JPH0791977B2 - Scavenging device for two-cycle internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a scavenging device for a Schneile scavenging-type crankcase compression two-cycle internal combustion engine.

[Conventional technology]

3 to 5 show the outline of the structure of a conventional schnee scavenging two-stroke gasoline engine. In FIG. 3, 1 is a cylinder, 2 is a crankcase, 3 is a piston, 4 is a spark plug, 5 is an intake hole, 6 is an exhaust hole, 7 is a scavenging hole, and 8 is a scavenging passage. The inlet side of the scavenging passage 8 is provided on the outer peripheral portion (outside) of the crankcase 2 as shown in FIG.

FIG. 4 is a plan view showing the positional relationship and shape of the exhaust hole 6, the scavenging hole 7, and the scavenging passage 8.

In FIG. 3, when the piston 3 rises, the negative pressure generated in the crankcase 2 during the compression stroke causes the air-fuel mixture to be sucked into the crankcase 2 through the intake holes 5. At this time, the air-fuel mixture in the combustion chamber surrounded by the cylinder 1 and the piston 3 is compressed, ignited by the spark plug 4 near the top dead center (TDC), burned, and the pressure in the combustion chamber rises, and the piston 3 Worked down. In the middle of this, the intake hole 5 closes. Next, the exhaust hole 6 is opened and the combustion gas is discharged.
Further, when the piston 3 descends, as shown in FIG.
The scavenging hole 7 is opened, communicates with the crank chamber 9 in the crankcase 2 through the scavenging passage 8, and the air-fuel mixture compressed in the crank chamber 9 flows into the cylinder 1 to push out combustion gas. , Instead of this, the cylinder 1 is filled. After passing through the bottom dead center (BDC), the scavenging hole 7 and the exhaust hole 6 are closed and the compression stroke starts again. Since the scavenging hole 7 and the exhaust hole 6 are simultaneously opened while the scavenging hole 7 is opened, the air-fuel mixture blows through the exhaust hole 6 as it is. Therefore,
In the schnee scavenging type, as shown in FIG. 4, the exhaust hole 6 and the transfer passage 8 are directed toward the opposite side of the exhaust hole 6 from the exhaust hole 6
The air-fuel mixture is made to flow in a direction away from the air-fuel mixture to reduce blow-by of the air-fuel mixture.

[Problems to be solved by the invention]

In the above-mentioned conventional one, the direction of the scavenging hole 7 is directed to the opposite side of the exhaust hole 6 in order to reduce the blow-by of the air-fuel mixture. However, since the exhaust hole 6 is opened before the scavenging hole 7, there is a strong flow to the exhaust hole, and since the period during which the exhaust hole 6 and the scavenging hole 7 are open simultaneously is long, The scavenging hole 7 is not enough if the air hole 7 is only directed to the opposite side of the exhaust hole 6.
It is difficult for the air-fuel mixture that flows in from to maintain a strong directivity toward the side opposite to the exhaust holes. For this reason, there is a problem that the amount of air-fuel mixture that has blown into the exhaust holes 6 is still large and fuel efficiency is poor.

The present invention addresses the above-mentioned problems, and an object of the present invention is to provide a two-cycle internal combustion engine that prevents blown air-fuel mixture into an exhaust hole and reduces fuel consumption.

[Means for solving problems]

The present invention is characterized by having the following configuration in order to solve the above problems.

(1) The scavenging hole and the scavenging passage that connects the crank chamber and the scavenging hole are divided into a plurality of parts, and the inlet of part of the scavenging passage is provided on the outer periphery (outer side) of the crank chamber and the inlet of the remaining scavenging passage is cranked. Provide near the center of the case.

(2) Further, the opening timing of the scavenging hole communicating with the scavenging passage from the central portion is earlier than the opening timing of the scavenging hole communicating with the scavenging passage from the outside, and is opened closer to the exhaust hole.

[Action]

By the above means, the air-fuel mixture having a low fuel concentration is supplied from the center of the crankcase, and the air-fuel mixture having a high fuel concentration is supplied from the outer periphery into the cylinders through the different scavenging passages. By supplying to the side, blow-through of the rich air-fuel mixture is reduced.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. In the drawings, 1 is a cylinder, 2 is a crankcase, 3 is a piston, 4 is a spark plug, 5 is an intake hole, and 6 is an exhaust. A hole, 15 is a crank web, 16 is a connecting rod, 19 is a crank chamber, and 20 is a crank shaft.

9 is the second scavenging passage, 11 is the second scavenging hole communicating with the second scavenging passage 9, 10 is the first scavenging passage, 12 is the first scavenging hole communicating with the first scavenging passage 10, and 13 is the second The scavenging inlet of the scavenging passage, 14 is a scavenging inlet of the first scavenging passage.

