JP6425240B2 - Air leading type stratified scavenging two-stroke internal combustion engine - Google Patents

Description

  The present invention relates generally to a two-stroke internal combustion engine, and more particularly to an air leading engine that first introduces air into the combustion chamber in a scavenging stroke.

  2. Description of the Related Art A two-stroke internal combustion engine of the type that uses mixture gas scavenging is widely used in portable working machines such as brush cutters and chain saws. A two-stroke internal combustion engine of this type has a transfer passage communicating the crank chamber with the combustion chamber. The mixture precompressed in the crank chamber is introduced into the combustion chamber through the scavenging passage, and scavenging is performed by this mixture.

As is well known, the two-stroke engine has a problem of "air-fuel (fresh air) blow through". To solve this problem, an air-guided stratified scavenging two-stroke internal combustion engine has been proposed and has already been put to practical use (Patent Document 1) . The air leading type stratified scavenging engine prefills the scavenging passage with air. In the scavenging process, first, the air accumulated in the scavenging passage is introduced into the combustion chamber, and then the mixture in the crank chamber is introduced into the combustion chamber through the scavenging passage.

  FIG. 8 is a diagram related to port opening and closing of a conventional air-guided stratified scavenging engine. The illustration of the piston is omitted in FIG. 8 in order to avoid confusion of the diagram. In the figure, reference numeral 100 indicates a cylinder wall. An air passage 102 and a mixture passage (not shown) are opened in the cylinder wall 100. The mixture is supplied to the crank chamber through the mixture passage. The air port of the air passage 102 is illustrated at 102a. In the cylinder wall 100, the scavenging port 104a of the scavenging passage 104 is also opened. The transfer passage 104 communicates with the crank chamber. Both the air port 102a and the scavenging port 104a are opened and closed by a piston. The piston has a groove 106 on its circumferential surface. The piston groove 106 extends in the circumferential direction.

  (I) to (III) in FIG. 8 show the state of the process of raising the piston in time series. (II) of FIG. 8 shows a state in which the piston is raised more than (I) of FIG. (III) of FIG. 8 shows a state in which the piston is raised more than the position of (II) of FIG.

  Referring to (I) of FIG. 8, until the piston ascends from the bottom dead center and the piston groove 106 just reaches the air port 102a, the piston groove 106 is mixed with the blowback gas at the previous scavenging. doing. The blowback gas contains a mixture component. The blowback gas remaining in the piston groove 106 is indicated by dots. (II) of FIG. 8 which shows the state which the piston further raised shows the state which the piston groove 106 connected with the air port 102a. In the state of (II) of FIG. 8, the piston groove 106 does not communicate with the scavenging port 104 a. From this, even if the piston groove 106 is in communication with the air port 102a, no air flow from the air port 102a to the piston groove 106 occurs at this time.

  Further, in (III) of FIG. 8 showing a state in which the piston is raised, a state in which the piston groove 106 communicates with the air port 102a and communicates with the scavenging port 104a is shown. In the state of (III) of FIG. 8, the scavenging passage 104 is filled with air.

US 6,857,402 B2

  In the conventional air leading type stratified scavenging two-stroke internal combustion engine, theoretically, the flow of the gas in the piston groove 106 is generated only when the piston groove 106 communicates with the scavenging port 104a. Then, the gas in the piston groove 106 first enters the scavenging passage 104, and then air enters the scavenging passage 104 from the air port 102a through the piston groove 106 ((III) in FIG. 8). Therefore, the timing at which air enters the scavenging passage 104 from the piston groove 106 is later than the timing at which the piston groove 106 begins to communicate with the scavenging passage 104.

  As is known, a two-stroke internal combustion engine for work machines is operated at a high speed of, for example, 10,000 rpm. From this, the timing delay mentioned above has a great influence on the air filling efficiency of the scavenging passage 104. Specifically, it has an essential problem that it is difficult to secure the certainty that the scavenging passage 104 is filled with air in each cycle. In order to cope with this problem, in the conventional air-guided stratified scavenging two-stroke internal combustion engine, it is a fact that a construction is adopted in which the timing at which the piston groove 106 communicates with the scavenging port 104a is made extremely early. However, when this configuration is adopted, the air-fuel mixture component remaining in the scavenging passage 104 tends to flow into the air passage 102 side, and the effect of improving the emission characteristic is reduced.

