JPH045429A - Scavenging passage of two-cycle engine - Google Patents

Abstract

PURPOSE:To correct unbalanced flow-in of right and left scavenging air and charge uniform air-mixture in the combustion chambers of cylinders by setting a connection passage which connects together those positions at approximately same height of right and left scavenging passages, as an arcuate passage behind the inner face of the cylinder. CONSTITUTION:Scavenging passages 4a, 5a are arranged on the right and left sides between which an intake port 8 is sandwiched. A connection passage 7 which connects together those positions at approximately same height of the scavenging passages 4a, 5a is set as an arcuate passage behind the inner face of a cylinder 1. Right and left scavenging pressures are equalized, uniformity of air-mixture in a combustion chamber is guaranteed so as to normalize the combustion.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a scavenging passage for a two-stroke engine that fills a cylinder with an air-fuel mixture from a crankcase.

(Prior Art) In a two-stroke engine, as is well known, the air-fuel mixture sucked into the crankcase is first compressed in the crankcase by the descent of a piston, and then filled into the cylinder via a scavenging passage. Ru.

The intake passage is often connected to the crankcase via a reed valve device. The exhaust passage is led out from the cylinder on the opposite side of the intake passage, and the scavenging passages are usually provided on both left and right sides with the exhaust passage in between.

If a sub-scavenging passage is provided, it should be placed along the cylinder on the same side as the intake passage.

In the above case, ideally, the center line of the intake passage should be perpendicular to the axis of the crankshaft when viewed from the direction of the cylinder axis. In order to avoid interference with the engine, some layouts have an intake passage with the introduction direction biased to one side.

Then, due to inertia, the vigorously sucked air-fuel mixture flows into the left and right scavenging passages unevenly, creating a pressure difference at both entrances. If this air is scavenged without being made uniform, the air-fuel mixture filled in the combustion chamber will lack uniformity due to the difference between the left and right scavenging pressures, resulting in abnormal combustion and a decrease in output. This tendency becomes noticeable in high-speed ranges where the intake air-fuel mixture is rich, the flow rate is high, and there is little time to spare.

As a countermeasure to prevent the above tendency, it is possible to change the position and cross-sectional area of the left and right scavenging passages in response to the eccentricity of the intake passage, but this is not effective in all speed ranges and may not be sufficient. I can't say it.

(Problems to be Solved by the Invention) The present invention was made in response to the above-mentioned problem, and in a two-stroke engine having a pair of left and right scavenging passages, unbalance of left and right scavenging air due to intake passage deflection or other reasons. It is an object of the present invention to provide a scavenging passage for a two-stroke engine that corrects a balanced inflow so that a combustion chamber in a cylinder is uniformly filled with air-fuel mixture.

[Structure of the invention]

(Means for Solving the Problems) In accordance with the above object, the scavenging passage of the two-stroke engine of the present invention is a two-stroke engine in which the scavenging passage is arranged on both the left and right sides with an intake port in between. A connecting passage that connects portions at approximately the same height is installed behind the inner surface of the cylinder as an arcuate passage.

(Function) Since the left and right scavenging passages are connected through the connecting passage, the left and right scavenging pressure becomes uniform, ensuring uniformity of the air-fuel mixture in the combustion chamber, normalizing combustion, and improving output. .

This characteristic is particularly noticeable in the high speed rotation range.

(Example) DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, explanation will be made with reference to figures showing embodiments of the present invention.

FIG. 1 is a longitudinal sectional side view of a two-stroke motorcycle engine equipped with a scavenging passage according to the present invention, FIG. 2 is a longitudinal sectional front view, and FIG. 3 is a plan view taken along arrow A-A in FIG. 1. .

The cylinder 1 has an exhaust port 3 and a main scavenging hole 4, whose opening and closing are controlled by the vertical movement of the piston 2. The sub-scavenging port 5 opens. In the case of a two-wheeled motor vehicle engine, the exhaust port 3 opens at the front of the cylinder 1, and an exhaust passage 3a is led out forward and downward.
The main scavenging air ports 4 are arranged oppositely on both the left and right sides, and the sub-scavenging air ports 5 are arranged on the opposite side of the exhaust port 3.
a and 5a are formed along the longitudinal direction behind the inner surface of the cylinder 1, and their starting ends open into the crankcase 6.

A thick connecting passage 7 formed laterally behind the inner surface of the cylinder is connected to a portion of the left and right main scavenging passages 4a near the main scavenging air port 4, so that both passages communicate with each other.

On the other hand, the intake port 8 opens into the crankcase 6 on the opposite side to the exhaust passage 3, and is connected to the intake passage 8a. Intake passage 8
Upstream of a, there is a carburetor 9 and an air cleaner 10.
A reed valve device 11 is interposed in the intake port 8.

XX indicates a center line of the engine perpendicular to the crankshaft 12, but the intake passage 8a is inclined laterally with respect to the center line XX for layout reasons.

When the piston 2 moves up and down as the crankshaft 12 rotates, the air-fuel mixture is drawn into the crankcase 6 and compressed within the cylinder 1.

