JP4481547B2 - Two-cycle internal combustion engine - Google Patents

Abstract

Crankcase scavenged two-stroke internal combustion engine (1) in which a piston ported air passage is arranged between an air inlet (2) and the upper part of a number of transfer ducts (3, 3'). The air passage is arranged from an air inlet (2) equipped with a restriction valve (4), controlled by at least one engine parameter, for instance the carburettor throttle control. The air inlet extends via at least one connecting duct (6, 6') to at least one connecting port (8, 8') in the engine's cylinder wall (12). The connecting port (8, 8') is arranged so that it in connection with piston positions at the top dead centre is connected with flow paths (10, 10') embodied in the piston (13), which extend to the upper part of a number of transfer ducts (3, 3'). Each flow path through the cylinder and piston is to a great extent arranged in the cylinder's lateral direction, on the one hand in that the connecting port (8, 8') and adjacent scavenging port (31, 31') of the cylinder are shifted sideways in relation to each other along the periphery of the cylinder wall (12), and on the other hand in that the transfer ducts (3, 3') of the cylinder are running essentially in the cylinder's lateral direction away from each transfer port (31, 31') respectively, i.e. tangentially in relation to the circumference of the cylinder wall (12).

Description

[0001]
〔Technical field〕
The present invention relates to a crankcase scavenging two-cycle internal combustion engine or a two-cycle engine in which an air path formed in a piston is disposed between an intake port and upper portions of a plurality of transfer ducts. Fresh air is supplied to the top of the transfer duct, which serves as a buffer for the air / fuel mixture. This shock absorber disappears at the exhaust outlet during the scavenging process. As a result, fuel consumption and harmful emissions are reduced. The internal combustion engine is like a hand-held work tool.
[0002]
BACKGROUND OF THE INVENTION
Internal combustion engines of the type described above are known. These internal combustion engines reduce fuel consumption and harmful emissions, but it is difficult to control the air / fuel ratio in such internal combustion engines.
[0003]
U.S. Pat. No. 5,425,346 discloses an engine having a shape that is somewhat different from the internal combustion engine described above. In this case, channels are formed in the piston of the engine, and when the piston is in a special position, these channels align with a duct formed in the cylinder. As a result, new air or exhaust gas is supplied to the upper portion of the transfer duct, as shown in FIG. This only occurs at the special position of the piston where the duct and cylinder in the piston are aligned. This occurs when the piston moves downward and when the piston moves upward away from top dead center. A check valve is placed at the inlet to the upper portion of the transfer duct to avoid misflowing when the piston moves upward away from top dead center. The amount of new air that can be added is limited to a maximum amount based on the overall short duration of air supply and the flow resistance at the check valve. However, this type of check valve, commonly referred to as a reed valve, has a number of other drawbacks. These check valves are often prone to resonant vibrations, and it is difficult to reach high rotational speeds that can be reached by many two-cycle internal combustion engines. In addition, this creates additional costs and increases the number of engine components. The amount of new air added is changed by a variable intake, that is, an intake that can be accelerated and decelerated in the operating cycle. However, this is a very complex solution.
[0004]
International Publication No. WO 98/57053 discloses a plurality of embodiments of engine in which air is supplied to the transfer duct through an L-shaped or T-shaped recess in the piston. Therefore, there is no check valve. In all embodiments, the piston recess leading to each transfer duct has a very limited height, which is approximately equal to the actual transfer port height. As a result of this embodiment, the path for flowing air through the piston to the transfer duct is opened much later than the path for supplying the air / fuel mixture to the crankcase is opened by the piston. As a result, the air supply time is significantly shorter than the air / fuel mixture supply time that can be counted from the crank angle or time. This complicates the control of the air / fuel ratio of the entire engine. This means that the amount of air that can be supplied to the transfer duct is greatly limited. This is because the pressure for supplying additional air is considerably reduced because the intake port is already open at some time when the air supply is open. This means that both the time for supplying air and the driving force are small. Further, since the cross section of the transfer duct is small near the transfer port and an acute bent portion is formed by the L shape or the T shape, the flow resistance in the L shape or T shape duct shown in the figure is Relatively large. As the air passes through the transfer port, the air is suddenly turned to the lateral direction of the cylinder, and the two curves consisting of 90 ° down and next to the outside of the transfer duct turn rapidly one after the other. Change. This is because the engine transfer duct extends radially into the cylinder. This increases the flow resistance and reduces the amount of air that can be supplied to the transfer duct. As a result, this device reduces the possibility of reducing fuel consumption and harmful emissions.
[0005]
(Object of invention)
The object of the present invention is to solve the aforementioned problems and to obtain advantages in a number of embodiments.
[0006]
[Summary of the Invention]
The above-mentioned problems are achieved by a two-cycle internal combustion engine according to the invention as defined in the claims.
[0007]
In a crankcase scavenging two-cycle internal combustion engine in which an air path formed in a piston is disposed between an air inlet and an upper portion of a plurality of transfer ducts, the air path extends from the air inlet provided with a restriction valve. And the restriction valve is controlled by at least one engine parameter, for example a carburetor throttle control, and the intake port passes through at least one connecting duct and is at least one in the cylinder wall of the internal combustion engine. Extending to one connecting port, the connecting port being arranged to connect to a flow path incorporated in the piston when the piston is at top dead center, the flow path being a plurality of transfer ports It extends to the upper part of the duct, and most of the flow paths in the cylinder and the piston are arranged in the lateral direction of the cylinder. The connecting port and the scavenging port adjacent to the cylinder can be moved laterally to each other along the periphery of the cylinder wall, and the transfer duct of the cylinder is distant from each scavenging port. It is characterized by a two-cycle internal combustion engine extending in a substantially lateral direction of the cylinder, that is, in a tangential direction with respect to the outer periphery of the cylinder wall.
[0008]
This assembly can create an almost non-existing or gently curving air flow that passes through the cylinder, thereby reducing flow resistance.
[0009]
At least one connecting port in the cylinder wall is arranged so that the connecting port is connected to a flow path formed in the piston when the piston is at top dead center. New air can be supplied to the upper part of the transfer duct without providing a check valve. This can occur due to the presence of pressure on the ambient air in the transfer duct at the piston location or near the top dead center of the piston. Thus, it is possible to arrange the air path formed in the piston without having a check valve, which is a great advantage. Since the air supply action takes place over a very long period of time, a large amount of air can be supplied, thereby significantly reducing harmful emissions. The control unit can be provided by a control valve that is controlled by at least one internal combustion engine parameter and is located at the intake port. Such a control is less complicated than a changeable inlet. The intake port preferably has two connecting ports, and in one embodiment, the connecting port is arranged so that the piston covers these connecting ports at bottom dead center. The limiting valve can be appropriately controlled by engine speed alone or in combination with other internal combustion engine parameters. These and other features, as well as these and other advantages, will become apparent in the detailed description of the different embodiments supported by the accompanying drawings.
[0010]
[Description of Embodiment]
The invention is described in detail below by means of various embodiments with reference to the accompanying drawings. The engine parts are symmetrically arranged, on one side of the part and the other side of the components are given the same reference numerals. In the drawing, the other part cannot be seen because it is located above the page.
[0011]
In FIG. 1, reference numeral 1 indicates an internal combustion engine according to the present invention. The internal combustion engine 1 is a two-cycle type and has two transfer ducts 3 . Since one duct 3 is arranged above the paper surface, it cannot be seen. The internal combustion engine 1 includes a cylinder 15, a crankcase 16, a piston 13 having a connecting rod 17, and a crank mechanism 18. Further, the internal combustion engine 1 has an intake tube 22 having an intake port 23 and an intermediate portion 24 connected to the intake tube and connected to a carburetor 25 via a throttle valve 26. Fuel 37 is supplied by a vaporizer. Normally, the carburetor 25 is connected to an intake muffler by a filter. These are not shown for the sake of clarity. The same applies to exhaust ports, exhaust ducts and mufflers of internal combustion engines. The exhaust port, the exhaust duct, and the muffler of the internal combustion engine are common and are disposed on both sides of the cylinder with respect to the intake port. The piston has a flat upper side that does not have a step or the like, so that the upper side cooperates equally with a cylinder port arranged in the periphery. Therefore, the height of the engine body has not changed compared to a normal engine. Each transfer duct 3 has a respective port 31 in the cylinder wall portion 12 of the engine. The engine has a combustion chamber 32 having a spark plug (not shown). All of this is general and will not be described further.
