JP2007255267A - In-cylinder injection spark ignition internal combustion engine - Google Patents

Abstract

In a direct injection spark ignition internal combustion engine in which a flammable mixture in the vicinity of a spark plug is directly formed by injected fuel and stratified combustion is performed, the mixture near the spark plug is excessively lean or excessively rich during stratified combustion. Do not become.
A cylinder in which a part of fuel injected from a fuel injection valve 3 passes through an ignition gap of a spark plug 4 and forms a combustible mixture in the vicinity of the spark plug at the ignition timing to perform stratified combustion. In an internal injection spark ignition internal combustion engine, during stratified combustion, the swirl flow S generated in the cylinder in the intake stroke is strengthened by the swirl flow generation means as the engine load increases.
[Selection] Figure 1

Description

  The present invention relates to a direct injection spark ignition internal combustion engine.

  There is known stratified combustion in which a lump of combustible air-fuel mixture is formed only in the vicinity of the spark plug and combustion in an air-fuel ratio leaner than the stoichiometric air-fuel ratio is possible as a whole in the cylinder. In a direct injection spark ignition internal combustion engine in which a combustible mixture in the vicinity of a spark plug is formed in a cavity formed on a piston top surface in order to perform stratified combustion, the spark plug is positioned by using swirl flow. It has been proposed to gather near the center of the cavity. (For example, refer to Patent Document 1).

  In this in-cylinder injection spark ignition internal combustion engine, when the engine load is small and the fuel injection amount is small, the air-fuel mixture formed near the spark plug becomes excessively lean by concentrating the injected fuel near the center of the cavity. The swirl flow is strengthened to prevent. On the other hand, when the engine load is large and the fuel injection amount is large, the swirl flow is weakened in order to prevent the air-fuel mixture formed near the spark plug from being excessively concentrated due to excessive concentration of injected fuel near the center of the cavity. The Thus, the smaller the fuel injection amount during stratified combustion, the stronger the swirl flow formed in the cylinder during the intake stroke.

JP 2004-225601 A JP 2002-371852 A

  By the way, in stratified combustion, a cylinder that directly forms a combustible air-fuel mixture in the vicinity of the spark plug in the cylinder so that a part of the fuel injected by the fuel injection valve directly passes through the ignition gap of the spark plug. Internal injection spark ignition internal combustion engines are known. In such an in-cylinder injection spark ignition internal combustion engine, as described above, if the swirl flow is strengthened as the fuel injection amount is small, the injected fuel is greatly dispersed by the strong swirl flow when the fuel injection amount is small. If the air-fuel mixture becomes excessively lean, misfires may occur. Further, when the fuel injection amount is large, if the injected fuel is hardly dispersed by a weak swirl flow, the air-fuel mixture becomes excessively rich and smoke may be generated.

  Accordingly, an object of the present invention is to provide an in-cylinder injection spark ignition internal combustion engine in which a flammable mixture in the vicinity of a spark plug is directly formed by the injected fuel and stratified combustion is performed. Avoid over-leaning or over-riching.

  An in-cylinder spark-ignition internal combustion engine according to claim 1 of the present invention includes a fuel injection valve that directly injects fuel into a cylinder, an ignition plug, and a swirl flow generating means. In-cylinder injection spark ignition internal combustion in which a part of the fuel injected from the valve passes through the ignition gap of the spark plug and performs stratified combustion by forming a combustible mixture in the vicinity of the spark plug at the ignition timing In the engine, during stratified combustion, the swirl flow generated in the cylinder in the intake stroke is strengthened by the swirl flow generation means as the engine load increases.

  A cylinder injection spark ignition internal combustion engine according to claim 2 of the present invention comprises a fuel injection valve for directly injecting fuel into a cylinder, an ignition plug, and a swirl flow generating means. In-cylinder injection spark ignition internal combustion in which a part of the fuel injected from the valve passes through the ignition gap of the spark plug and performs stratified combustion by forming a combustible mixture in the vicinity of the spark plug at the ignition timing In the engine, during stratified combustion, the smaller the combustion air-fuel ratio, the stronger the swirl flow generated in the cylinder in the intake stroke by the swirl flow generation means.

