JPH04224231A - Inner cylinder injection type internal combustion engine - Google Patents

Abstract

PURPOSE:To collect air-fuel mixture around an ignition plug in a two-cycle engine adopting an air blast valve. CONSTITUTION:A groove 20 is formed on a top face of a piston 2. Fuel is injected together with compressed air from an air blast valve 14 into the groove 20 in a latter half period of a compression process. A horizontal width of the groove 20 in a direction perpendicular to the fuel injection direction is narrower than the vertical width of the groove 20. Both side wall surfaces 20b of the groove 20 which determine the horizontal width thereof are arranged a little outer than an outer periphery of atomized fuel F. The atomized fuel F is prevented from diffusing in a transverse direction by means of the both side wall surfaces 20b of the groove. Air-fuel mixture is thus collected in the engine groove 20 and below an ignition plug 10.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct injection internal combustion engine.

0002

[Prior Art] A concave groove is formed on the top surface of the piston, and fuel is injected from the fuel injection valve into the concave groove to generate a swirling flow around the cylinder axis within the combustion chamber. A direct-injection internal combustion engine is known in which an ignitable air-fuel mixture is formed around the
(See Publication No. 4042).

0003

However, in this direct injection internal combustion engine, it is essential to generate a swirling flow around the cylinder axis, so if the swirling flow around the cylinder axis is not generated, this injection method cannot be adopted. In addition, the strength of the swirling flow changes depending on the operating condition of the engine, so if the formation of the mixture around the spark plug is completely dependent on the swirling flow, the optimum mixture will be ignited for every operating condition of the engine. The problem is that it is difficult to form around the stopper.

0004

[Means for Solving the Problems] In order to solve the above problems, according to the present invention, an ignition plug is disposed at the center of the inner wall surface of the cylinder head, and an air blast valve for injecting fuel with compressed air is installed in the cylinder head. A concave groove is formed on the top surface of the piston, which is placed on the peripheral edge of the wall and extends from below the ignition plug to below the air blast valve, so that the fuel spray injected from the air blast valve ignites while following the bottom wall of the concave groove. Fuel spray is injected from the air blast valve into the groove below the plug, and the width of the groove in the direction perpendicular to the fuel spray axis is the vertical width of the groove in the direction of the fuel spray axis. It is made narrower than the width, and both side wall surfaces of the groove defining the width are positioned slightly outside the outer surface of the fuel spray.

[0005]

Operation: By using the air blast valve, an ignitable fuel spray is formed in the groove. Since both side wall surfaces of the groove that define the width of the groove are positioned slightly outside the outer surface of the fuel spray, the fuel spray is guided into the groove below the ignition plug without spreading laterally. This fuel spray is then ignited by a spark plug.

[0006]

[Embodiment] Referring to FIGS. 1 and 2, 1 is a cylinder block, 2 is a piston that reciprocates within the cylinder block 1, 3 is a cylinder head fixed on the cylinder block 1, and 4 is an inner part of the cylinder head 3. The combustion chambers formed between the wall surface 3a and the top surface of the piston 2 are shown. A recessed groove 5 is formed on the cylinder head inner wall surface 3a, and a pair of air supply valves 6 are arranged on the cylinder head inner wall surface portion 3b forming the bottom wall surface of the recessed groove 5. On the other hand, the cylinder head inner wall surface portion 3c excluding the groove 5 is inclined and substantially flat, and a pair of exhaust valves 7 are arranged on this cylinder head inner wall surface portion 3c. The cylinder head inner wall surface portion 3b and the cylinder head inner wall surface portion 3c are connected to each other via the peripheral wall 8 of the groove 5. This concave groove peripheral wall 8 is arranged very close to the peripheral edge of the air supply valve 6 and extends in an arc shape along the peripheral edge of the air supply valve 6. It is constituted by a guide wall 8b and a pair of fresh air guide walls 8c located between the peripheral wall of the cylinder head inner wall surface 3a and the air supply valve 6. Each mask wall 8a extends toward the combustion chamber 4 below the intake valve 6 at the maximum lift position, and therefore the opening between the peripheral edge of the intake valve 6 and the valve seat 9 located on the exhaust valve 7 side is The air supply valve 6 is closed by the mask wall 8a throughout its opening period. In addition, each fresh air guide wall 8b
, 8c are located substantially in the same plane, and furthermore, these fresh air guide walls 8b, 8c extend substantially parallel to a line connecting the centers of both air supply valves 6. The ignition plug 10 is arranged on the cylinder head inner wall surface portion 3c so as to be located at the center of the cylinder head inner wall surface 3a. On the other hand, the exhaust valve 7 is not provided with a mask wall that covers the opening between the exhaust valve 7 and the valve seat 11. Therefore, when the exhaust valve 7 opens, a mask wall is formed between the exhaust valve 7 and the valve seat 11. The entire opening is the combustion chamber 4
It will open inward.

