JPH07166926A - Air intake device of internal combustion engine - Google Patents

Abstract

PURPOSE:To improve combustion stability at the time of controlling EGR by feeding an air-fuel mixture richer than a stoichiometric air-fuel ratio, to the surroundings of an ignition plug. CONSTITUTION:When an engine reaches a predetermined driving condition, a swirl control valve 6 is closed by a control unit 22 so as to limit the amount of air to a second intake port 4B. Assist air is fed by a fuel injection valve 8 from an auxiliary air channel 17 to only the second injection hole directed to the second intake port 4B. A first intake valve 5A is set so that its opening time and closing time become earlier than those of a second intake valve 5B, and the fuel injection timing of the fuel injection valve 8 is set so that the fuel injected from the second injection hole reaches the inside of the second intake port 4B when the second intake valve 5B is going to be closed. An air-fuel mixture layer of high air-fuel ratio, an air-fuel mixture layer of the air-fuel ratio closer to a stoichiometric air-fuel ratio, and an EGR gas layer are formed in this order from the center part to the outside of a cylinder 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake system for an internal combustion engine which performs stratified charge under a predetermined operating condition, and more particularly, to an intake system which improves stratification of an air-fuel mixture and EGR gas to improve combustion stability. Regarding the improvement of the device.

[0002]

2. Description of the Related Art EGR gas is introduced into an intake passage under predetermined operating conditions and the opening / closing timing of each intake valve is adjusted in order to reduce combustion temperature to reduce NO _X and improve fuel efficiency. An apparatus for stratifying the air-fuel mixture and the EGR gas is known, for example, from Japanese Utility Model Publication No. 62-154233.

That is, the one disclosed in the above publication is
In a device including a first intake valve and a second intake valve independent of each cylinder, a fuel injection valve is provided in a first intake port communicating with the first intake valve, while a second intake valve is provided in the second intake valve. An EGR passage is connected to the communicating second intake port downstream of the swirl control valve, so that the opening timing of the second intake valve is earlier than the opening timing of the first intake valve.

After the EGR gas is supplied into the cylinder through the second intake port, fresh air, that is, the air-fuel mixture is supplied through both intake ports, so that the air-fuel mixture is guided above the EGR gas. To achieve stratification in the axial direction.

[0005]

However, in the conventional device, the opening timing of the intake valve on the side to which the EGR passage is connected is merely advanced earlier than the opening timing of the intake valve on the fuel injection valve side. Even if the stratification of the EGR gas and the air-fuel mixture is realized in the early stage of the intake stroke, the two may be mixed before ignition and the stratification may be broken.

That is, when the intake stroke ends and the compression stroke starts, the piston rises and the axial dimension in the cylinder decreases, so that axial stratification cannot be maintained, and EGR gas is generated. The air-fuel mixture is mixed before ignition,
It may impair the stability of combustion.

[0007]

Therefore, according to the present invention, the EGR gas and the air-fuel mixture are stratified by adjusting the fuel injection timing of the fuel injection valve and the timing at which the fuel reaches each intake port. I decided. That is, the intake device for an internal combustion engine according to the present invention is provided for each cylinder of the internal combustion engine, and an intake passage whose front end is branched into a first intake port and a second intake port and a rotation of the engine are synchronized. Then, the first intake valve and the second intake valve for opening and closing the first intake port and the second intake port, respectively, are provided in the middle of the intake passage, and the fuel is injected toward each intake port. In an intake system for an internal combustion engine, comprising a fuel injection valve, and an ignition plug arranged near the center of the cylinder, a second intake port is provided in the middle of the intake passage by closing the valve under predetermined operating conditions. An intake control valve for limiting the amount of air flowing into the first intake valve is set earlier than the second intake valve is opened, and when the predetermined operating condition is satisfied, the opening timing of the first intake valve is set earlier than the opening timing of the second intake valve. The second intake time is later than the fuel arrival time at the first intake port. The arrival timing delay means for delaying the fuel arrival timing at the port is provided, and the fuel injection timing of the fuel injection valve is set so that the fuel arrival timing at the second intake port is just before the closing of the second intake valve. Is characterized by.

