JPH11294307A - Cylinder injection-of-fuel type spark ignition engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the direct hit escaping of injection fuel to an ignition plug and stability of combustion. SOLUTION: In a homogeneous combustion operation mode having high fuel quantity, the degree of the projection of an ignition plug 9 is reduced to escape the direct hit of injection fuel to the ignition plug 9 to reduce the fuel injection quantity. In a laminated combustion operation mode decreasing gas flow in a combustion chamber 4 increases the degree of the projection of the ignition plug 9. The results positively transport fuel to around the ignition plug 9, stabilizing the combustion even under the homogeneous combustion operation mode and the laminated combustion operation mode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Some cylinder-injection spark ignition engines include, for example, as disclosed in Japanese Patent Application Laid-Open No. 9-14103.
In the cylinder head constituting the upper surface of the combustion chamber, between the ignition plug protrudingly arranged at the center of the cylinder head and the fuel injection valve arranged on the side of the cylinder head on the side of the intake valve, the ignition plug is disposed. 2. Description of the Related Art There is a known configuration in which a projection surrounding a side portion on the side of a fuel injection valve is provided so that fuel injected from the fuel injection valve does not directly hit an ignition plug.

[0003]

The protrusion prevents the fuel injected from the fuel injection valve from directly impinging on the spark plug, but on the other hand the operating condition in which the gas flow in the combustion chamber is weak, for example, the engine speed. When the stratified charge combustion operation is small, the protrusions may hinder the fuel transport to the spark plug side, and the fuel may not properly reach around the spark plug, and the stability of the stratified charge combustion may be impaired.

Accordingly, the present invention can prevent the fuel injected from the fuel injection valve from being directly applied to the ignition plug, and can appropriately ignite the fuel in any of the stratified combustion operation and the homogeneous combustion operation. An object of the present invention is to provide an in-cylinder injection type spark ignition engine capable of performing stable combustion.

[0005]

According to the first aspect of the present invention, an ignition plug is disposed at the center of the upper surface of the combustion chamber, and a fuel injection valve is disposed at a side of the combustion chamber on the side of the intake valve. In the provided direct injection type spark ignition engine, the protrusion amount of the spark plug is variably controlled according to the operating state of the engine.

According to a second aspect of the present invention, the ignition plug is provided on the upper surface of the combustion chamber on the side of the intake valve, which is provided with the ignition plug and the fuel injection valve. An inclined land portion having a height that protrudes toward the installation portion side is provided, and the ignition plug is variably controlled so that the amount of protrusion is smaller than the inclined land portion at the retracted position and larger than the inclined land portion at the advanced position. It is characterized by doing so.

[0007] In the invention of claim 3, claims 1 and 2
The amount of protrusion of the spark plug is controlled to be small during the homogeneous combustion operation in which the fuel is injected during the intake stroke, and the amount of protrusion is variably controlled during the stratified combustion operation in which the fuel is injected during the compression stroke.

In the invention of claim 4, claims 1 and 2
Is characterized in that the amount of projection is variably controlled on the high engine speed side in the stratified combustion operation region in which the fuel is injected in the compression stroke and the amount of projection is largely increased on the low engine speed side.

According to the fifth aspect of the present invention, the first and second aspects are provided.
Is characterized in that the amount of projection is variably controlled on the engine high load side and large on the engine low load side in the stratified combustion operation region in which fuel is injected in the compression stroke.

According to the invention of claim 6, claims 1 to 5 are provided.
A tumble generating means for generating a tumble flow in a combustion chamber at the time of stratified combustion operation in which fuel is injected in a compression stroke is provided at an intake port provided with an intake valve described in (1).

According to the invention of claim 7, claims 1 to 5 are provided.
A swirl generating means for generating a swirl in a combustion chamber at the time of stratified combustion operation in which fuel is injected in a compression stroke is provided at an intake port provided with the intake valve described in (1).

