JPS63266120A - Exhauster for two-cycle engine - Google Patents

Abstract

PURPOSE:To keep out blow-by of fresh air in one cylinder with blowdown pressure in other cylinders as well as to prevent turbulence of the fresh air from occurring by installing each sub-exhaust port in opposition to each exhaust port in plural cylinder, and joining these sub-exhaust ports together. CONSTITUTION:In this two-cycle engine, each main exhaust port 26 is formed in respective cylinder sleeves 16 in plural cylinders 10, 12 and 14, and these exhaust ports are joined together to each other by a main exhaust passage 30 formed in a cylinder block 28. In this exhauster, each sub-exhaust port 34 is set up in each cylinder sleeve 16 at a position being opposed to each of the main exhaust ports 16, and, each sub-exhaust port 34 is made to converge on a sub-exhaust passage 36, while this sub-exhaust passage 36 is joined together with the main exhaust passage 30. With this constitution, the blow-by of fresh air in one cylinder is prevented by blowdown pressure in other cylinders, while turbulence of fresh air due to the blowdown pressure at time of low speed and low load is prevented from occurring.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an exhaust system for a two-stroke engine, and in particular,
The present invention relates to the structure of an exhaust port in a two-stroke engine with multiple cylinders.

[Prior Art] In general, each cylinder in a multi-cylinder engine has three exhaust ports that are merged together, so the blowdown pressure during exhaust in one cylinder affects the other cylinders.
In a cycle engine, the blowdown pressure caused by the exhaust from other cylinders overlaps between the time when one cylinder's scavenging air closes and the time when the exhaust air closes, preventing fresh air from blowing through the one cylinder, and improving the charging efficiency. This has the advantage of increasing engine output and reducing fuel consumption.

[Problems to be solved by the invention] However, in such a two-stroke engine, in the low speed and low load range, the amount of fresh air entering the cylinder is small, so the pressure due to the blowdown pressure during exhaust from other cylinders increases. The problem is that the waves disturb the fresh air in that cylinder, thus deteriorating the ignition performance in that cylinder.

The present invention has been made in view of the problems of the prior art, and its purpose is to maintain the advantage of preventing fresh air blow-through in one cylinder by the blowdown pressure of other cylinders. At the same time, it is an object of the present invention to provide an exhaust system for a two-stroke engine that can prevent fresh air from being disturbed by pressure waves of blowdown pressure in a low speed and low load range, thereby improving ignition performance.

[R-stage to solve the problem] In order to achieve such a goal, the K-111 has a two-stroke engine in which multiple cylinders merge through their exhaust ports or the main exhaust passage. Each sub-exhaust port is provided opposite to the exhaust port, and these sub-exhaust ports are configured to merge.

[Function] With this configuration, in contrast to the pressure waves that conventionally propagated in one direction from one cylinder to another, in the present invention, the pressure waves propagate from the sub-exhaust port in the direction opposite to the pressure waves. The disturbance of fresh air is prevented by canceling out these pressure waves.

[Example] Hereinafter, the present invention will be explained based on embodiments shown in the drawings.

Fig. 1 shows a sectional view of an embodiment in which the present invention is applied to a 3-cylinder 2-stroke outboard engine (with a vertical crankshaft), and Fig. 2 shows the H-TI line of Fig. 1. A cross-sectional view along the line is shown. Here, there are the first cylinder 10, the second cylinder 12, and the third cylinder 14, and in this embodiment, these cylinders are arranged vertically in parallel HjL.

It is the same for each cylinder, or a piston 18 is inserted into the cylinder leaf 16, and a connecting rod 20 is connected to the screws 1 to 18, and this connecting rod 20 is connected to a crankshaft (not shown). Further, 22 is a main scavenging passage, 24 is a third scavenging passage, and 23 in FIG. 2 is a scavenging port of the main scavenging passage 22 formed in the cylinder sleeve 16.

Further, a main exhaust port 26 is formed in the cylinder sleeve 16 of each cylinder, and these main exhaust ports 26 join together at a main exhaust passage 30 formed in the cylinder block 28, and pass through an expansion chamber (not shown) to the outside of the boat. It is designed to be discharged outside the machine. 32 is an over jacket.

Furthermore, in each cylinder, a sub-exhaust port 34 is formed in the cylinder sleeve 16, and the sub-exhaust port 34 is disposed at a position facing the main exhaust port 26. The sub-exhaust ports 34 each merge into a sub-exhaust passage 36, and the sub-exhaust passage 36 is configured to merge with the main exhaust passage 30 on the downstream side. Preferably, each sub-exhaust port 3
The passage axis of the sub-exhaust passage 36 adjacent to the main exhaust port 2
The main exhaust port 26 is located approximately coaxially with the passage axis of the main exhaust passage 30 adjacent to the main exhaust port 26.
The pressure waves propagating from the auxiliary exhaust port 34 to each cylinder or the pressure waves propagating from the sub-exhaust port 34 cancel each other out.

Next, the operation of this embodiment will be explained. Regarding the first cylinder 10, exhaust begins when the piston 18 descends from top dead center and opens the main exhaust port 26 and the auxiliary exhaust port 34. Next, when the main scavenging passage 22 and the third scavenging passage 24 are opened, fresh air is introduced into the first cylinder 10 from the main scavenging passage 22 and the third scavenging passage 24. When the piston 18 reaches the bottom dead center and then rises to close the main scavenging passage 22 and the third scavenging passage 24, the main exhaust port 26 and the sub-exhaust port 34 of the second cylinder 12 are opened. Exhaust begins. This: A pressure wave based on the blowdown pressure caused by the exhaust in the fS2 cylinder 12 propagates through the main exhaust passage 30 and the auxiliary exhaust passage 36 in the opposite direction to the exhaust, and from the main exhaust port 26 and the auxiliary exhaust port 34 of the first cylinder lO. Get inside that cylinder. This prevents fresh air from blowing through during scavenging in the first cylinder 10, and pressure waves due to the flow down pressure from the second cylinder 12 are introduced from the main exhaust port 26 and the sub-exhaust port 34 facing each other. Runote, 1st cylinder 1
Disturbance of fresh air within 0 is prevented.

Therefore, even if the amount of fresh air introduced into the cylinder is small in the low-speed, low-load region, the effects of pressure waves from other cylinders on this fresh air are canceled out, and stable ignition performance can be obtained. become.

In the above embodiments, a three-cylinder engine has been described, but the present invention need not be limited thereto, and can be applied to other multi-cylinder engines.

[Effects] As explained above, according to the present invention, the blowdown in the low speed and low load range is maintained while maintaining the advantage of preventing fresh air blow-through in one cylinder by the flowdown pressure in the other cylinder. This has the excellent effect of preventing fresh air from coming into contact with pressure waves, thereby improving ignitability.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an embodiment of an exhaust system for a two-stroke engine according to the present invention, and FIG. 2 is a cross-sectional view taken along the line ■-■ in the diagram of FIG. 1O112,14...Cylinder 26...Main exhaust date 30...Main exhaust passage 34...Sub-exhaust port 36...Sub-exhaust passage Agent Patent attorney Yoshiyuki Inaba Figure 1 5; PI 3 2!6: jy't/, a. Grapes;! Yuyu 1 shi Z every..., 謬j 2 V";74 2 [pi=:=;n 3 shi L
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Claims (1)

[Claims] (1) The exhaust ports of multiple cylinders meet in the main exhaust passage 2
An exhaust system for a two-stroke engine, in which a sub-exhaust port is provided for each cylinder facing an exhaust port, and the sub-exhaust ports are merged together.