JPS6025601B2 - Two-stroke engine using liquefied fuel gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a two-stroke engine that uses liquefied natural gas (LNG) or propane gas (LPG) as fuel.

When liquefied natural gas or propane gas is used as an engine fuel, it quickly vaporizes due to pressure reduction or heating, so there is no need for a special atomization device like in the case of liquid fuels such as gasoline. Fuel can be supplied at the required pressure using only the flow control device.

The present invention provides means for easily performing stratified air supply in a two-stroke engine using cinnular scavenging by taking advantage of such characteristics of liquefied fuel gas.

Further, the present invention provides a two-stroke engine that does not emit hydrocarbons due to fuel gas blow-through and is extremely simplified in structure.

The present invention will be described in more detail with reference to the drawings.
2 and 2 show an example of a two-stroke engine to which the present invention is applied, in which a cylinder 1 is installed on cylinder side walls la, la on both sides of an exhaust hole 2 provided in the example, and a cylinder facing the exhaust hole 2 A scavenging hole 3i3 is provided for ejecting a scavenging air flow toward the wall lb, and the cylinder wall lb is provided with a fuel gas hole 3i3 that opens toward the top dead center of the position where the exhaust hole 2 is closed by the piston 4. The ejection holes 5 are oriented and installed so that the fuel gas flows between the cylinder wall lb and the scavenging air flow along it in the same direction as the scavenging air flow to form a flow (dashed line arrow) toward the ignition plug 6.

As the air pump connected to the scavenging holes 3, 3 in order to form the striped airflow, a separate external air pump 7 is used instead of the crankcase compression pump, and the fuel gas jet A liquefied fuel gas cylinder 10 is connected to the hole 5 via a check valve 8 for preventing backflow of fuel gas and a flow control valve 9 that can control the flow rate of fuel gas depending on the load and the like.

The check valve 8 prevents the high-pressure fuel gas in the cylinder from flowing backward, and at the same time opens when the cylinder internal pressure decreases to automatically supply fuel gas into the cylinder. The pressure is set so that it can be ejected by balancing with the cylinder internal pressure before and after the time when the exhaust hole closes in the compression stroke, that is, after blowdown. In the two-stroke engine having the above-mentioned configuration, when the piston 4 is filled with fuel in the cylinder 1, the fuel gas injection hole 5 first closes inside the cylinder, but at this point, the pressure inside the cylinder is high, so the check valve is closed. 8 prevents backflow of fuel gas.

When the piston 4 moves further down and the exhaust hole 2 opens, the pressure inside the cylinder 1 decreases rapidly, and therefore the check valve 8
The check valve 8 begins to open depending on the balance between the pressure of the fuel gas supplied through the cylinder 1 and the pressure inside the cylinder 1, but the fuel gas is mainly supplied around the time when the exhaust hole 2 closes. Further, the fuel gas flows in the same direction as the cotton air flow between the cylinder wall lb facing the exhaust hole and the scavenging air flow along it, forming a flow toward the ignition plug. Coupled with the fact that the supply timing is mainly before and after the closing time of the exhaust hole 2, there is no blow-through of fuel gas, and the discharge of hydrocarbons is suppressed. After the exhaust hole 2 is closed, fuel gas leaks through the check valve 8 while the pressure inside the cylinder is low, but when the pressure inside the cylinder 1 increases or the piston 4
The supply of fuel gas is stopped by blocking the fuel gas injection hole 5.

Further, when driving such a two-stroke engine, the amount of fuel gas supplied to the cylinder 1 is adjusted by a flow rate control valve 9 that is controlled according to the load and the like.

In such a two-stroke engine of the present invention, the following effects can be expected.

{11 The position of the fuel gas injection hole and the timing of the fuel gas injection allow for stratified air supply, which ensures the supply of the air-fuel mixture to the spark ignition gap and enables stable combustion.

'21 The fuel gas forms a flow towards the spark plug through the cylinder wall and the scavenging air flow along it, and the fuel gas is ejected before and after the exhaust hole closes, eliminating the blow-through of the fuel gas and reducing carbonization. Hydrogen emissions can be suppressed.

{3} A check valve is installed in the fuel gas injection hole, and the fuel is injected based on the balance between the injection pressure and the Schilling internal pressure before and after the time when the exhaust hole closes during the compression stroke. As such, there is no need to synchronize with the movement of the piston and drive at the required timing.
Fuel injection can be performed automatically based on changes in cylinder internal pressure as the engine is driven.

'4- The flow control valve that controls the ejection of fuel gas has a much simpler structure with respect to temperature and pressure than commonly used overhead injection valves, etc. can do.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an outline of a two-stroke engine according to the present invention, and FIG. 2 is a cross-sectional view of its cylinder. 1...Cylinder, la...Cylinder side wall, lb...Cylinder wall, 2...Exhaust hole,
3...Scavenging hole, 4...Piston, 5...
... Fuel gas nozzle, 6... Spark plug, 7...
...Air pump, 8...Check valve, 9.
...Flow control valve, 10...Liquid fuel gas pump 10 Fig. 1 Fig. 2

Claims (1)

[Claims] 1 A scavenging hole is provided in the cylinder side wall on both sides of the exhaust hole provided on one side of the cylinder to eject a scavenging air flow toward the cylinder wall facing the exhaust hole, and the cylinder wall facing the scavenging hole is provided with The fuel gas flows through the fuel gas injection hole, which opens closer to top dead center than the position where the exhaust hole is closed by the piston, between the cylinder wall and the scavenging air flow along it, in the same direction as the scavenging air flow, and flows toward the ignition plug. A liquefied fuel gas cylinder is connected to the fuel gas injection hole through a check valve and a flow rate control valve to prevent backflow of fuel, and the injection pressure of the fuel is adjusted to determine when the exhaust hole closes during the compression stroke. A two-cycle engine using liquefied fuel gas, characterized in that the fuel gas is set to be able to be injected depending on the balance between the cylinder internal pressure before and after the injection.