Here, the air-fuel mixture is ignited and burned, and when the piston 2 descends, the air-fuel mixture sucked into the crankcase 6 is precompressed. In the cylinder 1, as the piston 2 descends, the exhaust port 3 opens first, followed by the main and sub-scavenging ports 4.5. Combustion gas is discharged from the exhaust port 3 to the exhaust passage 3K, and the precompressed air-fuel mixture in the crankcase 6 is alternately discharged from the main and sub-scavenging ports 4 and 5 to the main and sub-scavenging passages 4a.
.

5a. Subsequently, the above operations are repeated.

The two-stroke engine operates as described above, but as mentioned above, the intake passage 8a is aligned with the center line
If it is inclined with respect to X, the left and right main scavenging passages 4a
Due to inertia, more of the air-fuel mixture that is oriented toward one side than the other and is sucked in forcefully is supplied in the biased direction, creating a pressure difference between the left and right main scavenging passages 4a.

This pressure difference tends to be equalized over time, but due to the existence of the connecting passage 7, it is completely equalized before the main scavenging air port 4 opens, and both main scavenging air ports are in the cylinder 1. The air-fuel mixture is evenly filled from the scavenging lower. Therefore, the combustion condition is good and the output is improved.

The flow rate of the air-fuel mixture intake is fast, so the pressure difference becomes large,
Furthermore, even in a high-speed rotation range where the time for each stroke is short, the air-fuel mixture within the cylinder 1 can be made uniform. This connecting passage 7 becomes highly valuable in the high speed rotation range.

FIG. 5 shows another embodiment of the present invention, in which a connecting passage 7a is led out from behind the sub-scavenging passage 5a and connected to an intermediate portion of the connecting passage 7. As a result, the scavenging pressures in the left and right main scavenging passages 4a and the auxiliary scavenging passages 5a are equalized, and the combustion state within the cylinder 1 is further improved.

In particular, since the sub-scavenging passage 5a faces the exhaust port 3,
The air-fuel mixture blowout tends to cause this phenomenon, but the connection passage 7,
7a prevents the flow velocity of the sub-scavenging air from becoming excessive, and blow-by is suppressed.

FIG. 6 shows yet another embodiment of the invention.

Behind the left and right main scavenging passages 4a, there are vent holes 13 that exit to the outside surface.
A connecting pipe 14 connecting the two passage holes 13 is installed on the rear surface of the cylinder 1. The function and effect are the same as those of the connecting passage 7.

Note that the position from which the connecting passage 7 and the connecting pipe 13 are led out is not limited to the vicinity of the main scavenging air port 4 as described above.

As long as the left and right portions on the main scavenging passage 4a are approximately the same, they may be set closer to the crankcase 6.

〔Effect of the invention〕

As described above, the scavenging passage of the two-stroke engine according to the present invention is a connection that connects the left and right scavenging passages at substantially the same height in a two-stroke engine in which scavenging passages are arranged on both the left and right sides of the intake port. The passage is installed as an arc-shaped passage behind the inner surface of the cylinder, and corrects the unbalanced inflow of left and right scavenging air due to deflection of the intake passage or other reasons, and ensures that the combustion chamber in the cylinder is filled with a uniform air-fuel mixture. This has the effect of improving output, especially in the high-speed rotation range.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional side view of a two-stroke engine showing an embodiment of the present invention, FIG. 2 is a longitudinal sectional front view of the cylinder of FIG. FIG. 4 is a chart showing the output characteristics of the two-stroke engine shown in FIG. 1, FIG. 5 is a cross-sectional plan view of a two-stroke engine cylinder showing another embodiment of the invention, and FIG. 6 is a diagram showing still another embodiment of the invention. FIG. 2 is a cross-sectional plan view of an exemplary two-stroke engine cylinder. 1... Cylinder, 2... Piston, 3... Exhaust port, 4... Main scavenging air port, 4a... Main scavenging air passage, 5...
Sub-scavenging port, 5a...Sub-scavenging passage, 6...Crankcase, 7,7a...Connecting passage, 8...Intake port, 8a...
... Intake passage, 1-1... Riet valve device, 12.
...Crankshaft, 14...Connection pipe. Applicant's agent Hisashi Hatano Figure 2 5a Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. Scavenging passages are arranged on both left and right sides across the intake port. 2.
A scavenging passage for a two-stroke engine, characterized in that a connecting passage connecting left and right scavenging passages at substantially the same height is installed as an arc-shaped passage behind the inner surface of a cylinder. 2. The scavenging passage for a two-cycle engine according to claim 1, wherein the connecting passage is formed within the thickness of the cylinder block. 3. The scavenging passage for a two-stroke engine according to claim 1, wherein the connecting passage is formed by a separate pipe and is piped along the outer surface of the cylinder block. 4. The scavenging passage for a two-cycle engine according to claim 1, characterized in that a connecting passage led out from the sub-scavenging passage is connected in the middle of the connecting passage.