[0012]

According to the first aspect of the present invention, the amount of projection of the spark plug can be variably controlled in accordance with the operating state of the engine, so that the fuel injected from the fuel injector directly hits the spark plug. By reducing the amount of protrusion of the spark plug so as not to cause ignition, poor ignition and smoldering due to fuel covering of the spark plug can be avoided, while the amount of protrusion of the spark plug in an operating state in which fuel is difficult to reach the spark plug is reduced. By increasing the size, the fuel can be reliably transported around the spark plug, and stable combustion can be performed.

According to the second aspect of the present invention, the first aspect is provided.
In addition to the effects of the invention, in the retracted position of the spark plug, the spark plug is hidden behind the inclined land portion in the fuel injection direction of the fuel injection valve, so that direct impact of fuel can be reliably avoided. The projecting position of the spark plug at the advanced position is larger than that of the inclined land, so that the inclined land does not hinder fuel conveyance even in an operation state where the fuel does not easily reach the ignition plug, and the fuel can be reliably discharged from the ignition plug. It can be conveyed around and stable combustion can be performed.

According to the third aspect of the present invention, in addition to the effects of the first and second aspects of the present invention, in order to reduce the amount of protrusion of the spark plug during high-load high-speed operation in which homogeneous combustion is performed by intake stroke injection. Avoiding fuel cover and smoldering due to direct impact of the fuel ignition plug during the operation with a large amount of fuel injection,
High power can be obtained by performing stable homogeneous combustion, and exhaust emission can be improved. On the other hand, low-speed and medium-load low-speed operation, in which stratified combustion is performed by compression stroke injection, is compared with homogeneous combustion operation. Although the momentum of the gas flow in the combustion chamber becomes weaker, during the stratified charge combustion operation, the projection amount of the spark plug is increased, so that the fuel can be reliably transported around the spark plug and stable stratified charge combustion is performed, and the output Improvement and exhaust emission can be improved.

According to the fourth aspect of the present invention, in addition to the effects of the first and second aspects of the present invention, the amount of protrusion of the spark plug is reduced on the high rotation speed side where the fuel injection amount increases in the stratified combustion operation range. Therefore, while the fuel plug is prevented from being covered or smoldered by direct impact of the spark plug, the amount of fuel injection is small, and the amount of protrusion of the spark plug is increased on the low rotation speed side where the gas flow in the combustion chamber is weak, so that the spark plug is increased. Since the fuel can be reliably transported to the surroundings, stable combustion can be performed from the low rotation side to the high rotation side in the stratified combustion operation range.

According to the fifth aspect of the present invention, in addition to the effects of the first and second aspects of the present invention, the amount of protrusion of the spark plug is reduced on the high load side where the fuel injection amount increases in the stratified combustion operation range. In addition, it is possible to avoid fuel covering and smoldering due to direct impact of the spark plug on the fuel, while increasing the amount of protrusion of the spark plug on the low load side where the fuel injection amount is small, so that the fuel is reliably transported around the spark plug. Therefore, stable combustion can be performed from the low load side to the high load side of the stratified combustion operation range.

According to the invention described in claim 6, according to claim 1,
In addition to the effects of the inventions of (1) to (5), in the stratified charge combustion operation, the tumble flow is positively generated in the combustion chamber by the tumble generating means provided at the intake port, so that the fuel can be favorably transported around the ignition plug. More stable stratified combustion can be performed.

According to the invention of claim 7, according to claim 1,
In addition to the effects of the present invention, swirl is positively generated in the combustion chamber by the swirl generating means provided at the intake port during stratified charge combustion operation, so that fuel can be favorably transported around the spark plug and further improved. Stable stratified combustion can be performed.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings.

1 and 2, 1 is a cylinder block, 2 is a piston, 3 is a cylinder head, 4 is a cylinder block 1, a piston 2 and a cylinder head 3
1 shows a combustion chamber formed by

The cylinder head 3 is provided with two intake ports 5 opened and closed by intake valves 6 and two exhaust ports 7 opened and closed by exhaust valves 8 to face each other.

