JPH042776B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a scavenging device for a two-stroke engine, and particularly to a two-stroke engine in which the timing of opening and closing of a scavenging port formed on a cylinder side wall of a combustion chamber is variable. This invention relates to an engine scavenging device.

[Conventional technology]

A conventional two-stroke engine will be explained with reference to FIGS. 10 and 11.

In FIG. 10, a cylinder 10 has a combustion chamber 12 inside, and a spark plug 13 is connected to the cylinder 10.
is attached to the top of the combustion chamber 12, with its discharge gap facing into the combustion chamber 12. The piston 14 defines a lower portion of the combustion chamber 12 and slides within the cylinder 10 . The crankcase 16 is joined to the lower end of the cylinder 10, and the crankshaft 18 has an axially central portion disposed within the crankcase 16, and both ends rotatably attached to the crankcase via ball bearings 20a and 20b. It is pivotally supported by 16. The connecting rod 22 connects the piston 14 and the crankshaft 18 via pins at the upper and lower ends, respectively.
The seals 24a, 24b are rotatably connected to the
They are fitted on the outside of ball bearings 20a and 20b, respectively, in the axial direction of the crankshaft 18, and keep the inside of the crankcase 16 airtight.
An exhaust port 26 and a pair of scavenging ports 28 are formed below the exhaust port 26 in the side wall of the cylinder 10 that partitions the combustion chamber 12 in the radial direction. The scavenging passage 30 is formed in the cylinder 10 and the crankcase 16, communicates with the scavenging port 28 at the downstream end, and guides the mixed gas to the scavenging port 28.

FIG. 11 shows the opening/closing timing of the exhaust port 26 and the scavenging port 28 in terms of the rotation angle of the crankshaft 18.
The opening/closing timing of the scavenging port 28 is fixed regardless of the operating conditions of the two-stroke engine.

[Problem to be solved by the invention]

The opening and closing timing of the scavenging port 28 is preferably closer to the opening and closing timing of the exhaust port 26 when the two-stroke engine is running at high speed, since the scavenging effect and the efficiency of filling the mixture gas into the combustion chamber 12 are higher. During low-speed rotation, if the scavenging port 26 is close to the opening/closing timing, the scavenging port 28 will open before the gas pressure in the combustion chamber 12 is sufficiently low, and since the flow rate of the mixed gas is low, the combustion gas will not reach the scavenging gas. This may cause the gas to flow back into the passage 30, reduce the filling efficiency of the mixed gas into the combustion chamber 12, or reduce the output of the two-stroke engine.

However, in conventional two-stroke engines, the opening/closing timing of the scavenging port 28 is fixed, making it difficult to control the opening/closing timing of the scavenging port 28 to an optimal value according to the rotational speed of the two-stroke engine. .

In addition, preparing multiple cylinders with different opening and closing timings of the scavenging ports requires separate molds to manufacture those cylinders, which is disadvantageous in terms of cost, and also reduces the cost of two-cycle engines. It is necessary to switch the cylinder to be used depending on the rotation speed, which increases time and effort.

An object of the present invention is to provide a scavenging device for a two-stroke engine that can optimally adjust the opening and closing timing of a scavenging port depending on the operating conditions of the two-stroke engine.

[Means to solve the problem]

That is, the present invention is a two-cycle engine that includes a scavenging port formed on the cylinder wall of a combustion chamber, a scavenging passage that guides the mixed gas to the scavenging port, and a valve member that can adjust the closing timing of the scavenging port in the scavenging passage. In the engine, the scavenging port side edge of the valve member, which is disposed outside the combustion chamber 12 and is pivotably supported at the end opposite to the scavenging port 28 side, is
The upper side of the scavenging port 28 that introduces the mixed gas from the scavenging passage 30 into the combustion chamber 12 is defined, and the valve is displaceable along the scavenging port 28 in the axial direction of the combustion chamber 12. Member 32
is an operating member 5 disposed outside the cylinder 10
This paper proposes a scavenging device for a two-stroke engine having a 8-stroke engine.

[Effect]

By operating the operating member etc., the valve member moves,
An edge of the valve member on the scavenging port side is displaced in the axial direction of the combustion chamber substantially along the scavenging port. The edge of the valve member 32 on the side of the scavenging port becomes the upper side of the effective opening of the scavenging port that introduces the mixed gas into the combustion chamber, and therefore, the opening/closing timing of the scavenging port is determined by the crank angle of the piston passing through the upper side of the effective opening. Therefore, the opening/closing timing of the scavenging port changes depending on the displacement of the edge of the valve member on the scavenging port side.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 9.

In FIG. 1, the valve member 32 is arranged in the scavenging passage 30 in the vicinity of the scavenging port 28, and is rotatably supported by the cylinder 10 via a rotation shaft 34 at the upstream end. The free end 36 as the downstream end of the valve member 32 is formed in an arc shape that matches the circumferential portion of the combustion chamber 12, and the free end 36 is formed in an arc shape that corresponds to the circumferential portion of the combustion chamber 12. It is movable along the mouth 28 in the axial direction of the combustion chamber 12 . The length of the free end 36 is equal to the length of the scavenging port 28 in the circumferential direction of the combustion chamber 12, and since the valve member 32 partitions the space at the upper end of the scavenging passage 30, the free end 36 is equal to the length of the scavenging port 28 in the circumferential direction of the combustion chamber 12.
This is the upper side of the effective opening of the scavenging port 28 that introduces the mixed gas into the scavenging port 28. That is, the opening/closing timing of the scavenging port 28 is determined by the crank angle at which the piston 14 passes the free end 36. The solid line position and the two-dot chain line position of the valve member 32 in FIG. 1 illustrate different rocking positions of the valve member 32.

FIGS. 2a and 2b show details of the joint between the valve member 32 and the rotation shaft 34, and the rotation shaft 34 with the valve member 32 removed. Insertion part 3 inserted into
8, and a base portion 40 that is integrally coupled to the end of the insertion portion 38. Circumferential groove 42 and screw hole 44
are formed at both axial ends and the intermediate portion of the insertion portion 38, respectively. After the insertion portion 38 is inserted into the cylinder 10 , a retaining ring 46 is fitted into the circumferential grooves 42 , 42 to prevent the insertion portion 38 from coming off from the cylinder 10 . The screws 48, 48 are inserted into the insertion holes at the upstream end of the valve member 32, and then inserted into the rotation shaft 34.
is screwed into the screw hole 44 of the valve member 32.
is fixed to the rotation shaft 34 at its upstream end so as to be integrally rotatable therewith.

FIG. 3 is a perspective view showing another manner of coupling the valve member 32 and the rotating shaft 34. A square-shaped insertion hole 50 is formed at the upstream end of the valve member 32, and the rotation shaft 34
has an angular insertion portion 52 that is formed to have the same circumferential contour as this angular insertion hole 50 and is fitted into the angular insertion hole 50 . In this coupling mode, the square insertion portion 52 of the rotation shaft 34 fits into the square insertion hole 50 of the valve member 32, thereby ensuring integral rotation of the valve member 32 and the rotation shaft 34. So,
The screw 48 in FIG. 2 can be omitted.

Figure 4 shows the cylinder 1 at the height of the scavenging port 28.
A side view of 0 seen from the outside, Figure 5 is the − of Figure 4.
It is a sectional view along a line. The arm 54 is the rotation axis 3
4 is integrally fixed to the end of the base 40 of the bolt 5.
6 is screwed onto the outer surface of the cylinder 10 at the center of the two arms 54. The operating lever 58 is rotatably inserted into the bolt 56 , and the compression coil spring 60 is fitted onto the shaft of the bolt 56 in a compressed state between the head of the bolt 56 and the operating lever 58 . It is pressed against the outer surface of the cylinder 10. Due to the pressing of the operating lever 58 against the cylinder 10 by the compression coil spring 60, rotation of the operating lever 58 around the bolt 56 requires a rotational force of a predetermined value or more. That is, only when the operator grips and rotates the operating lever 58, a rotational force of a predetermined value or more is applied to the operating lever 58 and the operating lever 58 is rotated. When released, the operating lever 58 maintains its rotational position. The coil springs 62, 62 have one end hooked to both ends of the operating lever 58, and the other end hooked to the lower ends of the arms 54, 54, respectively. Rotation of the bolt 56 in the direction of arrow 64 causes the pivot shaft 34 to rotate in the direction of arrow 66, causing the free end 36 of each valve member 32 to reach the scavenging port 28 while remaining at the same height as each other. along the combustion chamber 12 in the axial direction.

FIG. 6 shows the free end 36 at the scavenging port 28, which corresponds to the solid line position and the two-dot chain line position of the valve member 32 in FIG. The lower the free end 36 is, the farther the scavenging port 28 opens and closes relative to the exhaust port 26.

