JPH11182331A - Direct injection spark ignition type internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the optimum arrangement of an inlet valve in a direct injection spark ignition type internal combustion engine so as to perform the homogenous combustion and the stratified combustion together satisfactorily. SOLUTION: A fuel injection valve 1 capable of jetting and supplying fuel directly into a combustion chamber and an ignition plug 2 are provided. moreover, two suction ports 8 are connected with the combustion chamber. When the minimum distance between both inlet valves provided between two suction ports 8 is X mm, they are arranged in such a manner that X>=4 mm. Moreover, when a distance between the inlet valve on a straight line connecting central points (a) of lower faces 6A of both inlet valves and an inner peripheral wall of a cylinder or an inner peripheral wall of the combustion chamber on cylinder head side is Y mm, they are arranged so as to satisfy the equation, Y>=3 mm. Since favorable air flow can be formed at the time of homogenous combustion when a direct injection spark ignition type internal combustion engine is constituted in this way, the vaporization of fuel can be promoted sufficiently, and a suction air amount due to the suction air cooling effect can be improved. Moreover, since favorable air flow can be formed at the time of stratified combustion, the combustion can be activated, and axial torque can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In recent years, fuel has been directly injected into a combustion chamber of an engine, and fuel is usually injected during an intake stroke to obtain a homogeneous mixture (a state in which fuel is uniformly dispersed throughout the combustion). ) To perform combustion (homogeneous combustion), and in a predetermined operation state (low rotation, low load state, etc.), fuel is injected during the compression stroke, and a mixture having a combustible mixture ratio that can be ignited by a spark plug in the combustion chamber A layer (1) comprising an air layer containing EGR or an air-fuel mixture having a combustible mixture ratio that is difficult to ignite with an ignition plug but can receive and burn the combustion flame in the layer (1); Combustion at an extremely lean air-fuel ratio (air-fuel ratio near the lean limit) (stratified combustion)
(Direct Injection Spark Ignition Type Internal Combustion Engine) has been proposed (Japanese Patent Application Laid-Open Nos. 62-191622 and 2-169834). Etc.).

[0003] For example, in JP-A-6-42352 and JP-A-9-14103, etc., a spark plug and a fuel injection valve of a direct injection spark ignition type internal combustion engine having two intake ports per cylinder are disclosed. A layout example of a system (hereinafter, referred to as a combustion injection system) related to combustion and fuel injection of an intake valve, a piston cavity, and the like is disclosed.

[0004]

However, conventionally, two intake ports are provided for each cylinder, and a fuel injection valve is arranged between the two intake ports and below the intake ports. No consideration has been given to the layout between the intake valves interposed in these intake ports.

[0005] That is, during homogeneous combustion (when fuel is injected during the intake stroke), an intake cooling effect due to latent heat of vaporization of fuel and an improvement in intake charging efficiency due to a reduction in air volume due to the intake cooling can be expected. However, in the prior art, such a point was not taken into consideration, and the above-mentioned effects could not be sufficiently exhibited.

In addition, during stratified combustion (when fuel is injected during the compression stroke), the fuel injected using the air flow in the combustion chamber is preferably formed near the ignition plug while forming a mixture suitable for ignition. Therefore, its combustion characteristics (ignitability, combustion stability, etc.) are susceptible to the air flow in the combustion chamber. For this reason, it is necessary to make the air flow in the combustion chamber more suitable for stratified combustion by sufficiently considering the influence of each intake valve arrangement.

[0007] When the operation is performed by switching between homogeneous combustion and stratified combustion, the combustion characteristics in both combustion modes are considered.
It is also necessary to be able to satisfy both drivability and the like. In view of such circumstances, the present invention has two intake ports per cylinder, and views the injection hole of the fuel injection valve between the two intake ports in the piston movement direction (cylinder center axis direction). Sometimes, an optimal intake valve layout is provided for a direct injection spark ignition type internal combustion engine which is arranged on the inner peripheral wall side of the cylinder from the line connecting the center points of the lower surfaces of both intake valves, thereby achieving homogeneous combustion and stratified combustion. It is an object of the present invention to be able to perform both satisfactorily.