The center of the cylinder head 3, that is,
A spark plug 9 is disposed at the center of the combustion chamber 4, and the side of the combustion chamber 4 on the side where the intake valve is disposed is located near the two intake valves 6 and 6. A fuel injection valve 10 for directly injecting fuel is disposed therein.

Here, the amount of projection of the spark plug 9 inside the combustion chamber 4 is variably controlled in accordance with the operation state of the engine.

FIGS. 3 and 4 show an example of the driving means of the ignition plug 9. Numeral 11 denotes a hydraulic cylinder comprising a fixed housing 11a and a movable housing 11b, and the ignition plug 9 is mounted on the movable housing 11b. It is.

The movable cylinder 1 is provided in the hydraulic cylinder 11.
A set spring 12 for urging 1b toward the reduction side is provided, and a fixed cylinder 11a is fixed to the cylinder head 3 via a retainer 13.

The hydraulic cylinder 11 is supplied with hydraulic oil from a hydraulic pump 14 whose operation is controlled by a control unit 15 in accordance with the operating state of the engine.
The hydraulic cylinder 11 shown in FIG.
As shown in FIG. 4, the hydraulic cylinder 11 is extended and the spark plug 9 is switched from the retracted position where the amount of protrusion into the combustion chamber 4 is small to the advanced position where the spark plug 9 protrudes largely into the combustion chamber 4.

In this embodiment, on the upper surface of the combustion chamber 4 on the side where the intake valve is disposed, that is, on the wall of the combustion chamber on the side where the intake valve of the cylinder head 3 is disposed, the ignition plug is disposed and the fuel injection valve is disposed. And an inclined land portion 16 of which the protruding height increases toward the spark plug disposing portion side.

The protrusion amount of the spark plug 9 and the protrusion height of the inclined land portion 16 are determined by the direction in which the electrode 9a of the spark plug 9 is injected from the fuel injection valve 10 when the spark plug 9 is operated to the retracted position. When the ignition plug 9 is operated to the advanced position, the electrode 9a is larger than the inclined land portion 16 and protrudes into the combustion chamber 4 when the ignition plug 9 is moved to the advanced position.

Further, a forward tumble control valve 17 is provided as a tumble generating means upstream of the branch portion of the intake ports 5 and 5.

The forward tumble control valve 17 is formed in a semicircular shape whose upper half is cut off. When the valve is closed during the stratified charge combustion operation, the intake air flows to the upper half of the intake ports 5 and 5. only it was circulated, to produce a forward tumble flow a ₁ toward downward the piston crown surface from the combustion chamber center side in the combustion chamber 4.

As one of the variable control modes of the protrusion amount of the spark plug 9 by the control unit 15, for example, during the homogeneous combustion operation in which the fuel is injected in the intake stroke, the spark plug 9 is moved to the retreat position where the protrusion amount is small, and During the stratified charge combustion operation in which the compression plug is injected in the compression stroke, the ignition plug 9 is variably controlled to the advanced position where the projection amount is large.

The control unit 15 includes, for example, a rotation sensor 21a, a negative pressure sensor 21b, and a water temperature sensor 2.
1c, a detection signal from the detection means 21 such as a knock sensor 21d is input, and based on the detection signal of the detection means, it is determined that the engine is in a homogeneous combustion operation range at the time of high load and high rotation, at the time of engine cold, and when knock occurs, During low / medium load low rotation, the engine is determined to be in the stratified combustion operation range, and the hydraulic cylinder 11 system, the injection timing of the fuel injection valve 10, the tumble generating means 17 and the like which are the driving means of the ignition plug 9 are controlled.

Accordingly, in this embodiment, when the engine is under high load and high speed, it is determined that the engine is in the homogeneous fuel operation range, the ignition plug 9 is operated to the retreat position as shown in FIG. 1, and the forward tumble control valve 17 is opened. Meanwhile, the fuel injection timing of the fuel injection valve 10 is switched to the intake stroke injection.

