JPH0726963A - Two-cycle engine - Google Patents

Abstract

PURPOSE:To prevent leakage of fuel into an exhaust port of fuel while securing stable ignition and combustion, in a two-cycle engine of such a type as a directly injecting the fuel inside a cylinder. CONSTITUTION:A fuel injection means 10 for injecting fuel toward the top part of a piston 5 is arranged and the guide curved face 12 and/or a guide passage for introducing the injected fuel toward a combustion chamber 3 are formed on a part subjected to fuel injection from the fuel injection means 10 on the top part of the piston 5, in a two-cycle engine equipped with scaventing ports 7, 8, 9 and an exhaust port 6 formed on the peripheral face of a cylinder 1, and the fuel injection means 10 arranged on the scaventing port 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-cycle engine, and more particularly to a two-cycle engine in which fuel is directly injected into a cylinder.

[0002]

2. Description of the Related Art In a two-cycle engine in which fuel is directly injected into a cylinder, when the fuel injection means is placed at a position facing the combustion chamber, it is exposed to high temperature, and therefore the fuel injection means is usually provided on the cylinder peripheral surface. Has been done. Particularly, as disclosed in, for example, Japanese Patent Laid-Open No. 3-18664, when the fuel injection means is arranged in the scavenging port, the fuel is constantly cooled by the scavenging air flow, so that it is difficult to be exposed to high temperature and stable operation is facilitated. It is desirable because it can be secured. Even in the case where the fuel injection means is arranged in the scavenging port as described above, two methods as shown in FIGS. 3 and 4 are known.

In FIGS. 3 and 4, 21 is a cylinder, 2
2 is a cylinder head, 23 is a combustion chamber, 24 is a spark plug, and 25 is a piston. An exhaust port 26 is provided at an appropriate position in the circumferential direction immediately above the bottom dead center of the piston 25 on the circumferential surface of the cylinder 21, and two pairs of scavenging air are provided on both sides of the direction connecting the exhaust port 26 and the center of the cylinder 21. Ports 27 and 28 are provided, and a booster port 29 is provided opposite to the exhaust port 26.
These scavenging ports 27, 28 and booster port 29 communicate with a single scavenging inlet (not shown) on the side opposite to the exhaust port 26, and are connected to a scavenging pump (not shown) via this scavenging inlet. Has been done. And booster port 2
A fuel injection means 30 is arranged at 9.

In the system shown in FIG. 3, the booster port 29 is arranged obliquely downward from the fuel injection means 30 to the piston 25.
Is a method of directly injecting fuel toward the top of the piston and evaporating the fuel by the heat of the top of the piston 25 to obtain an air-fuel mixture that is easy to ignite.

The system shown in FIG. 4 is a system in which fuel is injected from a fuel injection means 30 disposed obliquely upward in the booster port 29 toward a position near the ignition plug 24 in the combustion chamber 23.

[0006]

However, in the method shown in FIG. 3, there is a problem that a part of the air-fuel mixture generated at the top of the piston 25 leaks to the exhaust port 26. In particular, when the temperature of the top of the piston 25 is low, the evaporation rate is low and it easily stays at the top of the piston 25 so that it easily flows with the exhaust gas, and in the case of low speed rotation, the exhaust port 26
Has a problem in that it easily flows into the exhaust port 26 due to the long opening time.

The system shown in FIG. 4 is designed to prevent the air-fuel mixture from directly flowing from the top of the piston 25 to the exhaust port 26, but the scavenging air flow is as shown by the arrow in FIG. Since the fuel flows through the upper portion of the cylinder 21 to the exhaust port 26, when the jet speed of the injected fuel is high, there is a problem in that the scavenging air flows push the fuel into the exhaust port 26.

The present invention has been made in view of the above-mentioned conventional problems.
An object of the present invention is to prevent outflow of fuel to an exhaust port while ensuring stable ignition and combustion in a two-cycle engine in which fuel is directly injected into a cylinder.

[0009]

According to the present invention, in a two-cycle engine in which a scavenging port and an exhaust port are formed on a cylinder peripheral surface, and fuel scavenging port is provided in the scavenging port, fuel is ejected toward the top of the piston. Thus, the fuel injection means is arranged, and a guide portion for guiding the injected fuel toward the combustion chamber is formed at the portion of the piston top where the fuel is injected from the fuel injection means.

