JPH08260986A - In-cylinder injection type internal combustion engine - Google Patents

Abstract

PURPOSE: To reduce fuel cost at the time of load in an engine and improve exhaust emission by forming a stepped part having a wall surface for directing supplied fuel substatially right above on the just upstream side of a swirl from the entering position of a spark plug on the upper part of the side of a combustion chamber. CONSTITUTION: A recessed combustion chamber is formed on the top of a piston 1, and an intake port is formed in such a manner as to generate a swirl on the top of the piston 1 and in the combustion chamber. That is, the combustion chamber comprises a deep dish part 3 and a shallow dish part 4 formed on the side 3a thereof, wherein the bottom 4b of the shallow dish part 4 is disposed at a piston position during ignition time, in such a manner as to have a little gap up to the tip of a spark plug 5. A stepped part 7 is formed along the shallow dish part 4 on the just upstream side of a swirl from the entering position of the spark plug 5 on the upper part of the side 4a of the shallow dish part 4 on the top of the piston 1. A fuel injection valve 8 for injecting fuel to the upstream side of a swirl is disposed on the upper side of the periphery of the combustion chamber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a fuel injection valve for directly injecting fuel into a cylinder, a concave combustion chamber formed on the top surface of a piston, and a spark plug which enters the combustion chamber at ignition timing. Cylinder injection internal combustion engine.

[0002]

2. Description of the Related Art In such a cylinder injection type internal combustion engine, by injecting fuel in the latter half of the compression stroke, the fuel is concentrated only in the vicinity of the spark plug in the combustion chamber to form an air-fuel mixture having a good ignitability. By realizing stratified combustion in which this is ignited and burned, it becomes possible to burn a leaner air-fuel mixture than the stoichiometric air-fuel ratio in the entire combustion chamber, and fuel consumption can be reduced. However, when the amount of fuel injection increases to some extent during engine load, the air-fuel mixture formed in the vicinity of the spark plug becomes too rich, which conversely deteriorates ignitability and causes smoke during combustion.

To solve this problem, Japanese Unexamined Patent Publication (Kokai) No. 5-2
The in-cylinder injection type internal combustion engine described in Japanese Patent No. 40052 has a compression stroke by injecting a part of fuel into an intake stroke to form a uniform mixture in the cylinder before ignition when the engine has a medium load. The amount of fuel injected in the latter half is reduced, which prevents deterioration of the ignitability of the air-fuel mixture formed near the spark plug and the occurrence of smoke, thus ensuring that the flame ignited reliably near the spark plug produces a uniform mixture in the combustion chamber. It is supposed to be propagated to.

[0004]

In such combustion under a medium load, the amount of fuel injected in the intake stroke becomes very small, especially when the load is relatively small and the fuel injection amount is relatively small. The homogeneous mixture formed in the combustion chamber is extremely lean and difficult to burn, and the flame near the spark plug propagates into this homogeneous mixture, but part of it is not burned and is discharged as unburned fuel. Therefore, fuel efficiency and exhaust emission are deteriorated.

Therefore, an object of the present invention is to provide a cylinder injection type internal combustion engine capable of improving combustion under a medium load of the engine and improving fuel consumption and exhaust emission at this time.

[0006]

SUMMARY OF THE INVENTION An in-cylinder injection type internal combustion engine according to the present invention has a concave combustion chamber formed on the top surface of a piston, a spark plug that enters the combustion chamber at ignition timing, and a swirl in the cylinder. A swirl generating means for generating and a fuel which is formed on the upstream side of the swirl in the upper part of the side surface of the combustion chamber just upstream of the swirl and directs the supplied fuel almost directly above by utilizing its inertial force. And a fuel injection valve capable of injecting fuel to the swirl upstream side from the entry position of the ignition plug of the combustion chamber at the piston position in the latter half of the compression stroke, and the fuel is at the stage when the engine has a medium load. Fuel injection timing control means for controlling the injection timing of the fuel injection valve so that the fuel is injected from the above portion to the combustion chamber.

