TWI598501B - Two stroke engine - Google Patents

Description

Two-stroke engine

The present invention relates to a two-stroke engine, and more particularly to a hobby two-stroke engine mounted on a wirelessly operated model or the like.

Previously, in the two-stroke engine, the mixture gas flowing into the crank chamber from the intake port flows toward the bottom dead center side of the piston, flows in the scavenging passage formed in the cylinder wall, and communicates with the scavenging passage. The scavenging port is supplied to a cylinder bore (see, for example, Patent Document 1: Japanese Patent Laid-Open Publication No. 2010-084623). At this time, scavenging is performed to cause the inflowing mixed gas to exhaust the exhaust gas in the cylinder bore. If the amount of the mixture flowing into the cylinder bore in one cycle is increased, the explosive force can be increased to obtain a high output.

In the amateur two-stroke engine that requires high output, the method of expanding the scavenging port in the state of maintaining the opening and closing timing or the scavenging direction of the scavenging port which greatly affects the engine characteristics is performed by the user who purchases the two-stroke engine. The additional operation of expanding the scavenging port to the intake port side and extending it in the circumferential direction (hereinafter, this additional work is referred to as "extension processing of the scavenging port"). The reason why the scavenging port is expanded to the intake port side instead of the exhaust port side is to suppress so-called air leakage. In the two-stroke engine, there is a problem that the mixed gas that is not combusted during the exhausting step and the scavenging step leaks to the exhaust port, resulting in a low output. Therefore, by disposing the scavenging port at the intake port, Keeping the scavenging port away from the exhaust port, thereby suppressing the leakage of the mixture to obtain a high output. In the extension processing of the scavenging port, when the cylinder bore is viewed in the axial direction, the scavenging port is extended until it overlaps with the intake port.

When the scavenging port is extended to the structure in which the air inlet is overlapped in the mass production of the cylinder, it is not necessary to perform the extension processing of the scavenging port by the additional work, and the high output can be maintained in a commercially available state. However, in the previous two-stroke engine, the scavenging passage was formed by the die (punching die) which is extended to the side of the dead center, so that the scavenging port was not extended to the axial direction of the cylinder bore when the mold was formed. Overlaps the air inlet. Therefore, there is a problem in that it requires an extension process of the above-described scavenging port, which causes labor and labor.

It is an object of the present invention to provide a two-stroke engine that can exhibit high output and can be mass-produced.

The two-stroke engine of the present invention is characterized in that it is provided with an intake port and an exhaust port facing the wall of the cylinder bore formed in the cylinder, and includes: a pair of scavenging ports, which are respectively disposed on the intake air a port and the exhaust port substantially opposite to each other across an axis of the cylinder bore; a scavenging window communicating with the scavenging port and opening outside the cylinder; and a scavenging cover from the outer side of the cylinder Blocking the scavenging window; and each of the scavenging ports is provided with an extending portion extending to the inlet port side, and the end portion of the air inlet port when viewed in the axial direction of the cylinder bore overlapping.

According to the present invention, since the scavenging port is provided with an extending portion that is disposed on the intake port side and overlaps the end portion of the intake port when viewed in the axial direction of the cylinder bore, the area of the scavenging port can be increased by an equivalent amount. The area occupied by the extension department. Thereby, a large amount of the mixed gas can be burned in one cycle, so that the two-stroke engine can exert a high output.

Further, the cylinder includes a scavenging window that communicates with the scavenging port and is open to the outside of the cylinder. Therefore, when the cylinder is produced, the punching die can be pulled from the scavenging window side instead of the cylinder bore side, thereby forming a scavenging port provided with the extending portion. . Thereby, the extension portion can be formed in advance when the cylinder is produced, and the processing can be extended without performing the additional work previously performed by the user.

As described above, the two-stroke engine according to the present invention can exhibit high output and can be mass-produced.

In the two-stroke engine of the present invention, preferably, the scavenging port is located at a position facing the intake port in a circumferential direction of the cylinder bore.

According to the present invention, since the scavenging port is located at the position of the intake port in the circumferential direction of the cylinder bore, the scavenging port can be moved away from the exhaust port. Thereby, it is possible to prevent the unburned mixture from leaking (leakage) to the exhaust port when the mixture gas flows into the cylinder bore, so that more mixed gas can be burned, thereby making the two-stroke engine more reliable. Play high output.

In the two-stroke engine of the present invention, it is preferable that the total length of the extending portion in the circumferential direction is 5% to 26% of the length of the inlet port.

According to experiments conducted by the inventors, the output of the two-stroke engine is higher when the total length of the circumferential direction of the extended portion is 5% to 26% of the length of the circumferential direction of the intake port. According to the present invention, since the scavenging port is formed so that the total length of the extending portion in the circumferential direction is within the above range, the two-stroke engine can be made to have a high output.

Further, as described above, since the two-stroke engine of the present invention can be configured to be mass-produced, the scavenging port can be accurately formed at an position satisfying the above-described conditions confirmed by the inventors by an automatic machine tool. Thereby, the individual difference of the two-stroke engine which is easily generated in the extension processing by the user side can be surely eliminated.

In the two-stroke engine of the present invention, preferably, the scavenging port includes a first scavenging port provided at a position away from the intake port in the circumferential direction, and a second scavenging port provided at a position close to the intake port in the circumferential direction, And a partition separating the first scavenging port and the second scavenging port.

According to the present invention, since the scavenging port is divided in the circumferential direction by providing the partition in the middle of the scavenging port, even when the circumferential length of the scavenging port is long, the partition member is used as a reinforcing member to prevent heat of combustion or the like. The deformation of the scavenging port. Thereby, the two-stroke engine can be stably utilized as a high output.

Further, since the scavenging port is partitioned between the first scavenging port and the second scavenging port, the blowing angle of the mixture to the cylinder bore can be individually set at the first scavenging port and the second scavenging port.

In the two-stroke engine of the present invention, it is preferable that a rectifying portion that adjusts a flow direction of the mixed gas toward the scavenging port to a specific direction is protruded from a surface of the scavenging cover facing the scavenging port.

According to the invention, since the rectifying portion is protruded from the surface of the scavenging cover facing the scavenging port, the flow direction of the mixed gas can be adjusted to a specific direction and then directed toward the scavenging port 13. Further, in the trial production or improvement of the two-stroke engine 1, when searching for the flow direction of the mixed gas that can exhibit high output, it is only necessary to change the rectifying portion of the scavenging cover that is different from the cylinder. Low cost and short time to achieve high output of the two-stroke engine.

1‧‧‧ engine

2‧‧‧ cylinder

2A‧‧‧cylinder

2B‧‧‧ jack

3‧‧‧ crankcase

11‧‧‧air inlet

11A‧‧‧ Short side

12‧‧‧Exhaust port

13‧‧‧ Scavenging port

13A‧‧‧1st scavenging port

13B‧‧‧2nd scavenging port

13C‧‧‧Parts

13D‧‧‧Department

13E‧‧‧Short side

13F‧‧‧ Short side

21‧‧‧Intake passage

22‧‧‧Exhaust passage

23‧‧‧ scavenging pathway

23A‧‧‧ wall

23B‧‧‧ wall

24‧‧‧ Sweeping window

25‧‧‧ screw holes

26‧‧‧ scavenging cover

26A‧‧Rectifier

27‧‧‧ screws

L1‧‧‧ length

L2‧‧‧ length

X‧‧‧ direction

Y‧‧‧ direction

Z‧‧‧ direction

Fig. 1 is a perspective view of a two-stroke engine according to an embodiment of the present invention.

Figure 2 is a top view of a two-stroke engine.

Figure 3 is a side view of the cylinder as viewed from the direction of arrow III of Figure 2.

Figure 4 is a cross-sectional view taken along line IV-IV of Figure 2.

Figure 5 is a cross-sectional view taken along line V-V of Figure 2.

Figure 6 is a cross-sectional view taken along line VI-VI of Figure 2.

Hereinafter, a two-stroke engine 1 according to an embodiment of the present invention will be described with reference to Figs. 1 to 6 . The two-stroke engine 1 is a piston valve type engine.

In the following description, the two-stroke engine 1 is simply referred to as "engine 1". In addition, for the sake of easy understanding, the three directions orthogonal to each other are defined as "X direction", "Y direction", and "Z direction", and will be described with appropriate reference. The "X direction" is the left and right direction of the engine 1, and the arrow side is set to the right side. The "Y direction" is the front and rear direction of the engine 1, and the arrow side is set to the rear side. The "Z direction" is the upper direction of the engine 1, and the arrow side is set to the upper side.

