JPH11294207A - Spark ignition type internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spark ignition type internal combustion engine which performs positive internal EGR so as to improve NOx reduction effect. SOLUTION: According to operating condition of an engine, an intake stroke keeps closing an intake valve 2 at one side and opening only an intake valve 3 at other side, while opens an exhaust valve 6 when the intake valve 3 at the other side is opening, so that a number of intake valves opening is made same as that of exhaust valves opening in an intake stroke. Thereby, more positive internal EGR is performed to improve reduction of NOx.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spark ignition type internal combustion engine.

[0002]

2. Description of the Related Art Among spark ignition type internal combustion engines, as disclosed in, for example, JP-A-6-280581, N
In order to reduce Ox, only one of the two exhaust valves is opened during the intake stroke in which the two intake valves are opened.
There is known an engine in which internal exhaust gas recirculation (hereinafter referred to as internal EGR) is actively performed.

[0003]

As described above, in the intake stroke in which the two intake valves are opened, only one of the two exhaust valves is opened to perform the internal EGR. The ratio of the amount of internal EGR in
It is undeniable that it will affect the NOx reduction effect.

Accordingly, the present invention is to provide a spark ignition type internal combustion engine capable of more actively performing internal EGR without impairing the combustibility and improving the NOx reduction effect.

[0005]

According to the first aspect of the present invention, in a spark ignition type internal combustion engine having two intake valves and at least one exhaust valve, intake air varies depending on the operating state of the engine. During the stroke, one of the intake valves is kept closed and only the other intake valve is opened, and the one exhaust valve is opened during the opening period of the other intake valve. And

According to a second aspect of the present invention, in a spark ignition type internal combustion engine having two intake valves and two exhaust valves disposed opposite to the intake valves, the internal combustion engine according to the operating state of the engine. During the intake stroke, one of the intake valves is kept closed and only the other intake valve is opened, and at least one of the exhaust valves is opened during the opening period of the other intake valve. It is characterized by having.

According to a third aspect of the present invention, the other intake valve and one exhaust valve that are opened during the intake stroke according to the second aspect use an ignition plug provided at a substantially central portion of the combustion chamber. It is characterized by being arranged diagonally at the center.

[0008] In the invention of claim 4, claims 1 to 3 are provided.
The valve closing maintaining operation in the intake stroke of one of the intake valves described in
The valve opening operation in the intake stroke of the exhaust valve is performed in a low and medium load range of the engine.

In the invention of claim 5, claims 1 to 4 are provided.
In the spark ignition type internal combustion engine described in the above, a fuel injection valve for directly injecting fuel into the combustion chamber is provided on a side portion of the combustion chamber on the side of the intake valve, and the other fuel injection valve opens the other intake valve. It is characterized in that fuel is injected toward a new air flow to be sucked.

According to a sixth aspect of the present invention, in the spark ignition type internal combustion engine according to the fifth aspect, fuel is injected in a compression stroke in a low and medium load range of the engine, and in a middle and high load range of the engine. It is characterized in that fuel is injected during the intake stroke.

[0011]

According to the first and second aspects of the present invention, the number of intake valves and the number of exhaust valves that are opened during the intake stroke are made one-to-one, so that the amount of internal EGR occupied in the combustion chamber is greatly increased. Since the in-cylinder temperature rises due to the more aggressive internal EGR and the compression auto-ignition combustion is promoted, and the peak combustion temperature can be lowered to lower the overall combustion temperature, the NOx without loss of stability
Can be further improved.

According to the invention described in claim 3, according to claim 2,
In addition to the effects of the invention, the intake valve and the exhaust valve that are opened in the intake stroke are arranged diagonally about the ignition plug at the center of the combustion chamber, and the combustion chamber is sucked by opening the intake valve. And the internal EG sucked by the opening of the exhaust valve
Layered into the R region, ignition and flame propagation from the internal EGR region to the air-fuel mixture layer are reliably performed, and the combustibility can be further improved.

[0013] According to the invention described in claim 4, according to claim 1 of the present invention.
In addition to the effects of the third to third aspects, in a high load region, the intake / exhaust valve becomes the valve timing of the basic cycle and the internal EG
Since R is stopped, high output required for high load operation can be obtained.

According to the invention described in claim 5, according to claim 1 of the present invention,
In addition to the effects of the fourth to fourth aspects, in-cylinder injection of fuel is performed toward a fresh air flow sucked by opening an intake valve, so that fuel and fresh air are mixed well and combustion stability is improved. Can be improved.

According to the invention described in claim 6, according to claim 5,
In addition to the effects of the invention, in the low and medium load regions, stratified combustion at an ultra-lean air-fuel ratio can be performed by the compression stroke injection of fuel to improve fuel economy and exhaust emissions,
In the middle and high load regions, homogeneous combustion can be performed by fuel injection stroke injection, and high output can be obtained.

