Field of the invention

The invention relates to the lubrication of spark-ignition and compression-ignition two-stroke internal combustion engines in which the lubricating fluid is separated from the fuel mixture, thus preventing its degradation during engine operation as well as preventing insufficient combustion, and thus preventing the formation of carcinogenic oil aerosol and solid particles.

Background of the invention

Two-stroke internal combustion engines are lubricated by using a lubricating fluid which is either contained in the fuel mixture, or is distributed throughout the friction area of the piston and cylinder, from where it goes again to the combustion area of the cylinder.

Document CZ 2252-91 describes how the lubricating fluid is directed to the lubricating ring on the piston which then spreads it along the piston wall during piston movement. The excess lubricating fluid is captured by a trap and led off to a holding tank using channels. The disadvantage of this design is that the lubricating fluid stays in the exhaust and intake channel, from where it escapes with the exhaust fumes to the external atmosphere, thus increasing the emissions level of harmful substances.

In the published application DE 42 05 663 A1 , a system of lubricating two-stroke internal combustion engines is described in which the lubricating fluid is pumped into an area delimited by a sealing ring in the upper part of the piston and by a fixed wiper bearing down on the piston wall in the lower part of the cylinder. The disadvantage of this design is that it does not permit the lubrication along the entire trajectory of the piston movement inside the cylinder, since the wiper ring would be destroyed by the fixed wiper. Another disadvantage of this design is that the fixed wiper can not be replaced when worn out. In document WO 00/75497, the lubricating fluid is blocked from the crankshaft space area by an elastic barrier preventing it from entering the cylinder of the engine. Lubrication of the movement of the piston in the cylinder is ensured by the use of an alloy with higher graphite content in the production of the cylinder and piston. The disadvantage of this design is that the alloy with higher graphite content is fragile and subject to quicker wear, while the production costs are higher as a result of the use of the special alloy.

Patent CZ 292 891 describes a two-stroke engine piston with a valve that releases air or the fuel mixture into the cylinder, inside the piston. This is advantageous for a more rapid and easier venting of exhaust fumes, but this document does not resolve the separation of the lubricating fluid from the combusted fuel mixture, so the emission levels remain high.

The task of this invention is to create a two-stroke internal combustion engine with a separate lubricating fluid circuit that removes the deficiencies of the known designs, ensures uniform lubrication with lubricating fluid along the entire trajectory of piston movement within the cylinder, while at the same time preventing the escape of lubricating fluid into the combustion chamber and the subsequent escape of carcinogens from incomplete combustion into the exhaust system and into the atmosphere.

Summary of the invention

The deficiencies of the aforementioned designs are removed by a two-stroke internal combustion engine design with a separate lubricating fluid circuit with a reservoir and distribution system for lubricating the piston separate from the fuel mixture.

In the known method, the engine is formed by a fixed combustion cylinder assembly with a fixed floating piston with at least one piston sealing ring, where the piston is connected to the crankshaft by a connecting rod and piston rod. The cylinder is provided with an intake valve arranged in the intake chamber below the piston, with an exhaust valve arranged in the combustion chamber above the piston, with a lubricating fluid inlet and outlet in the side of the cylinder at a height below the piston sealing ring and in the dead center position of the piston.

The piston is provided with at least one relief valve and relief channel for relieving the fuel mixture from the intake chamber to the combustion chamber, which takes place inside the piston.

The essence of the invention is that the piston is provided with at least two wiper rings; the first wiper ring is arranged below the piston sealing ring in the part of the piston arranged closer to the combustion chamber, and the second wiper ring is arranged in the part of the piston extending closer to the intake chamber, while the lubrication fluid inlet and outlet to the cylinder is arranged in the area between the first and second wiper ring.

The essence of the invention is also that the exhaust valve and intake valve are arranged outside the' area between the first wiper ring and second wiper ring regardless of the working position of the piston. The wiper rings thus maintain all the lubricating fluid evenly divided along , the entire working length of the piston and cylinder, while at the same time preventing the penetration of lubricating fluid into the fuel mixture and subsequently into the exhaust valve and the atmosphere.

In an advantageous embodiment of a two-stroke combustion engine according to the invention, the lubricating fluid inlet is connected to the cylinder with a lubricating pump in the lubricating fluid reservoir by use of a lubricating tube bypassing the cylinder, thus enabling the supply of a sufficient amount of lubricating fluid to the working piston, while at the same time the engine construction is maximally simplified (resp. its moving parts which are not affected by the lubricating circuit at all). This also simplifies maintenance and the exchange of damaged or worn parts. In another advantageous embodiment of a two-stroke combustion engine according to the invention, the reservoir is attached to the cylinder and the lubricating fluid outlet leads out of the side of the cylinder directly into the lubricating fluid reservoir. This ensures an easier circulation of oil, reduces the length of pressure distribution, and minimizes the overall construction dimensions of the engine.