The engine 1 includes a cylinder 2, and a crankcase 3 is mounted on the lower side of the cylinder 2. The cylinder 2 has a cylinder bore 2A which is a substantially cylindrical space, and a piston (not shown) flows in the cylinder bore 2A in the up and down direction. Move back. The crank case 3 is configured to be divided in the left-right direction, and a crank shaft (not shown) is inserted in the dividing direction. The piston is coupled to a crank (not shown) that rotates integrally with the crankshaft via a connecting rod (not shown), and converts the reciprocating motion of the piston in the up and down direction into the rotation of the crankshaft.

Hereinafter, the detailed configuration of the cylinder 2 will be described.

The cylinder 2 is composed of a cast product of an aluminum alloy. In the cylinder bore 2A of the cylinder 2, an intake port 11 is provided on the wall surface on the front side, and an exhaust port 12 is provided on the wall surface on the rear side, and the wall surface on the left and right sides is provided with an axis substantially perpendicular to the cylinder bore 2A. One of the opposite pairs of scavenging ports 13, 13. The scavenging ports 13, 13 are arranged in plane symmetry with respect to the YZ plane passing through the center of the cylinder bore 2A. At the top of the cylinder bore 2A, a socket 2B for mounting a spark plug (not shown) is formed.

As shown in FIG. 4, the scavenging port 13 has a partition 13C at a substantially center in the circumferential direction, and is partitioned into a first scavenging port 13A on the exhaust port 12 side and a second scavenging port 13B on the intake port 11 side by the partition member 13C. . The scavenging port 13 is located at a position close to the intake port 11 in the circumferential direction of the cylinder bore 2A.

The intake port 11, the exhaust port 12, and the scavenging port 13 are opened and closed as the piston moves in the up and down direction. Further, the intake port 11, the exhaust port 12, and the scavenging port 13 are respectively provided at a height that can be opened and closed at a specific timing.

Further, as shown in FIGS. 4 and 5, an extension portion 13D is provided in each of the second scavenging ports 13B, and the extension portion 13D is extended on the side of the intake port 11 and spans when viewed from above. The length L1 overlaps the end of the intake port 11. Therefore, the vertical short side 13E on the side of the intake port 11 of the second scavenging port 13B is located on the short side 11A of the intake port 11 in a plan view including the XZ of the central axis (the one-point chain line of FIG. 5). More depends on the position of the central axis of the cylinder bore 2A.

It is preferable that the total length L1 (= L1 + L1) of the circumferential direction of the extending portion 13D is 5% to 26% of the length L2 of the circumferential direction of the intake port 11. According to experiments conducted by the inventors, when the overlap between the intake port 11 and the second scavenging ports 13B and 13B is within the above range, the output of the engine 1 is high. In the engine 1 of the present embodiment, a scavenging port is formed in such a manner as to satisfy the condition. 13,13.

Further, the cylinder 2 is provided with an intake passage 21 that penetrates in the front-rear direction and communicates with the intake port 11 (see FIGS. 4 and 5), and that penetrates in the front-rear direction and communicates with the exhaust port 12 The passage 22 (see FIGS. 4 and 6) and one of the pair of scavenging passages 23 and 23 extending in the vertical direction (see FIGS. 4 to 6). In the casting step of the cylinder 2, the intake port 11 and the intake passage 21 are formed by a punching die that is extended to the front side, and the exhaust port 12 and the exhaust passage 22 are formed by a punching die that is extended toward the rear side. The scavenging passages 23, 23 are formed by a punching die that is extended to the lower side. The intake passage 21 is connected to a vaporizer (not shown) that mixes fuel and air to generate a mixed gas. The exhaust passage 22 is connected to a silencer (not shown) that eliminates exhaust sound.

The scavenging passage 23 communicates with the first scavenging port 13A and the second scavenging port 13B via the scavenging window 24 at the upper end portion, and communicates with the crank chamber (not shown) formed in the crankcase 3 at the lower end portion. As shown in Fig. 4, in the side view, the wall 23A on the rearmost side of the scavenging passage 23 is located on the extension line of the vertical short side 13F on the rear side of the first scavenging port 13A. Further, the wall 23B on the foremost side of the scavenging passage 23 is disposed on the rear side of the vertical short side 13E on the front side of the second scavenging port 13B. In this manner, the length of the scavenging passage 23 in the circumferential direction is shorter than the scavenging port 13, and the scavenging port 13 is provided offset from the scavenging passage 23 toward the front side (the intake port 11 side).