[0016]

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

FIG. 1 is a plan view schematically showing an arrangement relationship between a combustion chamber, an intake / exhaust valve, a valve train, and the like in a four-cycle engine of a port fuel injection type. 3 and two exhaust valves 6 and 7 are opposed to each other, and have a cross flow port structure in which air is taken in from intake ports 4 and 5 on one side and exhausted from exhaust ports 8 and 9 on the other side. .

A fuel injection valve (not shown) is provided at one or both of the intake ports 4 and 5.
The air-fuel mixture sucked into the combustion chamber 1 from the intake ports 4 and 5 by opening the valve 3 is spark-ignited by a spark plug 10 disposed substantially in the center of the combustion chamber 1 and burned.

The intake valves 2 and 3 operate in a specific engine operating state,
Specifically, in the present embodiment, during the intake stroke in the low and medium load regions of the engine, for example, the intake valve 2 is kept in the closed state, and only the other intake valve 3 is opened. ing.

In the specific engine operation state, the exhaust valves 6 and 7 are paired with one exhaust valve, for example, the other intake valve 3 opened during the intake stroke and the ignition plug 10 at the center of the combustion chamber. Only the angularly arranged exhaust valve 6 opens during the opening period of the other intake valve 3.

The intake valve 2 and the exhaust valve 6 are operated by variable valve mechanisms 11 and 19, respectively.

Camshaft 1 of intake-side variable valve mechanism 11
2, two cams 13 and 14 for opening and closing the intake valve 2 and one cam 15 for opening and closing the intake valve 3 are provided.

As shown in FIG. 2, the cams 13 and 14 abut against rocker arms 16 and 17, respectively, and the intake valve 2 is opened and closed by the rocker arm 17 corresponding to the cam 14 immediately above.

The rocker arms 16 and 17 have a piston 18
a, Clutch mechanism 1 including return spring 18b
8 for contact and separation.

When the load is high on the back of the piston 18a, FIG.
The hydraulic pressure is introduced as shown in FIG.
a moves forward against the spring force of the return spring 18b, connects the rocker arms 16 and 17, and synchronizes the intake valve 2 with the other intake valve 3 by the cam 13 having the same profile and operating angle as the cam 15. When the load is low and medium load, the hydraulic pressure to the piston 18a is released and the piston 18a retreats by the spring force of the return spring 18b as shown in FIG. I let the rocker arm 16 miss the motion,
The cam 14 keeps the intake valve 2 closed during the intake stroke.

That is, as shown in FIG. 4, one intake valve 2 maintains a closed state during the intake stroke when the load is low or medium, while the other intake valve 3 opens during the intake stroke. In the intake stroke, switching control is performed to a valve timing that opens synchronously with the other intake valve 3.

The camshaft 2 of the exhaust-side variable valve mechanism 19
0 is provided with two cams 21 and 22 for opening and closing the exhaust valve 6 and one cam 23 for opening and closing the exhaust valve 7.

The cams 21 and 22 contact the rocker arms 24 and 25, respectively, as shown in FIG. 3, and the exhaust valve 6 is opened and closed by the rocker arm 25 corresponding to the cam 22 immediately above.

The rocker arms 24 and 25 have a piston 26
a, clutch mechanism 2 including return spring 26b
6.

When the load is low or medium, hydraulic pressure is applied to the back of the piston 26a as shown in FIG. 3 (a), and the piston 26a advances against the spring force of the return spring 26b, and the rocker arms 24 and 25 move. The exhaust valve 6 is opened by the cam 21 during the valve opening period of the other intake valve 3, and when the load is high, the oil pressure to the piston 26a is released and the piston 26a is released as shown in FIG. Is retracted by the spring force of the return spring 26b, and the rocker arm 2
Rocker arm 24 with cam 21 by separating 4 and 25
And the cam 22 having the same profile and operating angle as the cam 23 causes the exhaust valve 6 to move to the other exhaust valve 7.
Open and close in synchronization with.

That is, one exhaust valve 6 opens synchronously with the other exhaust valve 7 during the exhaust stroke as shown in FIG.
Only during the medium load operation, switching control is performed to the valve timing to open during the opening period of the other intake valve 3 that opens during the intake stroke.

FIG. 5 shows the relationship between the valve opening period of the other intake valve 3 and the in-cylinder pressure. The negative pressure in the combustion chamber 1 in the first half of the valve opening period of the intake valve 3, especially in the first half of the intake stroke. The pressure value rapidly increases, and the negative pressure value gradually decreases in the latter half of the intake stroke.

