JPH07102976A - Inter-cylinder injection type spark ignition engine - Google Patents

Abstract

PURPOSE:To form intended uniform fuel mixture by surely atomizing fuel injected in an air intaking stroke and attached to the top surface of a piston by utilizing a swirl. CONSTITUTION:A fuel injection valve 11 positioned in a peripheral part of upper side of a combustion chamber for taking charge of compression stroke fuel injection for forming concentrated fuel mixture adjacent to a sparking plug 1 and air intaking stroke fuel injection for forming uniform fuel mixture around this concentrated fuel mixture is mounted in an inter-cylinder injection type spark ignition engine. The inter-cylinder injection type ignition engine includes a swirl generating means for generating a swirl and a piston 2 extending to the fuel injection valve 11 from downward of the sparking plug 1 and having almost plane bottom face 101d and a top face formed in a recessed groove where the end face 101a of the sparking plug 1 side is extending upward. A slanting face reaches the recessed groove while gradually coming down to revolving direction of the swirl is mounted adjacently to the periphery of the top face of the piston.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-cylinder injection spark ignition engine in which fuel is directly injected into a cylinder and an air-fuel mixture formed thereby is ignited and burned by an ignition plug.

[0002]

2. Description of the Related Art This in-cylinder injection spark ignition engine is used to execute a fuel-efficient stratified combustion in which a rich air-fuel mixture is formed only in the vicinity of the spark plug when the load is low and medium, and a high output is provided when the load is high. It is known to carry out the obtainable homogeneous combustion. In Japanese Patent Laid-Open No. 2-125911, such a cylinder injection type spark ignition engine and an intake passage capable of generating a swirl that swirls around the axis of the combustion chamber are combined, and this swirl is used especially at low and medium loads. Those intended to achieve good stratified combustion are described.

The above-mentioned cylinder injection type spark ignition engine has a piston having a recess formed on the top surface thereof, and when stratified charge combustion is executed, fuel is injected toward the recess during the latter half of the compression stroke, and the recess is formed. Is used to raise atomized fuel near the spark plug located in the center of the cylinder to form a rich air-fuel mixture. The swirl described above can accelerate the combustion speed to improve the combustion and mainly swirl around the outer periphery of the combustion chamber, so that the rich air-fuel mixture formed in this way is ignited without scattering. Can be retained near the stopper.

[0004]

In the stratified charge combustion at the time of medium load of the engine, the fuel injection amount increases because a high output is required as compared with the time of low load. When all the fuel thus increased is injected in the latter half of the compression stroke, the air-fuel mixture formed in the vicinity of the spark plug becomes extremely rich and may cause misfire. Fuel is injected during the intake stroke and is intended to form a homogeneous mixture around the spark plug.

However, the fuel injection during the intake stroke is
Since the piston is descending and the collision speed of fuel to the piston is much lower than that in the compression stroke, the fuel injected into the recess does not atomize and rise as in the compression stroke, Not only cannot the intended homogeneous mixture be formed, it will remain attached, and it will cause smoke.

Therefore, a first object of the present invention is to reliably atomize the fuel injected in the intake stroke and adhering to the piston by using a swirl to form an intended uniform air-fuel mixture. An object is to provide an injection spark ignition engine.

A second object of the present invention is, in addition to the first object, an in-cylinder injection type spark capable of forming a better uniform air-fuel mixture by using atomized fuel by using a swirl. It is to provide an ignition engine.

[0008]

A first in-cylinder injection type spark ignition engine according to the present invention includes a spark plug located substantially in the center of an upper side of a combustion chamber, and a rich concentration near the spark plug at least in a specific engine operating state. A fuel injection valve located at the upper peripheral edge of the combustion chamber, which is in charge of compression stroke fuel injection for forming a rich air-fuel mixture and intake stroke fuel injection for forming a uniform air-fuel mixture around the rich air-fuel mixture. A swirl generating means for generating a swirl swirling around its axis in the combustion chamber at least in the operating state of the specific engine; and a substantially flat bottom surface extending from below the spark plug toward the fuel injection valve side. A piston having a top surface on which an end surface on the side of the spark plug extends upwardly is formed, and the fuel injected from the fuel injection valve is obliquely upward on the bottom surface of the recessed groove. Opposition from the direction Has become so doing, the vicinity of the outer periphery of the top surface of the piston, characterized in that the inclined surface reaches the concave groove while gradually falls in the turning direction of the swirl is provided.