[0007]

In the above-mentioned direct injection internal combustion engine, the step portion is formed immediately upstream of the swirl from the entry position of the spark plug in the upper side surface of the combustion chamber formed on the piston top surface, and the fuel injection timing control means is provided. In order to control the injection timing of the fuel injection valve so that fuel is injected from this step portion to the combustion chamber at the time of engine medium load, a part of the fuel amount injected at this time is supplied to the step portion, A part of the liquid fuel thus supplied to the step portion is vaporized on the step portion by the heat of the piston, and the rest is directed almost directly above by the wall surface of the step portion, colliding with the cylinder head and vaporized. By doing so, the air-fuel mixture having a sufficient combustible concentration is formed on the step portion without spreading in the entire cylinder, and the air-fuel mixture is moved to the position outside the combustion chamber adjacent to the spark plug at the time of ignition by the swirl. On the other hand, the fuel supplied into the combustion chamber forms a mixture with good ignitability in the vicinity of the spark plug in the combustion chamber.

[0008]

1 is a plan view of an upper portion of a piston in a cylinder injection type internal combustion engine according to the present invention, and FIG. 2 is a vertical sectional view at an ignition timing thereof. In these figures, reference numeral 1 denotes a piston, and a concave combustion chamber is formed at an eccentric position on the top surface thereof. Although not shown, the intake port is formed so as to generate swirl in the direction indicated by the arrow on the top surface of the piston 1 and the combustion chamber.

The combustion chamber comprises a basin 3 and a shallow L-shaped basin 4 which functions as a fuel guide passage formed on the side surface 3a of the basin 3a on the center side of the piston.
b is such that there is a slight gap between the piston position at the ignition timing and the tip of the spark plug 5, and in order to prevent the two from colliding due to dimensional error or the like, the spark plug 5 A partial spherical recess 6 is formed at a position facing the tip of the.

On the top surface of the piston 1, a step portion 7 is formed along the shallow dish portion 4 immediately upstream of the swirl position of the spark plug 5 at the upper portion of the side surface 4a of the shallow dish portion 4 of the combustion chamber. Has been done. The step portion 7 has a bottom surface 7a, a swirl downstream end surface 7b and a side surface 7c, and a swirl upstream end surface 7d that are substantially vertical. As shown in FIG. 3, the bottom surface 7a is formed obliquely so as to be deep in the direction of the side surface 7c,
It is smoothly connected to the side surface 7c by an arc, and is also smoothly connected to the swirl downstream side end surface 7b (not shown).

Reference numeral 8 is a fuel injection valve for injecting fuel to the swirl upstream side of the ignition plug 5, and is arranged above the periphery of the combustion chamber 2 at a position substantially facing the ignition plug 5. The fuel injection valve 8 is for injecting fuel in a column shape obliquely downward from the four injection ports. As shown in FIG. 1, the directions of the injection ports are the vertical direction passing through the tip of the fuel injection valve 8 and the center of the cylinder. The acute angle is different from the plane, and as shown in FIG. 2, the acute angle is different from the horizontal plane passing through the tip of the fuel injection valve 8, and the angle with respect to the vertical plane described above. The smaller the nozzle, the smaller the angle with respect to the horizontal plane.

In the fuel injection at a low engine load, the fuel injected from the injection port having the minimum angle with respect to the horizontal plane in the latter half of the compression stroke is, as shown in FIG. It starts from the time when it collides with the side surface 4a of the shallow plate portion 4 and ends when the required amount of fuel is injected by all the injection ports. Since the fuel injected from each injection port is directed at an acute angle with respect to the side surfaces 3a, 4a of the combustion chamber in this way, all the inertia in the spark plug direction at the time of collision with each side surface 3a, 4a. Power is applied, whereby the spark plug 5 evaporates by the heat of the combustion chamber.
Proceed in the direction.