Further, on the left and right sides of the cylinder 2, a scavenging window 24 is formed at a position corresponding to each scavenging port 13. The scavenging window 24 is formed in a rectangular shape surrounding the first scavenging port 13A and the second scavenging port 13B, and is opened to the outside. The scavenging window 24 communicates with the first scavenging port 13A and the second scavenging port 13B on the cylinder bore 2A side on the inner side thereof.

In the casting step of the cylinder 2, the scavenging window 24 is formed by a punching die which is extended in the left-right direction together with the first scavenging port 13A and the second scavenging port 13B. Two bottomed screw holes 25, 25 are formed in the vicinity of the scavenging window 24, and the scavenging cover 26 of the scavenging window 24 is fixed by the two screws 27, 27 using the screw holes 25, 25.

A rectifying portion 26A is protruded from a surface of the scavenging cover 26 facing the scavenging port 13. Rectification The portion 26A adjusts the flow direction of the mixed gas supplied from the scavenging passage 23 to an appropriate direction, and then faces the first scavenging port 13A and the second scavenging port 13B, and changes the amount of the mixed gas flowing into the second scavenging port 13B. It is limited in such a manner that the amount of the mixture flowing into the first scavenging port 13A is smaller than that. The flow direction of the mixed gas adjusted by the flow rectifying unit 26A is also supplied to the mixed gas flowing into the cylinder bore 2A from the first scavenging port 13A and the second scavenging port 13B.

According to the engine 1 configured as above, when the piston at the bottom dead center moves upward toward the top dead center, the crank chamber becomes a negative pressure, and when the piston reaches the vicinity of the top dead center, it is blocked by the skirt of the piston. The intake port 11 is opened, and the mixture supplied from the intake passage 21 flows into the crank chamber from the intake port 11. At the same time, in the cylinder bore 2A, the mixture gas on the upper side (top dead center side) of the piston is compressed as the piston rises. When the piston changes from rising to falling through the top dead center, the compressed mixture is ignited by the spark plug, and the combustion mixture expands to push the piston downward. As the piston descends, the exhaust port 12 that is first blocked by the piston is opened, and the mixed gas that has been burned becomes exhaust gas and is discharged through the exhaust passage 22. When the piston is further lowered, the first scavenging port 13A and the second scavenging port 13B are opened, and at the same time, the intake port 11 is opened at the lower end side of the piston. Then, the mixture in the crank chamber is pushed out by the downward movement of the piston, and flows into the cylinder bore 2A from the first scavenging port 13A and the second scavenging port 13B through the scavenging passage 23, and the cylinder is carried in along with the inflow.扫 2A within the scavenging. Then, the piston moves upward again from the bottom dead center toward the top dead center. The engine 1 is continuously driven by repeating the series of cycles.

[Effect of the embodiment]

According to the engine 1 configured as described above, the second scavenging port 13B on the intake port 11 side is provided with an end portion that extends to the intake port 11 side and that spans the length L1 and the intake port 11 when viewed from above. Since the overlapping portion 13D is overlapped, the area of the scavenging port 13 can be made larger than the area occupied by the extending portion 13D. Thereby, a large amount of the mixed gas can be burned in one cycle, so that the two-stroke engine 1 can be made to have a high output.

Further, since the cylinder 2 is provided with a sweep that communicates with the scavenging port 13 and is open to the outside of the cylinder 2 Since the louver 24 is formed, when the cylinder 2 is produced, the punching die can be drawn from the side of the scavenging window 24 instead of the cylinder bore 2A, and the second scavenging port 13B provided with the extending portion 13D can be formed. Thereby, the extension portion 13D can be formed in advance when the cylinder 2 is produced, and it is not necessary to perform the additional work previously performed by the user, that is, to extend the processing.

As described above, the engine 1 according to the present invention can exhibit high output and be mass-produced.

Since the scavenging port 13 is located at the position of the intake port 11 in the circumferential direction of the cylinder bore 2A, the scavenging port 13 can be moved away from the exhaust port 12. Thereby, when the mixture gas flows into the cylinder bore 2A from the scavenging port 13, the leakage of the unburned mixture gas to the exhaust port 12 can be suppressed (leakage), so that more mixed gas can be burned, so that the engine 1 can be made. More accurately play high output.

The condition that the engine 1 has a high output, that is, the total length L1 of the circumferential direction of the extension portion 13D (= L1 + L1) is 5% to 26% of the length L2 of the circumferential direction of the intake port 11 In this way, the scavenging port 13 is formed, so that the two-stroke engine can be made to have a high output.