Accordingly, the opening period of the one exhaust valve 6 may be opened over the entire intake stroke of the intake valve 3, but from the viewpoint of fuel mixing, promotion of vaporization, and increase in cylinder temperature. Therefore, it is desirable to set the exhaust valve 6 to be open during a substantially first half of the intake stroke in which a large in-cylinder gas flow can be obtained and high-temperature exhaust can be sucked immediately after the exhaust stroke.

According to the structure of the above embodiment, in the low and medium load range of the engine, one of the two intake valves 2 and 3 is maintained in the closed state during the intake stroke, and the other intake valve is maintained. Only the valve 3 is opened, and one of the two exhaust valves 6 and 7 is opened during the opening period of the other intake valve 3 to perform internal EGR. One-to-one relationship between the number of intake valves and the number of exhaust valves that open during the intake stroke
By doing so, the amount of internal EGR occupying in the combustion chamber 1 can be greatly increased.

As described above, by performing more aggressive internal EGR, the in-cylinder temperature rises, and as shown in FIG. 6, the operating range from low load to medium load (20% load to 50%
In the load range), compression auto-ignition combustion is promoted, and the peak combustion temperature can be lowered to lower the overall combustion temperature. As a result, the NOx reduction effect can be further improved without impairing combustion stability. be able to.

In particular, since the intake valve 3 and the exhaust valve 6, which are opened during the intake stroke as described above, are arranged diagonally about the ignition plug 10 at the center of the combustion chamber 1, FIG. As shown, the fresh air region where the inside of the combustion chamber 1 is sucked by opening the intake valve 3 and the internal EGR which is sucked by opening the exhaust valve 6.
Thus, ignition and flame propagation from the internal EGR region to the air-fuel mixture layer can be reliably performed, and the combustibility can be further improved.

On the other hand, in the high load region, the intake valves 2, 3 and the exhaust valves 6, 7 are returned to the valve timings corresponding to the basic four cycles, the internal EGR is stopped, and FIG.
As shown in (1), since spark ignition combustion is performed by the spark plug 10, a high output required for high load operation can be obtained.

FIGS. 7 and 8 show the present invention applied to a direct injection type spark ignition engine. The side of the combustion chamber 1 where the intake valves 2 and 3 are arranged is provided with these intake valves 2 and 3. A fuel injection valve 27 is disposed near the intermediate portion, and the fuel is directly injected into the combustion chamber 1 by the fuel injection valve 27. Other configurations are substantially the same as those of the first embodiment. is there.

The fuel injection valve 27 is connected to the intake valves 2 and 3
Among them, it is mounted at an angle at which fuel can be injected toward a new air flow sucked by opening the other intake valve 3 which is always opened in the intake stroke.

In this embodiment, as shown in FIG. 8, a cavity combustion chamber 29 is provided on the crown surface of the piston 28 at a position deviated in accordance with the position of the intake valve 3 to perform stratified combustion. It is designed to perform well.

In the direct injection type internal combustion engine, basically, for example, as shown in FIG.
In the low and medium load operation range of 5% load, fuel is injected into the combustion chamber 1 from the fuel injection valve 27 in the middle of the compression stroke to perform stratified combustion operation. In the operating range, the fuel injection is performed during the intake stroke to perform the homogeneous combustion operation. However, even when the engine is cold or knock occurs, the homogeneous combustion operation is performed to achieve combustion stability.

FIG. 9 schematically shows the behavior of the spray fuel and the internal EGR in each of the above-mentioned operation ranges.
Indicates a state in which the stratified charge combustion operation is performed in the low and medium load operation ranges of 30 to 35% load from the idling operation. The fuel injected in the compression stroke is received by the cavity combustion chamber 29 and is concentrated only around the spark plug 10. An air-fuel mixture can be formed, and stratified combustion can be performed stably with an air-fuel ratio having a very low overall air-fuel ratio.

In this operating range, the intake valve 2 is in a closed state and only the intake valve 3 is opened. During the opening period of the intake valve 3, one of the exhaust valves 6 is opened and the internal EGR is positive. In the combustion chamber 1, the fresh air region and the internal EGR region are stratified, and self-ignition combustion is promoted.

(B) in the same figure shows a state in which the homogeneous combustion operation is performed in a high load operation range in the range of 30 to 35% load or more.
The fuel injected in the intake stroke is promoted to be mixed and vaporized in the combustion chamber 1 to be homogenized, and to perform a homogeneous combustion at a relatively rich air-fuel ratio to achieve a high output.

In this operation region, for example, in a load region of less than 50%, the intake valve 2 is closed and the intake valve 3
During the opening period of the intake valve 3, one of the exhaust valves 6 is opened and the internal EGR is actively performed, so that a fresh air region and an internal EGR region are formed in the combustion chamber 1. Layered, auto-ignition combustion is promoted.