[0008]

According to the present invention, two intake ports are provided for each cylinder, and the injection hole of the fuel injection valve is moved between the two intake ports by a piston. In a direct-injection spark ignition type internal combustion engine arranged on the cylinder inner peripheral side from a line connecting the center point of the lower surface of the intake valve when viewed from the direction, the minimum clearance between both intake valves is X
mm, X ≧ 4.

With such a configuration, during homogeneous combustion, a good air flow can be formed in the central portion of the cylinder below the cylinder {see FIG. 6 (B) and the like}. The fuel can be sufficiently dispersed, and the vaporization of the fuel can be sufficiently promoted, whereby the intake air cooling effect by the latent heat of vaporization is promoted. As a result, the amount of intake air can be improved during homogeneous combustion. Further, by promoting the homogenization of the air-fuel mixture in the entire cylinder, the combustion speed is improved, and in combination with the increase in the amount of intake air, the shaft torque can be further increased.

In the stratified combustion, the center of the cylinder, which is an important air flow for transporting fuel to the vicinity of the spark plug or activating combustion in the piston cavity (FIG. 6B) Since the air flow in the reference (4) is well formed, the combustion during stratified combustion is activated, and the shaft torque can be improved during stratified combustion.

With this configuration, for example, when swirl is generated by the swirl control valve during stratified combustion, the intake valve on the side where the swirl control valve is provided becomes an obstacle, and the swirl flow is directed toward the inner circumferential wall of the cylinder. It is possible to avoid the fear that the swirl flow is not formed due to being bent to the side, so that the stratified combustion can be further activated and the stratified combustion can be further improved.

According to the second aspect of the present invention, two intake ports are provided for each cylinder, and the injection holes of the fuel injection valve are provided with the two intake ports.
In a direct injection spark ignition type internal combustion engine arranged between the two intake ports on the cylinder inner peripheral wall side from the line connecting the center point of the lower surface of the intake valve when viewed from the piston movement direction, the minimum The gap is Xmm and the cylinder bore diameter is B
mm, X / B ≧ 0.05.

With this configuration, the operation and effect according to the first aspect of the invention can be achieved in any engine. According to the third aspect of the invention, when the minimum gap between the intake valve and the inner peripheral wall of the cylinder or the peripheral wall of the cylinder head side combustion chamber on a line connecting the center points of the lower surfaces of both intake valves is Y mm, X> Y. It was configured as follows.

With this configuration, the function and effect of the invention described in claim 1 or 2 can be more effectively achieved. According to a fourth aspect of the present invention, in the direct injection spark ignition type internal combustion engine according to the first or third aspect, the intake valve and the cylinder inner peripheral wall or the cylinder head side on a line connecting the center points of the lower surfaces of both intake valves. When the minimum gap with the peripheral wall of the combustion chamber is Y mm, Y ≧ 3.

With this configuration, during homogeneous combustion, a good air flow can be formed on the inner peripheral wall side of the cylinder below the cylinder, so that the fuel can be dispersed throughout the cylinder, and the vaporization of the fuel can be sufficiently promoted. As a result, the intake air cooling effect by the latent heat of vaporization is promoted, and the amount of intake air can be improved during homogeneous combustion. Further, by promoting the homogenization of the air-fuel mixture in the entire cylinder, the combustion speed is improved, and in combination with the increase in the amount of intake air, the shaft torque can be further increased.

Also, during stratified combustion, excessive air flow in the center of the cylinder, which is an important air flow for transporting fuel to the vicinity of the spark plug or activating combustion in the piston cavity, is considered to be excessive. Therefore, since it is possible to suppress the occurrence of the stratification and to maintain it satisfactorily, it is possible to activate the combustion at the time of stratified combustion, and to thereby improve the shaft torque at the time of stratified combustion.

According to a fifth aspect of the present invention, in the direct injection spark ignition type internal combustion engine according to the second or third aspect, the intake valve and the cylinder inner peripheral wall on a line connecting the center points of the lower surfaces of both intake valves or When the minimum gap with the peripheral wall of the combustion chamber on the cylinder head side is set to Y mm and the cylinder bore diameter is set to B mm, Y / B ≧ 0.0375. With such a configuration, the same operation and effect as the operation and effect according to the invention described in claim 4 can be achieved in any engine.

