JPH0323740B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cylinder liner that improves the scavenging efficiency of a uniflow two-cycle engine.

Figure 1 shows a uniflow scavenging two-stroke engine, where 1 is a cylinder liner, 2 is a scavenging hole, 3 is a cylinder, 6 is a piston, 7 is a cylinder jacket,
8 is a cylinder cover, and 9 is an exhaust valve.

Scavenging hole 2 of a normal uniflow 2-cycle engine
As shown in FIGS. 2 to 4, scavenging holes 2 are arranged in the lower circumferential wall of the cylinder liner 1, and the combustion gas in the cylinder 3 is expelled upward in the axial direction by fresh air flowing in through the scavenging holes 2 to cause combustion. Replace it with the fresh air you need. The scavenging hole 2 is bored at its lower edge 2a so that its center line 5 is exactly facing the cylinder center 4, and while maintaining that direction, it is opened toward the upper edge 2b in the swirl S direction as shown in FIG. Perforated at an angle. Therefore, as shown in FIG. 4, the scavenging hole upper edge 2b is bored eccentrically from the cylinder center 4 by a radius R. Therefore, the air flowing into the cylinder 3 flows toward the cylinder center 4 below the scavenging hole 2, but is given a swirl S in the horizontal direction above.

In the case of such a scavenging hole 2, the flow of the scavenging hole in the cylinder 3 is as shown in Fig. 5a, and in the figure A,
The combustion gas from the previous cycle remains without being completely cleaned in parts B, C, and D. Part A in particular has a large volume and is an important factor that impedes scavenging efficiency. This part A is a region where the flow is relatively stable, and the larger the pressure difference between the inside and outside of the cylinder 3, the larger its volume becomes. Therefore, in engines with high scavenging pressure, it is essential to eliminate this part.

The method to remove the remaining gas in part A is as follows:
The eccentric angle when the upper edge 2b of the scavenging hole 2 faces the center of the cylinder 3 is increased. That is, as shown in FIG. 3, a method can be considered in which the upper edge 2b of the scavenging hole 2 is largely tilted in the swirl direction. However, if this method is carried out according to the conventional concept of the scavenging hole 2, the slope of the scavenging hole wall 2c shown in FIG. However, there is a drawback that the area of the scavenging hole 2 is insufficient.

However, as mentioned above, as is clear from the conventional example shown in FIG.
If the lower edge 2a of the scavenging hole 2 is bored so as to face the cylinder center 4, and the upper edge 2b of the scavenging hole 2 is bored eccentrically by a radius R from the cylinder center, the air flowing into the cylinder 3 will flow below the scavenging hole 2. Although the air flows toward the cylinder center 4, a strong clockwise swirl S is applied above, and the vertical center line of the scavenging hole 2 is largely tilted in the direction of the swirl S. The stronger the Swirl S, the greater the fall, and the weaker the wall becomes. This is clear from the fact that when the collapse is maximum and the wall becomes horizontal, the wall thickness becomes zero.

In order to prevent the wall from becoming weak in this way, the vertical center line Y ₁ − _{Y 1} of the scavenging holes on the outer periphery of the liner is tilted in the anti-swirl direction, and the swirl becomes stronger as it moves upwards based on this. If the scavenging hole is configured so that it is screwed smoothly like this, the tilting of the scavenging hole on the inner circumference of the cylinder will be reduced accordingly, and as a whole, even if the swirl strength is increased, weakening of the wall can be suppressed to a large extent. can.

SUMMARY OF THE INVENTION An object of the present invention is to provide a cylinder liner for a uniflow two-cycle engine that eliminates the drawbacks of the conventional device and improves scavenging efficiency while maintaining an appropriate shape of the wall between the scavenging holes.

A cylinder liner for a uniflow two-stroke engine according to the present invention is a liner in which a large number of rectangular scavenging holes are bored in a single step in the axial direction in the circumferential direction, and the scavenging holes are located along the center line Y ₁ − of the outer peripheral opening.
It is tilted at a predetermined angle α ₁ with respect to the axis Z-Z of the cylinder liner so that the upper side of Y ₁ is opposite to the direction S of the swirl flow, and the center line of the inner side lateral opening Y ₂ -
Y ₂ is tilted at an angle α ₂ smaller than α ₁ with respect to the axis Z-Z of the cylinder liner, and the center line of the scavenging hole in the cross section of the liner is tilted in the same direction as the swirl flow S as the cross-sectional position moves upward. In order to achieve the above object, the air passage of the scavenging hole is configured such that the upper swirl angle θ ₂ is larger than the lower swirl angle θ ₂ '.

