JPH04112944A - Fuel injection type internal combustion engine - Google Patents

Abstract

PURPOSE:To form am optimal mixed air around a spark plug regardless of engine load by forming a recessed groove of specific shape extended from the lower part of the spark plug to the lower part of a first fuel injection valve, on a piston top surface, and by arranging a second fuel injection valve in an intake route. CONSTITUTION:A pair of intake valves 6 are arranged on a cylinder head inner wall surface part 3b that forms a bottom wall surface of a recessed groove 5 formed on a cylinder head inner wall surface 3a, while a first fuel injection valve 14 is arranged on the peripheral part of the cylinder inner wall surface 3a between each intake valve 6, and a second fuel injection valve 18 is arranged in a communicating opening 17 communicating to the upper part of each intake port 12. A recessed groove 15 extended from the lower part of a spark plug 10 to the lower part of the point of the first fuel injection valve 14 is formed on the top surface of a piston 2, while the recessed groove 15 is formed almost into spherical shape which is symmetric to a vertical flat surface K-K including the spark plug 10 as well as the first fuel injection valve 14. Fuel injection is performed only by the first fuel injection valve 14 at the time of engine low load driving, while it is performed by both of the first and second fuel injection valves 14 and 18 at the time of engine middle and high load driving.

Description

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

[Conventional technology]

A first fuel injection valve is disposed within the combustion chamber, a groove is formed on the top surface of the piston, fuel is injected from the first fuel injection valve into the groove, and a second fuel injection valve is injected into the intake passage. By arranging the valve, during high-load engine operation, fuel is injected from the second fuel injection valve in addition to the fuel injection from the first fuel injection valve, generating a swirling flow around the cylinder axis in the combustion chamber. A fuel injection type internal combustion engine is known in which an ignitable air-fuel mixture is formed around a spark plug by
(Refer to Publication No.-191623).

[Problem to be solved by the invention]

However, since it is an essential requirement for this fuel injection type internal combustion engine to generate a swirling flow around the cylinder axis, this injection method can no longer be adopted if the swirling flow around the cylinder axis is not generated. 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.

[Means to solve the problem]

In order to solve the above problems, according to the present invention, the ignition plug is arranged at the center of the inner wall surface of the cylinder head, the first fuel injection valve is arranged at the periphery of the inner wall surface of the cylinder head, and the ignition plug is inserted from below the ignition plug. A concave groove extending below the first fuel injector is formed on the top surface of the piston, and fuel is injected from the first fuel injector toward the concave inner wall surface of the concave groove, and fuel is injected along the injection axis during high engine load operation. The fuel collides almost perpendicularly with the concave inner wall surface, and when the engine is operating at low load, the injected fuel along the injection axis makes an acute angle in order to divert most of the fuel colliding with the concave inner wall surface toward the concave inner wall surface portion ζ below the spark plug. The shape of the concave inner wall surface and the injection timing from the first fuel injector are determined so that the fuel injector collides obliquely with the concave inner wall surface, and a second fuel injector is further arranged in the intake passage to adjust the engine height. During load operation, fuel is injected from the second fuel injection valve in addition to the fuel injection from the first fuel injection valve.

[For production]

During high-load operation of the engine with a large amount of fuel injection, fuel is injected from the first fuel injection valve and the second fuel injection valve, and a lean mixture is formed in the combustion chamber by the fuel injected from the second fuel injection valve. The injected fuel along the injection axis from the first fuel injection valve collides almost perpendicularly with the concave inner wall surface of the concave groove, so after the collision, the injected fuel spreads in all directions along the concave inner wall surface, and one of the fuel spread in the four directions part of the fuel is guided to the concave inner wall surface below the ignition plug. On the other hand, during low engine load operation with a small fuel injection amount, fuel is injected only from the first fuel injection valve. The injected fuel from this first fuel injection valve along the injection axis forms an acute angle and collides with the concave inner wall surface of the diagonal concave groove,
Most of the collided fuel is guided to the concave inner wall surface below the spark plug.

