JPS5925030A - Two-cycle internal combustion engine - Google Patents

Abstract

PURPOSE:To increase the charging efficiency of mixture by deviding an exhaust port in two, upper and lower ports. CONSTITUTION:Since a two-cycle internal combustion engine is subject to reflecting negative pressure waves of exhaust only when the upper half of the exhaust port is open on the up stroke of a piston, it is not necessary to control the whole of the exhaust port for opening and closing with a rotary valve. Therefore, the exhaust port is divided at least in two, upper 31 and lower 32 ports and a rotary valve 41 is provided for the upper port 31, while the lower port 32 is controlled for its opening and closing through the reciprocating movement of a piston 5. The upper and lower sides of both exhaust ports 31 and 32 are formed in gentle curves and their four corners are rounded thereby smoothly pushing back a piston ring 6 which is going to project when positioned at the exhaust ports 31 and 32. As the exhaust rotary valve 41 carries out the opening and closing of only the upper half exhaust port 31, the capacity of a recess P1 between the valve 41 and the port 31 becomes less than half of the conventional type reducing the quantity of staying new air thereby improving the fuel cost and the output power.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust structure for a two-stroke internal combustion engine.

It is known to increase the charging efficiency of a mixture as a means of increasing the output of an internal combustion engine. For this purpose, it is necessary to actively push out the O exhaust gas in the cylinder, and a large amount of fresh air can be filled without mixing with the exhaust gas.

However, in a 71:2 cycle internal combustion engine equipped with a piston valve type exhaust structure, the relationship between the crank angle and the opening area of the exhaust port is like a sine curve. The amount of discharged lines is determined by the time the exhaust port is open and the area of the exhaust port.

Therefore, in the two-stroke internal combustion engine mentioned above, in order to discharge exhaust gas effectively and rapidly, it is sufficient to increase the dimension of the exhaust port along the direction of binuton motion. Even if the exhaust gas is discharged rapidly at first, it will open to the area where the negative pressure wave comes. There is a problem in that fresh air inside the cylinder is sucked out into the exhaust system due to the reflected negative pressure wave at the time of closing.

As a means of solving the above problems and increasing filling efficiency, a secondary exhaust structure using a rotary valve in place of the piston valve has been proposed.

However, the conventional rolling valve type exhaust structure is as shown in Figures 1 and 2.
As shown in the figure, in the exhaust passage 2 connected to the cylinder 1,
A large diameter cylindrical valve body 4 is placed close to the exhaust port 6 of the cylinder 1.
Since it is installed and rotates synchronously with the crankshaft, a recess P is inevitably formed between the valve body 4 and the exhaust ports 3 and 0.
is large, and fresh air accumulates in the recess P, resulting in poor fuel efficiency.

There is a problem that the output does not rise as expected.As a countermeasure, if the valve body 4 is made into a cone shape as shown by the chain line 4A in Figure 2, it can be brought closer to the exhaust port 3, which eliminates waste. Although the recess is small, due to the shape of the four valve bodies, it is impossible to assemble them within 11.2 minutes.

If the valve body 4At-2 split type is used, it will lack workability and structural reliability, and the thermal distortion of the valve body itself will become discontinuous, resulting in poor sealing performance and the ability to improve μ bottle φ.

In the present invention, even if the cylindrical valve body t is used as is as an exhaust p-meri valve, the recess between the valve body and the exhaust port, which would otherwise be a dead space, can be reduced in the two-stroke internal combustion engine. The purpose is to provide.

Although a two-stroke internal combustion engine is easily affected by the reflected negative pressure wave O of the exhaust, since the upper half of the exhaust port is open at the piston's ascending bridge, the entire exhaust port is affected by the rotary valve. There is no need to control opening and closing. As long as the piston rises from dead center to approximately half the height of the exhaust port, there will be no problem even if the piston is used to open and close the exhaust port.

The present invention has focused on the above point, and in a *22 cycle internal combustion engine equipped with an exhaust a-tally valve, the exhaust port is divided into at least two parts, upper and lower, 61 and 62, as shown in FIG. The rotary valve 4 is made to face the opening 61, and the opening and closing of the lower exhaust port 62 is controlled by the reciprocating motion of the piston 5.

The upper and lower sides of each of the exhaust ports 61 and 62 are made into a sharp curve as shown in FIG.

The qs attached to R' at the four corners serve to smoothly push back the piston rings 6 that are about to protrude when they come to the positions of the exhaust ports 31 and 62.

In the figure, 7 is a crankcase, 8 is a crank chamber, 9 is a conred, 10 is a crankshaft, 11 is a spark plug, 12 is an intake passage, and 13 is a check valve for intake control.

14 is a cooling water chamber. The crankshaft 10, rotary valve 41, and OJ1JIA structure are formed by gears or chains, but are omitted from the figure.

The two-stroke internal combustion engine of the present invention has an exhaust structure as described above.
It only opens and closes the la port 61, so the rotary valve 4
The volume of the recess P1 between the exhaust port 61 and the exhaust port 61 is less than half that of the recess P of the conventional example shown in FIGS.
The accumulation of fresh air is reduced and the cost and output are improved.

Furthermore, the diameter of the rotary valve 41 is smaller than that of the conventional rotary valve 4, and there is no need to make it into a drum shape, so the number of sealing points between the rotary valve 41 and the cylinder 1 is reduced, improving seal a, workability, and structural reliability. It has the effect of maintaining sex.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional front view of the main parts of the exhaust structure of a conventional two-stroke internal combustion engine, FIG. 2 is a cross-sectional plan view thereof, FIG.
The figure is a cross-sectional plan view of the cylinder and exhaust passage, and FIG. 5 is a front view of the exhaust port. 5 - valve, 5 is the piston, 7 is the crankcase, 10 is the crankshaft, P@Pi is the recess. Patent applicant: Honda Motor Co., Ltd. 61

Claims (1)

[Claims] (1) In an fc 2-cycle internal combustion engine, the exhaust passage is provided with a rotary valve that rotates in synchronization with the crankshaft in close proximity to the exhaust port of the cylinder in the exhaust passage connected to the inside of the cylinder, and the exhaust port is divided into at least two parts, an upper and a lower part. A two-stroke internal combustion engine characterized by having a rotary valve facing the upper exhaust port and opening and closing the lower exhaust port by piston oQ return.