At any engine speed, at the ignition timing, at least the spark plug 5 has at least the leading portion of the liquid fuel which travels on the shallow dish portion 4 which functions as a fuel guide passage.
Has reached near the tip. At this time, since the tip of the spark plug 5 is separated from the bottom surface 4b of the shallow dish portion 4, liquid fuel does not adhere to the tip of the spark plug 5 to cause misfire. On the shallow plate part 4 of the combustion chamber,
Fuel evaporated from the side surface 4a and the bottom surface 4b are combined to form an air-fuel mixture having a good ignitability. The evaporated fuel loses its inertial force and stays there, but at the ignition timing, since the liquid fuel reaches the vicinity of the tip of the ignition plug 5 as described above, the ignition plug 5 reliably ignites this mixture. Is guaranteed. Also, the side surface 3a of the deep plate portion 3
Similarly, the fuel supplied to is also evaporated to form an air-fuel mixture in the vicinity of the side surface 3a of the deep dish portion 3 adjacent to the shallow dish portion 4. The swirl formed in the combustion chamber moves the air-fuel mixture formed on the swirl upstream side of the entry position of the spark plug 3 on the shallow pan 4 and near the side surface 3 a of the deep pan 3 to the vicinity of the tip of the spark plug 3. Functioning as a result of which, the spark plug 3
It is possible to concentrate the air-fuel mixture in the vicinity of the tip of the and improve the ignitability.

When the engine has a low load, a mixture having a good ignitability is thus formed in the vicinity of the tip of the ignition plug 5, and this mixture is reliably ignited to realize low fuel consumption stratified combustion. At a low engine load, such a stratified charge combustion can be realized without problems because the fuel injection amount is relatively small. As shown in FIG. 4, the fuel injection start timing is the same crank angle θ1, The fuel injection end timing changes according to the injection amount.

Further, when the engine load increases and the engine is in the middle load, as shown in FIG. 4, as the fuel injection amount increases, the fuel is injected from the nozzle having the minimum angle with respect to the horizontal plane. The fuel injection start timing is gradually advanced to a crank angle at which the fuel does not collide with the top surface of the piston, and a part of the fuel is supplied to the step portion 7 as shown in FIG.

As a result, the fuel supplied into the combustion chamber forms an air-fuel mixture having a good ignitability in the vicinity of the tip of the ignition plug 5, as in the case of low engine load. On the other hand, the liquid fuel supplied to the step portion 7 may have a bottom surface 7a depending on the fuel start timing.
And then spreads to the swirl downstream side and reaches the side surface 7c and the swirl downstream end surface 7b while evaporating the bottom surface 7a by the piston heat, and this liquid fuel flows out to the piston top surface by the side surface 7c and the swirl downstream end surface 7b. Without being spread over the entire cylinder, the air-fuel mixture is vaporized by colliding with the cylinder head and being vaporized. Further, depending on the fuel injection start timing, there is fuel that directly collides with the side surface 7c, but in this fuel, the fuel injection direction of the fuel injection valve 8 is an acute angle toward the swirl downstream side with respect to the side surface 7c. For this reason, most of them proceed to the swirl downstream side along the side surface 7c, then proceed on the swirl downstream side end surface 7b, and all are vaporized by the heat of the piston before reaching the shallow plate portion 4 of the combustion chamber. Then, together with the fuel that is subsequently injected to the bottom surface 7a and vaporized, it floats on the stepped portion 7 to form an air-fuel mixture. The air-fuel mixture thus formed on the step 7 is
The swirl moves to a position adjacent to the spark plug 5 outside the combustion chamber at the time of ignition.

Even if the amount of fuel supplied to the step portion 7 is very small, this air-fuel mixture does not become lean as much as when it is made uniform in the entire combustion chamber, and in the vicinity of the spark plug as in the case of low engine load. Since the flame that is satisfactorily ignited is propagated to this air-fuel mixture and burns quickly, good stratified combustion can be realized even when the engine has a medium load. As described above, since the bottom surface 7a of the step portion 7 is gradually deepened in the direction of the side surface 7c, the radius of the arc connecting them can be increased, and the liquid fuel accumulates in this connection portion to cause smoke. It is prevented from occurring.

In this way, at the time of engine load,
The air-fuel mixture in the vicinity of the spark plug becomes too rich, which deteriorates the ignitability and causes smoke, and even when smoke is not generated when exhaust gas is recirculated, incomplete combustion due to insufficient oxygen causes monoxide. Generation of a large amount of carbon is prevented, and the flame ignited in the vicinity of the spark plug, as in the case of forming a homogeneous mixture in the entire combustion chamber with some fuel, dilutes this homogeneous mixture. It is prevented that a part of this homogeneous air-fuel mixture is discharged as unburned fuel and the fuel economy and exhaust emission are not deteriorated without propagating well to it.

