a piston pin  15  at one end being locked in the piston  13  and the other end connected to the crankshaft  17  within the crank case  16 . When the piston  13  comes up and compresses the gasoline mixture in the combustion chamber of cylinder  10 , an explosion follows as the spark plug  18  ignites the compressed gasoline mixture, and the piston  13  is thus moved down. When the piston  13  moves down to the exhaust way  12 , the exhaust flows out right at this moment. The flowing of the exhaust through the exhaust way  12  will create a venturi effect and a negative pressure in the combustion chamber in the cylinder  10  as compared with the preset pressure in the crank case  16 , the gasoline mixture will be sucked into the cylinder  10  through the intake way  11  (with one way valve), and the piston  13  and the connecting rod  14  will continue to move up by the rotary force of the crankshaft  17  to proceed the second compress ion and explosion and so on. It is easy to learn that the two stroke engine is simple in construction, less loss in power, benefiting greater horsepower and long service time. In down movement of the piston  13 , because there exist an intake way  11  and an exhaust way  12  on both sides, there is no way to reserve the engine oil in the crank case  16 . Therefore, the engine oil has to be added to the gasoline while refilling where the engine oil will form a lubricating film along the piston after explosion, resulted in an incomplete combustion, a culprit for pollution. 
     FIG. 3 shows a schematic diagram of a four stroke engine, where the engine oil is stored in the crank case  16 , and intake way  20  and the exhaust way  21  are moved to the top of the cylinder  10 . When the piston  13  moves upward in the cylinder  10 , it is not necessary for the piston  13  to bring up the engine oil to the intake way  20  and exhaust way  21 , the four stroke engine entails no engine oil to be mixed with the gasoline, a complete combustion is therefore achieved and the exhaust is more environmental-friendly. However, in the four stroke engine, the intake valve  20  and the exhaust valve  21  need to be controlled by the camshaft (not shown), inefficiency caused by a complicated mechanism, heavy consumption of energy and less horsepower is unavoidable. 
     Comparing the merits and demerits between the two stroke engine and the four stroke engine, after many years&#39; endeavor to the research and development, tests and experiments, the inventor has come up a practicable two stroke engine in which all merits are conserved and all demerits are removed in an attempt to upgrade the motorcycle industry and to solve the pollution the motorcycle yields. 
     SUMMARY OF THE INVENTION 
     The invention mainly employs a sleeve piston structure over the main piston which serves to block the engine oil from arousing to the intake way and exhaust way along the piston wall while the piston moves up. It therefore requires no adding engine oil to the gasoline to ensure a clean exhaust pursuant to the emission standard set forth by environmental protection requirements. 
    
    
     The invention is explained in great details with the aid of the preferable embodiments as presented in the drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is the schematic diagram showing the prior art of the two-stroke engine (in compression and ignition stage). 
     FIG. 2 is the schematic diagram showing the prior art of the two-stroke engine (in intake and exhaust stage). 
     FIG. 3 is a schematic diagram of four-stroke engine. 
     FIG. 4 is the schematic diagram showing the two-stroke engine of the invention (in compression and ignition stage). 
     FIG. 5 show the sleeve piston assembly is moving downward. 
     FIG. 6 is the schematic diagram showing the two-stroke engine of the invention (in intake and exhaust stage). 
     FIG. 7 is another embodiment of two-stroke engine of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As shown in FIGS. 4,  5 , and  6 , the structure and technique of the two stroke engine of the invention are similar to the prior art of the two stroke engine, except with better improvement. In the interior of the cylinder  10 , there is a sleeve piston over wrapped on the main piston. The sleeve piston moves up and down in the cylinder  10 , which controls the opening and closing of the intake way  11  and exhaust way  12  and blocks the engine oil from exuding from the crank case  16 , so that it is no longer required to mix engine oil  19  with the gasoline while refilling to gain a better clean exhaust in accordance with the environmental protection standards. The major characteristics of the invention are as follows. 
     The sleeve piston comprises a main piston  30  and a sleeve piston  40 , wherein the main piston  30  has provided a piston ring  31  and an oil ring  33  serving as a seal. The lower part of the piston  30  has a taper  32 . 
     The sleeve piston  40  has an internal chamber  41 , a large inner diameter groove race  42  and sealing rings  43  and  44 . 
     When the taper  32  of the main piston  30  is inserted into the chamber  41  of the sleeve piston  40 , it forms a complete sleeve piston assembly. 
     To fit the sleeve piston of the invention, the cylinder  10  is hereby designed into two sections where the inner diameter of the first section  22  of the cylinder  10  is tantamount to the outer diameter of the main piston  30 , and so the diameter of the second section  23  of the cylinder equals to the outer diameter of the sleeve piston  40 . The intake way  11  and the exhaust way  12  are located at the highest place within the second section  23 . The bottom of the cylinder  10  provides a retaining ring  24  employed for holding the compression spring  25  which touches the bottom of the sleeve piston  40  and also offers a uprising force to the sleeve piston  40 . 
     As shown in FIG. 4, the piston  30  is placed in the first section  23  of the cylinder  10 , and the compressed gasoline is sealed by the piston ring  31 . The sleeve piston  40  is located at the upper dead point of the second section  23  of the cylinder  10 , the sealing rings  43 ,  44  are located below the intake way  11  and exhaust way  12  to stop the engine oil  19  leaking out of the crank case  16  and entering the intake way  11  and exhaust way  12 . As shown in FIG. 5, immediately after the spark plug  18  ignites an explosion of the compressed mixture of gasoline and air, the main piston  30  begins to move downward and move into the chamber  41  of the sleeve piston  40  and touches the groove race  42 , so as to bring down the sleeve piston  40  together, the intake way  11  and the exhaust way are respectively opened (similar to the prior art of the tow stroke engine), and the spring  25  is compressed. When the main piston  30  arrives at the position as shown in FIG. 6, the rotary force from the crankshaft  17  turns the main piston  30  and the connecting rod  14  upward, and in turn the main piston  30  releases the pushing force exerted on the sleeve piston  40 . The spring  25  helps lifting the sleeve piston  40  upward along with the main piston  30  till they arrive at the position as shown in FIG.  4 . Then, the sleeve piston  40  closes the intake way  11  and exhaust way  12 , and the main piston  30  starts another compression and explosion processing. 
     As shown in FIG. 7, it is really a practicable embodiment where the exterior diameter of the sleeve piston  40  equals to that of the main piston  30 , and the inner diameter of the chamber  41  which goes through the interior of the sleeve piston  40  equals to outer diameter of the taper  32  of the main piston  30 . When the taper  32  of the main piston  30  is inserted into the chamber  41  of the sleeve piston  40 , the structure of the sleeve piston can be formed with which the main piston  30  can cause synchronized movement with the sleeve piston  40  as the main pistons  30  moves down. 
     Many changes and modifications in the sectional design of the cylinder and architecture of sleeve piston of the above-disclosed embodiment of the invention can, of course, be carried out without departing from the scope thereof. Accordingly, to promote the progress in science and the useful arts, the invention is disclosed and is intended to be limited only by the scope of the appended claims. 
     The two-stroke engine of the invention has removed the weaknesses the prior art of two-stroke engine prevails. It is a novel improvement, which promotes the product value, and is justified for a grant of a new patent.