Further, according to the second aspect of the invention, the intake passage is provided for each cylinder of the internal combustion engine, and the front end side is branched into the first intake port and the second intake port, and is synchronized with the rotation of the engine. Intake device for an internal combustion engine having a first intake valve for opening and closing the first intake port and a second intake port respectively for opening and closing the second intake port, and a spark plug arranged near the center of the cylinder. In the middle of the intake passage, an intake control valve that limits the amount of air flowing into the second intake port by closing the valve under predetermined operating conditions is provided, and the opening timing of the first intake valve is set. It is set earlier than the opening timing of the second intake valve, and further, in the middle of the intake passage, a first injection hole directed to the first intake port and a second injection directed to the second intake port. The fuel is burned from the hole toward the first intake port and the second intake port, respectively. A fuel injection valve for injecting fuel and supplying the assist air from the air source only to the second injection hole under the predetermined operating condition is provided, and the fuel injection timing of this fuel injection valve is set under the predetermined operating condition. It is characterized in that the fuel arrival timing at the second intake port is set to be close to the closing of the second intake valve.

Further, according to the third aspect of the invention, the intake passage is provided for each cylinder of the internal combustion engine, and the tip end side of the intake passage is branched into the first intake port and the second intake port, and is synchronized with the rotation of the engine. Intake device for an internal combustion engine having a first intake valve for opening and closing the first intake port and a second intake port respectively for opening and closing the second intake port, and a spark plug arranged near the center of the cylinder. In the middle of the intake passage, an intake control valve that limits the amount of air flowing into the second intake port by closing the valve under predetermined operating conditions is provided, and the opening timing of the first intake valve is set. It is set earlier than the opening timing of the second intake valve, and further, in the middle of the intake passage, a first injection hole directed toward the first intake port via a nozzle extending toward the first intake port, a second injection hole Of the first intake port from the second injection hole that is directed to the intake port of And a fuel injection valve for injecting fuel toward the second intake port, and for supplying the assist air from the air source to the first injection hole and the second injection hole under the predetermined operating conditions, The predetermined operating condition is characterized in that the fuel injection timing of the fuel injection valve is set so that the fuel arrival timing at the second intake port is just before the closing of the second intake valve.

Further, in claim 4, each of claims 1 to 3
In any one of the above, the fuel injection valve is configured to inject fuel supplied to the first intake port toward the center of the cylinder of the first intake port.

[0011]

When the engine enters a predetermined operating condition in which EGR control is possible, the intake control valve is closed and the fuel injection timing is set just before the second intake valve is closed.

At the beginning of the suction stroke, the second
By opening the first intake valve prior to the intake valve, the combustion gas (EGR gas) in the cylinder is blown back into the first intake port from around the first intake valve.

When the intake stroke proceeds, the combustion gas that has flowed back into the first intake port flows into the cylinder together with the intake air. Here, under a predetermined operating condition, since the intake control valve is closed and the amount of air to the second intake port is limited, most of the intake air is in the cylinder from the first intake port together with the combustion gas. It flows into and forms a swirl.

On the other hand, the arrival timing delay means delays the fuel arrival timing at the second intake port from the fuel arrival timing at the first intake port, so that the fuel arrival at the second intake port is reached. If the fuel injection timing is set so that the timing is just before the closing of the second intake valve, the fuel on the side of the first intake port flows into the cylinder in the middle of the intake stroke, while the fuel on the side of the second intake port is closed. The fuel on the side flows into the cylinder at the end of the intake stroke.

Therefore, the fuel flowing into the cylinder from the first intake port in the middle of the intake stroke rides on the swirl formed by the combustion gas and the intake air and is mainly guided to the vicinity of the peripheral portion of the cylinder.

On the other hand, at the end of the intake stroke, the moving speed of the piston decreases, and the intake control valve limits the amount of air on the side of the second intake port, so that the fuel from the second intake port is It flows into the cylinder at a relatively slow speed,
It is drawn to the swirl center of the swirl and guided to the approximate center of the cylinder.

Here, since the intake control valve limits the amount of air to the second intake port, the air-fuel ratio of the air-fuel mixture flowing into the cylinder from the second intake port becomes relatively rich. ing.

Thus, in the cylinder, a layer of the combustion gas and the air-fuel mixture is formed in the peripheral portion thereof, while a layer of the air-fuel mixture having a high air-fuel ratio is formed in the central portion corresponding to the spark plug. Radial stratification is realized.

According to the second aspect of the invention, since the fuel injection valve supplies the assist air only to the second injection hole under the predetermined operating condition, the fuel injected from this second injection hole Only the air is atomized by the assist air.

Here, when the diameter of the injected fuel particles is large, the air resistance is easily overcome, and the deceleration becomes small. On the other hand, when the particle size of the fuel particles is small, the air resistance is strongly received, and the deceleration increases,
Eventually, he loses his speed and is carried to the cylinder by the flow of intake air.