A second in-cylinder injection spark ignition engine according to the present invention is the above-described first in-cylinder injection spark ignition engine, wherein the end face of the concave groove on the spark plug side is offset from the center of the combustion chamber. It is characterized in that it extends in the upward direction.

[0010]

According to the above-described first in-cylinder injection type spark ignition engine, fuel is injected to the bottom surface of the concave groove during the intake stroke and adheres to the top surface of the piston during the intake stroke in the specific engine operating state. A part of the swirl swirling around is satisfactorily atomized because it flows into the concave groove, and together with this swirl, it is launched along the end surface on the spark plug side of the concave groove.

Further, according to the above-mentioned second cylinder injection type spark ignition engine, like the first cylinder injection type spark ignition engine,
The fuel adhering to the concave groove is atomized by a part of the swirl and rises along the end surface of the concave groove, and since this position is eccentric from the center of the combustion chamber, the swirl swirls immediately around the outer periphery of the combustion chamber. It is taken in and homogenized.

[0012]

1 is a schematic plan view of a cylinder injection type spark ignition engine according to the present invention. As shown in the figure, an ignition plug 1 is arranged substantially at the center of the upper side of the combustion chamber. In the combustion chamber, the first and second intake passages 2 and 3 and the first intake passage 2
And the second exhaust passages 4, 5 are the first and second intake valves 6, 7
And the first and second exhaust valves 8 and 9 are connected to each other.

The first intake passage 2 is a helical port that can generate a swirl that swirls around its axis in the direction indicated by the arrow in the combustion chamber, while the second intake passage 3 is a straight port, which is a swirl control valve (hereinafter referred to as a swirl control valve). SCV
10) are arranged. The opening of the SCV 10 is generally controlled so that the opening thereof increases as the engine load increases. As a result, the required intake air amount can be reliably supplied to the combustion chamber, and since the helical port 2 is mainly used until the engine medium load, swirl can be formed in the combustion chamber. The fuel injection valve 11 is arranged so as to inject fuel into the combustion chamber from between the first and second intake valves 6 and 7.

2 and 3 are schematic vertical sectional views of the cylinder injection type spark ignition engine of FIG. The intake passage and the exhaust passage described above are omitted for clarity of the drawing. Figure 2
3 shows the state in which the piston 12 is in the first half of the intake stroke.
Shows the state where the piston 12 is in the latter half of the compression stroke. The fuel injection valve 11 injects fuel in a conical shape toward the top surface of the piston 12, and the injected fuel is shown by a chain line.

4A and 4B are views showing the shape of the piston 12, FIG. 4A being a plan view and FIG. 4B being a sectional view taken along the line P--P. As shown in the figure, on the top surface of the piston 12 whose central portion is raised, the fuel injection valve 1
A fan-shaped groove 101 is formed on the first side. Although the spark plug 1 is located substantially in the center of the combustion chamber, in detail, it is installed on the opposite side of the fuel injection valve 11 with some eccentricity. Accordingly, the end of the groove 101 on the spark plug side is also centered in the combustion chamber. Is eccentric to. An arcuate end surface 101a that constitutes the spark plug side end of the groove 101 and the first side wall 1 in the vicinity thereof
01b and the second side wall 101c are smoothly connected to the substantially flat bottom surface 101d with an arc having a predetermined radius, and the recess 1 as shown by the dotted line on the bottom surface 101d side.
01e is formed, but extends substantially vertically.

On the outer periphery of the top surface of the piston 12, the first sidewall 101b on the swirl upstream side of the groove 101 is gradually lowered in the swirl turning direction, and the bottom surface 1 of the groove 101 is formed.
The inclined surface 102 that is smoothly connected to 01d is formed.

In the in-cylinder injection spark ignition engine thus constructed, the fuel injection start timing is determined based on the map shown in FIG. 5, and when the required fuel amount corresponding to the load is supplied to the combustion chamber, the fuel is injected. The injection is ended. In the low load region A in FIG. 5, the fuel injection start timing is set in the latter half of the compression stroke,
In the high load region C, it is set in the first half of the intake stroke. The fuel injected in the latter half of the compression stroke in the low load region A is, as shown in FIG. 3, the bottom surface 1 of the groove 101 on the top surface of the piston 12.
01d from diagonally above. The relative velocity between the fuel and the piston 12 at the time of collision is considerably high because the piston 12 is moving upward, and due to its momentum, the fuel that collides is gradually vaporized by the heat of the piston 12 and gradually moves into the groove 1
The inside of 01 is moved toward the end portion on the spark plug side. Groove 10
Since the distance between the two side walls 101b and 101c of No. 1 is gradually narrowed in this direction, the injected bottom surface 10
The fuel spread in 1d is mixed with the air in the groove 101 and concentrated on the end portion on the spark plug side, and rises as an appropriate rich air-fuel mixture along the arcuate end surface 101a.