〔Example〕

Referring to FIGS. 1 and 3, 1 is a cylinder block, 2 is a cylinder block] A piston that reciprocates within the cylinder block;
Reference numeral 3 indicates a cylinder head fixed on the cylinder block l, and reference numeral 4 indicates a combustion chamber formed between the inner wall surface 3a of the cylinder head 3 and the top surface of the piston 20. 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 has an air supply valve 6 in its maximum lift position.
The opening between the peripheral edge of the air intake valve 6 and the valve seat 9, which extends downward toward the combustion chamber 4 and is located on the exhaust valve 7 side, is covered with a mask throughout the opening period of the air intake valve 6. It will be closed by the wall 8a. Moreover, 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, the exhaust valve 7
The opening formed between the valve seat 11 and the valve seat 11 opens entirely into the combustion chamber 4.

In the cylinder vent 3, an air supply port 12 is formed for each air intake valve 6, and an exhaust port 13 is formed for each exhaust valve 7, respectively. On the other hand, a first fuel injection valve 14 is disposed at the peripheral edge of the cylinder head inner wall surface 3a between both intake valves 6, and fuel is injected into the combustion chamber from this first fuel injection valve 14.
It is sprayed inward.

On the other hand, as shown in FIGS. 1 and 4, the upper parts of each air supply boat 12 are communicated with each other through a communication opening 17, and a second fuel injection valve 18 is installed in this communication port 17. Placed. Fuel is injected from this second fuel injection valve 18 toward the back surface of each intake valve 6.

As shown in FIGS. 1 and 2, a groove 15 is formed on the top surface of the piston 2 and extends from below the ignition plug 10 to below the tip of the first fuel injection valve 14. In the embodiment shown in FIG. 1 and FIG.
It has an almost spherical shape that is symmetrical to the surface.

Further, a recess 16 having a spherical shape with a smaller curvature than the recess groove 15 is formed in the center of the top surface of the piston 2 .

This recess 16 is also formed upwardly in the vertical plane, and this recess 16 opens at the upper part of the concave inner wall surface of the groove 15. As shown in FIG. 1, when the piston 2 reaches the top dead center, the spark plug 10 enters the recess 16.

On the other hand, the piston 2 on the opposite side of the groove 15 with respect to the recess 16
The top surface portion 2a of the piston 2 is formed from an inclined, substantially flat surface, and as shown in FIG. It is formed.

As shown in FIG. 5, in the embodiment shown in FIGS. 1 to 4, the exhaust valve 7 opens before the intake valve 6, and the exhaust valve 7 closes before the intake valve 6. . Furthermore, in the embodiments shown in FIGS. 1 to 4, the first fuel injector 1 is
Fuel injection is performed only from the first fuel injection valve 14 and the second fuel injection valve 18 during engine medium-high load operation. In FIG. 5, Ir indicates the timing of fuel injection from the first fuel injection valve 14 during low engine load operation, and l hl indicates the fuel injection timing from the first fuel injection valve 14 during medium to high engine load operation. , and Ih□ indicates the fuel injection timing from the second fuel injection valve 18 during engine medium-high load operation. As shown in FIG. 5, the second fuel injection valve 1 during engine medium-high load operation
The fuel injection 1h□ from the first fuel injection valve 14 is performed in the latter half of the air intake stroke and slightly before the exhaust valve 7 closes, and the fuel injection Iゎ1 from the first fuel injection valve 14 during engine medium-high load operation is This is done at about 50 to 80 degrees before top dead center TDC. Furthermore, it can be seen from FIG. 5 that the fuel injection timing It from the first fuel injection valve 14 during engine low load operation is later than the fuel injection timing 1hl from the first fuel injection valve 14 during engine medium high load operation.

Next, the injection method during low load operation and medium to high load operation will be explained with reference to FIG.

As shown in FIG. 6(A), when the intake valve 6 and the exhaust valve 7 are opened, air flows into the combustion chamber 4 through the intake valve 6. At this time, the opening of the air supply valve 6 on the side of the exhaust valve 7 is connected to the mask wall 8.
Since the combustion chamber 4 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 flows along the inner wall surface of the cylinder bore below the intake valve 6 as shown by the arrow W, then 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. Air flows in a loop within the combustion chamber 4. The air W flowing in a loop causes the burnt gas in the combustion chamber 4 to be discharged through the exhaust valve 7, and the air W flowing in a loop causes a swirling flow X in the combustion chamber 4 that swirls in a vertical plane. is caused to occur. Next, the piston 2 passes the bottom dead center BDC and begins to rise, and when the intake valve 6 and the exhaust valve 7 close, fuel injection from the first fuel injection valve 14 is performed.