[0018]

According to the first and second aspects of the present invention, during homogeneous combustion, a good air flow can be formed in the central portion of the cylinder below the cylinder, so that the entire interior of the cylinder (ie, the air-fuel mixture generation space) is formed. ), The fuel can be dispersed
The vaporization of the fuel can be sufficiently promoted, whereby the intake air cooling effect by the latent heat of vaporization is promoted, and the amount of intake air can be improved during homogeneous combustion. Further, by promoting the homogenization of the air-fuel mixture in the entire cylinder, the combustion speed is improved, and in combination with the increase in the amount of intake air, the shaft torque can be further increased.

Also, during stratified combustion, the air flow in the center of the cylinder, which is an important air flow for transporting fuel to the vicinity of the spark plug or activating combustion in the piston cavity, is well formed. As a result, combustion during stratified combustion is activated, and the shaft torque can be improved during stratified combustion. Further, with such a configuration, for example, when swirl is generated by the swirl control valve during stratified combustion, the intake valve on the side where the swirl control valve is provided becomes an obstacle, and the swirl flow is bent toward the inner circumferential wall of the cylinder. Therefore, it is possible to avoid the fear that a good swirl flow cannot be formed, so that stratified combustion can be further activated and stratified combustion can be further improved.

According to the invention of claim 3, according to claim 1,
Alternatively, the function and effect of the invention described in claim 2 can be further effectively achieved. According to the fourth and fifth aspects of the present invention, at the time of homogeneous combustion, a good air flow can be formed on the inner peripheral wall side of the cylinder below the cylinder, so that the fuel to the entire inside of the cylinder (that is, the air-fuel mixture generation space) Can be sufficiently promoted, and the vaporization of fuel can be sufficiently promoted, whereby the intake air cooling effect by the latent heat of vaporization is promoted, and the amount of intake air can be improved during homogeneous combustion. Further, by promoting the homogenization of the air-fuel mixture throughout the entire cylinder (that is, the air-fuel mixture generation space), the combustion speed is improved, and the shaft torque can be further increased in combination with the increase in the intake air amount.

In addition, during stratified combustion, excessive air flow in the center of the cylinder, which is an important air flow for transporting fuel to the vicinity of the spark plug or activating combustion in the piston cavity, is considered to be excessive. Therefore, since it is possible to suppress the occurrence of the stratification and to maintain it satisfactorily, it is possible to activate the combustion at the time of stratified combustion, and to thereby improve the shaft torque at the time of stratified combustion.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a longitudinal sectional view showing a configuration of a direct injection spark ignition type internal combustion engine according to one embodiment of the present invention. As shown in FIG.
A fuel injection valve 1 is provided directly facing the combustion chamber 4 so that fuel can be injected and supplied directly into the inside. The combustion chamber 4 is separated by a crown surface 10 of the piston 3 inserted and held reciprocally in the cylinder 5, an inner wall of the cylinder 5, and a lower surface of the cylinder head 20. The ignition plug 2 for igniting the air-fuel mixture in the combustion chamber 4 is attached to the cylinder head 20 so as to face the combustion chamber 4.

The symbol F in the figure denotes the fuel injected by the fuel injection valve 1 and is directed obliquely downward. For example, during stratified combustion (during compression stroke injection), the injected fuel is Are enclosed in a concave portion (cavity) 11 provided on the intake side of the crown surface 10 of the piston 3. The fuel injection timing is set to an intake stroke in the case of homogeneous combustion, and to a compression stroke in the case of stratified combustion.

As shown in FIG. 1, an intake valve 6 is provided at an opening of the intake port 8 on the combustion chamber 4 side. As shown in FIG. 2, which is a view of the combustion chamber 4 as viewed from the piston side (the lower side of the head), the intake ports 8 are arranged substantially in parallel and communicate with one combustion chamber 4. The intake valve 6 is arranged at each of the ports 8. Similarly, an exhaust valve 7 is arranged at each of the exhaust ports 9 which are arranged substantially in parallel and communicate with one combustion chamber 4. Note that the exhaust port 9 and the exhaust valve 7 are not limited to such a configuration, and one exhaust chamber 9 and one exhaust valve 7 may be provided in one combustion chamber 4.