[0012]
The intake port 2 provided with the restriction valve 4 is arranged so that new air can be supplied to the cylinder. The intake port 2 has a connecting duct 6 formed up to the cylinder, and this connecting duct 6 includes an outer connecting port 7. In the following, the connecting port means a port of a connecting portion inside the cylinder, and a port outside the cylinder is called an outer connecting port. The air inlet 2 is appropriately connected to an air muffler via a filter, so that clean fresh air can be taken in. Of course, such a muffler is not necessary if the conditions are low. The intake muffler is not shown for clarity.
[0013]
Therefore, the connecting duct 6 is connected to the outer connecting port 7. This is an advantage. In later in this port or the port, duct branches into two branches 11 leading respectively to the two connection ports 8. As described above, these members are arranged symmetrically in the engine . Accordingly, the outer connecting port 7 is located below the intake tube 22, which has a number of advantages, such as lower air temperature and better space for hand-held processing tools. Meaning that it can be used, such a machining tool usually has a fuel tank 33 as shown in the drawing.
[0014]
However, the outer connecting port 7 can also be arranged above the intake tube 22, and the outer connecting port 7 is further directed in the horizontal direction. When these are arranged, two outer connection ports 7 can be used. These can then be placed on each side of the intake tube 22.
[0015]
The two flow paths 10 are arranged in the piston, so that when the piston is at top dead center, these flow paths connect each connecting port 8 to the upper part of each transfer duct 3 . These flow paths 10 are formed by local recesses in the piston. The piston is simply manufactured with these local recesses, usually by casting.
[0016]
Usually, each connecting port 8 is arranged in the axial direction of the cylinder, so that the piston covers the connecting port 8 when the piston is at bottom dead center. As a result, the exhaust gas cannot pass through the connection port, and finally cannot flow toward the air filter. However, by disposing these connecting ports 8 at a high position, it is possible to open a part of the connecting port when the piston is located at the bottom dead center. As a result, a desired amount of exhaust gas can be supplied to the connecting duct 6. When the connecting port is at the high position, it is possible to reduce the air flow resistance during the passing action from the connecting port to the scavenging port 31.
[0017]
The air supply time from each connection port 8 to each scavenging port 31 is extremely important, and is determined by the flow path in the piston, that is, each recess 10 in the piston.
[0018]
Since the upper edge of the recess is at a high position, when the piston moves upward from the bottom dead center, the lower edge of the piston reaches the lower edge of the intake port or at the same time or more. Early, the upper edge of the recess reaches the lower edge of each scavenging port 31 . As a result, the air connection portion between each connection port 8 and each scavenging port 31 is opened at the same time or earlier than when the intake port is opened. After reaching the top dead center, when the piston moves downward again, the air connection is shut off at the same time as or later than the intake port. As a result, the air supply time is approximately equal to or longer than the intake time that can be counted from the crank angle or time. This reduces the flow resistance. It is often desirable for the intake time and the air supply time to be approximately equal in length. Preferably, the air supply time is 90% to 110% of the intake time. Both of these times are limited by a maximum time that is sufficiently low that the pressure in the crankcase allows maximum inflow. Both times are preferably maximized and approximately equal. Therefore, the speed at which the concave portion is connected to each scavenging port 31 is determined by the position of the upper edge of each concave portion 10 . As a result, each recess 10 in the piston connected to each scavenging port 31 is locally 1.5 times the height of each scavenging port, preferably the height of the scavenging port. It preferably has an axial height greater than twice. This ensures that the port has a normal height that is at the level of the lower side of the scavenging port or protrudes by a few millimeters when the upper side of the piston is at bottom dead center. Become.
[0019]
Since the flow resistance can be reduced, the recess is preferably shaped downward so that the connection action between each recess 10 and each connection port 8 is maximized. This means that when the piston is at top dead center, as shown in FIG. 1, each recess 10 is considerably below, so that the piston cannot cover each connecting port 8 . Overall, this means that each recess 10 in the piston connected to each connecting port 8 is 1.5 times the height of each connecting port at this port, preferably twice the height of each connecting port. Means having a higher axial height locally.
[0020]
The significantly change the relative position of each connecting port 8 and the scavenging port 31 when the scavenging port and the coupling port side, for example, can be transferred in the tangential direction of the cylinder as shown in FIG. 1 can do. FIG. 1 shows that the connecting port and the scavenging port 31 overlap in the axial direction, that is, the upper edge of each connecting port is at the same height as the lower edge of each scavenging port and the axial direction of the cylinder. The case where it exists in a position higher than this is shown. One advantage is that the two ports are further aligned with each other in this type of assembly, so that flow resistance can be reduced when air is conveyed from the connecting port to the scavenging port. . As a result, a large amount of air can be conveyed, thereby enhancing the actual effects of this assembly, such as reducing fuel consumption and harmful emissions. In the case of many two-cycle internal combustion engines, when the piston is at bottom dead center, the upper side of the piston is at the level of the lower edge of the exhaust outlet and the lower edge of the scavenging port. However, it is common for the piston to extend from the lower edge of the scavenging port by a millimeter or a few millimeters. When the lower edge of the scavenging port is further lowered, a flat and larger axial overlap portion is formed between the connection port and the scavenging port. When air is supplied to the scavenging duct, the flow resistance is reduced due to the ports being at the same height and the larger surface of the scavenging port.
[0021]
In order to reduce the flow resistance when passing between the cylinder and the piston, it is pointed out that it is important to lengthen the air supply time described above. Further, it is pointed out that the connecting port is arranged at the same height or higher in the axial direction of the cylinder and the lower edge of each scavenging port. As a result, the connecting port / scavenging port can be moved sideways along the circumference of the cylinder wall. As a result, the passing action from the connecting port 8 through the piston to the scavenging port 31 can occur slightly upward with respect to the lateral direction of the cylinder. When the connection port 8 is disposed directly below the scavenging port 31, the passing action occurs in a straight line upward. As a result, the flow is initially directed upward and then directed horizontally after reaching the scavenging port. That is, two turning actions that change the direction at an acute angle occur sequentially. By moving the port to the side, a slightly upward flow occurs with a small turning action. As described above, it is a great advantage that the respective transfer ducts 3 are arranged substantially in the lateral direction of the cylinder. As a result, the slightly upward flow from the connection port 8 to the scavenging port 31 is slightly turned and continues in the lateral direction linearly in the transfer duct. Thus, in the illustrated case, the transfer duct extends in the lateral direction of the cylinder until the transfer duct reaches the height of the cylinder wall where a gentle turning action occurs, whereby the transfer duct is It connects with the place provided with the opening part 38 of the case. Each branch 11 leading to each connecting port 8 is incorporated such that these branches are oriented in the lateral direction of the cylinder or slightly upward from this lateral direction. As a result, the direction of the main flow made to pass through the cylinder and piston is emphasized. In the illustrated embodiment, each branch extends obliquely from the lower outer connection port 7 so that the branches turn upward after passing through the outer connection port. Continue to extend and then turn sideways to the position of each connecting port 8 in the cylinder wall 12. Therefore, a slightly upward flow is formed in the passing action from the cylinder to the piston. This flow is slightly interrupted in the transfer duct and is directed laterally in a straight line. Since it is necessary to arrange the connection port 8 below the scavenging ports 31, this arrangement is a normal arrangement. However, one or two outer connecting ports 7 can be arranged above the intake ports 22 to 25. In such a case, it is preferable to arrange the intake port so as to form an angle with respect to the lateral direction of the cylinder as compared with the case shown in the drawing. In this case, the intake ports are arranged so that each branch portion 11 faces substantially in the lateral direction of the cylinder up to the position of each connection port 8 .
[0022]
The inventor assumes that the inventor knows the flow from above, for example, the flow from the outer connection port 7 to the connection port 8, the flow over the scavenging port 31, and the flow into the transfer duct 3. It is quite advantageous that the transfer duct 3 extends almost tangentially to the cylinder to the scavenging port 31 and is in the same situation from the connecting port 8 to the first part of the branch 11. As a result, when the air passes from the branch portion 11 to the piston recess 10 and the transfer duct 3, the change in direction becomes small.
[Brief description of the drawings]
FIG. 1 is a side view of an engine according to the present invention, showing a cross-section of a cylinder and a piston at top dead center.

Claims (11)

In the crankcase scavenging two-cycle internal combustion engine in which the air path formed in the piston is disposed between the intake port and the upper part of the plurality of transfer ducts,
The air path is formed from the intake port provided with a restriction valve, the restriction valve is controlled by at least one engine parameter, and the intake port passes through at least one connecting duct and is connected to the internal combustion engine. Extending to at least one connecting port in the cylinder wall, the connecting port being arranged to connect to at least one flow path incorporated in the piston when the piston is at top dead center The flow path extends to an upper portion of a plurality of transfer ducts, and each of the flow paths in the cylinder and the piston is disposed in a horizontal direction of the cylinder, and the connection port and the positions of adjacent scavenging port of the cylinder is laterally offset from each other along the periphery of the cylinder wall, for the transfer of the cylinder Transfected almost horizontal direction, i.e., two-stroke internal combustion engine extending tangentially to the outer circumference of the cylinder wall of the cylinder remote from said port for each scavenging.   2. The crankcase scavenging two-cycle internal combustion engine according to claim 1, wherein each branch portion connected to each connection port faces a side of the cylinder or slightly above the cylinder. The recess in the piston connected to each scavenging port has the flow path arranged so that the air supply time of the air supply action is approximately equal to or longer than the air intake time that can be counted from the crank angle or time. The crankcase scavenging type two-cycle internal combustion engine according to claim 1 or 2, wherein   The crankcase scavenging two-cycle internal combustion engine according to any one of claims 1 to 3, wherein the air supply time is longer than 90% of the intake time but shorter than 110% of the intake time.   2. The recess in the piston connected to the scavenging port locally has an axial height that is greater than 1.5 times the height of the scavenging port at the scavenging port. 5. The crankcase scavenging two-cycle internal combustion engine according to claim 4.   The upper edge portion of each connection port has the same height as or higher than the lower edge portion of each scavenging port in the axial direction of the cylinder. Crankcase scavenging two-cycle internal combustion engine.   The crankcase scavenging two-cycle internal combustion engine according to any one of claims 1 to 6, wherein the intake port has at least two connection ports in the cylinder wall portion of the internal combustion engine.   The connection port in the cylinder wall portion of the internal combustion engine is arranged such that the piston covers the connection port when the piston is at bottom dead center. The crankcase scavenging two-cycle internal combustion engine according to one item.   The connection port in the cylinder wall portion of the internal combustion engine is such that when the piston is at bottom dead center, the piston does not cover the connection port, and exhaust gas from the cylinder passes through the intake port. The crankcase scavenging two-cycle internal combustion engine according to any one of claims 1 to 4, wherein the crankcase scavenging two-cycle internal combustion engine is disposed so as to be able to pass through.   The crankcase scavenging two-cycle internal combustion engine according to any one of claims 1 to 9, wherein at least a part of the flow path in the piston is arranged in the form of at least one recess in the periphery of the piston. organ.   5. The concave portion in the piston connected to the scavenging port locally has an axial height that is greater than twice the height of the scavenging port at the scavenging port. The crankcase scavenging two-cycle internal combustion engine according to any one of the above.

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