JPH0261364A - Fuel feeding device for two-cycle engine - Google Patents

Abstract

PURPOSE:To improve ignition performance by temporarily sending the jetted fuel and the fuel adhering on a fuel adhesion device under pressure into a combustion chamber by supplying the high pressure air into the upstream side of the fuel adhesion device by opening an air valve when the scavenge cycle proceeds by a certain degree, in the scavenge cycle. CONSTITUTION:An auxiliary scavenge port 21 is opened, directed towards a spark plug 8, onto the wall surface opposed to an exhaust port 7 on the inner wall of a cylinder 4, and a mixed gas nozzle 23 is opened, similarly directed towards the spark plug 8, into an auxiliary scavenge passage 22 connected with the auxiliary scavenge port 21. In the mixed gas nozzle 23, a fuel holding device 23c made of porous material is installed into a fuel passage 23b continuous to a frame body 23a, and a fuel nozzle 24 is screwed inside, and an air nozzle 25 is screwed outside. After the start of a scavenge cycle in which a piston 6 reaches a top dead center, the fuel nozzle 24 and the air nozzle 25 are opened nearly at the same time, and the jetted fuel and the fuel adhering on the fuel holding device 23c in the preceding cycle are splashed away by the pressurized air, and the gas is jetted as mixed gas towards the spark plug 8.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention provides a fuel injection port that opens toward the combustion chamber in the scavenging path of a two-stroke engine, and adjusts the supply timing of the air-fuel mixture supplied from the injection port to the combustion chamber. The present invention relates to an improvement in a device that prevents air-fuel mixture from blowing through in a low-load operating range by changing the device depending on the load state.

[Conventional technology]

Conventionally, in order to prevent this so-called atrium, in which part of the scavenging air is directly discharged from the exhaust port without contributing to combustion, a fuel injection device is installed in the auxiliary passage, and after the scavenging stroke has progressed, a fuel injection device is installed in the combustion chamber. There is a known technique to prevent fuel from being included in the scavenging air flow that quickly flows into the combustion chamber by injecting fuel towards the combustion chamber.
(Japanese Patent Publication No. 58-36183, etc.).

In addition, it is known that a part of the scavenging passage is provided with a honeycomb structure to prevent a part of the scavenging air flow from flowing back into the crank chamber (for example, Japanese Patent Publication No. 58-36183).
0 [Problem to be solved by the invention] However, in a device in which fuel is supplied from a fuel injection device installed in a scavenging passage after the scavenging stroke has progressed to a certain extent, the amount of fuel is increased by the amount of fuel injection that is delayed. In a two-stroke engine, fuel needs to be supplied for each revolution of the crankshaft, so as the engine load increases and the amount of fuel required increases, the scavenging port closes. Fuel injection cannot be completed during the open period. That is, if the amount of fuel to be injected is simply increased, the fuel particles to be sprayed will become coarser and will be more likely to be exhausted without being completely burned during the combustion stroke.

[Means to solve the problem]

The purpose of the present invention is to eliminate such problems and provide a device that prevents fuel from blowing through by supplying a large amount of fuel particles from the scavenging port into the combustion chamber in a relatively short period of time. In a two-stroke engine with an exhaust port and a scavenging port opened in the side wall, a fuel injection port that opens toward the top of the combustion chamber is provided in the scavenging port, and a portion of the fuel is deposited in a fuel passage connected to the fuel injection port. A fuel depositor made of a porous material of fc size is provided, and a pressurized air passage is connected to the fuel passage upstream of the fuel depositor and can be freely communicated with or shut off by an air valve, and after the start of the scavenging stroke, the air valve The valve is set to open.

[For production]

As shown in Figure 3, the scavenging stroke begins when the piston descends and the scavenging port opens. When the air valve opens after the scavenging stroke has progressed to a certain extent, high-pressure air is supplied to the upstream side of the fuel depositor. The fuel being injected from the fuel injection device and the fuel adhering to the fuel adhering device are simultaneously pumped into the combustion chamber.

〔Example〕

The present invention will be explained below with reference to the illustrated embodiments. In the figure, 1 indicates a two-stroke engine with precompression in the crank chamber;
is its crank chamber, and 3 is its combustion chamber. The combustion chamber 3 is formed by a cylinder 4, a cylinder head 5 and a piston 6. T is an exhaust port, and 8 is an ignition plug provided in the cylinder head. Reference numeral 9 denotes an intake passage, which is provided with a check valve 10 that only allows airflow into the crank chamber and a manual main throttle valve 11 that adjusts the intake flow rate. In this embodiment, the intake passage 9 is not provided with a carburetor or other fuel supply device, but a device that generates a leaner air-fuel mixture than auxiliary scavenging, which will be described later, may be provided. Further, the reversal valve 10
Instead, it is also possible to use a so-called piston valve in which the skirt portion of the piston 6 opens and closes an intake port provided in the cylinder.

Main scavenging air ports 12 are opened symmetrically on both sides of the exhaust lower and are connected to the crank chamber 2 through a main scavenging passage 13. Note that the above configuration is similar to the conventionally known configuration.