The injection hole of the fuel injection valve 1 is located between the two intake ports 8 and 8, as shown in FIG. 1, below each intake port 8, 8 in other words, as shown in FIG. In addition, when viewed from the direction of movement of the piston, in other words, when viewed from the direction of the center axis of the cylinder (the lower surface side of the cylinder head), on the side opposite to the ignition plug 2, It is arranged on the side.

A swirl control valve 12 as a swirl generating means is provided in one intake port 8 (or an intake pipe communicating with one intake port). The shaft 13 for driving the swirl control valve 12 is connected to, for example, an actuator (not shown) operated in response to a drive signal from an engine control unit (not shown).

In stratified combustion, it is necessary to transport the injected fuel to the vicinity of the spark plug 2 while forming a mixture suitable for ignition by utilizing the air flow in the combustion chamber. Therefore, the combustion characteristics (ignitability, combustion stability, etc.) during stratified combustion are easily affected by the air flow in the combustion chamber. It needs to be good.

Further, when the operation is performed by switching between the homogeneous combustion and the stratified combustion, it is necessary to satisfy both the combustion characteristics and the operability in both combustion modes. Then, the present inventors repeated various experiments, simulations, and the like to obtain X (minimum clearance between both intake valves 6; unit shown in FIG.
mm), Y (minimum gap between the intake valve 6 and the cylinder inner peripheral wall or the cylinder head side combustion chamber peripheral wall on a line connecting the center points a of the lower surfaces 6A of both intake valves 6; the unit is mm, for example) Suitable values have been found.

That is, as shown in FIG. 4, when X <4 mm,
At the time of homogeneous combustion (at the time of injection during the intake stroke), the reduction of the intake air amount and the reduction of the shaft torque become remarkable. This is shown in FIG.
As shown in FIG. 2 or FIG. 3 (a diagram showing the flow velocity distribution in the BB cross section), when the gap X between the intake valves becomes narrow, the intake flow velocity after passing through the gap X by the throttle effect of the intake valve gap. Is temporarily increased, but the flow rate of the air flow is reduced (below the cylinder) because the amount of intake air flowing through the intake valve gap X is small. This is considered to be due to the inability to form a sphere.

That is, during homogeneous combustion (during the injection of the intake stroke), a cross section BB below the cylinder (the center of the cylinder)
As a result, the fuel cannot be dispersed throughout the cylinder, resulting in insufficient vaporization of the fuel.As a result, the cooling effect of the intake air due to latent heat of vaporization is reduced, and During combustion, the amount of intake air is significantly reduced.

At the time of stratified combustion (during the compression stroke injection), important air for transporting fuel to the vicinity of the spark plug 2 or activating combustion in the concave portion 11 (piston cavity). Since the air flow in the BB cross section (the center of the cylinder), which is the flow, is not formed well, the combustion during the stratified combustion becomes inactive, and the reduction in the shaft torque during the stratified combustion becomes conspicuous. is there.

On the other hand, as shown in FIG.
Then, both the intake air amount during homogeneous combustion and the shaft torque during stratified combustion can be kept high. This is because, as shown in FIG. 6B, when the gap X between the intake valves is widened, the intake flow rate after passing through the intake valve gap X is low, but the amount of intake air flowing through the intake valve gap X increases. ,
After that, it is possible to suppress the deceleration of the flow velocity (below the cylinder), and the BB cross section below the cylinder (the center of the cylinder)
, A good air flow can be formed.

That is, during homogeneous combustion, a good air flow can be formed in the BB section below the cylinder (the center of the cylinder), so that the fuel can be dispersed throughout the cylinder and the fuel vaporization is sufficiently promoted. As a result, the effect of cooling the intake air by the latent heat of vaporization is promoted, so that the amount of intake air can be improved during homogeneous combustion. Further, by promoting the homogenization of the air-fuel mixture in the entire cylinder (that is, the air-fuel mixture generation space), the combustion speed is improved, and in combination with the increase in the intake air amount, the shaft torque can be further increased.