A cylinder liner for a uniflow two-stroke engine according to the present invention will be described below with reference to FIGS. 6 to 9.

Here, the same or equivalent components as those of the conventional device will be described using the same reference numerals.

FIG. 6 is a diagram showing the first embodiment.
2 is a cylinder liner, and 2 is a scavenging hole drilled in the lower part of the cylinder liner 1 at equal intervals in the circumferential direction. As shown in FIG.
Y ₁ - Y ₁ is inclined at an angle of α ₁ in the direction opposite to the swirl S with respect to the axis Z-Z of the cylinder liner 1, and the axis Y ₂ - of the opening 2e to the inner surface of the cylinder liner 1 _Y2 is formed to be inclined at an angle of _α1 (however, _α1 > _α2 ) with respect to the axis Z-Z of the cylinder liner 1. Therefore, the center line Y ₁ -Y ₁ of the scavenging holes on the outer circumference of the cylinder and the center line Y ₂ -Y ₂ of the scavenging holes on the inner surface of the cylinder have an angle of α ₁ +α ₂ (>0).

Figures 6b and c are A-A in Figure 6a, respectively.
In the cross section and the B-B cross section, the swirl angle θ ₂ at the upper edge of the scavenging hole is sufficiently larger than the swirl angle θ ₁ at the lower edge 2a, and the swirl angle at the middle part of the scavenging hole is θ ₂ '. , is slightly larger than the swirl angle θ ₁ at the lower edge 2a, that is, θ ₂ >θ ₂ ′>θ ₁ . In this way, the scavenging holes are continuously twisted in the vertical direction.

Next, the operation of the above embodiment will be explained. During the downward movement of the piston, at the initial stage when the piston begins to open the scavenging hole, scavenging air passes through the upper part of the scavenging hole. At this position, the scavenging hole is large and has a swirl angle of θ ₂ , so a strong swirling flow is created.
Blow out the residual exhaust gas from part A as shown in Figure 5b.
As the piston further descends, the swirl angle θ ₂ ' gradually decreases, and at the lower edge 2a of the scavenging hole, the swirl angle reaches the minimum θ ₁ , the swirl S weakens, and the scavenging air flows in a direction closer to the cylinder center, causing the residual air in the cylinder center to become smaller. Clean exhaust gas. Therefore, as shown in FIG. 5b, the scavenging inside the cylinder is further improved. Furthermore, since the inclination angle α ₂ of the scavenging hole wall 2c on the inner surface of the cylinder liner is small, the lubrication effect of the ring when the piston ring passes through the scavenging hole 2 is also improved.

FIG. 7 shows the second embodiment of the present invention, and FIG. 6 shows the first embodiment.
This corresponds to the case where α ₂ =0 in the embodiment, and the center line Y ₁ −Y ₁ of the cylinder outer peripheral opening of the scavenging hole 2 and the center line Y ₂ −Y ₂ of the cylinder inner surface opening form an angle of α ₁ >0. have
In addition, in the third embodiment shown in FIG. 8, the center line Y ₂ - _{Y 2} of the cylinder inner surface opening of the scavenging hole 2 is aligned with the center line Y ₁ - Y ₁ of the outer peripheral opening of the scavenging hole 2 and the cylinder axis Z-Z. In this example, the angle between the center lines _{Y 1 − Y 1} and Y ₂ − _{Y 2} is α ₁ − α ₂ (>0).
However, its operation and effect are almost the same as in the first embodiment.