  An object of the present invention is to provide an air-guided stratified scavenging two-stroke internal combustion engine capable of improving the filling efficiency of air into the scavenging passage by generating a flow of gas in the piston groove while the piston groove communicates with the air port. To provide.

According to the invention, the above technical problem is:
An air port open to the cylinder wall and opened and closed by the piston;
A transfer passage having a transfer port open to the cylinder wall and opened and closed by the piston, the transfer passage communicating with the crank chamber;
A piston groove formed on a circumferential surface of the piston and capable of communicating the air port with the scavenging port, the piston groove for supplying air from the air port to the scavenging port in the scavenging process; Have
The piston groove is provided with a pressure transmission through hole for communicating pressure to the crank chamber and causing the pressure of the crank chamber to act on the piston groove ;
This is achieved by providing an air-guided stratified scavenging two-stroke internal combustion engine, characterized in that the negative pressure of the crank chamber acts on the piston groove through the pressure transmission through-hole in the process of raising the piston. Be done.

  FIG. 1 is a diagram for explaining a first concept of the present invention. Referring to FIG. 1, reference numeral 2 denotes a cylinder wall, which corresponds to the cylinder wall 100 shown in FIG. Reference numeral 4 in FIG. 1 denotes an air passage, and 4a denotes an air port, which corresponds to the air passage 102 and the air port 102a shown in FIG. Reference numeral 6 in FIG. 1 denotes a scavenging passage, and 6a denotes a scavenging port, which corresponds to the scavenging passage 104 and the scavenging port 104a shown in FIG. Reference numeral 8 in FIG. 1 denotes a piston groove, which corresponds to the piston groove 106 in FIG.

  Still referring to FIG. 1, the piston groove 8 has a relatively small pressure transmission through hole 10 as a pressure transmission port, and the pressure transmission through hole 10 is in constant communication with the crank chamber. (I) to (IV) in FIG. 1 show the state of the process of raising the piston in time series. (II) of FIG. 1 shows a state in which the piston is raised more than the position of (I) of FIG. (III) of FIG. 1 shows a state in which the piston is raised above the position of (II) of FIG. (IV) of FIG. 1 shows a state in which the piston is raised more than the position of (III) of FIG.

  When the pressure in the crank chamber becomes negative in the process of raising the piston from (I) to (II) in FIG. 1, the negative pressure in the crank chamber acts on the piston groove 8 through the pressure transmission through hole 10. Thereby, the pressure in the piston groove 8 escapes to the crank chamber through the pressure transmission through hole 10. From this, when the piston groove 8 communicates with the air port 4a, gas flow occurs in the piston groove 8 and air enters the piston groove 8 through the air port 4a ((III) in FIG. 1). Then, at the same time as the piston groove 8 communicates with the scavenging port 6a, air is supplied from the air passage 4 to the scavenging passage 6 via the piston groove 8 ((IV) in FIG. 1).

  According to the present invention, the filling efficiency of air into the piston groove 8 can be enhanced, and at the same time the piston groove 8 communicates with the scavenging port 6a, the scavenging passage 6 can be filled with air.

  The function of the scavenging port 6a is the same as that of the scavenging port of a conventional air-guided stratified scavenging two-stroke internal combustion engine. In the scavenging process, first, the air stored in the scavenging passage 6 is discharged from the scavenging port 6a to the combustion chamber, and then the mixture of the crank chamber is discharged to the combustion chamber.

  According to the present invention, the flow of gas inside the piston groove can be generated while the piston groove is in communication with the air port. And thereby, the filling efficiency of the air to the scavenging passage through the piston groove can be improved.

  The two-stroke internal combustion engine for a working machine is operated at a high rotation speed of, for example, 10,000 rpm as described above. In such an engine, according to the present invention, it is possible to increase the certainty that the scavenging passage is filled with air in each cycle.