  The in-cylinder injection spark ignition internal combustion engine according to claim 3 according to the present invention is the in-cylinder injection spark ignition internal combustion engine according to claim 1 or 2, wherein at least two intake ports are connected into the cylinder, One of the two intake ports is provided with a swirl flow control valve as the swirl flow generating means, and both of the two intake ports are provided with tumble flow control valves. During stratified combustion, the tumble flow control valve is fully opened. The swirl flow control valve is controlled as follows, and at the time of homogeneous combustion, the swirl flow control valve is fully opened to control the tumble flow control valve.

  According to a fourth aspect of the present invention, there is provided the in-cylinder injection spark ignition internal combustion engine according to the first or second aspect, wherein the spark plug is disposed at an upper portion of the cylinder, and the spark plug Has an L-shaped electrode, and the L-shaped electrode has a parallel portion parallel to the spark plug axis and a vertical portion perpendicular to the spark plug axis, and the tumble flow when passing through the spark gap of the spark plug is The L-shaped electrode of the spark plug is oriented so as not to collide perpendicularly to the width direction surface of the parallel portion of the L-shaped electrode.

  According to the in-cylinder injection spark ignition internal combustion engine of the first aspect of the present invention, a part of the fuel injected from the fuel injection valve passes through the ignition gap of the ignition plug, and the ignition plug is set at the ignition timing. In an in-cylinder spark-ignition internal combustion engine that performs stratified combustion by forming a combustible mixture in the vicinity, during stratified combustion, the swirl flow generated in the cylinder in the intake stroke by the swirl flow generation means becomes stronger as the engine load increases. As a result, the fuel that is injected in large quantities when the engine load is high is spread to the downstream side of the swirl flow by the strengthened swirl flow, and a lump of combustible that is not excessively rich in the vicinity of the spark plug. An air-fuel mixture can be formed. Further, the fuel that is injected only in a small amount when the engine load is low is hardly dispersed by the weakened swirl, and a lump of combustible air-fuel mixture that is not excessively lean can be formed in the vicinity of the spark plug.

  According to the in-cylinder spark-ignition internal combustion engine of the second aspect of the present invention, a part of the fuel injected from the fuel injection valve is allowed to pass through the ignition gap of the ignition plug, and the ignition plug is set at the ignition timing. In an in-cylinder spark ignition internal combustion engine that performs stratified combustion by forming a combustible mixture in the vicinity, during stratified combustion, the smaller the combustion air-fuel ratio, the more the swirl flow that is generated in the cylinder in the intake stroke by the swirl flow generation means As a result, the fuel that is injected in large quantities when the combustion air-fuel ratio is small is spread to the downstream side of the swirl flow by the strengthened swirl flow, and a lump that is not excessively rich in the vicinity of the spark plug. A flammable gas mixture can be formed. Further, the fuel that is injected only in a small amount when the combustion air-fuel ratio is large is hardly dispersed by the weakened swirl, and a lump of combustible air-fuel mixture that is not excessively lean can be formed in the vicinity of the spark plug.

  According to the in-cylinder injection spark ignition internal combustion engine according to claim 3 of the present invention, in the in-cylinder injection spark ignition internal combustion engine according to claim 1 or 2, at least two intake ports are connected into the cylinder. , A swirl flow control valve as a swirl flow generating means is arranged at one of the two intake ports, a tumble flow control valve is arranged at both of the two intake ports, and the tumble flow control valve is fully opened during stratified combustion. By controlling the flow control valve, a combustible air-fuel mixture that is not excessively rich or excessively lean can be formed in the vicinity of the spark plug, and at the time of homogeneous combustion, the swirl flow control valve is fully opened to control the tumble flow control valve. A strong tumble flow that lasts until the latter half of the compression stroke is generated in the cylinder during the intake stroke, and this tumble flow is well homogenized by the ignition timing. The ignition timing it is possible to form a homogeneous air-fuel mixture can generate turbulence in the cylinder, it is possible to realize a quick good homogeneous combustion of combustion rate.

  According to the in-cylinder injection spark ignition internal combustion engine according to claim 4 of the present invention, in the in-cylinder injection spark ignition internal combustion engine according to claim 1 or 2, the ignition plug is disposed at an upper portion of the cylinder, and the ignition plug The L-shaped electrode of the spark plug is oriented so that the tumble flow when passing through the ignition gap does not collide perpendicularly to the widthwise surface of the parallel portion of the L-shaped electrode. Thereby, the arc generated in the ignition gap is extended to the downstream side by the tumble flow, and particularly when the fuel injection amount is large, the combustible mixture spread to the downstream side of the swirl flow can be favorably ignited.