Figure 6 (BL) (C) shows the engine running at low load, and Figures 6 (D), (E), and (F) show the engine running at medium and high load.

As shown in FIG. 6(B), fuel is injected from the first fuel injection valve 14 toward the concave inner wall surface of the concave groove 15. As shown in FIG. In the embodiment shown in FIGS. 1 to 4, the spray of the injected fuel has, for example, a conical shape as shown in FIG. 6(B), and the injection axis Z of the injected fuel is shown in FIG. 2. Located within - in the vertical plane.

During low engine load operation, as shown in FIG. 6(B), the injected fuel from the first fuel injection valve 14 along the injection axis Z obliquely collides with the concave inner wall surface of the concave groove 15 at an acute angle θ. . In this way, when the injected fuel obliquely collides with the concave inner wall surface of the concave groove 15, the collided fuel becomes Fl in FIG. 6(C).
As shown in the figure, the inertial force causes the gas to vaporize along the concave inner wall surface of the concave groove 15 and proceed below the ignition plug 10, and then to be fed into the concave portion 16. When the engine is operating at low load, the injection amount is small, but at this time most of the injected fuel is carried below the ignition plug 10, so an ignitable air-fuel mixture is formed around the ignition plug 10. In addition, as shown in FIG. 6(A), the swirling flow X generated in the combustion chamber 4 is attenuated as the piston 2 rises, and the swirling radius gradually becomes smaller (as the piston 2 approaches the top dead center). As shown in FIG. 6(B), a swirling flow X forms along the concave inner wall surface of the groove 16. This swirling flow X also gives the injected fuel a force directed downward to the spark plug 10. 2 further approaches the top dead center (as shown by the arrow S in FIG. 6(C), a squish flow ejects from the squish area 19, and this squish flow S also advances along the concave inner wall surface of the concave groove 15. .

Therefore, the injected fuel is also given a force directed downward to the spark plug 10 by the skinsh flow S.

Furthermore, the fuel flowing downward along the concave inner wall surface of the concave groove 15 is vaporized by the swirl flow X and the squish flow S, and thus a sufficiently vaporized combustible mixture is created around the spark plug 10. We will get together. In this way, even when the engine is operating at low load with a small injection amount, good ignition and subsequent good combustion can be obtained.

On the other hand, during engine medium and high load operation, the exhaust valve 7
Fuel injection I6□ is performed from the second fuel injection valve 18 a little before the valve closes. This injected fuel is shown in Figure 6 (D).
As shown by arrow Y, the air flows into the combustion chamber 4 from the opening of the intake valve 6 on the opposite side to the exhaust valve 7. In this way, 1hz of fuel injection from the second fuel injection valve 18 is performed by the exhaust valve 7.
The injected fuel flows into the combustion chamber 4 through the opening of the intake valve 6 on the opposite side from the exhaust valve 7, so the injected fuel flows through the exhaust valve 7 to the exhaust port 13. This means that it will hardly blow through. In addition, during engine medium-high load operation, fuel injection is divided into two times: 1 hz fuel injection from the second fuel injection valve 18 and fuel injection (1) from the first fuel injection valve 14, so the second fuel injection valve Injected fuel I from 18. Therefore, the air-fuel mixture formed in the combustion chamber 4 is an extremely lean air-fuel mixture. Therefore, even if part of the air-fuel mixture blows through into the exhaust port 13, the amount of fuel that blows through is extremely small. Furthermore, since a strong swirling flow X as shown in FIG. 6(A) is generated in the combustion chamber 4, the injected fuel flowing into the combustion chamber 4 is well mixed with air, and at this time, the piston 2 is still located below, giving the injected fuel sufficient time to vaporize.

Therefore, a uniform air-fuel mixture is formed in the combustion chamber 4 before ignition by the spark plug 10.