  Other objects of the present invention and effects of the present invention will be apparent from the detailed description of the preferred embodiments of the present invention below.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure for demonstrating the structure and effect | action of the 1st concept of this invention, (I) shows the state which the piston started rising from the bottom dead center, (II) shows the state which piston further raised. (III) shows that the piston is further raised and the piston groove is in communication with the air port, and (IV) is that the piston is further raised and the piston groove in communication with the air port is in communication with the scavenging port Indicates BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of a piston included in an air leading type stratified scavenging two-stroke internal combustion engine of an embodiment. It is a figure for demonstrating the structure of the cylinder contained in the air leading type | formula stratified scavenging 2 cycle internal combustion engine of an Example. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view of an air-leading stratified two-stroke internal combustion engine according to an embodiment cut at a height level of its exhaust passage. FIG. 3 is a front view of a piston groove provided in the piston illustrated in FIG. 2; It is a figure for demonstrating the state in the piston raising process of the 2 cycle engine of the Example containing the piston provided with the piston groove with a comparatively large vertical width, (I) is located in a bottom dead center (II) shows that the piston has risen from the bottom dead center, (III) shows that the piston further rises and the piston groove is in communication with the air port, and (IV) shows that the piston is further Indicates a raised state, and (V) indicates a state where the piston is located at the top dead center. It is a figure for demonstrating the state in the piston raising process of the 2 cycle engine of the Example containing the piston provided with the piston groove with a comparatively small vertical width, (I) is located in a bottom dead center (II) shows that the piston has risen from the bottom dead center, (III) shows that the piston has risen further and the piston groove is in communication with the air port, and (IV) shows Further, the piston is raised to indicate that the piston groove is in communication with the air port, and (V) indicates a state where the piston is located at the top dead center. It is a figure for demonstrating the state in the piston rise process of the conventional air leading type | mold layering scavenging two-stroke engine, (I) shows a state just before a piston groove | channel communicates with an air port, (II) shows The piston is raised to indicate that the piston groove is in communication with the air port, and (III) indicates that the piston is further raised to communicate the piston groove in communication to the air port to the scavenging port.

  Hereinafter, preferred embodiments of the present invention will be described based on the attached drawings.

  FIG. 2 shows a piston included in the air-guided stratified scavenging two-stroke internal combustion engine of the embodiment. Referring to FIG. 2, the piston 20 has a piston groove 22 in its circumferential surface. The piston 20 has a piston pin hole 24 and is connected to a connecting rod (not shown) by a piston pin (not shown) inserted in the piston pin hole 24.

  The piston 20 is vertically movably fitted in a cylinder 26 shown in FIG. The cylinder 26 has first and second scavenging passages 30 and 32 on the left and right, respectively, in a plan view, and the first and second scavenging passages 30 and 32 communicate with the crank chamber 34. In the cylinder wall 28, first and second scavenging ports 30a and 32a are opened. The first scavenging port 30 a communicates with the first scavenging passage 30. The second scavenging port 32 a communicates with the second scavenging passage 32. That is, the engine of the embodiment is a scavenging four-flow engine.

  In the figure, reference numeral 36 indicates an exhaust passage. Reference numeral 38 denotes an air passage. Also, reference numeral 40 indicates a mixture passage. The air passage 38 is supplied with air. The mixture passage 40 is supplied with the mixture generated by a vaporizer (not shown). Reference numeral 42 denotes a spark plug.

  FIG. 4 is a cross-sectional view of the example air leading stratified scavenging two-stroke internal combustion engine 50. Referring to FIG. 4, the first scavenging port 30 a and the second scavenging port 32 a positioned on the left and right, respectively, are directed in the direction opposite to the exhaust passage 36. That is, the two-stroke engine 50 of the embodiment is a reverse scavenging type engine.

  Returning to FIG. 2, the piston groove 22 extends in the circumferential direction of the piston 20. FIG. 5 is a front view of the piston groove 22. As shown in FIG. Referring to FIGS. 2 and 5, piston groove 22 has pressure transmission through hole 52.

  The pressure transfer holes 52 may have a diameter of 0.1 mm to 3.0 mm, preferably 0.5 mm to 2.5 mm, and most preferably 1.0 mm to 2.0 mm. In the embodiment, the pressure transfer through hole 52 is disposed at the downstream end of the piston groove 22 in the air flow direction, that is, at the left end (end on the exhaust port side) of FIG. Is positioned below the

The pressure transmission through hole 52 may be disposed at any position of the piston groove 22, but it is effective to dispose the pressure transmission through hole 52 on the downstream side of the air flow direction of the piston groove 22. Referring to FIG. 5, the alternate long and short dash line is a perpendicular line VL passing through the piston pin hole 24. As a matter of fact, arranging the pressure transmission through hole 52 on the downstream side (left side in FIG. 5) of the perpendicular line VL passing through the piston pin hole 24 generates an initial movement of gas flow in the piston groove 22 Is effective.

  That is, the piston groove 22 extends in the circumferential direction of the piston 20. The pressure transfer through hole 52 is disposed at a position adjacent to the first scavenging port 30 a located on the exhaust port side.

  6 and 7 illustrate a specific example of supplying air to the scavenging passages 30, 32 through the piston groove 22 in the process of raising the piston. In the figure, reference numeral 44 denotes a crankshaft. The engine 50A illustrated in FIG. 6 has an upwardly expanded configuration to expand the volume of the piston groove 22. In the engine 50B illustrated in FIG. 7, the piston groove 22 is located below the piston pin hole 24. The upper and lower widths of the piston groove 22 are smaller than those of the piston groove 22 shown in FIG.

The engine 50A of FIG. 6 in which the vertical width of the piston groove 22 is relatively large will be described. (I) of FIG. 6 shows the piston 20 located at the bottom dead center. When the piston 20 rises from the bottom dead center, the pressure in the crank chamber 34 becomes negative. The negative pressure of the crank chamber 34 acts on the piston groove 22 through the pressure transmission through hole 52 ((II) in FIG. 6). The piston 20 is further raised and the piston groove 22 communicates with the air port 38a. Then, the air in the air passage 38 is drawn into the piston groove 22 ((III) in FIG. 6). That is, when the piston groove 22 communicates with the air port 38 a, gas flow occurs inside the piston groove 22. This condition, the piston groove 22 is continued until the first and second scavenging ports 30a, to 32a communicates with (in FIG. 6 (IV)).

  When the piston 20 is further raised after the piston groove 22 communicates with the air port 38a, the piston groove 22 communicating with the air port 38a communicates with the first and second scavenging ports 30a, 32a. As a result, air already filled in the piston groove 22 is supplied to the first and second scavenging passages 30 and 32. Further, air is supplied from the air passage 38 to the first and second scavenging passages 30 and 32 through the piston groove 22. The state in which the air port 38a is in communication with the first and second scavenging ports 30a and 32a via the piston groove 22 is continued until the piston 20 reaches the top dead center ((V) in FIG. 6).

  The engine 50B of FIG. 7 in which the vertical width of the piston groove 22 is relatively small will be described. (I) of FIG. 7 shows the piston 20 located at the bottom dead center. When the piston 20 rises from the bottom dead center, the pressure in the crank chamber 34 becomes negative. The negative pressure of the crank chamber 34 acts on the piston groove 22 through the pressure transmission through hole 52 ((II) in FIG. 7). This state is continued until the piston 20 is further raised and the piston groove 22 communicates with the air port 38a ((III) in FIG. 7).

  When the piston 20 is further raised and the piston groove 22 is in communication with the air port 38 a, air in the air passage 38 is drawn into the piston groove 22. That is, when the piston groove 22 communicates with the air port 38 a, gas flow occurs inside the piston groove 22. This state is continued until the piston groove 22 communicates with the first and second scavenging ports 30a, 32a ((IV) in FIG. 7). Then, when the piston 20 is further raised and the piston grooves 22 communicate with the first and second scavenging ports 30a and 32a, the air already filled in the piston grooves 22 flows to the first and second scavenging passages 30 and 32. Supplied. Also, air in the air passage 38 is supplied to the first and second scavenging passages 30 and 32 through the piston groove 22. The state in which the air port 38a communicates with the first and second scavenging ports 30a and 32a via the piston groove 22 is continued until the piston 20 reaches the top dead center ((V) in FIG. 7).

  According to the engine 50A (FIG. 6), 50B (FIG. 7) of the embodiment, the negative pressure of the crank chamber 34 is pressure transmitted before the piston groove 22 communicates with the first and second scavenging ports 30a, 32a. It acts on the piston groove 22 through the through hole 52. Thereby, a flow of gas is generated in the piston groove 22. Then, this gas flow induces an action of drawing air into the piston groove 22 when the piston groove 22 communicates with the air port 38a. As a result, the piston groove 22 communicates with the air port 38a and at the same time air is drawn into the piston groove 22 from the air port 38a. After the piston groove 22 is in communication with the air port 38a, when the piston groove 22 in communication with the air port 38a is in communication with the scavenging ports 30a, 32a, air immediately passes through the piston groove 22 into the scavenging passages 30, 32. Be filled. Thereby, the air charging efficiency to the scavenging passages 30, 32 can be enhanced.