FIG. 3C shows a state in which the homogeneous combustion operation is performed in a high-load operation range of 50% load or more. In this operation range, the intake valves 2 and 3 and the exhaust valves 6 and 7 have the basic 4 Returning to the valve timing corresponding to the cycle, the internal EGR is stopped, and spark ignition combustion is performed by the spark plug 10, so that high output required for high load operation is achieved.

Therefore, according to the structure of the second embodiment, in addition to the effect of the first embodiment, stratified combustion at an ultra-lean air-fuel ratio can be achieved by injection of fuel in the compression stroke in the low and medium load regions of the engine. The fuel consumption and the exhaust emission can be improved by performing the fuel injection. In the medium and high load regions, the fuel can be homogeneously combusted by the intake stroke injection to obtain a high output.
As described above, during the intake stroke, one of the intake valves 2 is kept closed and only the other intake valve 3 is opened, and the other exhaust valve 6 is opened to actively perform the internal EGR. In the region, the fuel is injected in-cylinder toward the fresh air flow sucked by opening the other intake valve 3, so that the fuel and fresh air are mixed well and the stability of combustion is improved. be able to.

In each of the above embodiments, only one of the exhaust valves 6 is opened during the intake stroke. However, in some cases, the two exhaust valves 6, 7 may be opened for a required period during the opening period of the intake valve 3. It is also possible to open the valves simultaneously or in multiple stages to perform positive internal EGR.

Further, the number of exhaust valves is not limited to two.
One or three or more may be provided.

[Brief description of the drawings]

FIG. 1 is a plan view schematically showing a first embodiment of the present invention.

FIGS. 2A and 2B show an intake-side variable valve mechanism according to the first embodiment of the present invention, wherein FIG. 2A shows a low and medium load condition, and FIG. 2B shows a high load condition.

3A and 3B show an exhaust-side variable valve mechanism according to the first embodiment of the present invention, wherein FIG. 3A shows a low and medium load condition, and FIG. 3B shows a high load condition.

FIG. 4 is an explanatory diagram showing valve timing of intake and exhaust valves according to the first embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a relationship between an opening period of an intake valve and in-cylinder pressure according to the first embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a relationship between an engine operating state and a combustion state in the first embodiment of the present invention.

FIG. 7 is a plan view schematically showing a second embodiment of the present invention.

FIG. 8 is a plan view showing an arrangement relationship between a piston crown surface and a fuel injection valve according to a second embodiment of the present invention.

FIG. 9 is an explanatory diagram showing a change in an engine operating state and behaviors of spray fuel and internal EGR in a second embodiment of the present invention.

FIG. 10 is an explanatory diagram showing a relationship between an engine operating state and a combustion state in a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Combustion chamber 2, 3 Intake valve 6, 7 Exhaust valve 10 Spark plug 27 Fuel injection valve

Claims (6)

[Claims] In a spark ignition type internal combustion engine having two intake valves and at least one exhaust valve, one of the intake valves is maintained in a closed state during an intake stroke according to an operation state of the engine. A spark ignition type internal combustion engine, wherein only the other intake valve is opened and the one exhaust valve is opened during the opening period of the other intake valve. 2. In a spark ignition type internal combustion engine including two intake valves and two exhaust valves disposed opposite to the intake valves, one of the intake valves is operated during an intake stroke in accordance with an operation state of the engine. A spark, wherein the valve is kept closed and only the other intake valve is opened, and at least one of the exhaust valves is opened during the opening period of the other intake valve. Ignition internal combustion engine. 3. The fuel cell system according to claim 1, wherein the other intake valve and one exhaust valve that are opened during the intake stroke are arranged diagonally about a spark plug provided substantially at the center of the combustion chamber. The spark ignition type internal combustion engine according to claim 2. 4. The valve closing operation of the one intake valve during the intake stroke and the valve opening operation of the exhaust valve during the intake stroke are performed at low engine speeds.
The spark ignition type internal combustion engine according to any one of claims 1 to 3, wherein the operation is performed in a medium load region. 5. A fuel injection valve for directly injecting fuel into the combustion chamber on a side of the combustion chamber on the side where the intake valve is disposed, and the fuel injection valve directs a new airflow sucked by opening the other intake valve. The spark ignition type internal combustion engine according to any one of claims 1 to 4, wherein the fuel is injected by using an internal combustion engine. 6. The fuel injection system according to claim 5, wherein fuel is injected in a compression stroke in a low and medium load range of the engine, and fuel is injected in an intake stroke in a middle and high load range of the engine. Spark ignition internal combustion engine.