Therefore, by restricting the amount of air on the side of the second intake port by the intake control valve and atomizing the fuel toward the second intake port by the assist air,
The fuel arrival timing at which the atomized fuel reaches the second intake port can be delayed from the fuel arrival timing at the first intake port. As a result, the stratification of the combustion gas and the air-fuel mixture can be realized as in the case of the first aspect.

Further, according to the structure of claim 3, the fuel injection valve is injected by the assist air from the first injection hole and the second injection hole under a predetermined operating condition in which the intake control valve is closed. Claim 2 for atomizing each fuel.
Similarly to the action of, the fuel injected from the second injection hole is
The speed decreases due to the influence of air resistance.

Since the first injection hole is directed to the first intake port via the nozzle extending toward the first intake port, the fuel injected from the first injection hole is assisted by the assist air. Even if atomized, the deceleration in the nozzle is small. That is, the fuel is almost at the same time as the nozzle tip and the second
The fuel from the second injection hole, which is injected from a farther distance, is greatly affected by the speed reduction due to atomization, and the fuel arrival timing to the second intake port Is later than the fuel arrival timing at the first intake port. As a result, the stratification of the combustion gas and the air-fuel mixture can be realized as in the case of the first aspect.

Further, according to the fourth aspect of the invention, the fuel supplied to the first intake port is injected toward the center of the cylinder of the first intake port, so that the fuel on the side of the first intake port is injected. Will ride on the inner circumference side of the swirl formed by combustion gas and the like.

As a result, in the cylinder, the EGR gas layer formed on the outer peripheral side and having a high abundance ratio of the combustion gas, and the fuel from the first intake port formed on the inner peripheral side of the EGR gas layer are formed. Is mainly composed of the first air-fuel mixture layer, and the fuel from the second intake port formed in the inner peripheral side of the first air-fuel mixture layer, that is, substantially in the center of the cylinder, has a high concentration. A total of three types of layers including the second air-fuel mixture layer are formed.

[0026]

Embodiments of the present invention will now be described in detail with reference to FIGS.

First, FIG. 1 is a structural explanatory view of an intake system for an internal combustion engine according to a first embodiment of the present invention. The internal combustion engine is provided with a plurality of cylinders 1 (only one is shown). Cylinder 1
An ignition plug 3 that faces the inside of the combustion chamber 2 is disposed substantially in the center of the cylinder head.

An intake passage 4 is provided for each cylinder 1. The upstream side of the intake passage 4 is collected in a collector and connected to an air cleaner (neither is shown), and the intake passage 4 is downstream. The side is bifurcated into a first intake port 4A and a second intake port 4B, and the intake ports 4A and 4B communicate with the same combustion chamber 2.

Each intake port 4A, 4B of the intake passage 4 is provided with a first intake valve 5A and a second intake valve 5B, respectively. The intake valves 5A and 5B are connected to a valve operating mechanism (not shown), and the valve operating mechanism opens and closes the intake ports 4A and 4B in conjunction with the rotation of the engine. Also, as will be described later with reference to FIG.
Both the intake valve 5A and the second intake valve 5B have earlier opening and closing times.

The swirl control valve 6 as the intake control valve is
It is provided on the downstream side of a throttle valve (not shown) and on the upstream side of a fuel injection valve 8 described later, and is connected to a swirl control valve drive mechanism 7. The portion of the swirl control valve 6 on the fuel injection valve 8 side is the first intake port 4
A notch 6A is cut out in a rectangular shape over a range from a portion corresponding to A to a substantially middle portion of a portion corresponding to the second intake port 4B.

The fuel injection valve 8 is provided upstream of the branch portions of the intake ports 4A and 4B of the intake passage 4 and downstream of the swirl control valve 6. Also,
The fuel injection valve 8 is attached to the cylinder head side.

As shown in FIG. 2, the fuel injection valve 8 has an injection valve main body 9 for injecting fuel by opening and closing an injection hole formed at the tip by a valve body (none of which is shown).
And the injection nozzle 1 provided at the tip of the injection valve body 9.
0 and a cover 11 provided to cover the outside of the injection nozzle 10 except the tip thereof, and a substantially stepped tubular air chamber 12 is defined between the cover 11 and the injection nozzle 10. There is.

In addition, the injection nozzle 10 has a first injection hole 1 which is independently directed to each of the intake ports 4A and 4B.
0A and the 2nd injection hole 10B are formed, and the upstream end of each of these injection holes 10A and 10B is connected to the injection hole of the injection valve body 9, and when a valve body opens, both will be substantially equal amount. Each of the fuels is designed to flow in.