FIG. 9 shows the effect of improving scavenging efficiency obtained by the scavenging holes according to the present invention. Diagrams b and c show that by fixing the swirl angle of the lower edge of the scavenging hole to θ ₁ = 5° as shown in diagram a, and tilting the upper edge of the scavenging hole 2 toward the anti-swirl S side, the upper edge swirl angle can be changed. The solid line results are obtained by changing θ ₂ from 10° to 40°. Figure b is the relationship between the air supply ratio ρ and scavenging efficiency η _s when θ ₁ and θ ₂ are used as parameters, and diagram c is the relationship between θ ₁ is a relationship diagram between the swirl angle θ ₂ and the scavenging efficiency η _s when fixed at 1 = 5° and ρ = 1.1. c.
As is clear from the figure, when ρ = 1.1 and θ ₁ = 5°, the swirl angle θ ₂ at the upper part of the scavenging hole tends to increase from about 10° and reaches its maximum value at around 30°. The inclination angles α ₁ and α ₂ of the cylinder outer peripheral openings of the scavenging holes are determined as functions of the height of the scavenging holes, the number of scavenging holes, and the swirl angle θ ₂ '.

As described above, in the cylinder liner of the scavenging device for a uniflow two-cycle engine according to the present invention, the center line of the scavenging hole opening on the outer circumference of the cylinder is
Since Y ₁ - _{Y 1} is tilted in the opposite direction to the direction of the swirl flow S, and the upper swirl angle θ ₂ is made larger than the lower swirl angle θ ₂ ', the air passage of the scavenging hole is twisted in the vertical direction. It is possible to improve the scavenging effect while maintaining the appropriate shape of the ribs between the scavenging holes.

[Brief explanation of the drawing]

Figure 1 is an explanatory cross-sectional view of the cylinder liner of a Uniflow two-stroke engine, Figure 2 is a longitudinal cross-sectional view of the cylinder liner including scavenging holes, Figure 3 is a view taken in the direction of the arrows in Figure 2, and Figure 4 is the figure 3. FIG. 5a is a diagram showing the state of residual combustion gas after scavenging by the conventional scavenging hole, and FIG. 5b is a diagram showing the same situation by the scavenging hole of the present invention. FIG. 6 relates to the first embodiment of the present invention, and FIG.
-A sectional view, c is a BB sectional view of a, FIG. 7 is a second embodiment, and a is an exit surface corresponding to FIG. 6a, and b is A'-A of A. ' cross-sectional view, Figure c is a cross-sectional view B'-B' of Figure A, Figure 8 is the third embodiment, Figure A is a drawing corresponding to Figure 6 A, and Figure B is a diagram corresponding to Figure A.
A″-A″ cross-sectional view, Figure c is a B″-B″ cross-sectional view of Figure A, and Figure 9 is a lower edge swirl angle θ ₁ of the scavenging hole as shown in Figure a.
Experimental data when the upper edge swirl angle θ 2 was fixed at 5° and the upper edge swirl angle θ ₂ was varied from 10° to 40°. Figure a is an explanatory diagram of angles θ ₁ and θ ₂ , and diagram b shows θ ₁ and θ ₂ as parameters. A diagram showing the relationship between the air supply ratio ρ and the scavenging efficiency η _s when θ ₁ = 5°, ρ =
FIG. 2 is a relationship diagram between the swirl angle θ ₂ and the scavenging efficiency η _s when it is set to 1.1. 1...Cylinder liner, 2...Scavenging hole, 2d...
... Cylinder outer periphery opening of scavenging hole, 2e... Cylinder inner surface opening of scavenging hole, Y ₁ - Y ₁ ... Cylinder outer periphery opening center line, θ ₂ ... Upper swirl angle of scavenging hole, θ ₂ '... Lower swirl angle of scavenging hole, S...Swirl flow.

Claims (1)

[Claims] 1. In a liner in which a large number of rectangular scavenging holes are bored in one step in the axial direction in the circumferential direction, the scavenging holes have a direction above the center line Y ₁ - Y ₁ of the outer peripheral opening in the opposite direction to the direction S of the swirl flow. _The center line of the inner surface opening is tilted at _a predetermined angle α ₁ with respect to the axis Z _- Z of the cylinder liner so that In addition to tilting the liner at an angle α ₂ , the center line of the scavenging hole in the cross section of the liner is continuously twisted so that it is in the same direction as the swirl flow S as the cross-sectional position moves upward, and the upper swirl angle θ ₂ is changed to the lower swirl angle θ A cylinder liner for a uniflow two-cycle engine, characterized in that an air passage in a scavenging hole is configured to be larger than ₂ '.