JPH07247847A - Spark ignition type internal combustion engine - Google Patents

Abstract

PURPOSE:To provide a spark ignition type internal combustion engine to prevent worsening of exhaust gas emission owing to stratification of a fuel-air mixture. CONSTITUTION:A swirl control valve 5 to throttle an intake air flow, sucked in a combustion chamber 9 after the flow of it through a second intake air port 12, according to an operation condition is arranged upstream from a branch point between first and second intake air ports 11 and 12. The opening timing of a second intake air valve 2 is more advanced than that of a first intake air valve 1 and set more advanced than the piston top dead center of an intake stroke.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art As a method for obtaining stable combustion even with a lean air-fuel mixture, an appropriate swirl is generated in the combustion chamber and
Stratification of the air-fuel mixture that makes the air-fuel ratio near the spark plug richer than the other is effective.

As a fuel supply device used for a lean burn engine, there is a conventional fuel supply device as shown in, for example, FIG. 7 (see JP-A-62-91619).

Explaining this, a helical first intake port 41 opening to the combustion chamber 40 of one cylinder and a straight second intake port 42 are branched. A first fuel injection valve 51 and a second fuel injection valve 52 are arranged in the middle of the intake ports 41, 42, respectively.

A swirl control valve 43 is provided in the middle of the second intake port 42, and the swirl control valve 43 throttles the intake flow drawn into the combustion chamber 40 from the second intake port 41 under a predetermined operating condition. The swirl is generated in the combustion chamber 40 by strengthening the force of the intake flow sucked into the combustion chamber 40 from the second intake port 42.

Under an operating condition in which the swirl is generated in the combustion chamber 40 by the intake air flow flowing from the first intake port 41, the fuel injection amount of the second fuel injection valve 52 is made larger than that of the first fuel injection valve 51, From the intake port 42, the air-fuel mixture that is richer than the first intake port 41 flows toward the central region of the combustion chamber 40, and the air-fuel mixture is stratified.

Under operating conditions in which the swirl control valve 43 is opened and intake air is evenly taken in through the intake ports 41, 42, the first fuel injection valve 51 and the second fuel injection valve 52 are provided.
The fuel is evenly injected from.

[0008]

However, in such a conventional spark ignition type internal combustion engine, the combustion chamber 4 is operated under the operating condition that the swirl control valve 43 is closed.
When the fuel is collected near the spark plug 46 by the swirl generated at 0, the mixture is stratified, and the spark plug 4 is discharged.
The combustion temperature in No. 6 becomes high, and the amount of NOx generated may increase.

In order to suppress the amount of NOx produced, it is conceivable to recirculate the EGR gas (burnt gas) discharged from the combustion chamber 40 to the intake system, but a lean mixture is supplied to the combustion chamber 40. If the amount of EGR gas is increased during a certain operation, the combustion speed may decrease and the amount of unburned HC generated may increase.

The present invention focuses on the above-mentioned problems, and an object thereof is to prevent deterioration of exhaust emission due to stratification of air-fuel mixture.

[0011]

The invention according to claim 1 is
An ignition plug is arranged in the center of the combustion chamber, and a first intake port and a second intake port that open to the combustion chamber of one cylinder are formed in a branched manner, and upstream from the branch point of the first and second intake ports. Provided with a swirl control valve that throttles the intake flow that is drawn into the combustion chamber through the second intake port according to operating conditions.
Fuel supply means for supplying fuel to the first intake port and the second intake port is provided, and first and second intake valves are provided for opening and closing the first and second intake ports with respect to the combustion chamber in synchronization with engine rotation. The opening timing of the second intake valve is set to advance from the opening timing of the first intake valve and to advance from the piston top dead center in the intake stroke.

According to a second aspect of the present invention, in the first aspect of the invention, the fuel supply means supplies fuel toward the first and second intake ports upstream of the branch point of the first and second intake ports. A fuel injection valve for injection is provided.