When the engine load further increases and the fuel injection amount increases, the concentration at which the entire combustion chamber 2 is satisfactorily combusted with the fuel amount other than forming the air-fuel mixture having good ignitability in the vicinity of the spark plug 5 in the combustion chamber. As shown in FIG. 4, at this time, the fuel injection start timing in the latter half of the compression stroke is set to the crank angle θ1 similar to that at the time of low load, and the fuel other than the fuel injected at this time is taken in the intake stroke. It is designed to be sprayed on.

Further, at the time of high engine load, fuel injection in the compression stroke is not performed, all fuel is injected in the intake stroke, and at the time of ignition, a uniform mixture is formed in the combustion chamber to obtain a high output. It is designed to carry out uniform combustion which is advantageous to

In this embodiment, the fuel is injected in the compression and intake strokes in the high load region when the engine is under medium load, but of course, the combustion chambers 3, 4 and the step portion 7 are used.
Depending on the size and shape, the fuel injection can be performed only in the latter half of the compression stroke, and the fuel injection divided into two times including the intake stroke injection at the time of high load becomes unnecessary, and the fuel injection control can be simplified. .

[0022]

As described above, according to the in-cylinder injection type internal combustion engine of the present invention, the fuel supplied to the upstream side of the swirl of the ignition plug at the upper side surface of the combustion chamber is utilized by its inertial force. Then, a step portion having a wall surface for directing it substantially upward is formed, and the fuel injection timing control means causes the fuel injection valve to inject fuel so that fuel is injected from the step portion to the combustion chamber when the engine is under medium load. In order to control the timing, part of the fuel supplied to the stepped portion is vaporized on the stepped portion by the heat of the piston, and the rest is directed almost directly above by the wall surface of the stepped portion and collides with the cylinder head. Vaporize to form a mixture on the step with a concentration that allows sufficient combustion,
This mixture moves to a position adjacent to the spark plug outside the combustion chamber at the time of ignition by the swirl, and the fuel supplied into the combustion chamber forms a mixture with good ignitability in the vicinity of the spark plug in the combustion chamber, The flame that is reliably ignited in the vicinity of the spark plug propagates to the air-fuel mixture that has moved to the position adjacent to the spark plug outside the combustion chamber, and it is possible to satisfactorily combust it.

In this way, when the load is too rich to concentrate near the spark plug in the combustion chamber, a part of the fuel injection amount is concentrated at the position adjacent to the spark plug outside the combustion chamber, so to speak, outside the combustion chamber. Including the ignition plug, a mixture with good ignition and combustibility is formed in a wide area in the vicinity of the spark plug. It becomes possible to realize combustion.

[Brief description of drawings]

FIG. 1 is a plan view of an upper portion of a piston of a cylinder injection internal combustion engine according to the present invention.

FIG. 2 is a vertical cross-sectional view at the ignition timing of FIG.

FIG. 3 is a vertical cross-sectional view of a combustion chamber and a step portion for explaining a fuel collision position at each engine load, (A) shows a low engine load, and (B) shows a medium engine load.

FIG. 4 is a graph showing a fuel injection start timing in a compression stroke with respect to an engine load.

[Explanation of symbols]

 1 ... Piston 3 ... Deep Pan 4 ... Shallow Pan 5 ... Spark Plug 7 ... Step 8 ... Fuel Injection Valve

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location F02B 23/08 F02B 23/08 E F02D 41/34 9523-3G F02D 41/34 F F02F 3/26 F02F 3/26 A

Claims (1)

[Claims] 1. A concave combustion chamber formed on a top surface of a piston, a spark plug which enters the combustion chamber at an ignition timing, a swirl generating means for generating swirl in a cylinder, and an upper side surface of the combustion chamber. In the piston position in the latter half of the compression stroke, a step portion having a wall surface formed immediately upstream of the ignition plug in the swirl and for directing the supplied fuel almost upward by utilizing its inertial force. A fuel injection valve capable of injecting fuel to a swirl upstream side of a position where the ignition plug of the combustion chamber enters, and the fuel injection valve such that fuel is injected from the stepped portion to the combustion chamber when the engine is under medium load. And a fuel injection timing control means for controlling the injection timing of the in-cylinder injection internal combustion engine.