  FIG. 1 is a bottom view of a cylinder head showing an embodiment of a direct injection spark ignition internal combustion engine according to the present invention, and FIG. 2 is a schematic longitudinal sectional view of the direct injection spark ignition internal combustion engine of FIG. 1 and 2 both show the latter half of the compression stroke. 1 and 2, 1 is a pair of intake valves, and 2 is a pair of exhaust valves. Reference numeral 3 denotes a fuel injection valve that is disposed substantially at the center of the cylinder upper portion and directly injects fuel into the cylinder, and 4 is an ignition plug that is disposed closer to the exhaust valve than the fuel injection valve 1 at the upper portion of the cylinder.

  The first intake port 51 and the second intake port 52 that lead into the cylinder via the corresponding intake valve 1 are divided into two vertically by the partition wall 6 in the downstream portion, and the tumble that allows the lower portions of each to be closed. A flow control valve 7 is provided. The second intake port 52 is provided with a swirl flow control valve 8 that can close the inside of the port immediately upstream of the partition wall 6. Reference numeral 9 denotes an exhaust port communicating with the corresponding exhaust valve 2 into the cylinder. Reference numeral 10 denotes a piston.

  The in-cylinder injection spark ignition internal combustion engine performs stratified combustion when the engine load is equal to or lower than the set load, and performs homogeneous combustion when the engine load is larger than the set load. During stratified combustion, the fuel injection valve 3 injects fuel in the latter half of the compression stroke. The fuel injection valve 3 has a slit-shaped injection hole, and injects the fuel into a flat, substantially fan shape having a relatively small thickness. The center in the width direction of the substantially fan-shaped fuel spray is ignited. The fuel injection direction is set so as to pass through the ignition gap of the plug 4.

  The substantially fan-shaped fuel spray is atomized and vaporized by friction with intake air during flight in the cylinder, and forms a lump of air-fuel mixture directly in the vicinity of the spark plug 4. When the fuel injection amount is considerably small, the air-fuel mixture formed in the vicinity of the spark plug 4 in this way has an appropriate fuel concentration, and reliable ignition combustion is realized. However, when the fuel injection amount is relatively large, the air-fuel mixture formed in the vicinity of the spark plug 4 becomes excessively rich, and smoke may be generated during combustion.

  In this embodiment, the swirl flow control valve 8 is disposed in the second intake port 52, and the amount of intake air supplied from the second intake port 52 into the cylinder as the opening of the swirl flow control valve 8 is reduced. And the swirl flow S formed by the intake air supplied from the first intake port 51 in the tangential direction of the cylinder bore can be strengthened. Accordingly, the swirl flow S generated in the cylinder in the intake stroke is controlled in consideration of the damping until the latter half of the compression stroke, so that the swirl flow S having a desired strength is generated in the cylinder in the second half of the compression stroke. Can exist. The tumble flow control valve 7 disposed in the first intake port 51 and the second intake port 52 is fully opened during stratified combustion.

  In the present embodiment, as shown in FIG. 3, during stratified combustion, the larger the fuel injection amount, the smaller the opening of the swirl flow control valve 8 and the more the swirl flow S generated in the cylinder in the intake stroke. By strengthening, the swirl flow S existing in the cylinder in the latter half of the compression stroke is made stronger. Thereby, as the fuel injection amount increases, the mixture that becomes richer as it is as it is is forced to spread further toward the downstream side of the swirl flow S by the stronger swirl flow S, and a lump near the spark plug 4 The fuel concentration of the air-fuel mixture is made appropriate to suppress the generation of smoke.

  In FIG. 3, when the fuel injection amount is considerably small, the swirl flow control valve 8 is fully opened so that a swirl flow is not generated in the cylinder. Thereby, the lump of air-fuel mixture formed in the vicinity of the spark plug 4 is prevented from being excessively leaned by being spread by the swirl flow, and the occurrence of misfire is suppressed.