At this time, the SCV 10 is almost fully closed, and a strong swirl is formed in the combustion chamber. This swirls the outer peripheral portion of the combustion chamber, and thus the central portion of the combustion chamber is The rising rich air-fuel mixture can be concentrated in the vicinity of the spark plug 1 arranged right above it without being scattered by the swirl, ensuring a reliable ignitability, and then extremely It is possible to realize low fuel consumption stratified combustion in which a lean air-fuel mixture is satisfactorily burned by using a swirl.

Most of the fuel injected in the first half of the intake stroke in the high load region C is atomized and mixed by a large amount of intake air before reaching the top surface of the piston 12, and the fuel adhering to the top surface of the piston 12 is the same. It is vaporized by heat and forms a sufficiently homogenized mixture by ignition. At this time, the SCV 10 is almost fully opened and no swirl is formed in the combustion chamber, but good uniform combustion advantageous for obtaining a higher output than that of stratified combustion is realized without using the swirl.

In the middle load region B in FIG. 5, the fuel injection start timing is set separately for the first half of the intake stroke and the second half of the compression stroke. The fuel injected in the latter half of the compression stroke is used to form a rich air-fuel mixture in the vicinity of the spark plug 1 as in the low load region A, and the fuel injected in the first half of the intake stroke is of this rich air-fuel mixture. Used to form a relatively lean homogeneous mixture around. Such mixture formation is intended to realize stratified combustion with a higher output than in the low load region A.

In detail, the fuel injection timing control in the medium load region B is provided with a slight deviation according to the engine speed as shown in FIG. This figure shows the opening / closing valve timing of the fuel injection valve 11 under a predetermined load. When the valve opening timing is the same, the higher the engine rotational speed, the shorter the time from valve closing to ignition, and the desired mixture Since it is difficult to form the valve, the higher the engine speed, the earlier the valve opening timing.
This idea is based on the low load area A and the high load area C described above.
It is also applicable to.

The fuel injection amount in the first half of the intake stroke in the medium load region B is the total required amount at this time, excluding the fixed amount injected in the latter half of the compression stroke for ignition. This fuel injection is similar to that in the high load region C described above, but since the intake amount is small, it is not sufficiently atomized and mixed with the piston 1
2 Collide with the top surface. In this collision, the fuel injection valve 11
Since the distance from the piston to the top surface of the piston 12 is relatively long, the fuel speed is slow, and because the piston 12 is descending, the relative speed of the fuel and the piston 12 at the time of collision is considerably low. Also, the collision range of the top surface of the piston 12 is
Since the fuel velocity is slow at the tip portion of the sprayed fuel and does not spread so much, it is in the groove 101 as in the low load region A as shown in FIG.

As described above, the fuel colliding with the top surface of the piston 12 has a low collision speed, so that the fuel remains attached to the place without much movement. Therefore, normally, as in the compression stroke injection described above, the groove 1
01 does not rise along the end face 101a, and a uniform mixture cannot be formed on the outside in the vicinity of the spark plug 1, so that a desired output cannot be obtained, and thereafter the fuel is injected in the latter half of the compression stroke. A very rich air-fuel mixture is formed in the vicinity of the spark plug 1 together with the fuel, which adversely deteriorates the ignitability,
It also causes smoke.

However, since the above-described inclined surface 102 is formed on the top surface of the piston 12 of this embodiment, as shown in FIG. 2, a part of the swirl generated in the intake stroke is formed on this inclined surface. Along with, into the groove 101, the fuel attached there is atomized and rises along the end surface 101a of the groove 101. The fuel thus atomized should gradually spread in the outer peripheral direction and be sufficiently homogenized by the swirls present therein by the time the fuel injection in the compression stroke is started to form a good homogeneous mixture. You can

In particular, in this embodiment, since the spark plug side end having the end surface 101a of the groove 101 is eccentric with respect to the center of the combustion chamber, the atomized fuel rising from the groove 101 spreads in the outer peripheral direction by itself. Since it was previously taken into the swirl that swirls the outer peripheral portion of the combustion chamber, homogenization by the swirl is promoted, and a more uniform air-fuel mixture can be formed.