According to a third aspect of the present invention, in the second aspect of the invention, the fuel injection timing of the fuel injection valve from the combustion chamber to the first and second intake ports is the time point at which the gas flow backflows toward the combustion chamber. Set it at about the center.

The invention according to claim 4 is the invention according to claim 2 or 3.
In any one of the inventions described above, in the lean combustion region in which the swirl control valve is closed, the fuel injection timing of the fuel injection valve from the combustion chamber to the first and second intake ports is a gas flow that flows backward toward the combustion chamber. The control means for advancing the fuel injection start timing of the fuel injection valve from the valve opening timing of the second intake valve is provided in the operating region where the swirl control valve is opened by setting the time point toward the center substantially.

[0015]

In the invention of claim 1, the opening timing of the second intake valve is set to advance from the opening timing of the first intake valve and to advance from the piston top dead center in the intake stroke. ,
Due to the negative pressure generated in the intake passage in the early stage of the intake stroke, the EGR gas (burnt gas) from the combustion chamber is blown back to the second intake port, and the supply fuel is atomized.

In an operating condition in which the intake flow sucked into the combustion chamber through the second intake port via the swirl control valve is throttled, the air flow sucked into the combustion chamber through the first intake port enters the combustion chamber. A swirl is generated, and a rich mixture containing a large amount of EGR gas is made to flow into the combustion chamber from the second intake port into the center of the combustion chamber, and the mixture of fuel and EGR gas is stratified in the center of the combustion chamber. Get off.

By distributing a large amount of atomized fuel in the vicinity of the spark plug, ignition is surely performed, and by distributing a large amount of EGR gas in the vicinity of the spark plug, the combustion temperature in the first half of the combustion stroke is increased. Lowering N
The amount of Ox generated can be suppressed.

In the latter half of the combustion stroke, as the flame propagates to the cylinder wall side, even if the fuel mixture ratio becomes lean on the cylinder wall side, the oxygen partial pressure is restored to sufficiently increase the combustion speed, Combustion is performed in the entire combustion chamber, the amount of unburned HC generated can be suppressed, and the engine output can be increased. Moreover, since the fuel mixture ratio is lean on the cylinder wall side, the combustion temperature is lowered and the N
The amount of Ox generated can be suppressed.

In the invention according to claim 2, as the fuel supply means, a fuel injection valve for injecting fuel toward the first and second intake ports is provided upstream of the branch point of the first and second intake ports. , The intake flow that is drawn into the combustion chamber through the second intake port is not throttled through the swirl control valve Under high operating conditions such as high load, the intake air is split into the first intake port and the second intake port evenly. In this case, the fuel spray injected from the fuel injection valve can be evenly divided into the first intake port and the second intake port. In this way, the air-fuel mixture with the same air-fuel ratio is sucked from the first intake port and the second intake port, and at high speeds, the mixing of fuel spray and air is promoted as the intake flow velocity rises, and good combustibility is obtained. To be As a result, the output can be improved and the amount of unburned HC discharged can be reduced.

In the third aspect of the present invention, the fuel injection timing of the fuel injection valve is set mainly at the time point when the gas flow flowing back from the combustion chamber to the first and second intake ports is directed toward the combustion chamber. The fuel spray injected from the valve opposes the EGR gas that flows backward in the intake passage, and the EGR gas promotes atomization and evaporation of the fuel spray to enhance combustibility.

In a fourth aspect of the present invention, in the lean combustion region where the swirl control valve is closed, the gas flow that causes the fuel injection timing of the fuel injection valve to flow back from the combustion chamber to the first and second intake ports is increased. The fuel spray injected from the fuel injection valve is opposed to the EGR gas flowing backward in the intake passage, and the EGR gas promotes atomization and evaporation of the fuel spray. A rich mixture containing a large amount of EGR gas is retained in the second intake port to stratify the mixture that collects the fuel and the EGR gas in the central portion of the combustion chamber, thereby improving combustibility.