Note that since the fuel injection is performed in two steps, the mixture formed in the combustion chamber 4 at this time is a fairly lean mixture as described above, and therefore a fairly lean and uniform mixture is formed in the combustion chamber 4. Qi will be formed. This air-fuel mixture is heated by the high-temperature burnt gas remaining in the combustion chamber 4, but since the air-fuel mixture is lean, the fuel density is low, and therefore this air-fuel mixture does not self-ignite. That is, there is no self-ignition and no combustion noise, and no knocking occurs.

Next, as shown in FIG. 6(E), fuel injection 1h+ from the first fuel injection valve 14 is started when the piston 2 is at a lower position than when the engine is operating at low load. At this time, as shown in FIG. 6(E), the first fuel injector 1
The injected fuel along the injection axis Z from 4 impinges on the concave inner wall surface of the concave groove 15 almost perpendicularly. When the injected fuel collides almost perpendicularly onto the concave inner wall surface of the concave groove 15, the collided fuel will move around the collision point of the injected fuel along the injection axis Z, as shown by F2 in FIG. 6(F). Concave 71!1
It spreads in all directions on the concave inner wall surface of 5. Therefore, in this case, a part of the collided injected fuel travels below the ignition plug 1o, and then is sent into the recess 16 and buried therein. In this way, when the engine is operated under medium to high load with a large amount of injection, a portion of the injected fuel is sent around the spark plug 100, so the air-fuel mixture formed around the spark plug 10 does not become too rich.
A mixture that can be ignited well is formed around 0. In addition, during engine medium and high load operation, the injected fuel is heated to the high temperature concave groove 15.
Since the injected fuel is widely dispersed on the concave inner wall surface of the concave groove 15, vaporization of the injected fuel is promoted, and since the fuel is injected in two steps, the amount of fuel injected into the concave groove 15 is small, so the injected fuel is sufficient. Be vaporized. Therefore, the fuel injected into the groove 15 is combusted in the presence of sufficient air, so no smoke is generated. Furthermore, even during medium-high load operation of the engine, the swirling flow X and the
A squish flow S as shown in Figure (C) is generated, and the swirling flow X and squish flow S sufficiently mix the injected fuel 1h+ with air, resulting in good combustion without smoke. Obtainable.

[Effects of the Invention] An optimal air-fuel mixture can be formed during ignition logging regardless of the engine load, and good combustion without self-ignition, knocking, or smoke can be obtained.

[Brief explanation of drawings]

Figure 1 is a side sectional view of a two-stroke internal combustion engine, Figure 2 is a plan view of the piston in Figure 1, Figure 3 is a bottom view of the cylinder head in Figure 1, and Figure 4 is the cylinder head in Figure 1. FIG. 5 is a diagram showing the opening timing of the intake and exhaust valves and fuel injection timing, and FIG. 6 is a diagram for explaining the inside of the combustion chamber during engine operation. 2...Piston, 4...Combustion chamber, 6...
Air supply valve, 7... Exhaust valve, 10... Spark plug, 14... First fuel injection valve, 15... Concave groove, 16... Recess, 18... Second fuel injection valve. Figure (A) Figure (A) Figure (C) Figure (E) Figure (D) Figure (F)

Claims (1)

[Claims] An ignition plug is arranged at the center of the inner wall surface of the cylinder head, a first fuel injection valve is arranged at the peripheral edge of the inner wall surface of the cylinder head, and a concave groove extending from below the ignition plug to below the first fuel injection valve is connected to the piston. Formed on the top surface, fuel is injected from the first fuel injection valve toward the concave inner wall surface of the groove, and when the engine is operated under high load, the injected fuel along the injection axis collides almost perpendicularly with the concave inner wall surface. In order to direct most of the fuel that collides with the concave inner wall surface to the concave inner wall surface below the spark plug during low-load engine operation, the concave shape is designed such that the injected fuel along the injection axis collides obliquely with the concave inner wall surface at an acute angle. The shape of the inner wall surface and the timing of injection from the first fuel injection valve are determined, and a second fuel injection valve is arranged in the intake passage to control fuel injection from the first fuel injection valve during high engine load operation. A fuel injection type internal combustion engine in which fuel is also injected from a second fuel injection valve.