FIG. 7 shows the opening/closing timing of the exhaust port 26 and the scavenging port 28 in terms of the rotation angle of the crankshaft 18, and FIG. It shows the time. By rotating the operating lever 58,
It becomes possible to adjust the opening/closing timing of the scavenging port 28. When a two-cycle engine rotates at high speed, the flow rate of the mixed gas flowing through the scavenging passage 30 is high, and the time during which the scavenging port 28 is in communication with the combustion chamber 12 is short, so in order to improve the scavenging effect and charging efficiency, By moving the free end 36 of the valve member 32 closer to the exhaust port 26, that is, raising it (as shown by the two-dot chain line in FIGS. 1 and 6), the opening/closing timing of the scavenging port 28 is adjusted to the opening/closing timing of the exhaust port 26. get closer to During low speed rotation of a two-cycle engine, the flow rate of the mixed gas flowing in the scavenging passage 30 is small, so the combustion chamber 12
If the combustion gas pressure decreases slowly and the opening/closing timing of the scavenging port 28 is close to the opening/closing timing of the exhaust port 26, the combustion gas may flow back into the scavenging passage 30 or the efficiency of filling the combustion chamber 12 with the mixed gas may be reduced. Therefore, valve member 3
The free end 36 of the scavenging port 28 is moved away from the exhaust port 26, that is, is lowered (solid line position in FIGS. 1 and 6), and the opening/closing timing of the scavenging port 28 is separated from the opening/closing timing of the exhaust port 26.

FIG. 9 is a graph showing the relationship between engine speed and horsepower in a two-stroke engine to which the present invention is applied and a conventional two-stroke engine. In this invention, since the timing of opening and closing of the scavenging port 28 can be adjusted to an optimal value according to the engine rotation speed, the horsepower of the two-stroke engine increases over the entire engine rotation speed range, and engine performance can be improved. .

〔Effect of the invention〕

As described above, according to the present invention, by operating the operating member etc. from the outside, the valve member swings, and the edge of the valve member on the scavenging port side moves inside the scavenging port in the axial direction of the combustion chamber, thereby opening the valve. The scavenging port side edge of the member defines the upper side of the effective opening of the scavenging port that introduces the mixed gas from the scavenging passage into the combustion chamber, and the displacement of the upper side of the effective opening changes the crank angle at which the piston passes through the upper side. Therefore, it becomes possible to adjust the timing of opening and closing of the scavenging port by displacing the valve member. Therefore, the opening/closing timing of the scavenging port can be adjusted to an optimal value according to the rotational speed of the two-stroke engine, and the output of the two-stroke engine can be increased.

[Brief explanation of drawings]

Figures 1 to 9 relate to this invention, Figure 1 is a structural diagram of the main part, Figures 2 a and b show the joint between the valve member and the rotation shaft, and the rotation with the valve member removed. FIG. 3 is a perspective view showing another manner of coupling the valve member and the rotating shaft; FIG.
Fig. 4 is a side view of the cylinder seen from the outside at the height of the scavenging port, Fig. 5 is a sectional view taken along the - line in Fig. 4, and Fig. 6 is the position of the valve member in Fig. 1 shown in solid line and two points. A diagram showing the position of the free end corresponding to the chain line position in the scavenging port, FIG. 7 is a diagram showing the opening/closing timing of the exhaust port and the scavenging port in terms of the rotation angle of the crankshaft, and FIG. 8 is a two-stroke engine to which this invention is applied. FIG. 9 is a diagram showing the opening/closing timing of the exhaust port and the scavenging port in the acupressure diagram of FIG. The figure is an overall schematic diagram of a conventional two-stroke engine.
FIG. 1 is a diagram showing the opening/closing timing of the exhaust port and the scavenging port in terms of the rotation angle of the crankshaft. 10...Cylinder, 12...Combustion chamber, 28...Scavenging port (opening), 30...Scavenging passage, 32...Valve member, 36
...free end, 58...operation lever (operation member).

Claims (1)

[Claims] 1. In a two-stroke engine that includes a scavenging port formed on the cylinder wall surface of a combustion chamber, a scavenging passage that guides mixed gas to the scavenging port, and a valve member that can adjust the closing timing of the scavenging port in the scavenging passage, The edge on the scavenging port 28 side of the valve member 32, which is disposed outside the combustion chamber 12 and is pivotably supported at the end opposite to the scavenging port 28 side, is separated from the scavenging passage 30. The valve member 32 defines the upper side of the scavenging port 28 that introduces the mixed gas into the combustion chamber 12 and is movable along the scavenging port 28 in the axial direction of the combustion chamber 12. A scavenging device for a two-stroke engine, comprising an operating member 58 disposed outside of the engine.