In the operating region where the swirl control valve is opened, the fuel injection start timing of the fuel injection valve is set to an exhaust stroke advanced from the valve opening timing of the second intake valve, so that the first valve in the closed state, Fuel stays near the back of the second intake valve, and in response to an increase in the fuel injection amount, the heat transfer from the first and second intake valves promotes atomization of the fuel and enhances combustibility. .

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1, in the intake passage 10, a first intake port 11 and a second intake port 12 which open into the combustion chamber 9 of one cylinder are formed in a branched manner.

As shown in FIG. 2, the combustion chamber 9 has a first,
First and first intake valves 1 and 2 for opening and closing the second intake ports 11 and 12 in synchronization with engine rotation are provided, respectively.
Two exhaust valves 8 are arranged facing the first intake valves 1 and 2, and a spark plug 7 is arranged facing the center of the combustion chamber 9.

A swirl control valve 5 is provided in the intake passage 10 upstream of a branch point between the first intake port 11 and the second intake port 12.

The disk-shaped swirl control valve 5 is provided with a cutout portion 5a for allowing intake air to pass therethrough at its closed position. The cutout portion 5a is offset and opened in the rotation axis direction so as to face the first intake port 11 more than the second intake port 12. As a result, the swirl control valve 5 throttles the intake flow that is drawn into the combustion chamber 9 through the second intake port 12 when the swirl control valve 5 is closed.

Rotating shaft 1 of swirl control valve 5
An actuator (not shown) is connected to the actuator 3, and the actuator controller closes the swirl control valve 5 in a lean burn region where the load is lower than a predetermined value based on a preset map, and swirl control in a region other than the lean burn region. The valve 5 is opened.

As shown in FIG. 3, the opening timing of the first intake valve 1 is set to the piston top dead center (TDC) of the intake stroke,
The opening timing of the second intake valve 2 is set to the advance side from the piston top dead center. That is, the opening timing of the second intake valve 2 is advanced from the first intake valve 1 by a predetermined crank angle. A variable valve mechanism that makes the lift characteristics of the first and second intake valves 1 and 2 different according to the operating state is provided so that the swirl control valve 5 is closed in the operating state other than the lean combustion region. The opening timing of the intake valve 2 may be set to be the same as the opening timing of the first intake valve 1.

A fuel injection valve 6 is arranged upstream of the swirl control valve 5 in the intake passage 10. The fuel injection valve 6 has two injection holes, and each injection hole is directed toward the back side of the first and second intake valves 1 and 2, and even when the swirl control valve 5 is closed. The injected fuel spray is divided into the first intake port 11 and the second intake port 12 through the cutout portion 5a.

The fuel injection valve 6 opens the injection port according to the pulse signal sent from the control device, and the fuel injection amount is controlled according to the operating state and the fuel injection start timing is controlled. In the lean combustion region in which the swirl control valve 5 is closed, the control device delays the fuel injection start timing from the opening timing of the first intake valve 1 as shown in FIG. The time (crank angle) 4 at which the gas flow flowing back to the second intake ports 11 and 12 heads toward the combustion chamber 9 is set substantially at the center, and the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber 9 is set to 20-24. Control to the range of.

On the other hand, under operating conditions other than the lean combustion region in which the swirl control valve 5 is opened, the fuel injection start timing is advanced from the valve opening timing of the second intake valve 2, and the mixture is supplied to the combustion chamber 9. The air-fuel ratio of air is controlled near the stoichiometric air-fuel ratio.

Next, the operation will be described.

In the lean combustion region where the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber 9 is controlled to be leaner than the stoichiometric air-fuel ratio,
By closing the swirl control valve 5,
The combustion chamber 9 is generated by the intake air flow that flows in from the first intake port 11.
A swirl is generated in the combustion chamber 9 and a rich mixture containing a large amount of EGR gas is introduced from the second intake port 12 into the combustion chamber 9.
To generate NOx and unburned HC, and increase the output.