At the time of high load and high rotation, the projection amount such that the electrode 9a is hidden behind the inclined land portion 16 in the fuel injection direction from the fuel injection valve 10 by setting the spark plug 9 to the retracted position as described above. Therefore, it is possible to prevent the fuel injected from the fuel injection valve 10 from directly hitting the electrode 9a of the ignition plug 9 during the operation in which the fuel injection amount is large and causing fuel covering or smoldering.

At the time of such high load and high rotation, the fuel injection amount from the fuel injection valve 10 is large and the average air-fuel ratio in the combustion chamber 4 is high as described above.
Good ignitability can be obtained even when a is around the mixed air mass, and therefore, stable homogenous combustion can be performed in combination with the above-described direct impact of fuel on the ignition plug 9 and high output. And exhaust emission can be improved.

Also, when the engine is cold or a misfire occurs, the ignition plug 9 is determined to be in the homogeneous combustion operation range and the ignition plug 9 is operated to the reverse position. By doing so, it is possible to avoid fuel deterioration of the ignition plug 9 and combustion deterioration due to smoldering and the like.

On the other hand, when the engine is running at a low or medium load at a low speed, it is determined that the engine is in the stratified combustion operation range, and as shown in FIG.
Is operated to the advanced position and the forward tumble control valve 17 is operated.
Is closed, the fuel injection timing of the fuel injection valve 10 is switched to the compression stroke injection.

At low and medium load low revolutions, the momentum of gas flow in the combustion chamber 4 is weaker than at the high load and high revolution, but the ignition plug 9 is set to the advanced position as described above. As a result, the electrode 9a is disposed so as to protrude more in the combustion chamber 4 than the inclined land portion 16, and furthermore, as shown in FIG. is generated piston crown surface strong forward tumble flow a ₁ toward the downward is, the fuel injected from the fuel injection valve 10 in the compression stroke combustion chamber riding sequentially tumble flow a ₁ inverted by the crown surface of the piston 2 Since the air-fuel mixture is conveyed toward the center of the ignition plug 9, the air-fuel mixture having a relatively high air-fuel ratio can be distributed only around the electrode 9 a of the ignition plug 9, and as a whole, it is extremely lean. Low stratified combustion at air-fuel ratio It can be set and performed.

In addition, during stratified charge combustion, the combustion chamber 4
To generate a forward tumble flow a ₁ within the fuel injection valve 10
Does not adhere to the crown surface of the piston 2 to form a liquid film, it is possible to eliminate the generation of unburned HC and the generation of smoke, so that the stratified combustion is performed stably. In addition, it is possible to improve the output and the exhaust emission.

FIG. 5 schematically shows the behavior of the fuel spray during the above-described stratified charge combustion operation. As shown in FIG. 5A, when the intake valve 6 opens during the intake stroke, the inside of the intake port 5 is opened. air circulation is sucked into halves side combustion chamber 4 through the upper of the intake port 5, a forward tumble flow a ₁ directed downward from the combustion chamber center side crown surface of the piston 2 is generated.

In the compression stroke, fuel is injected from the fuel injection valve 10 as shown in (b) and (c) of FIG. _The piston 2 is deflected upward by ₁
With adhesion to the crown surface is avoided, this order tumble flow on stream of a ₁ is transported toward the ignition plug 9 in the combustion chamber center, the ignition plug as shown in the same figure (d) 9
, An air-fuel mixture having a relatively high air-fuel ratio is formed.

In the above-described embodiment, the amount of protrusion of the spark plug 9 is controlled to be small during homogeneous combustion operation, and the amount of protrusion is controlled to be large during stratified combustion. It is also possible to adopt a control mode in which the amount is small and the amount of protrusion is variably controlled to be large on the low engine speed side.

In this case, even in the stratified charge combustion operation range, the fuel injection amount naturally increases on the high rotation side. However, the projection amount of the spark plug 9 is reduced on the high rotation side where the fuel injection amount increases. Fuel covering and smoldering due to direct hit can be avoided.

