JPH0225026B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention belongs to the technical field of a fuel supply system for a two-stroke engine, and its prerequisite structure is a mixing passage that forms an air-fuel mixture and supplies it to the crank chamber, and an air supply system that supplies air to a scavenging passage. A passage is formed in the mixer, and an opening/closing valve is provided in the air passage that opens and closes in conjunction with the throttle valve of the mixing passage, and the air supplied from the air passage to the scavenging passage is combusted before the mixture from the crank chamber. The present invention relates to a fuel supply device for a two-stroke engine that scavenges air by injecting it into a chamber.

Conventionally, this type of apparatus has been constructed as shown in FIG.

That is, a mixer 24 provided between the engine 3 and the air cleaner 26 is provided with a mixing passage 28 that mixes clean air from the air cleaner 26 and fuel sucked out from the fuel supply source 25 and supplies the mixture to the crank chamber 8.
An air passage is provided at the bottom of the mixing passage 28 for supplying clean air from the air cleaner 26 as it is to the scavenging passage 22, and a throttle valve 32 of the mixing passage 28 is also provided.
The air passage 29 has a structure in which an opening/closing valve 34 interlocked with the air passage 29 is provided.

However, in such a case, the throttle valve 3
2, the amount of air flowing through the mixing path 28 increases in a sinusoidal manner as shown by the solid line W in FIG. 4A, and the amount of fuel sucked out increases accordingly. The concentration of air tends to be denser on the heavy load side and thinner on the no load side.

Therefore, in general, as shown in Figure 4B, the mixture concentration is set to be appropriate between heavy load and light load, so the mixture concentration is lean between light load and no load. As a result, from light load to no load, the rotational torque decreases, resulting in insufficient engine output and the rotational speed becoming unstable.

The present invention provides an air amount limiting valve in the air passage, fully opens this air amount correction valve under light load,
It closes as the load changes from light to no load, and when there is no load, it closes completely to block air flowing through the air path, increasing the amount of air flowing through the mixing path,
This prevents the concentration of the mixture from decreasing due to insufficient amount of air flowing through the mixing path.

The present invention is configured and operates as described above, and thus has the following effects.

In other words, as the load changes from light load to no load, the throttle valve closes and the amount of air in the intake path decreases, reducing the amount of fuel sucked out and making the mixture leaner. This increases the amount of air flowing through the intake passage and prevents the concentration of the mixture from decreasing.

As a result, the concentration of the air-fuel mixture supplied to the engine can be kept constant, so the rotational torque increases under light load or no-load conditions, the output increases, and the rotational speed of the engine can be stabilized.

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows a schematic front view of a heat pump unit for air conditioning.

This heat pump unit 1 includes a water-cooled two-stroke engine 3 and a compressor 4 driven by the water-cooled two-stroke engine 3 inside a soundproof case 2. A condenser 5 is provided in front of the compressor 4, and an evaporator 6 for cooling intake air is provided above the compressor 4. The refrigerant compressed by the compressor 4 is cooled and liquefied by the condenser 5, and then
Heat is exchanged in an evaporator 6 installed outside the soundproof case 2, and the heat is exchanged with the intake air cooling evaporator 6, where the heat is exchanged again to cool the intake air of the engine 3. This is designed to prevent a decrease in output due to a decrease in the filling efficiency of the intake air of the engine 3 due to an increase in temperature of the intake air.

As shown in FIG. 2, this engine 3 has a cylinder block 11 above a crankcase 10 in which a crankshaft 9 is rotatably supported in a crank chamber 8.
At the same time, the cylinder block 11 is placed and fixed.
A cylinder head 12 is fixed above, and a combustion chamber 13 is formed on the lower surface of the cylinder head 12.

A piston 15 connected to the crankshaft 9 by a connecting rod 14 is housed in the cylinder block 11 so as to be vertically slidable. Also, piston 1
There is an exhaust port 1 on the inner circumferential surface 16 of the cylinder on which the cylinder 5 slides.
7. A scavenging port 18 and an intake port 19 are opened in order from the top, and each of these openings 17, 18, 19 is in the form of a so-called piston valve that is opened and closed by the vertical movement of the piston 15.

