JPH0417718A - Uni-flow type two cycle internal combustion engine - Google Patents

Abstract

PURPOSE:To reduce the quantity of scavenging air blowing through a cylinder by providing an air in-take hole, which communicates a scavenging chamber in the top section of a liner and an opening and closing valve on the outer periphery of the scavenging hole. CONSTITUTION:In a 2 cycle uni-flow type internal combustion engine, an air in-take hole 51 communicating to a scavenging chamber 10 is provided to the portion upper than the scavenging hole 14 of a liner 20. In addition, an opening and closing control valve 52 is provided on the outer periphery of the air in-take hole 51. Since owing to this constitution, an exhaust valve 32 closes at nearly the same time as a crank angle at the time when a scavenging hole 11 closes, the scavenging air blowing through a cylinder 21 becomes little, as a result, the temperature of exhaust air is raised. Thus, utilization factor of the heat of exhausted air is improved.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a uniflow two-stroke internal combustion engine.

[Conventional technology]

FIG. 5 shows the scavenging and exhaust system of a conventional two-stroke uniflow scavenging engine. Scavenging air in the scavenging chamber 10 flows into the cylinder 21 through the scavenging hole 11 provided in the liner 20, and is discharged through the exhaust passage 31 from the exhaust valve 32 provided in the cover 30.

The exhaust valve 32 is opened and closed by hydraulic pressure 35 from a hydraulic pump connected to a camshaft (not shown).

FIG. 6 shows the opening area of the scavenging hole 11 and the scavenging valve 32, which are opened and closed by the piston 13, with respect to the crank angle.

The exhaust valve 32 opens and closes at the crank angle E1, and the scavenging hole 11 begins to open at the crank angle S1.

After the bottom dead center (BCD) of the piston 13, the scavenging hole 11 closes at S2, and the exhaust valve 32 closes at E2.

FIG. 7 shows the fluctuating flow rate of the scavenging hole section and the exhaust valve section corresponding to FIG. 6. In FIG. 7, the exhaust valve 32 begins to open at a crank angle E, and the exhaust gas flows from the cylinder 21 to the exhaust 111.
Stop the leak to 31. After that, the scavenging hole 11 opens at S, and the scavenging air in the scavenging chamber 10 begins to flow into the cylinder 21. After that, the exhaust gas is discharged and the scavenging air is inflowed at the same time.
After the scavenging hole 11 closes at S2 and scavenging ends, the exhaust gas continues to flow out until E2.

In order to delay the start of compression by the piston 13 in the cylinder 21, E2 is set after S2.

[Problem to be solved by the invention]

In the conventional example, in the hatched portion between S2 where the scavenging hole closes and R2 where the exhaust valve closes in FIG. It turns out. As a result, the amount of scavenging air that blows through cylinders that are not involved in combustion increases, resulting in a decrease in the utilization rate of exhaust heat, resulting in power loss and a problem of lowering the thermal efficiency of the engine.

SUMMARY OF THE INVENTION An object of the present invention is to provide a uniflow two-stroke internal combustion engine that solves the problems of the conventional apparatus, reduces scavenging air flowing through the cylinder, increases exhaust temperature, and improves exhaust heat utilization.

[Means to solve the problem]

The uniflow type two-stroke internal combustion engine of the present invention has a bleed hole communicating with the scavenging chamber above the scavenging hole of the liner, so that the exhaust valve closes earlier and the bleed hole closes the same as the conventional exhaust valve. Make it.

[Operation] By speeding up the closing and closing of the exhaust valve, the outflow of scavenging air through the exhaust valve is reduced, the exhaust gas temperature is increased, and the utilization rate of exhaust heat is improved.

Furthermore, in this embodiment, since the bleed hole is open even after the exhaust valve is closed, the working gas in the cylinder is bled from the bleed hole to the scavenging chamber, and the timing at which compression by the piston starts can be delayed.

Since this air bleed hole is provided above the liner's scavenging hole, most of the bleed air is scavenging air that has once flowed into the cylinder, and the proportion of residual exhaust air in the bleed air is small, so there is little contamination of the scavenging air chamber due to bleed air. .

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

Figure 1 is an overall system diagram of the present invention, and Figure 2 is the n of Figure 1.
-n sectional view, FIG. 3 is an opening area diagram of the scavenging hole, exhaust valve, and bleed hole, and FIG. 4 is a fluctuating flow rate diagram for scavenging and exhausting.

In the present invention, a bleed hole 51 is provided above the scavenging hole 11 of the liner 20.
Further, a control valve 52 is provided outside the bleed hole 51. Further, the scavenging hole 51 communicates with the scavenging chamber 1°.

As shown in FIG. 2, a control valve 52 having a control hole 53 corresponding to the bleed hole 51 is rotated by a hydraulic pressure 54 generated by a camshaft (not shown) in the same way as the exhaust valve 35, and opens and closes the bleed hole 51. ing.

In FIG. 3 showing the opening areas of the scavenging hole 111, the exhaust valve 32, and the bleed hole 51, when the exhaust valve 32 opens at a crank angle E1, exhaust gas flows out into the exhaust pipe.

Thereafter, when the scavenging hole opens at crank angle SI, scavenging air in the scavenging chamber 10 flows into the cylinder 21, and exhaust gas outflow and scavenging air inflow into the cylinder occur simultaneously. Next, the exhaust valve 32
and the scavenging hole 11 are closed at substantially the same crank angles E3 and 32, respectively.

Therefore, unlike the conventional example, the scavenging air blowing through the cylinder is reduced. The bleed hole 51 begins to open at crank angle R2 before the scavenging hole 11 is closed by the control valve 52, and closes at R2 after the exhaust valve 32 closes. At this time, the flow of each part is as shown in FIG.

After the bottom dead center BDC, the scavenging hole 11 and the exhaust valve 32 are closed at the same crank angles Sz and E*, respectively, and then a part of the scavenging air is extracted from the open bleed hole 51 and the scavenging air chamber 1
Since the value is returned to 0, the time at which compression begins will not be delayed. After the bleed hole 51 is closed, compression within the cylinder 21 is started.

〔Effect of the invention〕

The uniflow two-stroke internal combustion engine of the present invention is configured as described above, and the exhaust valve 32 closes at approximately the same timing E3 as the crank angle S2 at which the scavenging hole 11 closes, so that the cylinder 21
There is less scavenging air blowing through the exhaust gas, raising the exhaust temperature and improving the utilization rate of exhaust heat. Furthermore, since the bleed air hole is provided above the scavenging hole, the bleed air is only scavenging air that has once flowed into the cylinder. As a result, the proportion of residual exhaust gas in the bleed air is small, and the scavenging chamber is less contaminated by the bleed air.

[Brief explanation of the drawing]

1 to 4 are related to the present invention. FIG. 1 is a sectional view of the main part of the first embodiment, FIG. 2 is a sectional view taken along the line n-■ in FIG.
The figure shows the opening area of the scavenging hole, exhaust valve, and bleed hole. Figure 4 shows the fluctuating flow rate of scavenging and exhaust. ...Liner, 1...Cylinder, 0...Cylinder head, 2...Exhaust valve, 1...Bleed hole, 2...Control outlet valve. fig fig fig fig fig fig fig fig fig fig fig fig fig fig fig fig fig fig fig fig fig fig.

Claims (1)

[Claims] A two-stroke uniflow internal combustion engine, characterized in that a bleed hole communicating with a scavenging chamber is provided above the scavenging hole of a liner, and an opening/closing control valve is provided around the periphery of the bleed hole.