JPH0514088B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a scavenging control device for a two-stroke uniflow scavenging diesel engine.

[Conventional technology]

FIG. 3 shows the general structure of the upper part of the cylinder, etc. of a conventional two-stroke uniflow scavenging diesel engine.

In Figure 3, 1 is the cylinder cover, 2 is the exhaust valve, and 3
4 is a fuel injection valve, 4 is a cylinder liner, 41 is a scavenging hole, 5 is a piston, and 6 is a scavenging chamber.

Next, the operation of the conventional example will be explained.

When the piston 5 rises, the gas in the combustion chamber surrounded by the cylinder cover 1, exhaust valve, cylinder liner 4, and piston 5 is compressed and heated to a high temperature. Fuel is injected from the fuel injection valve 3, ignites, and burns. When the pressure inside the chamber increases, the piston 5 is pushed down, transmitting its work to a crankshaft (not shown), and outputting it to the outside as power.

When the piston 5 descends, the exhaust valve first opens, and the combustion gas in the combustion chamber flows out to an exhaust pipe (not shown).The pressure in the combustion chamber drops, and when the pressure in the combustion chamber 6 reaches the same level as that in the scavenging chamber 6, the piston 5 opens the scavenging hole 41 provided at the bottom of the liner. When the scavenging hole 41 opens, fresh air flows from the scavenging chamber 6 into the cylinder 4 through the scavenging hole 41, and pushes out the combustion gas to the exhaust hole for scavenging. When the piston 5 passes through the bottom dead center and rises again to close the scavenging hole 41, the inflow of fresh air ends and the scavenging ends.

FIG. 4 shows an example of this scavenging hole 41, and the scavenging hole 41 is oriented eccentrically with respect to the axis of the cylinder 4 so as to give an appropriate swirl to the flow of scavenging air.

In the example shown in the figure, there is a case where the inflow angles at the upper and lower parts of the scavenging hole 41 are different, such as θ _ST and θ _SB (θ _ST upper part>θ _SB lower part).

As a result, the strength of the swirling flow is changed by the piston 5 in the cylinder depending on whether the opening of the scavenging hole 41 is only at the upper part or when all the holes are open, improving the scavenging efficiency and the combustion efficiency during combustion. is running.

[Problem that the invention seeks to solve]

Although the above-described structure improves the scavenging efficiency and combustion efficiency, the area and inlet angle of the scavenging hole remain constant regardless of the rotational speed and load of the engine.

For this reason, even in areas where the air flow rate is low during partial loads, the scavenging holes are wide open and the strength of the swirl remains unchanged.

Therefore, the scavenging efficiency is insufficient, and moreover, the air utilization rate for combustion does not increase, and combustion often deteriorates.

In other words, in order to improve the efficiency of an engine, it is necessary to have an appropriate scavenging area and swirl strength for the load, rotational speed, and outside air conditions, and in general, partial loads have the disadvantage of not being able to handle the need for strong swirl. .

An object of the present invention is to provide a scavenging control device for a uniflow scavenging internal combustion engine that eliminates the drawbacks of the conventional device and can achieve high performance over a wide range.

[Means for solving problems]

The scavenging control device for a uniflow scavenging internal combustion engine according to the present invention is such that the inflow angle of the scavenging hole is large at the top and small at the bottom, and the scavenging area is reduced by closing from the bottom during partial load. At the same time, the swirl strength is increased and made variable to suit the load and rotational speed, thereby achieving the above object.

〔Example〕

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

In the figure, 4 is a cylinder liner, 41 is a scavenging hole, and _the variable _swirl device 7 is similar _{to FIG .} The variable swirl device 7 is provided with a scavenging hole inlet area control section 71 that opens and closes the scavenging hole by partially covering the scavenging hole. Reference numeral 72 denotes a drive unit of the variable swirl device 7, 73 a claw thereof, and 74 a motor for moving the claw 73 from side to side.

In the case shown in the figure, the variable swirl device 7 has a groove provided at the lower part of the scavenging hole 41 of the cylinder liner 4, and is configured to fit into this groove and be slidable, so that the outer circumference of the cylinder can be rotated. .

Next, the operation of the above embodiment will be explained.

FIG. 2 shows three positional relationships when the variable swirl device 7 is operated.

FIG. 2a shows the position of the swirl control devices 7, 71 when the engine output is in the normal output or high load range, and exhibits the same performance as the conventional device shown in FIG. 4.

In FIG. 2b, the variable swirl device 7 is moved to the left by the motor 74 and the drive device 72, and the scavenging hole 4 is moved to the left by the motor 74 and the drive device 72.
1 is partially covered by the area control section 71. In this state, the scavenging hole 4
1, the flow rate increases in the portion with a large swirl generation ability, and the swirl becomes stronger.

In Fig. 2c, the variable swirl device 7 is moved further to the left, and the lower area of the scavenging hole 41 is covered further by 71, and the area of the upper part where the inflow angle is large is increased, and a strong swirl of scavenging air is generated. Obtainable.

As described above, by appropriately controlling the swirl control device in the low-speed, low-load and low-speed, high-load ranges according to the engine load and rotational speed conditions, an appropriate scavenging hole area and scavenging swirl can be obtained. I can do it.

〔Effect of the invention〕

As mentioned above, the scavenging air control device for a uniflow scavenging internal combustion engine of the present invention strengthens the swirl to improve scavenging efficiency in the low power range where the amount of air used is smaller than when the load is high, and also improves the combustion efficiency by strong swirl. As a result, a two-stroke uniflow scavenged internal combustion engine with high combustion efficiency can be realized over a wide range of areas.

[Brief explanation of the drawing]

FIG. 1a is a front view of a scavenging control device for a two-stroke uniflow scavenging internal combustion engine according to the present invention;
Figure b is a sectional view taken along line A-A in Figure 1a, Figure 2 is an explanatory diagram of the operation of the scavenging control device, Figures 3 and 4 are conventional examples, and Figure 3 is a longitudinal cross-section of a two-stroke uniflow scavenged diesel engine. 4A is a front view of the cylinder liner, and FIG. 4B is a sectional view taken along line BB in FIG. 4A. 4... Cylinder, 41... Scavenging hole, 7, 71... Scavenging control device, 72, 73, 74... Drive device.

Claims (1)

[Claims] 1. In a two-stroke uniflow scavenging internal combustion engine, a uniflow scavenging system is provided in which a swirl control device that partially opens and closes the scavenging hole from the bottom of the hole is rotatably and slidably attached to the outer circumference of the cylinder, and a drive device that drives the control device. Scavenging control device for internal combustion engines.