  Thus, instead of controlling the opening degree of the swirl flow control valve 8 according to the fuel injection amount, the higher the engine load corresponding to the depression amount of the accelerator pedal, the higher the fuel injection amount. The swirl flow generated in the intake stroke may be strengthened by reducing the opening of the swirl control valve 8. In stratified combustion, the intake air amount in the cylinder is substantially constant regardless of the fuel injection amount, and the fuel injection amount increases as the combustion air-fuel ratio in the entire cylinder decreases. Thus, the smaller the combustion air-fuel ratio detected by the air-fuel ratio sensor of the engine exhaust system, the smaller the opening of the swirl flow control valve 8 and the stronger the swirl flow generated in the intake stroke. .

  By the way, as shown in FIG. 4, the spark plug 4 generally has a center electrode 41 on the high voltage side and an L-shaped electrode 42 on the ground side in general. The L-shaped electrode 42 has a parallel part 42 a parallel to the central axis of the spark plug 4 and a vertical part 42 b perpendicular to the central axis. In the present embodiment, the width direction surface of the parallel portion 42a of the L-shaped electrode 42 is oriented substantially parallel to the swirl flow S (even in the point-symmetrical arrangement with respect to FIG. 4, the width direction surface of the parallel portion 42a is the same as the swirl flow S. Almost parallel). Thereby, the arc A generated between the center electrode 41 and the L-shaped electrode 42 of the spark plug 4 is easily extended to the downstream side of the swirl flow S by the swirl flow S as shown in FIG. Thus, during stratified combustion, the stronger the swirl flow in the second half of the compression stroke, the more the air-fuel mixture in the vicinity of the spark plug 4 is expanded further downstream by the swirl flow S, and the arc A also flows downstream. Since it is further extended, the ignitability of the air-fuel mixture is improved.

  On the other hand, when the swirl flow S passes through the ignition gap between the center electrode 41 and the L-shaped electrode 42 of the spark plug 4, as shown by a dashed line in FIG. 4, the parallel portion of the L-shaped electrode 42. When the L-shaped electrode 42 is oriented so as to collide perpendicularly to the width direction surface of 42a, the arc A is not extended downstream by the swirl flow. Thereby, in order to improve the ignitability of the air-fuel mixture, it is preferable not to orient the L-shaped electrode 42 in this way. If the swirl flow S does not collide perpendicularly to the width direction surface of the parallel part 42a of the L-shaped electrode 42 when passing through the ignition gap of the spark plug 4, the arc A is extended slightly downstream by the swirl flow S. It is. Further, even when the swirl flow S flows into the ignition gap of the spark plug 4, the orientation of the L-shaped electrode 42 collides perpendicularly to the width direction surface of the parallel portion 42a of the L-shaped electrode 42 (one point in FIG. 4). The swirl flow S is able to extend the arc A downstream by passing through the ignition gap of the spark plug 4 through the parallel portion 42a.

  As described above, the in-cylinder injection spark ignition internal combustion engine performs homogeneous combustion when the engine load is larger than the set load. During the homogeneous combustion, the swirl flow control valve 8 is fully opened. On the other hand, the opening degree of the two tumble flow control valves 7 of the first intake port 51 and the second intake port 52 is similarly controlled. The smaller the opening of the two tumble flow control valves 7, the stronger the tumble flow that descends the exhaust valve side generated in the cylinder and rises the intake valve side in the intake stroke. The amount of intake air supplied to is reduced.

  In the homogeneous combustion on the low load side where the engine output is not so high, the combustion air-fuel ratio is preferably made leaner than the stoichiometric air-fuel ratio in order to reduce fuel consumption. In such a homogeneous combustion at a lean air-fuel ratio, it is preferable that the tumble flow is reliably maintained in the cylinder until this time at the ignition timing at the end of the compression stroke so that turbulence exists, and the two tumble flow control valves 7 are opened. The degree is reduced and a strong tumble flow is generated in the cylinder in the intake stroke.

  The strong tumble flow is advantageous for sufficiently stirring the fuel injected from the fuel injection valve 3 during the intake stroke and forming a good homogeneous mixture by the ignition timing. On the top surface of the piston 10 is a cavity 10a having an arc cross-sectional shape for suppressing the attenuation of the tumble flow that descends the exhaust valve side and rises the intake valve side in the cylinder to facilitate the tumble flow until the ignition timing. Is formed.