On the other hand, the fuel injection amount is small on the low rotation speed side of the stratified combustion operation range and the momentum of the gas flow in the combustion chamber is weak. On the low rotation speed side, the protrusion amount of the spark plug 9 is increased. Therefore, the fuel can be reliably transported around the ignition plug 9.

Therefore, stable combustion can be performed as a whole from the low rotation speed side to the high rotation speed side of the stratified combustion operation range.

Further, as another embodiment, it is possible to variably control the amount of protrusion of the spark plug 9 on the engine high load side in the stratified combustion operation region and increase the amount of protrusion on the engine low load side.

In this case, the fuel injection amount naturally increases on the high load side even in the stratified charge combustion operation range. However, in order to reduce the protrusion amount of the spark plug 9 on the engine high load side where the fuel injection amount increases, the fuel ignition amount is increased. Fuel covering and smoldering due to direct plug impact can be avoided.

On the other hand, the fuel injection amount decreases on the engine low load side in the stratified combustion operation range, but on the engine low load side, the amount of projection of the ignition plug 9 is increased, so that the fuel is transported around the ignition plug 9. The combustion can be reliably performed, and therefore, stable combustion can be performed as a whole from the low load side to the high load side of the engine in the stratified combustion operation range.

In the above-described embodiment, an example is shown in which the forward tumble control valve 17 is provided as a tumble generating means in the intake port 5, but in addition to this, as shown in FIG. A reverse tumble control valve 18 may be provided.

The reverse tumble control valve 18 is connected to the intake port 5
Is formed in a substantially semicircular shape in which a substantially lower half portion is cut off so as to be able to close a substantially upper half portion on the center side of the combustion chamber. By closing a substantially upper half portion of the intake port 5 on the center side of the combustion chamber, the airflow flowing through the intake port 5 is moved substantially along the combustion chamber side on the side where the fuel injection valve 10 is disposed, so that the crown of the piston 2 is closed. forming a reverse tumble flow a ₂ toward the downward surface.

Therefore, also in this embodiment, the amount of protrusion of the spark plug 9 is variably controlled in accordance with the operation state of the engine, and at the same time, the reverse tumble flow a ₂ is positively introduced into the combustion chamber 4 during the stratified charge combustion operation. When the stratified charge combustion operation is performed, the fuel can be satisfactorily transported around the ignition plug 9 during the stratified charge combustion operation, so that more stable stratified charge combustion can be performed.

As means for positively causing the gas flow in the combustion chamber 4 during the stratified charge combustion operation, swirl generation shown in FIG. 7 is used instead of the tumble generation means 17 and 18 shown in the first and second embodiments. Means can also be used.

In FIG. 7, an upstream portion near the branch portion of the intake ports 5, 5 is provided at the intake ports 5, 5 during stratified combustion operation.
A swirl control valve 19 for closing one of them is provided.

The fuel spray injected from the fuel injection valve 10 during the compression stroke is held in a substantially half portion of the crown surface of the piston 2 on the intake valve arrangement side, and the swirl generated in the combustion chamber 4 is compressed. A cavity 20 is provided for good holding until the later stage of the stroke.

The cavity 20 is provided in a range where the ignition plug 9 can be received in the compression stroke.

The projection amount of the spark plug 9 is variably controlled in accordance with the operation state of the engine. For example, the projection amount is variably controlled to be small during the homogeneous combustion operation and large during the stratified combustion operation. This is the same as in the second embodiment.

When the swirl control valve 19 is closed during the stratified charge combustion operation as shown in FIG. 7A, the intake air flows into the combustion chamber 4 through only one intake port 5, and
The swirl a ₃ is generated by imparting swirl directivity in one direction to the gas flow in the combustion chamber 4.

When fuel is injected from the fuel injection valve 10 at the beginning of the compression stroke, as shown in (b) and (c), the fuel spray is combusted by the action of the swirl a ₃ in the combustion chamber 4. The upward deflection of the chamber 4 is suppressed and the swirl a ₃
While being deflected in the flow direction of the piston 2 toward the cavity 20 on the crown surface of the piston 2.