In this invention, the concave surface of the cylinder head 5 forming the combustion chamber 3 has a shallow spherical shape as a whole, and a deep hemispherical ignition recess 5a is formed in a part of the concave surface toward the exhaust port T side, which will be described later. Eight electrodes are placed facing the center. As shown in this embodiment, the combustion recess 5 is provided offset from the center of the cylinder 4 hole and toward the exhaust port γ side, and its diameter in a plan view is set to approximately half the cylinder diameter.

On the inner wall of the cylinder 4 constituting the combustion chamber 3, an auxiliary scavenging port 21 with a relatively small area is opened on the wall surface facing the exhaust lower and is oriented toward the spark plug 8. A mixture nozzle 23 is similarly opened in the scavenging passage 22 and oriented toward the spark plug 8 .

As shown in FIG. 1, the mixture nozzle 23 is fitted into a frame 23m attached to the cylinder 4, and a fuel passage 23b connected to the frame 23m is made of wire mesh, a sintered body, a honeycomb structure, or the like. A fuel retainer 23e made of porous material is provided. In this embodiment, the fuel retainer 23c uses an emulsion pipe used for air bleed of a carburetor as a substitute for the wire mesh. A fuel nozzle 24 of a conventionally known electronic fuel injection device is screwed onto the inside of the emulsion tube, and an air nozzle 25 having a similar structure is screwed onto the outside. 26 is the fuel tank, pump 2
It is connected to the fuel nozzle 24 via T. 28 is a relief valve for keeping fuel pressure constant. Similarly, the air nozzle 25 includes a filter 29 and an air pump 3.
0 and a relief valve 31 are provided. Note that 32 is an accumulator.

Next, the operation of this engine will be explained. When the engine is operated, fresh air is sucked into the crank chamber 2 during the upward stroke of the piston 6.

When the piston 6 reverses and descends and the exhaust port T and main scavenging port 12 open sequentially, the burnt gas in the combustion chamber 3 is ejected from the exhaust port T into the exhaust passage, and in an instant, the inside of the combustion chamber 3 is It becomes negative pressure. At the same time, the fresh air in the crank chamber is forced into the combustion chamber as a scavenging air flow, and the burnt gas remaining there is pushed out from the exhaust lower.

During low-load operation, the main scavenging airflow is generally weak, and most of it remains near the surface of the piston 6, and is sufficient to scavenge the burnt gas that remains in the upper part of the combustion chamber.
When the fuel nozzle 24 and air nozzle 25 reach the bottom dead center,
The cylinder opens at the same time as the fuel is injected, and compressed air is supplied at the same time as the fuel is injected.The injected fuel and the fuel that was injected during the previous stroke and that had adhered to the fuel retainer 23c are blown away by the pressurized air, forming the mixture. This is injected from the air-fuel mixture nozzle 23 and becomes a thin, high-speed air stream that is ejected from the auxiliary scavenging boat 21 toward the spark plug 8. The flow of this air-fuel mixture breaks through the main scavenging air and burnt gas layer floating above the piston 6 at high speed and reaches the combustion recess 3 & near the spark plug 8. At the end of the subsequent compression stroke, the air-fuel mixture flows into the vicinity of the spark plug 8. form a layer.

FIG. 3 shows the opening timings of the fuel nozzle 24 and the air nozzle 25. In other words, when the engine load increases,
As shown by the two-dot chain line in the figure, the operating times of the fuel nozzle 24 and the air nozzle 25 increase, but only the air nozzle 25 is closed at the same time or before the piston rises and closes the scavenging port.

In this way, as the load increases, the fuel adheres to the fuel retainer 23a to which fuel is supplied from the fuel nozzle 24 even when the scavenging port is closed, and is retained for the next stroke. Therefore, according to the present invention, A predetermined amount of fresh air is always prepared near the spark plug 8, so when the spark plug 8 ignites, stable ignition is obtained, and the flame spreads stably and rapidly into the combustion chamber, preventing irregular combustion. It can be prevented.

〔Effect of the invention〕

As described above, the fuel supply system for a two-stroke engine according to the present invention reliably supplies a certain amount of fresh air to the vicinity of the ignition plug even when the load on one engine is small, thereby ensuring that ignition occurs reliably. There is no risk of irregular combustion. Additionally, even if the load on the engine increases and the amount of fuel to be supplied from the fuel injection device increases, it is possible to supply the necessary amount of fuel in a relatively short time and without worsening fuel atomization. be.

[Brief Description of the Drawings] The drawings show one embodiment of the present invention, and FIG.
FIG. 2 is a sectional view of the engine, and FIG. 3 is a pulp diagram. 5a...Fist/ignition recess, 21/Kobe/auxiliary scavenging bow), 23/Φ...Mixture mixture nozzle, 23c...ms fuel holder, 24...Fuel nozzle, 25Φ...Air nozzle. Patent applicant Yamaha Motor Co., Ltd.

Claims (1)

[Claims] In a two-stroke engine in which an exhaust port and a scavenging port are opened in the side wall of the cylinder, a fuel injection port that opens toward the upper part of the combustion chamber is provided in the scavenging port, and a portion of the fuel is injected into the fuel passage connected to the fuel injection port. A fuel depositor made of a porous material for depositing is provided, and a pressurized air passage located in the fuel passage on the upstream side of this fuel depositor and which can be freely communicated and shut off by an air valve is connected to the fuel depositor, and after the start of the scavenging stroke, A fuel supply system for a two-stroke engine, the air valve being set to open.