Further, in the injection nozzle 10, an air passage 13 which communicates between the second injection hole 10B and the air chamber 12 is formed obliquely along the traveling direction of the fuel.
Only the fuel injected from the second injection holes 10B is atomized by the assist air supplied from the air passage 13. In addition, 14 shown in FIG. 2 is a seal member for sealing between the cover 11 and the injection valve main body 9,
Reference numeral 15 is a seal member that seals between the injection nozzle 10 and the injection valve body 9, and 16 is a seal member that seals between the injection nozzle 10 and the cover 11.

Here, each injection hole 10 of the injection nozzle 10
A, 10B, respectively with respect to the axis O-O of the fuel injection valve 8 predetermined directivity angle theta _A, inclined by theta _B, is directed intake ports 4A, a 4B. That is, the directivity angle θ _B of the second injection hole 10B is set so as to aim substantially at the center of the second intake port 4B, and the directivity angle θ _A of the first injection hole 10A is set to be larger than the angle θ _B. Small, which makes the first
Is directed closer to the center of the cylinder 1 than the center of the intake port 4A.

The air chamber 12 of the fuel injection valve 8 and the intake passage 4 upstream of the intake control valve 6 are connected by an auxiliary air passage 17, and an opening / closing valve 18 is provided in the middle of the auxiliary air passage 17.
Is provided. The auxiliary air passage 17, the on-off valve 18, the air chamber 12, and the air passage 13 constitute an assist air supply mechanism that is a means for delaying the arrival time. Here, the upstream end of the auxiliary air passage 17 is on the rear surface side of the swirl control valve 6 other than the cutout portion 6A, that is,
The swirl control valve 6 is opened on the rear surface side of the shielding portion, and air is taken in through the opening.

The control unit 2 which will be described later
When the on-off valve 18 is opened by the control signal from the control valve 2, the part of the intake air upstream of the intake control valve 6 is partially discharged from the auxiliary air passage 1
7 into the air chamber 12 and the second injection hole 10B from the air chamber 12 through the air passage 13.
Will be supplied in the middle of.

Reference numeral 19 is a crank angle sensor for detecting the crank angle of the engine, 20 is a throttle sensor for detecting the opening of the throttle valve, and 21 is an air flow meter provided upstream of the throttle valve for measuring the intake air amount. The crank angle sensor 19, the throttle sensor 20, and the air flow meter 21 are oxygen sensors (not shown),
It is connected to the control unit 22 together with a water temperature sensor, an ignition switch and the like.

The control unit 22 for electrically centrally controlling the engine is constructed as a microcomputer system. And the control unit 22
Detects the operating state of the engine by the detection signals from the crank angle sensor 19, the throttle sensor 20, and the air flow meter 21, and, as will be described later with reference to FIG. 3, under a predetermined operating condition capable of EGR control such as in a low load range. When it is determined that the switch has entered, the swirl control valve 6 is closed, and as described later,
The fuel injection timing of the fuel injection valve 8 and the like are controlled.

Reference numeral 23 is an exhaust passage, and the upstream side of the exhaust passage 23 is bifurcated into a first exhaust port 23.
A, the second exhaust port 23B, and a catalytic converter (not shown) is provided on the downstream side of the exhaust passage 23. The exhaust ports 23A and 23B are opened and closed by the first exhaust valve 24A and the second exhaust valve 24B, respectively. The number of exhaust ports does not have to be two, and may be single.

Next, the operation of the structure of this embodiment will be described in detail with reference to FIGS.

First, the control of the swirl control valve 6, the on-off valve 18, etc. by the control unit 22 will be described with reference to FIG.

That is, FIG. 3 is a control operation switching map for changing the control state between the normal control and the EGR control, which is a predetermined rotation speed Na and a predetermined torque Ta.
In the following EGR control region A, the swirl control valve 6 is closed and the opening / closing valve 18 is opened to supply the assist air to the second injection hole 10B of the injection nozzle 10.

Further, the other part including the range from the predetermined torque Ta to the torque Tb is the normal control area B,
In this region B, the swirl control valve 6 is opened to stop the swirl, and the on-off valve 18 is closed to stop the supply of assist air. Note that WOT in FIG. 3 indicates that the throttle valve is fully open.

The above is summarized in Table 1 below.

[0046]

[Table 1]

Next, the relationship between the opening / closing timing of each intake valve 5A, 5B and the fuel injection timing of the fuel injection valve 8 will be described with reference to FIG.

The opening timing of the first intake valve 5A is advanced from the opening timing of the second intake valve 5B by a predetermined phase difference Δθ ₁ , and the closing timing of the first intake valve 5A is also the second. The intake valve 5B is closed by a predetermined phase difference Δθ ₂ .

The fuel injection timing of the fuel injection valve 8 is set before the intake stroke in the normal control area B, but from the injection timing map (not shown) previously stored in the control unit 22 in the EGR control area A. It is read according to the engine speed.

This injection timing map is set so that the fuel injected from the second injection hole 10B reaches the second intake port 4B just before the second intake valve 5B is closed, as shown in FIG. It is what is done. That is, the second injection hole 1
The fuel injected from 0B reaches the second intake port 4B after the delay time t elapses because the speed of the fuel decreases due to the reason described later, but all of this injected fuel is contained in the second intake valve 5B. Set to reach before closing.

Next, the control operation during the EGR control will be described along each time in FIG.

First, at time T ₁ immediately after the start of the suction stroke,
Since the first intake valve 5A opens earlier than the second intake valve 5B and the pressure in the intake passage 4 is low, as shown in FIG. 5, the combustion chamber 2 and the exhaust passage 23 The internal combustion gas (EGR gas) blows back in the F direction to generate internal EGR.

Next, at time T ₂ , fuel is injected from the fuel injection valve 8. Here, since the assist air is supplied only to the second injection holes 10B and the fuel injected from the injection holes 10B is atomized, the second injection is performed more than the fuel injected from the first injection holes 10A. The velocity of the fuel injected from the hole 10B becomes slower.

In other words, the larger the particle size of the fuel particles, the smaller the influence of the air resistance and the more difficult the deceleration is.
The smaller the particle size of the fuel particles, the stronger the influence of the air resistance and the more easily the vehicle is decelerated. In addition to this, EGR control area A
However, since the swirl control valve 6 is closed, the amount of air flowing to the second intake port 4B is small.

Therefore, there is a speed difference between the fuels injected from the respective injection holes 10A and 10B and having different particle sizes, and the relative high speed fuel injected from the first injection hole 10A is shown by the diagonal lines in FIG. As indicated by the pattern arrow, it flows into the combustion chamber 2 together with the combustion gas (dotted arrow) that has flowed back into the first intake port 4A.

Here, the first injection hole 10A is formed with a predetermined directivity angle θ _A so that it is directed toward the center of the cylinder 2 rather than the center of the first intake port 4A. The fuel injected from the injection hole 10A of the above flows into the combustion chamber 2 from the inside of the combustion gas and forms a swirl flow S together with the combustion gas.

On the other hand, the fuel having a relatively low velocity injected from the second injection hole 10B loses its initial velocity immediately after the injection, as shown in the mesh pattern portion in FIG. 6, and enters the second intake port 4B. It is carried on a small stream of air flowing toward it.

Next, at time T ₃ in FIG. 4, the low-velocity fuel injected from the second injection hole 10B reaches the inside of the second intake port 4B by the air flow, and the second intake valve 5B is reached. Flows from the surroundings into the combustion chamber 2 as an air-fuel mixture.

When the low-velocity air-fuel mixture reaches the second intake port 4B, the second intake valve 5 is already in operation.
Since B is about to be closed, that is, at the end of the intake stroke, the moving speed of the piston is low, and the swirl control valve 6 limits the amount of air directed to the second intake port 4B. Therefore, the air-fuel ratio of this low-velocity mixture becomes richer than, for example, the stoichiometric air-fuel ratio.

A swirl flow S is formed in the combustion chamber 2 by the air-fuel mixture and the combustion gas from the first intake port 4A, and the vortex center of the swirl flow S has a relatively lower pressure than the surroundings. As shown in FIG. 7, the rich air-fuel mixture that has flowed into the combustion chamber 2 from the second intake port 4B that substantially faces the center of the vortex is attracted to the center of the vortex and is guided to the substantially central portion corresponding to the spark plug 3. To be done.

As a result, in the combustion chamber 2, the EGR gas layer (dot pattern) formed on the outermost peripheral side by the combustion gas.
And a first air-fuel mixture layer (hatched pattern) formed in the middle by the air-fuel mixture from the first intake port 4A and a rich air-fuel mixture from the second intake port 4B in the substantially central portion. Three-layer stratification with the second mixture layer (mesh pattern) is realized. The air-fuel ratio of the first air-fuel mixture layer is approximately the stoichiometric air-fuel ratio.

Explaining the case in the normal control region B, the swirl control valve 6 is opened to stop the swirl, and the fuel injection timing is set before the intake stroke which is the normal fuel injection timing. .

The opening / closing timing of each intake valve 5A, 5B is the same as that in the EGR control region A, and the first intake valve 5A has the same opening and closing timings as the second intake valve 5B. Faster than. However, in this normal control region B, the valve opening of the throttle valve is also large, so the negative pressure in the intake passage 4 becomes small, and internal EGR is unlikely to occur. Also,
Since the supply of assist air is also stopped, each injection hole 10
There is no difference in the fuel speed injected from A and 10B,
There is no risk of the output decreasing.

As described above, according to this embodiment, the predetermined E
In the GR control region A, the swirl control valve 6 is closed to limit the amount of air to the second intake port 4B, and the low-velocity fuel injected while being atomized from the second injection hole 10A The fuel injection timing is set so as to reach the second intake port 4B immediately before the second intake valve 5B is closed, and the opening timing of the first intake valve 5A is set to a phase difference Δθ more than the opening timing of the second intake valve 5B. _{Since the} configuration is advanced by 1, the stratification can be achieved by one fuel injection from the fuel injection valve 8.

Further, since the rich air-fuel mixture is introduced at the end of the intake stroke, which is relatively close to the ignition timing, and the swirl flow S of combustion gas or the like is used to guide the air-fuel mixture to the substantially central portion, this rich air-fuel mixture diffuses. It is possible to maintain the stratification until just before the ignition while preventing the above, and to improve the combustion stability.

Further, the first injection hole 10A is formed with a narrow directivity angle θ _A so that it is aimed closer to the center of the cylinder 1 than the center of the first intake port 4A. Fuel (fuel mixture) injected from hole 10A
Can be made to flow into the combustion chamber 2 from the inside of the combustion gas. Therefore, as shown in FIG. 7, the second air-fuel mixture layer having a high air-fuel ratio, the first air-fuel mixture layer having an air-fuel ratio of about the stoichiometric air-fuel ratio, and the EGR having a small amount of combustible components are provided from the vicinity of the spark plug 3 to the outside. The three layers can be sequentially formed according to the magnitude of the air-fuel ratio, and the combustion stability can be improved.

Also, paying attention to the fact that the speed varies depending on the size of the fuel particles, the assist air is supplied only to the second injection holes 10B to atomize the fuel, so that the structure is relatively simple. Despite this, the fuel arrival timing can be reliably delayed, and stratification can be easily realized.

On the other hand, since the upstream end of the auxiliary air passage 17 is opened to the back side other than the notch 6A of the swirl control valve 6, the auxiliary air passage is closed in the EGR control region A where the swirl control valve 6 closes. A differential pressure can be easily generated between the upstream end and the downstream end of 17, and the assist air required for atomization can be secured.

Next, a second embodiment of the present invention will be described with reference to FIGS. In this embodiment, the above-mentioned first
The same components as those of the embodiment are given the same reference numerals and the description thereof will be omitted.

FIG. 8 is an explanatory view showing the overall construction of this embodiment, in which the upstream side of the swirl control valve 6 and the exhaust passage 2 are shown.
3, an EGR passage 31 is provided, and an EGR control valve 32 is provided in the middle of the EGR passage 31.

FIG. 9 is a control operation switching map according to the present embodiment. In this control operation switching map, the portion below the predetermined rotation speed N _a1 and the predetermined torque T _a1 is the first EGR control region. A ₁ , which is the predetermined rotation speed N _a2 and the predetermined torque T _a2 excluding the _first EGR control region A _1.
The following portion is the second EGR control area A ₂ , and the other portion including the range from the predetermined torque T _a2 to the torque T _b is the normal control area B.

Then, in each EGR control region A ₁ , A ₂ ,
The swirl control valve 6 is closed and the opening / closing valve 18 is opened to supply the assist air. Further, in the first EGR control region A ₁ , the EGR control valve 32 is opened to externally perform EGR control.
The gas is introduced into the intake passage 4, and in addition to the internal EGR, the external E
Also activate GR.

On the other hand, in the normal control region B, the swirl control valve 6 is opened to stop the swirl generation and the on-off valve 1
The valve 8 is closed to stop the supply of the assist air, and the EGR control valve 32 is closed to stop the external EGR.

The above results are summarized in Table 2 below.

[0075]

[Table 2]

Also in this embodiment having such a configuration, it is possible to obtain substantially the same effect as that of the first embodiment described above.

Next, a third embodiment of the present invention will be described with reference to FIGS.

First, FIG. 10 is an explanatory view showing the overall construction of an intake device according to a third embodiment of the present invention. The fuel injection valve 8 according to this embodiment is provided with respective intake ports 4A, 4B. Directing nozzles 41A and 41B are provided.

That is, as shown in FIG. 11, the first injection hole 10A and the second injection hole 1 are provided at the tip of the injection nozzle 10.
0B corresponding to the first nozzle 41A and the second nozzle 41
B is provided. In order to extend the first injection hole 10A toward the cylinder 1, the first nozzle 41A has its tip extended into the first intake port 4A at a predetermined directivity angle θ _A. Further, the second nozzle 41B has a predetermined directivity angle θ _B so as to slightly extend the second injection hole 10B.
And extends to the upstream side from the branch portion of each intake port 4A, 4B.

Further, the injection nozzle 10 has a first air passage 13A communicating with the first injection hole 10A and a second air passage 13B communicating with the second injection hole 10B in the fuel injection direction. Each of these air passages 1 is formed obliquely along
The air in the air chamber 12 is supplied to each of the injection holes 10A and 10B as assist air through the holes 3A and 13B.

In this embodiment having such a configuration, the injection holes 10A, 10B are provided via the air passages 13A, 13B.
As a result of each being supplied with assist air, each injection hole 1
Both the fuel injected from 0A and 10B are atomized.

However, since the first injection hole 10A is extended to the first intake port 4A by the elongated first nozzle 41A, the actual injection point is the first injection port 4A.
It is close to A and the distance affected by the speed reduction due to atomization of the fuel is short, so that there is no delay in the fuel arrival timing to the first intake port 4A. On the other hand, the second injection hole 10B is connected to the intake ports 4A, 4B by the short second nozzle 41B.
Since the injection point is relatively distant only by being extended to the upstream part of the branch portion, the atomized fuel ejected from the second nozzle 41B immediately loses its initial velocity and then becomes an air flow with a low velocity. It will be taken and carried to the second intake port 4B.

Therefore, the fuel arrives at the second intake port 4B later than the fuel arrives at the first intake port 4A.

As a result, this embodiment, which is constructed in this way, can also obtain substantially the same effects as those of the first embodiment described above. In particular, in this embodiment, each injection hole 10A, 1
Since the fuel injected from 0B is atomized together,
The combustion stability can be further improved.

In each of the above embodiments, the fuel injection valve 8 injects approximately the same amount of fuel toward each intake port 4A, 4B, but the present invention is not limited to this, and, for example, an injection hole. The fuel may be appropriately distributed by changing the hole diameter of the fuel.

Further, in the third embodiment, the case where the short nozzle 41B is provided also in the second injection hole 10B is illustrated, but substantially the same effect can be obtained even if the second nozzle 41B is omitted. .

[0087]

As described in detail above, according to the intake system for an internal combustion engine according to the present invention, a layer composed of the combustion gas and the air-fuel mixture from the first intake port is formed around the cylinder by a single fuel injection. And a rich air-fuel ratio layer formed of the air-fuel mixture from the second intake port is formed substantially in the center of the cylinder to realize stratification and maintain it just before the ignition timing. .

Further, according to the second aspect, since only the fuel injected from the second injection hole is atomized by the assist air, the speed of the fuel injected from the second injection hole can be reduced. The fuel arrival timing at which the atomized fuel reaches the second intake port can be delayed from the fuel arrival timing at the first intake port. As a result, the stratification can be realized similarly to the effect of the first aspect.

Further, in claim 3, the fuel injected from the first injection hole and the second injection hole is atomized by the assist air, respectively, and the first injection hole is directed toward the first intake port. Because of the configuration of directing through the extending nozzle, there is a difference in the distance from the actual injection point to each port, and the fuel arrival timing at the second intake port is more than that at the first intake port. Will also be delayed. As a result, the stratification can be realized similarly to the effect of the first aspect.

Further, according to the present invention, the fuel supplied to the first intake port is injected toward the center of the cylinder of the first intake port, so that the fuel on the first intake port side is burned. The EGR gas layer, which can be placed on the inner peripheral side of the swirl formed of gas or the like and has a high combustion gas abundance ratio, and the fuel from the first intake port formed on the inner peripheral side of the EGR gas layer The first air-fuel mixture layer, which is the main constituent, and the high-concentration first-fuel mixture, which is mainly composed of fuel from the second intake port formed on the inner peripheral side of the first air-fuel mixture layer, that is, in the approximate center of the cylinder. It is possible to form a total of three types of layers including two mixed gas layers.

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing an intake device for an internal combustion engine according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a main part of a fuel injection valve.

FIG. 3 is a control operation switching map for performing operation switching between EGR control and normal control.

FIG. 4 is an opening / closing characteristic diagram showing the opening / closing timing of an intake valve.

FIG. 5 is an explanatory diagram showing a state in which a first intake valve is opened and internal EGR is generated.