In the stratified combustion, a cross section taken along the line BB (the center of the cylinder), which is an important air flow for transporting fuel to the vicinity of the ignition plug 2 or activating combustion in the concave portion 11, is provided. Since the air flow in the part (1) is well formed, the combustion during stratified combustion is activated, so that the shaft torque can be improved during stratified combustion.

Also, when the swirl control valve 12 is closed during stratified combustion, if X ≧ 4 mm (when X = large), as shown in FIG. 7, X <4 mm
As in the case of (X = small), the intake valve on the opposite side (the side on which the swirl control valve 12 is provided) becomes an obstacle, and the swirl flow is bent toward the inner circumferential wall of the cylinder, so that a good swirl flow is generated. Since it is possible to avoid the fear that the fuel cell cannot be formed, the stratified combustion can be activated, and the stratified combustion can be further improved.

That is, it has been confirmed by the present inventors that X is preferably set to a value of 4 mm or more. When the present invention can be applied even when the cylinder bore diameter Bmm is different, it can be expressed by X / B. In this case, it is preferable that X / B ≧ 0.05. It is.

However, if X ≦ Y, various effects caused by setting the gap X to 4 mm or more are slightly diminished.
It is even more preferable that the relationship be Y. By the way, as shown in FIG. 5, when Y <3 mm, the reduction of the intake air amount during homogeneous combustion (during the intake stroke injection) and the reduction of the shaft torque during stratified combustion (during the compression stroke injection) become significant.

This is because, when the gap Y between the intake valve and the inner peripheral wall of the cylinder becomes narrow, the flow rate of intake air after passing through the gap Y temporarily increases, but the amount of intake air flowing through the gap Y is small. It is considered that the cause is that the flow velocity is reduced, so that a good air flow cannot be formed on the inner peripheral wall side of the cylinder below the cylinder. In other words, during homogeneous combustion (during the injection of the intake stroke), the fuel cannot be dispersed throughout the cylinder (ie, the air-fuel mixture generation space), so that the fuel is not sufficiently vaporized, and thus the intake air is cooled by the latent heat of vaporization. The effect is reduced, and the amount of intake air is significantly reduced during homogeneous combustion.

During stratified combustion (during the compression stroke injection), B is an important air flow for transporting fuel to the vicinity of the spark plug 2 or activating combustion in the recess 11. The air flow in the -B cross section (the center of the cylinder) becomes excessive, so that the combustion during stratified combustion is rather inactivated, and the reduction in the shaft torque during stratified combustion becomes conspicuous.

On the other hand, as shown in FIG.
Then, both the intake air amount during homogeneous combustion and the shaft torque during stratified combustion can be kept high. This is because, when the gap Y between the intake valve and the inner peripheral wall of the cylinder or the cylinder head side is widened, the intake flow velocity after passing through the gap Y is low, but the amount of intake air flowing through the gap Y increases. The flow velocity can be suppressed from decelerating, and a good air flow can be formed on the cylinder inner peripheral wall side below the cylinder.

That is, during homogeneous combustion, a good air flow can be formed on the inner peripheral wall side of the cylinder below the cylinder, so that the fuel can be dispersed throughout the entire cylinder (ie, the air-fuel mixture generation space) and the fuel can be vaporized. Sufficient promotion can be achieved, and the effect of cooling the intake air by the latent heat of vaporization can be promoted. As a result, the amount of intake air can be improved during homogeneous combustion. Furthermore, by promoting the homogenization of the air-fuel mixture throughout the cylinder,
The combustion speed is improved, and the shaft torque can be further increased in combination with the increase in the intake air amount.

During stratified charge combustion, an important air flow for transporting fuel to the vicinity of the spark plug 2 or activating combustion in the recess 11 is a cross section taken along a line BB (cylinder center). Since the air flow in the section (1) can be made good, combustion during stratified combustion can be activated, and the shaft torque can be improved during stratified combustion.

That is, it has been confirmed by the present inventors that Y is preferably set to a value of 3 mm or more. When the present invention can be applied even when the cylinder bore diameter Bmm is different, it can be expressed by Y / B. In this case, it is preferable that Y / B ≧ 0.0375. It is.