[0010]

According to the present invention, since the fuel is ejected from the fuel injection means toward the top of the piston, the heat of the piston favorably evaporates the fuel, and at the same time, the ejected fuel is guided by the guide portion to the combustion chamber. The flow of fuel toward the combustion chamber is slower than that of the scavenging air, and it is possible to reliably prevent the fuel from directly flowing to the exhaust port. It is formed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, 1 is a cylinder, 2 is a cylinder head, 3 is a combustion chamber, 4 is a spark plug, and 5 is a piston. An exhaust port 6 is provided at an appropriate position in the circumferential direction immediately above the bottom dead center of the piston 5 on the circumferential surface of the cylinder 1, and two pairs of scavenging air are provided on both sides of the direction connecting the exhaust port 6 and the center of the cylinder 1. Ports 7 and 8 are provided, and a booster port 9 is provided opposite to the exhaust port 6. These scavenging ports 7, 8 and booster port 9 communicate with a single scavenging inlet (not shown) on the side opposite to the exhaust port 6, and are connected to a scavenging pump (not shown) via this scavenging inlet. Has been done.

A fuel injection means 10 is arranged in the booster port 9 so as to inject fuel in a substantially horizontal direction toward the top of the piston 5. A projection 11 is formed on the top of the piston 5 so as to face the fuel injection means 10. The fuel injected from the fuel injection means 10 in a substantially horizontal direction is formed on the surface of the projection 11 facing the fuel injection means 10. The curved guide surface 12 is formed so as to squirt upward.

According to the above structure, when the fuel is ejected from the fuel injection means 10 in a substantially horizontal direction, the ejected fuel comes into contact with the protrusion 11 at the top of the piston 5, and the heat of the piston 5 evaporates the fuel. And the fuel injected at the same time is bent toward the combustion chamber 3 by the guide curved surface 12 and ejected, and flows toward the combustion chamber at a speed slightly slower than the scavenging air flow. An air-fuel mixture that easily ignites is formed. Thus, fuel is exhaust port 6
It is possible to surely prevent the fuel from directly flowing to the exhaust chamber, and a mixture that is easily ignited is formed in the vicinity of the combustion chamber 3. Therefore, it is possible to prevent the fuel from flowing to the exhaust port while ensuring stable ignition and combustion.

Next, another embodiment of the present invention will be described with reference to FIG. In the above embodiment, the guide curved surface 12 is formed on the top of the piston, but in this embodiment, the projection 13 is provided on the top of the piston 5 so as to face the fuel injection means 10, and the fuel injection means 10 is provided on this projection 13. Forming an L-shaped guide passage 14 through which the fuel injected in a substantially horizontal direction passes, and evaporates the ejected fuel while passing through the guide passage 14 and redirects it upward so that the combustion chamber 3
I am trying to make it squirt toward.

According to this embodiment, the direction of fuel injection can be regulated more strongly in the guide passage 14, so that the air-fuel mixture can be more reliably collected near the ignition plug 4 than in the case of the embodiment of FIG. Also, stable ignition and combustion can be secured even in lean combustion.

[0017]

According to the two-cycle engine of the present invention,
As described above, the fuel is ejected from the fuel injection means toward the top of the piston, so that the heat of the piston favorably evaporates the fuel, and at the same time, the ejected fuel is bent by the guide portion toward the combustion chamber. As a result, it is possible to reliably prevent the fuel from directly flowing to the exhaust port, and to form an air-fuel mixture that is easy to ignite in the vicinity of the combustion chamber, while ensuring stable ignition / combustion while allowing the fuel to flow to the exhaust port. Can be prevented.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an embodiment of a two-stroke engine of the present invention.

FIG. 2 is a vertical sectional view of another embodiment of the two-stroke engine of the present invention.

FIG. 3 is a vertical sectional view of a conventional two-cycle engine.

FIG. 4 is a vertical cross-sectional view of another conventional two-cycle engine.

[Explanation of symbols]

 1 Cylinder 3 Combustion Chamber 5 Piston 6 Exhaust Port 9 Booster Port (Scavenging Port) 10 Fuel Injection Means 12 Guide Curved Surface 14 Guide Passage

Claims (1)

[Claims] 1. A two-cycle engine in which a scavenging port and an exhaust port are formed on a cylinder circumferential surface, and fuel scavenging means is provided in the scavenging port, and the fuel injecting means is arranged so as to inject fuel toward the top of the piston. A two-cycle engine, characterized in that a guide portion for guiding the injected fuel toward the combustion chamber is formed at a portion of the piston top where the fuel is injected from the fuel injection means.