FIG. 6 is an explanatory view showing a state where fuel is injected.

FIG. 7 is an explanatory view showing a state in which a mixture having a high air-fuel ratio is guided to a substantially central portion of a cylinder to realize stratification.

FIG. 8 is a structural explanatory view showing an intake device for an internal combustion engine according to a second embodiment of the present invention.

FIG. 9 is an explanatory diagram of a control operation switching map according to the second embodiment.

FIG. 10 is a structural explanatory view showing an intake device for an internal combustion engine according to a third embodiment of the present invention.

FIG. 11 is a sectional view showing a main part of a fuel injection valve according to a third embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Cylinder 2 ... Combustion chamber 3 ... Spark plug 4 ... Intake passage 4A ... 1st intake port 4B ... 2nd intake port 5A ... 1st intake valve 5B ... 2nd intake valve 6 ... Swirl control valve (intake Control valve) 8 ... Fuel injection valve 10 ... Injection nozzle 10A ... First injection hole 10B ... Second injection hole 41A ... First nozzle 41B ... Second nozzle

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display area F02D 21/08 301 AC C 43/00 301 J NZ F02M 25/07 550 R 69/00 310 E

Claims (4)

[Claims] 1. An intake passage which is provided for each cylinder of an internal combustion engine and whose front end is branched into a first intake port and a second intake port, and the first intake port in synchronization with the rotation of the engine. , A first intake valve and a second intake valve that open and close the second intake port, respectively, and are provided in the middle of the intake passage,
In an intake device for an internal combustion engine, which comprises a fuel injection valve for injecting fuel toward each intake port, and an ignition plug is disposed near the center of the cylinder, in the middle of the intake passage, under a predetermined operating condition. An intake control valve that limits the amount of air flowing into the second intake port by closing the valve is provided, and the opening timing of the first intake valve is set earlier than the opening timing of the second intake valve. When the predetermined operating condition is satisfied, the arrival timing delay means for delaying the fuel arrival timing at the second intake port relative to the fuel arrival timing at the first intake port is provided, and the fuel injection timing of the fuel injection valve is set. An intake system for an internal combustion engine, wherein the fuel arrival timing at the second intake port is set to be close to the closing of the second intake valve. 2. An intake passage which is provided for each cylinder of an internal combustion engine and whose front end is branched into a first intake port and a second intake port, and the first intake port in synchronization with rotation of the engine. , A first intake valve for opening and closing a second intake port, a second intake valve, respectively, and an ignition device for an internal combustion engine in which an ignition plug is arranged near the center of the cylinder, in the middle of the intake passage. Is provided with an intake control valve that restricts the amount of air flowing into the second intake port by closing the valve under predetermined operating conditions, and the opening timing of the first intake valve is set to the opening timing of the second intake valve. The timing is set earlier than the timing, and further, in the middle of the intake passage, the first injection port directed to the first intake port and the second injection port directed to the second intake port from the first injection port to the first intake port. , While injecting fuel toward the second intake port, Under a predetermined operating condition, a fuel injection valve for supplying assist air from an air source is provided only to the second injection hole, and under the predetermined operating condition, the fuel injection timing of this fuel injection valve is set to the second intake port. An intake system for an internal combustion engine, wherein the fuel arrival timing is set so as to be close to closing the second intake valve. 3. An intake passage which is provided for each cylinder of an internal combustion engine and whose front end is branched into a first intake port and a second intake port, and the first intake port in synchronization with the rotation of the engine. , A first intake valve for opening and closing a second intake port, a second intake valve, respectively, and an ignition device for an internal combustion engine in which an ignition plug is arranged near the center of the cylinder, in the middle of the intake passage. Is provided with an intake control valve that restricts the amount of air flowing into the second intake port by closing the valve under predetermined operating conditions, and the opening timing of the first intake valve is set to the opening timing of the second intake valve. The timing is set earlier than the time, and further, in the middle of the intake passage, the first intake port is directed toward the first intake port via a nozzle extending toward the first intake port.
Fuel is injected from the second injection port directed toward the second intake port toward the first intake port and the second intake port toward the second intake port, respectively.
A fuel injection valve for supplying assist air from an air source is provided in each of the injection holes and the second injection hole, and the fuel injection timing of the fuel injection valve is set to reach the second intake port under the predetermined operating condition. An intake system for an internal combustion engine, wherein the timing is set so as to be close to closing the second intake valve. 4. The fuel injection valve is configured to inject fuel supplied to the first intake port toward the center of the cylinder of the first intake port.
4. An intake system for an internal combustion engine according to any one of 3 to 3.