[0007] In the cylinder head 3, an air intake port 12 is formed for the air intake valve 6, and an exhaust port 13 is formed for the exhaust valve 7. On the other hand, an air blast valve 14 is disposed at the peripheral edge of the cylinder head inner wall surface 3 a between both the air supply valves 6 . This air blast valve 14 has its housing 1
A compressed air passage 16 formed in the combustion chamber 5 and connected to a compressed air source (not shown), a fuel injection valve 17 arranged in the compressed air passage 16, and a fuel injection valve 17 arranged in the combustion chamber 4 driven by a solenoid (not shown). and a valve body 19 that opens and closes the nozzle port 18. The compressed air passage 16 is always filled with compressed air, and fuel is injected from the fuel injection valve 17 into the compressed air within the compressed air passage 16. Next, when the valve body 19 opens the nozzle port 18, the nozzle port 18 opens.
Fuel is injected into the combustion chamber 4 together with compressed air.

As shown in FIGS. 1 and 3, an air blast valve 1 is placed on the top surface of the piston 2 from below the ignition plug 10.
A concave groove 20 is formed that extends to below the tip of 4. In the embodiment shown in FIGS. 1 and 3, this groove 20 is
0 and the air blast valve 14. As shown in FIG. 4, in the embodiment shown in FIGS. 1 to 3, the exhaust valve 7 opens before the intake valve 6, and the exhaust valve 7 opens before the intake valve 6. Further, in FIG. 4, I indicates the fuel injection timing. Therefore, as shown by F in FIGS. 1 and 3, fuel is injected together with compressed air in the form of a conical fuel spray from the nozzle port 18 of the air blast valve 14 in the latter half of the compression stroke. At this time, the fuel spray F flows from the nozzle port 18 to the vertical plane K-
K and is injected into the groove 20 below the ignition plug 10 along the bottom wall surface 20a of the groove 20. As can be seen from FIG. 3, the groove 20 is perpendicular to the axis of the fuel spray F, that is, perpendicular to the vertical plane K-K.
The width S is in the axial direction of the fuel spray F, that is, in the vertical plane K-K.
It is formed narrower than the vertical width L of the groove 20 in the direction along the direction. Further, both side wall surfaces 20b of the groove 20 that define the width S of the groove 20 are substantially vertical, and these side wall surfaces 20b are substantially vertical.
0b is positioned slightly outward from the outer surface of the fuel spray F. Further, as shown in FIG. 3, the upper edge 2 of the groove 20 located on the opposite side from the air blast valve 14
The outline shape of 0c is an arc shape, and on the end face of the groove 20 rising from the bottom wall surface 20a of the groove 20 toward the ignition plug 10 on the opposite side from the air blast valve 14, as shown in FIG. A recessed portion 20d having an arc-shaped cross section is formed with respect to the upper edge portion 20c, receding in a direction away from the air blast valve 14. On the other hand, as shown in FIG. 1, the top surface portion 2a of the piston 2 on the opposite side of the groove 20 with respect to the upper edge portion 20c is formed as an inclined, substantially flat surface, and when the piston 2 reaches the top dead center, the inside of the cylinder head is A squish area is formed between the wall surface portion 3c and the piston top surface portion 2a.