Explaining the combustion stroke in the lean burn region in detail, the time 1 at which the piston rises in FIG.
In the crank angle range from 1 to 2, the second intake valve 2 opens,
The first intake valve 1 is closed. At this time, the EGR gas from the combustion chamber 9 is blown back to the second intake port 12 by the negative pressure generated in the intake passage 10 on the downstream side of the throttle valve, as shown by the arrow in FIG. As the piston rises, the amount of EGR gas blown back into the second intake port 12 increases, so that the negative pressures of the first and second intake ports 11 and 12 downstream of the swirl control valve 5 gradually decrease. The increase rate of the amount of EGR gas blown back from the combustion chamber 9 to the second intake port 12 decreases.

When the crank angle at time 2 is reached in FIG. 3, the first intake valve 1 opens. As a result, the EGR gas from the combustion chamber 9 is blown back to both the first and second intake ports 11 and 12, as shown by the arrow in FIG. When the first intake valve 1 opens, the first and second intake ports 11, 1 have already been opened.
Since the negative pressure of 2 is considerably lowered, the amount of EGR gas blown back to the first and second intake ports 11 and 12 after the first intake valve 1 is opened is small.

At the crank angle at time 4 in FIG. 3, the negative pressure in the intake passage 10 decreases, while the negative pressure in the cylinder rises as the piston descends. The pressure increases, and the gas flow in the intake passage 10 reverses in the cylinder direction, but the gas flow velocity near the fuel injection valve 9 becomes zero at the moment when the flow reverses.

In FIG. 3, when the crank angle at time 3 is reached, fuel injection from the fuel injection valve 6 is started, and this fuel injection is centered at time 4 at which the gas flow velocity in the first and second intake ports 1 and 12 becomes zero. Done as. Therefore, in the crank angle range from time 3 to time 4, as shown in FIG. 5, the fuel spray injected from the fuel injection valve 6 is the same as the injection speed of the EGR gas that flows backward in the intake passage 10. Since it opposes the flow, the atomization and evaporation of the fuel spray are promoted by the EGR gas, and the fuel spray mixed with the EGR gas causes the fuel spray mixed in the first and second intake ports 11, 11
12 to the upstream side of the fuel injection valve 7. At this time, the second intake valve 2 opens early, and the force of the EGR gas blown back into the second intake port 12 is the first intake port 1
Since it is stronger than that of No. 1, atomization and vaporization of the fuel spray staying in the second intake port 12 are particularly achieved.

Further, fuel is injected mainly at time 4, and the fuel in the latter half of the injection is injected into the mixture in the first half of the injection mixed with the backflow gas, so that the fuel is concentrated in a very narrow region of the intake flow. A rich air-fuel mixture is supplied to the combustion chamber 9 from the second intake port 12 on which the intake air is throttled, so that the air-fuel mixture is stratified.

In the crank angle range from time 4 to 5, as shown in FIG. 5, when the gas flow in the intake passage 10 is in the same forward direction as the fuel spray injected from the fuel injection valve 6, the fuel injection is performed. The fuel spray injected from the valve 6 is injected into the mixed gas of the fuel spray injected from the time 3 to 4 and the EGR gas, and is sucked into the combustion chamber 9 through the first and second intake ports 11 and 12. To be done. At this time, most of the intake flow collected in the cutout portion 5a of the swirl control valve 5 is sucked into the combustion chamber 9 through the first intake port 11,
A part of the intake air flow passing through the swirl control valve 5 is taken into the combustion chamber 9 through the second intake port 12.
The air-fuel mixture sucked through the first intake port 11 has a large amount of fresh air taken in from the air cleaner, while the air-fuel mixture sucked through the second intake port 12 has a large amount of EGR gas and fuel. A large amount of atomized fuel is distributed.

When the crank angle at time 5 is reached in FIG. 3, the fuel injection from the fuel injection valve 6 ends, and substantially the entire amount of fuel injected in this cycle over the intake stroke after time 5 is supplied to the combustion chamber 9. It

As shown by the arrow in FIG. 6 (A), the swirl generated in the combustion chamber 9 by the high-speed intake air flow introduced from the first intake port 11 as the piston descends with respect to the cylinder. It swivels around an inclined axis, a region with a small gas flow is generated in the vicinity of this axis, and the second intake port 12 is opened facing the region where the swirl has a weak force. The low-speed intake air flow introduced from 12 flows into the combustion chamber 9 so as to be sucked into the central part of the swirl. The mixture that has been atomized by the EGR gas that has flowed from the second intake port 12 into the central portion of the swirl moves toward the combustion chamber 9 as shown in FIG. 6B as the piston rises. It is collected in the vicinity of the spark plug 7 located in the central portion.

In this way, the EGR gas and the atomized fuel are collected in the center of the combustion chamber 9, and the so-called air-fuel mixture is stratified so that the lean air-fuel mixture is distributed on the cylinder wall side. Ignition is reliably performed by distributing a large amount of atomized fuel in the vicinity of the spark plug 6. Moreover, by distributing a large amount of EGR gas together with the fuel in the vicinity of the spark plug 6, the oxygen concentration in the vicinity of the spark plug 6 is low, so that the combustion temperature is lowered and the amount of NOx generated can be suppressed.

In the process in which the flame propagates from the central portion of the combustion chamber 9 to the cylinder wall side after ignition, the fuel mixture ratio on the cylinder wall side of the combustion chamber 9 becomes lean, so that the combustion temperature is lowered. , NOx generation amount can be suppressed. Moreover, on the cylinder wall side of the combustion chamber 9, the oxygen partial pressure is recovered, so that the combustion speed is sufficiently increased, combustion is performed in the entire region of the combustion chamber 9, and the amount of unburned HC generated is suppressed. The engine output can be increased.

In an operating state such as a high load when the air-fuel ratio supplied to the combustion chamber 9 is switched to the stoichiometric air-fuel ratio, the swirl control valve 5 is opened and the fuel injection start timing of the fuel injection valve 6 is the second intake air. The exhaust stroke is advanced from the valve opening timing of the valve 2.

By opening the swirl control valve 5, the intake air is divided into the first intake port 11 and the second intake port 12 evenly, and the fuel spray injected from each injection hole of the fuel injection valve 6 is the first. The flow is evenly divided into the intake port 11 and the second intake port 12. In this way, the air-fuel mixture having the same air-fuel ratio is sucked from the first intake port 11 and the second intake port 12, but when the load is high, the mixture of the fuel spray and the air proceeds as the intake flow velocity increases.

By advancing the fuel injection start timing of the fuel injection valve 6 from the valve opening timing of the second intake valve 2, the fuel spray injected from the fuel injection valve 6 is in the closed state. Remains near the back of the second intake valves 1 and 2,
Due to the heat transfer from the second intake valves 1 and 2, the fuel is atomized and vaporized to obtain good combustibility, the output is increased, and the emission of unburned HC is suppressed.

[0048]

As described above, according to the first aspect of the present invention, the spark plug is arranged in the central portion of the combustion chamber, and the first intake port and the second intake port opening to the combustion chamber of one cylinder are provided. A swirl control valve that forms a branch and restricts the intake flow that is drawn into the combustion chamber through the second intake port upstream of the branch point of the first and second intake ports according to operating conditions is provided. And fuel supply means for supplying fuel to the second intake port, and first and second intake valves for opening and closing the first and second intake ports, respectively, in synchronization with the engine rotation with respect to the combustion chamber. Since the opening timing of the intake valve is set to advance from the opening timing of the first intake valve and to advance from the piston top dead center in the intake stroke, fuel and EGR are set in the center of the combustion chamber.
By stratifying the air-fuel mixture that collects gas, the amount of NOx and unburned HC generated can be suppressed, and stable lean combustion can be realized to reduce fuel consumption.

According to a second aspect of the present invention, in the first aspect of the invention, the fuel supply means supplies fuel toward the first and second intake ports upstream of the branch point of the first and second intake ports. Since the fuel injection valve for injecting is provided, the mixture of fuel and air is promoted at the time of high load to improve the output and the exhaust emission.

According to a third aspect of the present invention, in the second aspect of the invention, the fuel injection timing of the fuel injection valve from the combustion chamber to the first and second intake ports is the time when the gas flow backflows toward the combustion chamber. Is set substantially at the center, the atomization and evaporation of the fuel spray are promoted by the EGR gas flowing back through the intake passage, and the combustibility is enhanced. Also, since the fuel in the latter half of the injection is injected into the mixture in the first half of the injection mixed with the backflow gas, the fuel is concentrated in a very narrow region of the intake flow, and a rich mixture is drawn from the intake port where the intake is throttled. By supplying the mixture to the combustion chamber, the air-fuel mixture is stratified.

The invention according to claim 4 is the invention according to claim 2 or 3.
In any one of the inventions described above, in the lean combustion region in which the swirl control valve is closed, the fuel injection timing of the fuel injection valve from the combustion chamber to the first and second intake ports is a gas flow that flows backward toward the combustion chamber. Since the time point is set substantially at the center, and a control means for advancing the fuel injection start timing of the fuel injection valve from the opening timing of the second intake valve is provided in the operating region where the swirl control valve is opened, stable operation is achieved. While realizing lean combustion to reduce fuel consumption, the output and exhaust emission can be improved by promoting mixing of fuel and air at high load.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an intake passage showing an embodiment of the present invention.

FIG. 2 is a sectional view of the same engine.

FIG. 3 is a diagram showing lift characteristics of intake / exhaust valves, fuel injection timing, and the like.

FIG. 4 is an explanatory view showing the distribution of fuel spray and the state of gas flow.

FIG. 5 is an explanatory view showing the distribution of fuel spray and the state of gas flow.

FIG. 6 is an explanatory view showing the distribution of fuel spray and the state of gas flow.

FIG. 7 is a configuration diagram of an intake passage and a combustion chamber showing a conventional example.

[Explanation of symbols]

 1 First intake valve 2 Second intake valve 5 Swirl control valve 6 Fuel injection valve 7 Spark plug 9 Combustion chamber 10 Intake passage 11 First intake port 12 Second intake port

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location F02M 69/00 360 C

Claims (4)

[Claims] 1. A spark plug is provided in the center of a combustion chamber, and a first intake port and a second intake port opening to the combustion chamber of one cylinder are formed in a branched manner, and a first and a second intake port are branched. A swirl control valve that restricts the intake flow that is drawn into the combustion chamber through the second intake port upstream of the point according to the operating conditions, and supplies fuel to the first intake port and the second intake port. The first and second intake valves that open and close the first and second intake ports in synchronization with the engine rotation are provided for the combustion chamber, and the opening timing of the second intake valve is set to the opening timing of the first intake valve. A spark ignition type internal combustion engine, which is set to advance from a valve timing and advance from a top dead center of a piston in an intake stroke. 2. A fuel injection valve for injecting fuel toward the first and second intake ports is provided upstream of a branch point of the first and second intake ports as the fuel supply means. Item 1. A spark ignition type internal combustion engine according to item 1. 3. The fuel injection timing of the fuel injection valve is set to be substantially centered at a time point when a gas flow flowing back from the combustion chamber to the first and second intake ports is directed toward the combustion chamber. The spark ignition internal combustion engine described. 4. A fuel injection timing of a fuel injection valve in a lean combustion region in which a swirl control valve is closed is approximately at a time point when a gas flow flowing backward from the combustion chamber to the first and second intake ports is directed toward the combustion chamber. A control means is provided which is set at the center and which advances the fuel injection start timing of the fuel injection valve from the valve opening timing of the second intake valve in an operating region where the swirl control valve is opened. 2. A spark ignition type internal combustion engine according to any one of 2 and 3.