  In other words, according to the engine of the embodiment, the initial action of supplying air to the scavenging ports 30a, 32a through the piston groove 22 communicating with the air port 38a can be induced. This makes it possible to increase the certainty that the scavenging passages 30, 32 are filled with air in each cycle.

  This means that it can contribute to optimization of the timing at which the piston groove and the scavenging port communicate with each other and the timing at which the piston groove and the air port communicate with each other. As a result, it is possible to increase the output while improving the emission characteristics of the exhaust gas of the air leading type layered scavenging two-stroke internal combustion engine.

  In the embodiment, as an example, an engine having two scavenging ports 30a and 32a on one side and the two scavenging ports 30a and 32a on each side are disposed symmetrically to each other is described as an example, but the present invention is not limited thereto. Needless to say, it is not limited to The present invention includes, for example, the following modifications.

(1) An engine equipped with one scavenging port on one side.
(2) An engine in which one or more scavenging ports on each side are disposed asymmetrically.
(3) In the embodiment, each of the plurality of scavenging ports 30a, 32a is provided with the independent scavenging passages 30, 32 on one side, but this is an engine configured with one scavenging passage extending in, for example, a Y-shape.

  The present invention is applicable to an air-guided stratified scavenging two-stroke internal combustion engine. The present invention is suitably applied to a single-cylinder air-cooled engine mounted on a portable working machine such as a bush cutter or a chain saw.

Reference Signs List 20 piston 22 piston groove 24 piston pin hole VL vertical line passing through piston pin hole 26 cylinder 28 cylinder wall 30 first scavenging passage 30a first scavenging port 32 second scavenging passage 32a second scavenging port 34 crank chamber 36 exhaust passage 38 air passage 38a air port 40 mixture passage 50 air leading stratified scavenging two-stroke internal combustion engine 52 pressure transmission through hole

Claims (6)

Air ports (4a, 38a) which open into the cylinder wall (2, 28) and are opened and closed by the piston (20) ;
Wherein a cylinder wall (2, 28) scavenging port opened and closed by the opening and and the piston (20) to (6a, 30a) transfer passages (6, 30) having a scavenging passage (6 communicating with the crank chamber , 30) ,
A piston groove (8, 22) formed on the circumferential surface of the piston (20) and capable of communicating the air port (4a, 38a) with the scavenging port (6a, 30a) , in a scavenging stroke A piston groove (8, 22) for supplying air from the air port (4a, 38a) to the scavenging port (6a, 30a) ;
The piston groove (8, 22) comprises a pressure transfer through hole (10, 52) for pressure transmission communicating with the crank chamber and causing the pressure of the crank chamber to act on the piston groove (8, 22) ;
In the process of raising the piston (20), the negative pressure of the crank chamber acts on the piston groove (8, 22) through the pressure transfer through hole (10, 52). Stratified scavenging two-stroke internal combustion engine. The piston groove (22) extends in the circumferential direction of the piston (20) ,
The air leading type stratified scavenging two-stroke internal combustion engine according to claim 1, wherein the pressure transfer through hole (52) is disposed downstream of the piston groove (22) in the air flow direction. The piston groove (22) extends in the circumferential direction of the piston (20) ,
The air lead according to claim 1, wherein the pressure transmission through hole (52) is disposed on the opposite side of the air port (38a) across a perpendicular (VL) passing through a piston pin of the piston (20). Type stratified scavenging two-stroke internal combustion engine. The pressure transmission through hole (52) is arranged at the end of the piston groove (22) opposite to the air port (38a) across the perpendicular (VL) passing through the piston pin The air leading type stratified scavenging two-stroke internal combustion engine according to Item 3. The method according to any one of claims 1 to 4, wherein the piston groove (22) communicates with the air port (38a) and does not communicate with the scavenging port (30a) while the piston (20) is moving up. Air-guided stratified scavenging two-stroke internal combustion engine according to one of the claims. A plurality of the scavenging ports (30a) are disposed on one side of the engine,
The pressure transmission through hole (52) is disposed at a position adjacent to the scavenging port (30a) farthest from the air port (38a) among the plurality of scavenging ports (30a). An air-leaded stratified scavenging two-stroke internal combustion engine according to any one of the preceding claims.

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