Next, as in the low load region A, fuel injection in the latter half of the compression stroke is executed, and a rich air-fuel mixture with good ignitability is formed in the vicinity of the spark plug 1, and stratified combustion with a relatively high output is performed. Will be realized. Also in the fuel injection in the latter half of the compression stroke, since a part of the swirl flows into the groove 101, atomization of the injected fuel is further improved, and the rising speed of the atomized fuel is increased, Even if the rising position is eccentric with respect to the center of the combustion chamber, the rich air-fuel mixture can be reliably directed to the vicinity of the spark plug 1 without being affected by the swirl.

[0027]

As described above, according to the first in-cylinder injection type spark ignition engine of the present invention, the spark plug located substantially in the center of the upper side of the combustion chamber and at least the specific engine operating state
Responsible for the compression stroke fuel injection for forming a rich mixture near the spark plug and the intake stroke fuel injection for forming a uniform mixture around this rich mixture, and is located on the peripheral edge of the upper side of the combustion chamber. A fuel injection valve, a swirl generation means for generating a swirl swirling around its axis in the combustion chamber at least in this specific engine operating state, and a fuel injection valve extending from below the spark plug toward the fuel injection valve side and having a substantially flat surface. A piston having a bottom surface and an end surface on the spark plug side having a top surface provided with a concave groove extending upward, and the fuel injected from the fuel injection valve is obliquely upward on the bottom surface of the concave groove. In the vicinity of the outer periphery of the top surface of the piston, an inclined surface reaching the concave groove while gradually descending in the swirl turning direction is provided in the vicinity of the outer periphery of the piston. Intake line The fuel that is injected into the bottom of the concave groove inside and adheres to it is atomized well because a part of the swirl that swirls in contact with the top surface of the piston flows into the concave groove. Along the
After that, it spreads in the outer circumferential direction of the combustion chamber and is made uniform by swirl.

Further, according to the second in-cylinder injection type spark ignition engine of the present invention, since the end face of the concave groove on the spark plug side extends eccentrically from the center of the combustion chamber, The fuel that is atomized by the swirl and rises along the end surface of the concave groove is taken into the swirl that swirls around the outer peripheral portion of the combustion chamber before it spreads in the outer peripheral direction, and the homogenization time by the swirl increases. A good homogeneous mixture can be formed.

[Brief description of drawings]

FIG. 1 is a schematic plan view of a cylinder injection type spark ignition engine according to the present invention.

FIG. 2 is a schematic vertical sectional view of the first half of an intake stroke of a cylinder injection type spark ignition engine according to the present invention.

FIG. 3 is a schematic vertical sectional view of the latter half of the compression stroke of the cylinder injection type spark ignition engine according to the present invention.

4A and 4B are diagrams showing a piston shape, FIG. 4A being a plan view and FIG. 4B being a P-P sectional view thereof.

FIG. 5 is a map for determining a combustion injection start timing.

FIG. 6 is a diagram showing an opening / closing valve timing of a fuel injection valve with respect to a rotation speed at a predetermined load in a medium load region.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Spark plug 2 ... 1st intake passage (helical port) 3 ... 2nd intake passage (straight port) 4 ... 1st exhaust passage 5 ... 2nd exhaust passage 10 ... Swirl control valve 11 ... Fuel injection valve 12 ... Piston 101 ... groove 101a ... end surface on spark plug side 101b ... first side wall 101c ... second side wall 101d ... bottom surface 102 ... inclined surface

Claims (2)

[Claims] 1. A spark plug located substantially in the center of an upper side of a combustion chamber, a compression stroke fuel injection for forming a rich air-fuel mixture near the spark plug, and a fuel mixture of the rich air-fuel mixture at least in a specific engine operating state. A fuel injection valve that is in charge of intake stroke fuel injection to form a uniform air-fuel mixture around it, and a fuel injection valve located at the peripheral edge of the upper side of the combustion chamber, and a swirl that swirls around its axis in the combustion chamber at least in the specific engine operating state. A swirl generating means for generating and a concave groove extending from below the spark plug toward the fuel injection valve side, having a substantially flat bottom surface, and having an end surface on the spark plug side extending upward are formed. And a piston having a top surface which is formed such that the fuel injected from the fuel injection valve collides with the bottom surface of the concave groove from an obliquely upper direction, and the vicinity of the outer peripheral portion of the top surface of the piston is provided. Has An in-cylinder injection spark ignition engine, wherein an inclined surface is provided which reaches the concave groove while gradually lowering in a swirling direction of the swirl. 2. The in-cylinder injection spark ignition engine according to claim 1, wherein an end surface of the recessed groove on the spark plug side extends eccentrically from the center of the combustion chamber and extends upward.