Next, a method for forming an air-fuel mixture will be explained with reference to FIGS. 1, 3, and 5. As shown in FIG. 5, when the intake valve 6 and the exhaust valve 7 are opened, air flows into the combustion chamber 4 via the intake valve 6. At this time, since the opening of the intake valve 6 on the side of the exhaust valve 7 is covered by the mask wall 8a, air flows into the combustion chamber 4 from the opening of the intake valve 6 on the side opposite to the mask wall 8a. This air descends along the inner wall surface of the cylinder bore below the air supply valve 6 as shown by arrow W. Then, a portion W1 of this air W flows into the groove 20, and the groove 20 is thus scavenged by this air W1. On the other hand, the remaining portion W2 of the air W travels along the top surface of the piston 2 and rises along the inner wall surface of the cylinder bore below the exhaust valve 7, so that the air W2 flows in a loop inside the combustion chamber 4. . The air W2 flowing in a loop causes the burnt gas in the combustion chamber 4 to be discharged via the exhaust valve 7.
Furthermore, the air W2 flowing in this loop shape causes the combustion chamber 4 to
A swirling flow X that swirls in a vertical plane is generated inside the tube. Next, the piston 2 passes the bottom dead center BDC and begins to rise, and the intake valve 6 and the exhaust valve 7 open to reach the end of the compression stroke. As shown in FIGS. 1 and 3, fuel is discharged from the air blast valve 14. The spray F is injected into the groove 20 below the ignition plug 10 along the bottom wall surface 20a of the groove 20.

When the fuel is injected using compressed air, the fuel is atomized well, so the fuel spray F becomes ready to be ignited immediately. However, since the fuel spray F is gaseous, it spreads throughout the combustion chamber 4. It becomes easier to spread. However, if the fuel spray F spreads throughout the combustion chamber 4, a relatively rich mixture cannot be collected around the spark plug 10, especially during low-load operation with a small amount of fuel injection, and good ignition cannot be achieved. . However, in the embodiment shown in FIGS. 1 and 3, as described above, both side wall surfaces 20b of the groove 20 defining the width S of the groove 20 are slightly outward from the outer surface of the conical fuel spray F. It is located. Therefore, the fuel spray F is shaped as if it is sandwiched between both side wall surfaces 20b of the groove 20, and thus the fuel spray F is prevented from being spread in the lateral direction. Therefore, the air-fuel mixture gathers in the groove 20 below the ignition plug 10, and this air-fuel mixture is ignited by the ignition plug 10. Thus the spark plug 1
This means that a good ignition effect can be ensured due to the zero. Further, as described above, the recess 20 formed on the end face of the recess groove 20
d has a concave shape toward the side opposite to the air blast valve 14, so the fuel spray F flows through the concave portion 20d to the exhaust valve 7.
Diffusion into the combustion chamber 4 below is prevented. Therefore, by providing such a recess 20d, the spark plug 1 can be further tightened.
The air-fuel mixture can now be collected in the groove 20 below zero. Further, as shown in FIG. 5, a swirling flow X is generated in the combustion chamber 4, and this swirling flow X causes fuel spray F.
The traveling direction of the groove 20 is deflected toward the inside of the groove 20. Therefore, this swirling flow X also prevents the mixture from diffusing.

[0011]

[Effects of the Invention] When an air blast valve is used, even when the engine is operating at low load with a small amount of fuel injection, it is possible to collect an ignitable air-fuel mixture around the spark plug, thus ensuring good ignition. Obtainable.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of a two-stroke internal combustion engine.

FIG. 2 is a bottom view of the cylinder head.

FIG. 3 is a plan view of the piston.

FIG. 4 is a diagram showing the opening timing of the supply and exhaust valves and the fuel injection timing.

FIG. 5 is a side cross-sectional view of the two-stroke internal combustion engine showing the supply and exhaust valves opened.

[Explanation of sign]

6...Air supply valve 7...Exhaust valve 8a...Mask wall 10...Spark plug 14...Air blast valve 20...concave groove

Claims (1)

[Claims] Claim 1: An ignition plug is arranged in the center of the inner wall of the cylinder head, and an air blast valve that injects fuel using compressed air is arranged at the periphery of the inner wall of the cylinder head. A concave groove extending downward is formed on the top surface of the piston so that the fuel spray injected from the air blast valve is directed from the air blast valve into the concave groove below the ignition plug while following the bottom wall of the concave groove. The width of the groove in the direction perpendicular to the fuel spray axis is narrower than the vertical width of the groove in the direction of the fuel spray axis, and both sides of the groove defining the width are A direct-injection internal combustion engine in which the wall surface is located slightly outside the outer surface of the fuel spray.