However, considering the relationship with X, X is 4 mm.
In this case, it is more preferable to set the value to 3 mm ≦ Y <4 mm. When represented by Y / B, X / B = 0.
In the case of 05, it is more preferable to satisfy 0.0375 ≦ Y / B <0.05. As described above, according to the present embodiment, two intake ports are provided for each cylinder, and the injection hole of the fuel injection valve is positioned between the two intake ports when viewed from the piston movement direction. In the direct injection spark ignition type internal combustion engine arranged on the inner peripheral wall side of the cylinder from the line connecting the center points of the above, both homogeneous combustion and stratified combustion are excellent by considering X (or X / B). It can be. Further, by considering Y (or Y / B), both homogeneous combustion and stratified combustion can be improved. If both X (or X / B) and Y (or Y / B) are taken into consideration, it is possible to achieve both combustion at a higher level.

Incidentally, Y is the smaller of the gap between the intake valve 6 and the inner peripheral wall of the cylinder, and the gap between the intake valve 6 and the peripheral wall of the combustion chamber on the cylinder head side (see reference numeral Z in FIG. 1). It can be.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a cylinder head, an intake port, an intake valve, a piston, and the like according to an embodiment of the present invention.

FIG. 2 is a view of the combustion chamber according to the embodiment as viewed from a lower surface side of a cylinder head.

FIG. 3 is a view as viewed in the direction of arrows AA in FIG. 1;

FIG. 4 is a diagram showing changes in an intake air amount and a shaft torque with respect to X.

FIG. 5 is a diagram showing changes in an intake air amount and a shaft torque with respect to Y.

6 (A) is a simulation result showing the air flow vector (direction, speed) in the combustion chamber in the section BB of FIG. 2 (or FIG. 3) when X = small.
FIG. 2B shows a case where X = large (for example, 6 mm) in FIG.
It is the simulation result which showed the air flow vector (direction, speed) of the combustion chamber in BB cross section of (or FIG. 3).

FIG. 7 is a schematic diagram (as viewed from above the cylinder head) for explaining a difference in a swirl flow state depending on the magnitude of X when the swirl control valve 12 is closed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fuel injection valve 2 Spark plug 3 Piston 4 Combustion chamber 5 Cylinder 6 Intake valve 6A Lower surface of intake valve 8 Intake port 12 Swirl control valve

Claims (5)

[Claims] 1. A vehicle comprising two intake ports per cylinder,
A direct-injection spark ignition type in which the injection hole of the fuel injection valve is disposed between the two intake ports and on the inner peripheral wall side of the cylinder from a line connecting the center point of the lower surface of the intake valve when viewed from the piston moving direction. A direct-injection spark ignition type internal combustion engine, wherein X ≧ 4 when the minimum clearance between both intake valves is X mm. 2. A fuel cell system comprising: two intake ports per cylinder;
A direct-injection spark ignition type in which the injection hole of the fuel injection valve is disposed between the two intake ports and on the inner peripheral wall side of the cylinder from a line connecting the center point of the lower surface of the intake valve when viewed from the piston moving direction. A direct-injection spark-ignition internal combustion engine, wherein X / B ≧ 0.05 when the minimum clearance between both intake valves is X mm and the cylinder bore diameter is B mm. . 3. The configuration is such that X> Y when the minimum gap between the intake valve and the inner peripheral wall of the cylinder or the peripheral wall of the combustion chamber on the cylinder head side is Y mm on a line connecting the center points of the lower surfaces of both intake valves. The direct injection spark ignition type internal combustion engine according to claim 1 or 2, wherein: 4. When the minimum clearance between the intake valve and the inner peripheral wall of the cylinder or the peripheral wall of the combustion chamber on the cylinder head side on a line connecting the center points of the lower surfaces of both intake valves is Y mm, Y ≧ 3. The direct injection spark ignition type internal combustion engine according to claim 1 or 3, wherein: 5. The minimum clearance between the intake valve and the inner peripheral wall of the cylinder or the peripheral wall of the combustion chamber on the cylinder head side on a line connecting the center points of the lower surfaces of both intake valves is Y mm, and the cylinder bore diameter is B.
The direct-injection spark ignition type internal combustion engine according to claim 2 or 3, wherein Y / B ≧ 0.0375 when mm is set.