In this compression stroke, the swirl a ₃ is well held in the cavity 20,
As shown in FIG. 4 (d), the fuel received within 0 is vaporized and mixed in the cavity 20 and swirl a
_The piston 2 turns in _three directions, and the ignition plug 9
And an air-fuel mixture having a relatively rich air-fuel ratio is formed around the ignition plug 9 as shown in FIG.

During the stratified charge combustion operation, the amount of protrusion of the spark plug 9 is increased, so that stable stratified charge combustion can be performed.

In each of the above embodiments, the control of the protrusion amount of the ignition plug 9 includes a control that is linearly variably controlled in accordance with the operating state of the engine.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional explanatory view showing a retracted state of an ignition plug according to a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional explanatory view showing a spark plug advanced state in the embodiment.

FIG. 3 is a schematic cross-sectional explanatory view showing when the ignition plug driving means is retracted.

FIG. 4 is a schematic cross-sectional explanatory view showing when the spark plug driving means advances the plug.

FIG. 5 is a schematic diagram showing the behavior of fuel spray during stratified charge combustion in the first embodiment of the present invention.
(B) and (c) show the fuel injection timing in the compression stroke,
(D) shows the ignition timing.

FIG. 6 is a schematic sectional view showing a second embodiment of the present invention.

FIG. 7 is a schematic diagram showing the behavior of fuel spray during stratified charge combustion in the third embodiment of the present invention.
(B), (c) and (d) show the fuel injection timing in the compression stroke, and (e) shows the ignition timing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder block 2 Piston 3 Cylinder head 4 Combustion chamber 5 Intake port 9 Spark plug 10 Fuel injection valve 17, 18 Tumble generating means 19 Swirl generating means

Claims (7)

[Claims] 1. An in-cylinder injection spark ignition engine in which a spark plug is disposed at a center portion of an upper surface of a combustion chamber and a fuel injection valve is disposed on a side of the combustion chamber on a side where an intake valve is disposed. An in-cylinder injection spark ignition engine, wherein the protrusion amount of the spark plug is variably controlled according to a state. 2. An inclined land portion on the upper surface of the combustion chamber on the side where the intake valve is disposed, the projection height of which rises toward the side where the ignition plug is disposed, over the portion where the ignition plug is disposed and the portion where the fuel injection valve is disposed. 2. The spark plug according to claim 1, wherein the amount of protrusion of the spark plug is controlled to be smaller at the retracted position than at the inclined land portion and larger at the advanced position than at the inclined land portion. In-cylinder injection spark ignition engine. 3. The spark plug according to claim 1, wherein the amount of protrusion is controlled to be small during a homogeneous combustion operation in which fuel is injected during an intake stroke, and to be large during a stratified combustion operation in which fuel is injected during a compression stroke. The in-cylinder injection spark ignition engine according to claim 1 or 2, wherein: 4. A small amount of protrusion of the spark plug on a high-speed side of the engine in a stratified combustion operation region in which fuel is injected in a compression stroke,
The in-cylinder injection spark ignition engine according to claim 1 or 2, wherein the amount of projection is largely variably controlled on a low engine speed side. 5. A small amount of protrusion of the spark plug on a high engine load side in a stratified combustion operation region in which fuel is injected in a compression stroke,
The in-cylinder injection spark ignition engine according to claim 1 or 2, wherein the amount of protrusion is largely variably controlled on the engine low load side. 6. The intake port is provided with tumble generating means for generating a tumble flow in the combustion chamber during stratified charge combustion operation in which fuel is injected in a compression stroke.
In-cylinder injection spark ignition engine according to any one of the above. 7. The in-cylinder according to claim 1, wherein a swirl generating means for generating swirl in the combustion chamber during stratified charge combustion operation in which fuel is injected in a compression stroke is provided at the intake port. Injection spark ignition engine.