A two-stroke combustion engine with separate lubricating fluid circuit, according to the invention, produces much lower emissions than a two-stroke engines which mix the fuel with the lubricating fluid for operation; the invention also removes the undesirable combustion of adherent lubricating fluid during the operation of engines with separate lubrication. The two-stroke engine, according to the invention, is produced from commonly used materials, so its manufacture is not expensive.

Description of the drawings

The invention is described in detail by means of the drawings, where Fig. 1 depicts a cross-section of a two-stroke spark-ignition engine with separate lubricating fluid circuit at the moment of the beginning of compression; Fig. 2 depicts a cross-section of a two-stroke spark-ignition engine with separate lubricating fluid circuit during compression and suction; Fig. 3 depicts a cross-section of a two-stroke spark-ignition engine with separate lubricating fluid circuit at the moment of the beginning of expansion; Fig. 4 depicts a cross-section of a two-stroke spark-ignition engine with separate lubricating fluid circuit during exhaust and flushing of exhaust fumes.

Examples of the preferred embodiments of the invention

It should be understood that the following described and illustrated specific examples of the realization of the invention are presented solely for illustrative purposes and not as a limitation of the examples of the embodiments of the invention for the cases indicated. Experts who are familiar with the state of technology shall find, or using routine experimentation will be able to determine, a larger or smaller number of equivalents to the specific realizations of the invention which are specifically described here. These equivalents shall also be included into the scope of the claims.

A two-stroke internal combustion engine 19 consists of a combustion cylinder 1_, in which a piston 2 moves, connected with a connecting rod 9, which is connected via a piston rod 10 to a crankshaft 11.. The crankshaft 11. is stored in an oil bath 13\

Lubrication of the movement of the piston 2 is ensured by the lubricating fluid 3 stored in the reservoir 15 with an integrated lubricating pump 14. The lubricating pump 14 pushes the lubricating fluid 13 through a lubricating tube 7 and inlet 21 into the area between the cylinder 1_ and piston 2, which is axially delimited by the wiper piston rings 4 and 4J placed on the opposite sides of the piston 2. The sealing piston rings 3 and arranged on the piston 2 prevent the emergence of the fuel mixture 20 from the combustion chamber 18 into the lubrication area delimited by the wiper piston rings 4 and 4\ The wiper rings 4 and do not permit the lubricating fluid 13 to leave the delimited area between the piston 2 and cylinder Λ in any other way than through the outlet of the lubricating fluid from the cylinder 22 in the cylinder wall, which leads directly to the reservoir 15 of the lubricating fluid 13.

Movement of the piston 2 to the upper dead centre position of a two-stroke spark- ignition engine leads to the compression of the fuel mixture 20 in the combustion chamber 18. The exhaust valve 12 is closed and the sealing piston rings 3 and 3 prevent the fuel mixture 20 from escaping into the area around the piston 2. The intake valve 8 opens, and more fuel mixture 20 is released into the suction chamber 1Z

As soon as the piston 2 reaches the upper dead centre position, the fuel mixture 20 is ignited by a spark from the electrical spark plug 16, resulting in expansion. The piston 2 is arranged into motion in the direction towards the lower dead centre position. The intake valve 8 closes, and the exhaust valve 12 and relief valve 5 close. The fuel mixture 20 is pushed from the suction chamber 17 through the relief channel 6 and the relief valve 5 into the combustion chamber 18, from where the exhaust fumes formed by the combustion of the fuel mixture 20 are pushed through the exhaust valve 12. The entire cycle then repeats.

Ing the second example of the preferred embodiment of a two-stroke engine 19 (not depicted) is a two-stroke compression ignition engine. Here, the fuel mixture 20 is replaced by air 20, and the electrical spark plug 16 is replaced by a fuel injection valve 16.

During compression, the air 20 above the piston 2 is compressed in the combustion chamber 18 and new air 20 is released into the suction chamber 17 via the intake valve 8. When the piston is in the upper dead centre position, the air 20 is heated by the increased pressure to the point that the fuel released by the fuel injection valve 16 ignites by itself, resulting in expansion. In the subsequent movement towards the lower dead centre position, the exhaust valve \ 2 and the relief valve 5 open. The exhaust fumes are pushed out by the new air 20, and the entire cycle repeats.

Industrial applicability

The two-stroke internal combustion engine with separate lubricating fluid circuit is suitable for replacing presently used two-stroke and four-stroke spark-ignition and compression-ignition engines everywhere where combustion engines are used to propel devices.

Overview of the positions in the drawing

1 combustion cylinder

2 engine piston

3 and 3' sealing piston ring

4 and 4' wiper piston ring

5 relief valve

6 relief channel

7 lubricating tube

8 intake valve

9 connecting rod

10 piston rod

11 crankshaft

12 exhaust valve

13 lubricating fluid

13' oil bath

14 lubricating pump

15 lubricating fluid reservoir

6 electrical spark plug

17 suction chamber

18 combustion chamber

19 two-stroke internal combustion engine

20 fuel mixture

21 inlet of lubricating fluid in the cylinder

22 outlet of lubricating fluid from the cylinder