The first scavenging hole 12 is provided in the upper part so as to be opened earlier than the second scavenging hole 11, and the scavenging inlet 14 of the first scavenging passage 10 is located in the central portion of the crank chamber 19 (close to the axis of the crankshaft 20). Part). Further, the scavenging inlet 13 of the second scavenging passage 9 is configured to open at an outer peripheral portion of the crank chamber 19 (a portion farther from the axial center of the crankshaft 20 than the scavenging inlet 14).

Further, as shown in FIG. 1, the first scavenging hole 12 has a second
It is opened at a position closer to the exhaust hole 6 than the scavenging hole 11.

In the above embodiment, the scavenging holes 11 and 12 and the scavenging passage are provided.
Although two 9,10 are provided, the second scavenging hole 11 and the second scavenging passage 9 may be further added to form three or more scavenging holes and scavenging passages as a whole.

In the two-cycle internal combustion engine having the above configuration, the air-fuel mixture introduced into the crankcase 2 is discharged from the scavenging inlet 14.
It is supplied into the cylinder 1 through the second scavenging passage 9 and the second scavenging hole 11. On the other hand, the air-fuel mixture flowing from the scavenging inlet 14 is supplied into the cylinder 1 through the first scavenging passage 10 and the first scavenging hole 12. At this time, the first scavenging hole 12 is opened earlier than the second scavenging hole 11, and is opened on the side closer to the exhaust hole 6.

The air-fuel mixture is supplied into the crank chamber 19 from a vaporizer (not shown). Since the crankshaft 20 and the like rotate at high speed in the crank chamber 19, a heavy component in the air-fuel mixture that has flowed in due to centrifugal force, that is, a fuel-rich air-fuel mixture is distributed to the outer periphery of the crank chamber 19, and A thin air-fuel mixture with a high air concentration is distributed in the center. Therefore, first, a thin air-fuel mixture near the center of the crank chamber 19 is introduced into the cylinder 1 from the first scavenging passage 10. Then, the exhaust gas is pushed out to the exhaust hole 6 with this thin air-fuel mixture having a small fuel component, and thereafter, a rich air-fuel mixture having a large fuel component distributed in the vicinity of the outer peripheral portion of the crank chamber 19 is introduced into the cylinder 1 from the second scavenging passage 9. Lead. Exhaust gas is pushed out by a thin air-fuel mixture having a small amount of fuel components, and since the thin air-fuel mixture is positioned so as to flow out to the side close to the exhaust hole 6, it is thin that it directly blows out to the exhaust hole 6. It becomes a mixture. Since the rich air-fuel mixture having a large fuel component introduced from the outer peripheral portion of the crank chamber 19 flows into the cylinder 1 from a position away from the exhaust hole 6, the rich air-fuel mixture is sealed in a thin air-fuel mixture layer and exhausted from the exhaust gas. The blow-through to the hole 6 is eliminated. For this reason, finally, the air-fuel mixture having a larger fuel component than the conventional one remains in the cylinder 1 as a whole.

〔The invention's effect〕

The present invention is configured as described above, and according to the present invention, the amount of fuel components remaining in the cylinder is increased by reducing the amount of fuel components blown through the exhaust holes. This can improve engine output and reduce fuel consumption.

[Brief description of drawings]

1 and 2 show the schnee scavenging type 2 according to the present invention.
FIG. 2 is a schematic sectional view in the vicinity of a scavenging passage of a cycle gasoline engine (FIG. 2 is a sectional view taken along line II-II in FIG. 1). Fig. 3 is a schematic cross-sectional view of a conventional schnee scavenging two-stroke gasoline engine, Fig. 4 is a plan view showing the positional relationship and shape of the scavenging and exhaust holes, and Fig. 5 is a schematic of the positional relationship of scavenging and exhaust holes. It is a figure. 1 ... Cylinder, 5 ... Intake hole, 6 ... Exhaust hole, 9 ... First scavenging passage, 10 ... Second scavenging passage, 11 ... First scavenging hole, 12 ...
2nd scavenging hole, 13 …… Scavenging inlet, 14 …… Scavenging inlet, 19 …… Crank chamber

Claims (1)

[Claims] 1. A schneile scavenging two-cycle internal combustion engine in which a mixture introduced into a crank chamber is compressed on the back surface of a piston and fed into a cylinder through a scavenging passage and a scavenging hole. A plurality of scavenging inlets of the first scavenging passage communicating with the first scavenging hole that is opened closest to the exhaust hole are opened near the center of the crank chamber, and other scavenging holes are opened at different times. A two-cycle system characterized in that it is configured to be slower than the first scavenging hole and that a scavenging passage communicating with the other scavenging holes is opened closer to the outer periphery of the crank chamber than the first scavenging passage. Scavenging device for internal combustion engine.