  For homogeneous combustion on the high load side where high engine output is required, the combustion air-fuel ratio is preferably the stoichiometric air-fuel ratio or rich air-fuel ratio. In such homogeneous combustion at the stoichiometric air-fuel ratio, if there is a strong turbulence in the cylinder at the ignition timing, the combustion speed becomes too fast and the thermal efficiency deteriorates, so the opening degree of the two tumble flow control valves 7 is In the intake stroke, the tumble flow is not generated so strongly in the cylinder. At this time, a relatively large amount of intake air is required. However, since the opening degree of the two tumble flow control valves 7 is increased, there is no shortage of intake air.

  By the way, at the time of homogeneous combustion, the swirl flow control valve 8 is fully opened, but the intake resistance of the second intake port 52 where the swirl flow control valve 8 is disposed is still the first where the swirl flow control valve 8 is not disposed. It becomes larger than the intake resistance of the intake port 51. In the cylinder, two tumble flows parallel to each other are initially generated by the two intake ports 51 and 52, and then the two tumble flows are combined into one tumble flow. If the intensity of these two tumble flows is the same, there will be no significant attenuation when one tumble flow is formed. However, if the strengths of the two tumble flows generated in the cylinder differ due to the influence of the swirl flow control valve 8, a relatively large attenuation occurs when the tumble flow becomes one, and the tumble flow is reduced until the ignition timing. It becomes difficult to maintain.

  As a result, a valve member similar to the tumble flow control valve of the second intake port 52 is disposed in the first intake port 51 so that the valve member is always fully open, and when the tumble flow control valve 8 is fully open, the intake air of the second intake port 52 is It is preferable that the resistance and the intake resistance of the first intake port 51 are substantially equal. Of course, since the valve member of the first intake port 51 is always fully open, an actuator is not required, and even if it is not a valve member, the same intake resistance of the tumble flow control valve 8 when fully open is obtained. It is good also as a member of the shape brought about.

It is a bottom view of a cylinder head showing an embodiment of a cylinder injection type spark ignition internal combustion engine by the present invention. FIG. 2 is a schematic longitudinal sectional view in the latter half of the compression stroke of the direct injection spark ignition internal combustion engine of FIG. 1. It is a map of the swirl flow control valve opening degree with respect to the fuel injection amount. It is an enlarged view of the ignition plug of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Intake valve 2 Exhaust valve 3 Fuel injection valve 4 Spark plug 7 Tumble flow control valve 8 Swirl flow control valve 51 1st intake port 52 2nd intake port S Swirl flow

Claims (4)

  A fuel injection valve for directly injecting fuel into the cylinder, an ignition plug, and a swirl flow generating means are provided, and a part of the fuel injected from the fuel injection valve passes through the ignition gap of the ignition plug. In a direct injection spark ignition internal combustion engine that performs stratified combustion by forming a combustible mixture in the vicinity of the spark plug at the ignition timing, the intake air is increased by the swirl flow generating means as the engine load increases during stratified combustion. An in-cylinder spark ignition internal combustion engine characterized by strengthening a swirl flow generated in a cylinder in a stroke.   A fuel injection valve for directly injecting fuel into the cylinder, an ignition plug, and a swirl flow generating means are provided, and a part of the fuel injected from the fuel injection valve passes through the ignition gap of the ignition plug. In a cylinder injection spark ignition internal combustion engine that performs stratified combustion by forming a combustible mixture in the vicinity of the spark plug at the ignition timing, during stratified combustion, the smaller the combustion air-fuel ratio, the more the swirl flow generating means An in-cylinder injection spark ignition internal combustion engine characterized by strengthening a swirl flow generated in a cylinder in an intake stroke.   At least two intake ports are connected to the inside of the cylinder, a swirl flow control valve as the swirl flow generating means is disposed in one of the two intake ports, and a tumble flow control valve is disposed in both of the two intake ports. The tumbling flow control valve is fully opened to control the swirl flow control valve during stratified combustion, and the tumble flow control valve is controlled to open the swirl flow control valve during homogeneous combustion. The in-cylinder injection spark ignition internal combustion engine according to 1 or 2.   The spark plug is disposed at an upper portion of the cylinder, the spark plug has an L-shaped electrode, and the L-shaped electrode has a parallel portion parallel to the spark plug axis and a vertical portion perpendicular to the spark plug axis. The L-shaped electrode of the spark plug is oriented so that the tumble flow when passing through the ignition gap of the plug does not collide perpendicularly to the widthwise surface of the parallel portion of the L-shaped electrode. The in-cylinder injection spark ignition internal combustion engine according to claim 1 or 2.

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