Further, as described above, since the engine 1 is configured to be mass-produced, the scavenging port 13 can be accurately formed at an position that satisfies the above-described conditions confirmed by the inventors by an automatic machine tool. Thereby, it is possible to surely eliminate the individual difference of the engine 1 which is easily generated in the extended processing by the user.

Since the separator 13 is provided in the middle of the scavenging port 13 and the scavenging port 13 is divided in the circumferential direction, even when the length of the scavenging port 13 in the circumferential direction is long, the partition member 13C serves as a reinforcing member to prevent heat from being burned. The deformation of the scavenging port 13 caused by the same. Thereby, the engine 1 can be stably exhibited with a high output.

Further, since the scavenging port 13 is partitioned into the first scavenging port 13A and the second scavenging port 13B, the blowing angle of the mixture to the cylinder bore 2A can be set in each of the first scavenging port 13A and the second scavenging port 13B.

Since the rectifying portion 26A is protruded from the surface of the scavenging cover 26 facing the scavenging port 13, the flow direction of the mixed gas can be adjusted to an appropriate direction and then directed toward the scavenging port 13.

Further, when the engine 1 is in trial production or improvement, when the flow direction of the mixed gas that can exhibit high output is sought, the rectifying portion 26A of the scavenging cover 26 that is different from the cylinder 2 may be changed. Further, by disassembling the scavenging cover 26, the cylinder 2 can be machined from the outside in the circumferential direction, and the port timing of the cylinder 2 can be easily changed. With this, it is possible to achieve high output of the engine 1 at a low cost and in a short time.

[variation]

The present invention is not limited to the above-described embodiments, and modifications, improvements, etc. within the scope of the object of the invention are included in the present invention.

For example, in the embodiment, the separator 13C is provided in the scavenging port 13, but the separator 13C may be omitted. In this case, it is preferable that the rectifying portion 26A of the scavenging cover 26 protrudes to the vicinity of the inner circumferential surface of the cylinder bore 2A.

Further, although the engine 1 is an example of a piston valve type, the engine 1 may be a reed valve type or a rotary valve type. Further, although the embodiment engine 1 is a single cylinder, the engine 1 may be a plurality of cylinders.

2‧‧‧ cylinder

2A‧‧‧cylinder

2B‧‧‧ jack

11‧‧‧air inlet

11A‧‧‧ Short side

13‧‧‧ Scavenging port

13A‧‧‧1st scavenging port

13B‧‧‧2nd scavenging port

13C‧‧‧Parts

13D‧‧‧Department

13E‧‧‧Short side

21‧‧‧Intake passage

23‧‧‧ scavenging pathway

24‧‧‧ Sweeping window

26‧‧‧ scavenging cover

26A‧‧Rectifier

L1‧‧‧ length

L2‧‧‧ length

X‧‧‧ direction

Y‧‧‧ direction

Z‧‧‧ direction

Claims (5)

A two-stroke engine is characterized in that: an air inlet and an exhaust port are disposed substantially opposite to each other on a wall surface formed on a cylinder bore of the cylinder, and includes: a pair of scavenging ports, which are respectively disposed at the air inlets Between the exhaust port and the exhaust port, substantially opposite to the axis of the cylinder bore; the scavenging window is connected to the scavenging port and open to the outside of the cylinder; and the scavenging cover is sealed from the outside of the cylinder The scavenging window is blocked, and each of the scavenging ports is provided with an extending portion extending from the intake port side and overlapping the end portion of the intake port when viewed in the axial direction of the cylinder bore. The two-stroke engine of claim 1, wherein the scavenging port is located in the circumferential direction of the cylinder bore and is located at the position of the air inlet. In the two-stroke engine of claim 1, wherein the total length of the circumferential direction of the extending portion is 5% to 26% of the length of the circumferential direction of the air inlet. The two-stroke engine of claim 1, wherein the scavenging port includes a first scavenging port disposed at a position away from the air inlet port in the circumferential direction, a second scavenging port disposed at a position close to the air inlet port in the circumferential direction, and a partition a separator for the first scavenging port and the second scavenging port. The two-stroke engine according to any one of claims 1 to 4, wherein a rectifying portion that adjusts a flow direction of the mixture toward the scavenging port to a specific direction is protruded from a surface of the scavenging cover facing the scavenging port .