The exhaust port 17 is connected to a muffler 21 through an exhaust path 20, the scavenging port 18 is connected to the crank chamber 8 through a scavenging path 22, and the intake port 19 is connected to a mixer 24 through an intake path 23. be.

The mixer 24 sucks fuel gas from the gas supply source 25 by the pumping action of the engine 3.
It is mixed with clean air from an air cleaner 26 attached to the front of the engine 3 and supplied to the crank chamber 8 of the engine 3, and its internal structure is as shown in FIG.

That is, the mixer 24 has a large diameter mixer 28 in its casing 27 that communicates with the intake passage 23, and a scavenging passage 22.
They are arranged above and below the air passage 29 leading to the air passage 29 and run back and forth.

A bench lily portion 31 from which a fuel nozzle 30 projects is formed at the front end of the mixing passage 28, and a valve shaft 33 for opening and closing a throttle valve 32 is supported through the rear end end thereof.

This valve shaft 33 passes through a portion near the rear end of the air passage 29, and the portion of the valve shaft 33 that passes through the air passage 29
3 is equipped with an on-off valve 34.

An air amount limiting valve 35 that limits the amount of air flowing through the air path 29 is provided near the front half of the air path 29. Opening and closing operations are performed by a solenoid 37 that is limited by a throttle valve opening sensor 36 provided, and the full opening amount is set by an adjustment screw 41.

The throttle valve opening sensor 36 fully opens the air amount limiting valve 35 in the air passage 29 when the throttle valve 32 is open between a heavy load and a light load. When the solenoid 37 is operated toward no-load and becomes closed, the solenoid 37 is controlled so that the air amount limiting valve 35 is fully closed under no-load.

The operation of the fuel limiting device for a two-stroke engine configured as described above will now be described.

First, when the engine 3 is operated between a heavy load and a light load, the throttle valve 32 is opened relatively wide, so that a large amount of air flows through the mixing passage 28, and a large amount of air flows from the fuel gas source 25. This fuel is sucked out and a mixture of appropriate concentration is supplied to the crank chamber 8.

Then, during light load to no-load operation when the throttle valve 32 tends to close, the amount of air flowing through the mixing passage 28 decreases, and the amount of fuel sucked out further decreases, so that the concentration of the mixture becomes the appropriate concentration (the fourth It tends to become thinner than the dotted line Y) in Figure B. At this time, the air amount limiting valve 35 in the air passage 29 closes to a greater extent than the closing amount of the throttle valve 32 to limit the air amount in the air passage 29, so the amount of air flowing through the mixing passage 28 increases accordingly. , the fuel is sufficiently sucked out to prevent the concentration of the air-fuel mixture from decreasing (see the dot-dashed line X in FIG. 4B).

In addition, the reference numeral 39 in the figure indicates a check valve device, and this device 39 is connected to the mixing passage 28 in front of the throttle valve 32.
The reed valve 40 is provided diagonally across the air passage 29, and the reed valve 42 is provided diagonally across the air passage 29 in front of the opening/closing valve 34 of the air passage 29. This is to improve the filling efficiency of intake air.

[Brief explanation of drawings]

Figure 1 is a schematic front view of an air conditioning heat pump unit, Figure 2 is a vertical side view of a water-cooled two-stroke gas engine, Figure 3 is a vertical side view of the main parts, and Figures 4A and B are for each load operation. A graph showing the relationship between fuel supply amount and mixture concentration, FIG. 5, is a diagram corresponding to FIG. 2 showing a conventional example. 8...Crank chamber, 13...Combustion chamber, 28...
Mixing path, 29...Air path, 32...Throttle valve, 34...Opening/closing valve, 35...Air amount limiting valve.

Claims (1)

[Claims] 1 A mixing passage 28 that forms a mixture and supplies it to the scavenging passage 22; and an air passage 29 that supplies air to the combustion chamber 13;
In a fuel supply device for a two-stroke engine, the air passage 29 is provided with an opening/closing valve 34 that opens and closes in conjunction with a throttle valve 32 of the mixing passage 28, and an air amount limiting valve 35 is provided in the air passage 29; The air amount limiting valve 35 is configured to open at light load and close as the load changes from light load to no load, thereby reducing the amount of air flowing through the air path 29 and increasing the amount of air flowing through the mixing path 28. A fuel supply device for a two-stroke engine, characterized by: