JP3357450B2 - Engine control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control system for an engine having at least a two-valve intake structure, which achieves lean burn by stratification by in-cylinder flow of intake air (swirl or the like).

[0002]

2. Description of the Related Art Conventionally, as an intake device of an engine, for example, Japanese Utility Model Laid-Open No. 4-47165 and Japanese Patent Laid-Open No.
There is an apparatus described in JP-A-126.

That is, the former device disclosed in Japanese Utility Model Laid-Open Publication No. 4-47165 has a primary intake port and a secondary intake port for a single cylinder, one intake port being a straight port, and the other intake port being a straight port. The port is configured as a swirl port, and the straight port is provided with an intake control valve.

[0004] The latter device disclosed in JP-A-3-237216 has a straight port and a swirl port for a single cylinder, and a so-called SCV, a swirl control valve, is interposed in the straight port. At the same time, the stoichiometric air-fuel ratio (A / F = 14.7,
This is a device configured to generate swirl by closing the above-described swirl control valve when performing lean burn operation with an air-fuel ratio leaner than λ = 1).

As described above, in an engine having at least a two-valve intake structure, an in-cylinder flow (swirl) is obtained by means for stopping one of the intake ports (the above-described intake control valve and swirl control valve). An engine that achieves lean burn by enabling combustion to improve fuel efficiency is known. However, such a conventional engine has a problem that HC emission and NOx emission are deteriorated. there were.

Hereinafter, the reason why such a problem occurs will be described in detail. First, the deterioration of the HC emission will be described. If a relatively strong in-cylinder air flow is applied for the purpose of making the lean burn limit (lean limit) even leaner, combustion can be improved by the in-cylinder air flow. On the other hand, the cooling loss (so-called cooling loss) increases due to the air flow, and the lean air-fuel mixture causes a decrease in the combustion speed. As shown by the characteristic a in FIG.
There is a problem that C (hydrocarbon, hydrocarbon) increases.

Next, the deterioration of the NOx emission will be described. As shown by the characteristic b in FIG.
The emission amount is A / F = 14.7 from the region where the air-fuel ratio is rich.
Gradually increases toward the stoichiometric air-fuel ratio, the emission amount becomes maximum near A / F = 16, and N
Although the amount of Ox emissions decreases, the NOx purification rate by the three-way catalyst in the catalytic converter provided in the exhaust system can be obtained only in a small region around the stoichiometric air-fuel ratio. However, when the air-fuel ratio is lean, NOx is not purified in the three-way catalyst, so that there is a problem that the NOx emission increases as a result.

In order to solve such a problem, for example, without using an air-fuel ratio (A / F = 16 to 20), a so-called intermediate air-fuel ratio, in which NOx emission is large and NOx purification cannot be expected in a three-way catalyst, Lean air-fuel ratio (for example, A
/ F = 24 to 26) and a stoichiometric air-fuel ratio (A / F = 14.7) that enables exhaust gas purification with a three-way catalyst,
There is a problem that a torque shock occurs when the air-fuel ratio is switched. On the other hand, in order to enable the use of the above-mentioned intermediate air-fuel ratio (A / F = 16 to 20), the combustion speed is reduced by performing external EGR. Thus, although there is an advantage that NOx can be reduced, a low-temperature inert gas (burned gas) is brought into the cylinder as shown by a dotted line characteristic C in FIG. In addition, although a NOx reduction catalyst is being developed for the purpose of purifying NOx even at a lean air-fuel ratio, a sufficient NOx purification rate has not yet been obtained.

[0009]

SUMMARY OF THE INVENTION According to the first aspect of the present invention, there is provided an internal combustion engine for connecting a primary intake port and a secondary intake port in a lean burn engine.
By providing a communication path for GR (residual gas control) and controlling the opening and closing timing of the intake valve of the secondary intake port singularly, the primary intake port is opened to the secondary intake port until late. Thus, the in-cylinder flow is strengthened, stratified combustion is achieved by this in-cylinder flow, and lean burn is achieved. In addition, a cooling loss occurs due to the in-cylinder flow described above, and the amount of HC emission tends to increase. However, the internal EGR, which has a higher temperature than the external EGR, suppresses deterioration of combustion and improves the recombustibility of the existing gas, suppresses an increase in the amount of HC emitted by the internal EGR, and reduces NOx emissions in the lean region by the EGR effect. An object of the present invention is to provide an engine control device capable of reducing the amount.

According to a second aspect of the present invention, in addition to the object of the first aspect, the primary intake port is formed as a swirl generation port, so that a good swirl (lateral in-cylinder vortex) is obtained. It is an object of the present invention to provide a control device for an engine capable of improving the lean burn limit (lean limit) and improving fuel economy.

According to a third aspect of the present invention, in addition to the object of the first or second aspect of the present invention, the swirl is strengthened by actively performing intake from the primary intake port, and the lean limit is reduced. It is an object of the present invention to provide a control device for an engine that can be improved.

According to a fourth aspect of the present invention, in addition to the object of the first, second, or third aspect of the present invention, a valve timing for varying an overlap amount between an intake valve and an exhaust valve of a secondary intake port is provided. By providing a variable device,
An object of the present invention is to provide an engine control device capable of freely controlling the above-mentioned overlap amount by using this variable valve timing device, and thereby adjusting the internal EGR amount arbitrarily and appropriately according to the operating state of the engine.

The invention according to claim 5 of the present invention, together with the object of the invention according to claim 4, provides an intermediate air-fuel ratio A
It is an object of the present invention to provide an engine control device capable of increasing the internal EGR amount in the / F = 16 to 20 region and suppressing an increase in HC emission while reducing NOx.

According to a sixth aspect of the present invention, in addition to the object of the first or second aspect, the internal EG
By setting the connection opening with the primary intake port in the R communication passage at a specific position, the internal EGR gas can be guided to the outer peripheral portion in the cylinder, and the internal EGR gas is not brought around the ignition plug, and And an internal EGR gas as much as possible, and to provide an engine control device which does not impair stratification and combustibility.

According to a seventh aspect of the present invention, in addition to the object of the first aspect, the position of the fuel injection valve (injector) is specified so that the injection hole portion of the fuel injection valve is provided. To prevent the internal EGR gas from reaching the nozzle hole, thereby preventing clogging of the injection holes, and an engine control device capable of avoiding mixing of fuel and internal EGR gas.

[0016]

According to a first aspect of the present invention, there is provided a primary intake port and a secondary intake port provided for a single cylinder, and a connection for an internal EGR which communicates the intake ports. A control apparatus for an engine, comprising: a passage; and a lean burn means that operates at an air-fuel ratio leaner than a stoichiometric air-fuel ratio at least on a load side lower than the full load range, wherein the air-fuel ratio is lower than the lean full load range. On the load side, at least the opening timing of the intake valve of the secondary intake port overlaps the closing timing of the exhaust valve, and the intake valve of the secondary intake port opens and closes early with respect to the primary intake port. It is an engine control device provided with control means for controlling.

According to a second aspect of the present invention, in addition to the configuration of the first aspect of the present invention, there is provided an engine control device in which the primary intake port is configured as a swirl generation port. .

According to a third aspect of the present invention, in addition to the configuration of the first or second aspect of the present invention, at least a full load region is provided at an upstream side of the communication path connecting portion for the internal EGR in the secondary intake port. The present invention is characterized in that it is a control device for an engine that is provided with a swirl control valve that operates in the valve closing direction on a lower load side and controls the in-cylinder flow.

According to a fourth aspect of the present invention, in addition to the configuration of the first, second or third aspect of the present invention, the amount of overlap between the intake valve and the exhaust valve of the secondary intake port is varied. And an engine control device provided with a variable valve timing device for adjusting the internal EGR amount.

According to a fifth aspect of the present invention, in addition to the configuration of the fourth aspect of the invention, there is provided an engine in which the amount of overlap is larger in the A / F = 16-20 region than in other regions. It is a control device.

According to a sixth aspect of the present invention, in addition to the configuration of the first or second aspect of the present invention, the connection opening for the primary intake port in the communication passage of the internal EGR is provided near the cylinder wall. It is a control device of the provided engine.

According to a seventh aspect of the present invention, in addition to the configuration of the first aspect of the present invention, a fuel injection valve is provided upstream of a connection opening of a communication path for internal EGR of the primary intake port. It is a control device of the engine arranged.

[0023]

According to the first aspect of the present invention, as shown in FIG. 10, a primary intake port P2 and a secondary intake port P3 are provided for a single cylinder P1. A communication passage P4 for internal EGR which is provided and communicates the two intake ports P2 and P3.
Is provided.

The above-described lean burn means P5 has at least a stoichiometric air-fuel ratio (A) on the lower load side than the full load range.
/F=14.7), the engine is operated at a leaner air-fuel ratio, and the above-mentioned control means P6 determines at least the opening timing of the intake valve P7 of the secondary intake port P3 on the low-load side where the air-fuel ratio is leaner. Is overlapped with the closing timing of the exhaust valve P8, and the intake valve P7 of the secondary intake port P3 is controlled to open and close early with respect to the intake valve of the primary intake port P2.

At this time, the secondary intake port has an intake amount,
In-cylinder flow strength and internal EGR control are performed, and the valve closing timing does not need to be synchronized with or slower than the primary intake port. Therefore, the above-described primary intake port P2 can be opened late to the secondary intake port P3.
2, the in-cylinder flow is enhanced and the in-cylinder flow is strengthened, and stratified combustion can be achieved by the in-cylinder flow to achieve lean burn.

Also, due to the overlap between the opening timing of the intake valve P7 of the secondary intake port P3 and the closing timing of the exhaust valve P8, the internal EGR gas brought into the intake port in the exhaust stroke is changed in the next intake stroke. Since the internal EGR with good recombustibility is performed by being supplied into the cylinder, the cooling loss occurs due to the above-mentioned in-cylinder flow, and the external EGR tends to increase the HC discharge amount. There is an effect that it is possible to suppress by the EGR and to reduce the NOx emission amount by the EGR effect.

That is, the internal EGR has a high temperature of the recirculated inert gas (existing gas), has good recombustibility, and also has good vaporization and atomization of fuel. An increase in the amount can be suppressed.

According to the invention described in claim 2 of the present invention,
In addition to the effect of the first aspect of the present invention, since the primary intake port is configured as a swirl generation port,
A good swirl (lateral in-cylinder vortex) can be generated, and as a result, there is an effect that the lean burn limit (lean limit) can be improved and the fuel efficiency can be improved.

According to the third aspect of the present invention, in addition to the effect of the first or second aspect of the present invention, at least the full load is provided at the secondary intake port on the upstream side of the internal EGR communication passage connection portion. The swirl control valve that operates in the valve closing direction on the low load side of the region and controls the strength of the in-cylinder flow is provided, so that the swirl is strengthened by actively taking in air from the primary intake port described above. This has the effect that the lean limit can be improved.

According to the invention described in claim 4 of the present invention,
In addition to the effects of the first, second, and third aspects of the present invention, a variable valve timing apparatus for adjusting the internal EGR amount by changing the amount of overlap between the intake valve and the exhaust valve of the secondary intake port, so-called VVT. Was established,
The valve timing of the secondary intake port is adjusted by adjusting the valve timing, especially the valve opening timing, of the secondary intake port to vary the overlap amount. When it is small, the internal EGR amount can be reduced. As a result, there is an effect that the internal EGR amount can be arbitrarily and appropriately adjusted according to the operating state of the engine.

According to the invention described in claim 5 of the present invention,
In addition to the effect of the fourth aspect of the present invention, since the overlap amount is larger in the A / F = 16 to 20 region than in other regions, the overlap amount is larger in the A / F = 16 to 20 region which is the intermediate air-fuel ratio. The internal EGR amount can be increased, and as a result, there is an effect that NOx can be reduced while suppressing an increase in the amount of HC emission.

According to the sixth aspect of the present invention,
In addition to the effect of the first or second aspect of the present invention, since the connection opening for the internal EGR communication passage with the primary intake port is provided near the cylinder wall, the communication passage is formed from the secondary intake port. And the internal EGR brought into the cylinder via the primary intake port
The gas can be guided to the outer peripheral portion in the cylinder (the outer peripheral region of the swirl). Therefore, the above-mentioned internal EGR gas is not brought around the ignition plug provided substantially corresponding to the center of the cylinder. Mixing with EGR gas can be avoided as much as possible, and there is an effect that stratification and flammability are not impaired.

According to the invention described in claim 7 of the present invention,
In addition to the effect of the first aspect of the present invention, since the fuel injection valve (injector) is disposed upstream of the connection opening of the communication path for the internal EGR of the primary intake port, the internal recirculated air is recirculated. This prevents the EGR gas from reaching the injection hole of the fuel injection valve, thereby preventing clogging of the injection hole, and has the effect of avoiding mixing of fuel and internal EGR gas.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings. The drawings show a control device of the engine, and FIGS.
Inline four-cylinder engine (however, in FIG.
A single cylinder is shown in FIG. 2), and a total of four cylinders 1... Are formed in a cylinder block. An intake valve 7 and an exhaust valve 8 which form intake ports 3 and 4 and two exhaust ports 5 and 6 and open and close these intake and exhaust ports appropriately.
Are provided to form an intake two-valve exhaust two-valve structure.

Here, one of the two intake ports 3 and 4 is a primary intake port (hereinafter simply abbreviated as P intake port). And is configured as a swirl generation port to form a good swirl (in-cylinder lateral vortex), and the other intake port 4 is a secondary intake port (hereinafter simply abbreviated as S intake port). The S intake port 4 is opened in the direction of the center of the cylinder so as to have directionality at the center of the cylinder, and is configured to form a tumble flow (in-cylinder longitudinal vortex) that minimizes interference with the swirl flow. I have.

A primary intake passage 10 (hereinafter simply abbreviated as P intake passage) formed in an intake manifold 9 is connected to the above-mentioned P intake port 3 so as to communicate therewith.
A secondary intake passage 11 (hereinafter simply referred to as an S intake passage) formed in an intake manifold 9 is continuously connected to the intake port 4, and a surge tank (see FIG. 1) is provided upstream of the P intake passage 10 and the S intake passage. (Not shown).

On the other hand, the above-mentioned two exhaust ports 5 and 6 are gathered at the gathering portion 12 to form one exhaust passage 1 per single cylinder.
It communicates with 3.

A communication passage 14 for the internal EGR is provided for communicating the above-mentioned intake ports 4 and 3, and the internal EGR is transferred from the S intake port 4 through the P intake port 3 into the cylinder 1 through the communication passage 14. It is configured to do so.

That is, the above-described communication path 14 for the internal EGR
One of the connection openings 14a is opened at a position near the end of the cylinder head 2 of the S intake port 4, and the other connection opening 14b of the communication passage 14 is opened at the side of the P intake port 3 near the cylinder wall. , Each element 4, 14a, 14, 14
The internal EGR is performed via b and 3.

An ignition plug 15 is arranged in the above-mentioned cylinder head 2, and a spark gap of the ignition plug 15 is provided substantially at the center of the cylinder 1, while a communication path 14 for the internal EGR of the P intake port 3 is connected. The injector 16 is disposed upstream of the opening 14b. In this embodiment, an injector 16 is provided in the P intake passage 10 of the intake manifold 9.

A swirl control valve 17 as an on-off valve is located upstream of the connection opening 14a of the internal EGR communication passage 14 in the S intake port 4 described above.
(Hereinafter simply abbreviated as SCV), and this SCV17
With this, the in-cylinder flow is controlled to be strong or weak. As shown in FIG. 9, an EGR control valve 1 is provided downstream or upstream of the SCV 17.
Alternatively, the EGR control valves 18 and 19 may be provided alternatively or simultaneously to control the recirculation amount and the recirculation timing of the internal EGR by adjusting the opening degrees of the EGR control valves 18 and 19 described above.

When the above-mentioned EGR control valve 18 is provided downstream of the SCV 17, the SCV 17 can be fully closed or slightly opened depending on the required swirl ratio for combustion, the required air amount, and the like, particularly in an operating condition such as a lean region or idling. In the region where it is desired to minimize the EGR amount due to combustion stability,
By closing the EGR control valve 18 downstream of the CV 17, the volume of the closed space is reduced, and the blowback amount of the existing gas (internal EGR gas) is suppressed, so that good combustion stability can be achieved.

On the other hand, the EGR control valve 19 is set to SCV1
7, the SCV 17 is fully opened in a region where the required amount of EGR is large and the opening degree of the SCV 17 is large in a middle rotation and middle and high load region, and the like, and the EGR control valve 1
9 to strongly control the in-cylinder flow,
The ventilation resistance to the GR is reduced, and the response delay when the internal EGR gas flows into the cylinder is reduced, so that the EGR in each cycle can be stabilized.

The above-described intake valve of the P intake port 3 and the intake valve 7 of the S intake port 4 are independently provided with a variable valve timing device 20 (hereinafter simply referred to as VVT).
Here, a specific configuration of the VVT 20 that changes the valve timing of the intake valve 7 of the S intake port 4, the valve opening timing, the valve closing timing, and the valve lift amount will be described. The exhaust valve 8 is driven by a normal valve train (not shown).

As shown in FIG. 2, a VVT oil pump 23 whose piston 22 is driven by a cam 21 having a cam nose is provided. The inlet of the VVT oil pump 23 is connected to the engine side through a check valve 24. The outlet of the VVT oil pump 23 is connected to an inlet of an actuator 27 through an outlet line 26. A plunger 28 of the actuator 27 is connected to an upper end of a valve stem of the intake valve 7 by an oil pump 25. Is pressed against. A drain line 29 is connected to the outlet of the actuator 27, and a solenoid valve 30,
The oil pressure to be distributed to the oil chamber of the actuator 27, the distribution timing, and the drain amount are interposed between the solenoid valves 30,
31 controls the intake valve 7 of the S intake port 4.
And the amount of overlap between the exhaust valve 8 and the internal EGR
It is configured to adjust the amount. The VVT (not shown) for varying the valve timing and the valve lift in the P intake port 3 intake valve has substantially the same configuration. FIG. 2
In the figure, 32 is an oil suction line, and 33 is an oil pan corresponding to a tank.

FIG. 3 shows a control circuit of the engine control device. The CPU 40 controls the engine speed Ne from the distributor 34, the intake air amount Q from the air flow sensor 35 (or air flow meter), and the actual speed from the linear O ₂ sensor 36. Based on various necessary signal inputs such as air-fuel ratio A / F, CE
= Q / Ne, and the load CE is calculated.
The injector 16, the VVT 20, the SCV 17, and the EGR control valves 18 and 19 are drive-controlled, and the RAM 38 stores a first map M1 shown in FIG. 4, a second map M2 shown in FIG.
Necessary maps and data such as a third map M3 shown in FIG.

In the first map M1 (see FIG. 4), the horizontal axis indicates the engine speed Ne, the vertical axis indicates the load, and the target air-fuel ratio is A / F = 14.7 (λ = 1), A
/ F = 18, A / F = 20, A / F = 24, A / F = 2
6, in which the amount of overlap between the intake valve and the exhaust valve of the secondary intake port is adjusted by VVT in the vicinity of A / F = 16 on the lower load side than λ = 1 as the full load area. Is used to perform internal EGR. In the region of A / F = 16, the internal EG
The R amount is small (the overlap amount is also small), and the internal EGR amount is large (the overlap amount is large) in the region of A / F = 18.
In the region of / F = 20, the internal EGR amount is reduced together with the target air-fuel ratio so that the internal EGR amount becomes small (the overlap amount is also small).
This is a map in which the GR amount is also set. In order to control the actual air-fuel ratio to the target air-fuel ratio, the fuel injection amount from the injector 16 may be controlled based on the difference between the two air-fuel ratios.

The above-mentioned second map M2 (see FIG. 5) is an SCV control map in which the horizontal axis indicates the engine speed Ne and the vertical axis indicates the load, and the open / close area and the linear control area of the SCV 17 are partitioned. In the low-rotation low-load region shown by hatching in FIG. 5, the SCV 17 is fully closed and λ
In the full load region corresponding to = 1, the SCV 17 is fully opened, and the opening of the SCV 17 is linearly controlled between both regions.

Further, the above-mentioned third map M3 (see FIG. 6)
Is an intake air amount control map in which the horizontal axis indicates the engine speed Ne and the vertical axis indicates the load, and the load is controlled by the intake air amount throttle valve, and the intake valve control region by the VVT 20 when the throttle valve is fully opened. In a region hatched in FIG. 6 (idle region, a region below the trade-off point t shown in FIG. 7), the valve timing and the valve lift amount by the VVT 20 are fixedly set to a state of high load and high rotation. Then, the intake air amount is controlled by the throttle valve. That is, in the idle range, the oil temperature, oil viscosity, oil pressure, etc. are unstable, and the intake air amount and internal EGR
In order to avoid this, the intake valve 7 of the S intake port 4 is connected to the P intake port 3 in the idle region as described later.
If the intake valve is closed early, the closing timing is too early and the in-cylinder temperature decreases, resulting in deterioration of combustion. Therefore, in order to avoid this, the VVT 20 is hydraulically driven. Therefore, a response delay due to hydraulic pressure occurs, and
Since the error at the time of the small lift by the VT 20 becomes large, the intake air amount is controlled by the throttle valve in the above-mentioned idle region for the purpose of preventing the fluctuation of the error.
In addition, in the intake valve control region by the VVT 20, the throttle opening TVO is set to the fully open WOT to reduce the pumping loss, while the VVT 20 is fully loaded even in a cold state (a cold state is detected using a water temperature sensor or the like). The state is fixedly set, and the intake air amount is controlled by the throttle valve.

On the other hand, the CPU 40 reads the information stored in the RAM 38 and operates the engine at a low load side with an air-fuel ratio at least leaner than the stoichiometric air-fuel ratio (A / F = 14.7, λ = 1). On the lean burn means and at the low load side where the air-fuel ratio is lean, at least the opening timing of the intake valve 7 of the S intake port 4 overlaps the closing timing of the exhaust valve 8 and the intake valve 7 of the S intake port 4 It also serves as control means (specifically, controlling the VVT 20 to vary the amount of overlap) to control the opening and closing of the valve early corresponding to the intake valve of the P intake port 3.

That is, FIG. 7 shows a valve lift curve of each valve. In FIG. 7, d is a valve lift curve of the exhaust valve 8, and e, f, and g are VVT values of the intake valve 7 of the S intake port 4.
20 are valve lift curves h, i, j when the intake valve of the P intake port 3 is controlled by VVT (not shown), and the air-fuel ratio A / F is lean. On the low load side, the opening timing of the intake valve 7 of the S intake port 4 (see valve lift curves e, f, g) is determined by the exhaust valve 8.
And the intake valve 7 of the S intake port 4 (see valve lift curves e, f, and g) overlaps with the valve closing timing (see valve lift curve d). i, j) are controlled so as to open early and close early.

The operation of the embodiment shown in FIG. The CPU 40 shown in FIG. 3 includes an engine speed Ne from the distributor 34, an intake air amount Q from the airflow sensor 35, the linear O ₂ sensor 3
4, 5, and 6 based on various necessary signal inputs such as the actual air-fuel ratio A / F from FIG.
Injector 1 according to the storage contents of M1, M2 and M3
6, VVT20, SCV17, EGR control valves 18, 19
, A small amount of internal EGR gas is recirculated in the region of A / F = 16 shown in FIG. 4, and a large amount of internal EGR gas is recirculated in the region of A / F = 18 shown in FIG. Then, a small amount of the internal EGR gas is recirculated in the region of A / F = 20 shown in FIG.

That is, the above-described CPU 40 makes the opening timing of the intake valve 7 of the S intake port 4 overlap with the opening timing of the exhaust valve 8 (see FIG. 7) on the low load side where the air-fuel ratio is lean (see FIG. 7). The intake valve 7 of the intake port 4 is the P intake port 3
, The P intake port 3 can be opened to the S intake port 4 late, so that the in-cylinder flow from the P intake port 3 is controlled. , And stratified combustion can be achieved by the in-cylinder flow to achieve lean burn.

Further, due to the overlap between the opening timing of the intake valve 7 of the S intake port 4 and the closing timing of the exhaust valve 8 (see FIG. 7), internal EGR with good recombustibility is performed. The internal EGR gas is supplied to each element 4, 14a, 1 according to the amount of overlap between the intake valve and the exhaust valve of the secondary intake port.
4, 14b, 3, 1 are recirculated to the outer peripheral area of the swirl.

By performing the internal EGR in this manner, it is possible to suppress the occurrence of a cooling loss due to the in-cylinder flow and the tendency of the HC discharge amount to increase with respect to the external EGR, and to reduce the EGR.
The effect can also reduce NOx emission. That is, the internal EGR has a high temperature of the recirculated inert gas (burned gas), has good recombustibility, and has good fuel vaporization and atomization. The amount of HC emission is represented by the dotted line characteristic c,
As shown by the solid line characteristic k, the amount of HC emission by GR can be reduced, and at the same time, the amount of HC emission can be reduced.
Due to the EGR effect, the NOx emission can be reduced as shown by the characteristic m in FIG. Note that the characteristic n indicated by the dotted line in FIG. 8 is a change in the NOx emission amount when the external EGR is performed.

Since the above-mentioned P intake port 3 is configured as a swirl generation port, good swirl (in-cylinder lateral vortex) is obtained.
As a result, there is an effect that the lean burn limit (lean limit) can be improved and the fuel efficiency can be improved.

Further, the communication path 14 for the internal EGR described above
Since the connection opening 14d with the P intake port 3 is provided near the cylinder wall, the internal EGR gas brought into the cylinder from the S intake port 4 via the communication passage 14 and the P intake port 3 is supplied to the cylinder. Therefore, the above-mentioned internal EGR gas is not brought into the vicinity of the ignition plug 15 provided substantially corresponding to the center of the cylinder 1 and mixing of the fuel and the internal EGR gas can be performed. This has the effect of preventing stratification and flammability.

In addition, the above-described intake valve 7 of the S intake port 4
The VVT 20 for adjusting the internal EGR amount by varying the amount of overlap between the exhaust gas and the exhaust valve 8 (see valve lift curves e, f, and g in FIG. 7) is provided. By adjusting the valve timing of the intake valve 7, especially the valve opening timing, the amount of overlap is varied,
When the overlap amount is large, the internal EGR amount can be increased, and when the overlap amount is small, the internal EGR amount can be reduced. As a result, there is an effect that the internal EGR amount can be arbitrarily and appropriately adjusted according to the engine operating state.

In addition, when the A / F is 16 to 20, the internal EGR is controlled by adjusting the overlap amount by the above-mentioned VVT.
Is performed, the NOx emission can be reduced most effectively by the EGR effect, and the use of a so-called intermediate air-fuel ratio can be achieved.

Further, the internal EGR of the aforementioned P intake port 3
The injector 16 is disposed on the upstream side of the connection opening 14b of the communication passage 14, so that the recirculated internal EGR gas is prevented from reaching the injection hole of the injector 16, and the injection hole is clogged. And mixing of the fuel and the internal EGR gas can be avoided.

In this embodiment, since the above-mentioned P intake port 3 is a swirl generation port and the above-mentioned S intake port 4 is a tumble flow generation port, the in-cylinder flow is strongly swirled according to the engine load. To an appropriate diagonal swirl (in-cylinder flow obtained by combining swirl and tumble), and the mixture formation can be controlled from stratification near the spark plug 15 to uniformity in the cylinder.

In the correspondence between the configuration of the present invention and the above-described embodiment, the engine of the present invention corresponds to the in-line four-cylinder engine of the embodiment, and similarly, the primary intake port corresponds to the P intake port 3. The secondary intake port corresponds to the S intake port 4, and the lean burn means
First map M1 and CPU 40 stored in AM 38
The control means corresponds to the CPU 40, and the communication path connecting portion for the internal EGR in the secondary intake port is:
Although the opening / closing valve corresponds to the connection opening 14a, the opening / closing valve corresponds to the SCV17 or the EGR control valves 18 and 19, the variable valve timing device corresponds to the VVT20, and the fuel injection valve corresponds to the injector 16. However, the present invention is not limited to the configuration of the above-described embodiment.

[Brief description of the drawings]

FIG. 1 is a schematic plan view showing an engine control device of the present invention.

FIG. 2 is a system diagram showing an engine control device of the present invention.

FIG. 3 is a control circuit block diagram.

FIG. 4 is an explanatory diagram of a first map stored in a RAM.

FIG. 5 is an explanatory diagram of a second map stored in a RAM.

FIG. 6 is an explanatory diagram of a third map stored in a RAM.

FIG. 7 is an explanatory diagram showing a valve lift curve of an intake / exhaust valve.

FIG. 8 is a characteristic diagram showing the amounts of NOx and HC emitted with respect to the EGR rate.

FIG. 9 is a schematic plan view showing another embodiment of the on-off valve provided on the secondary intake port side.

FIG. 10 is a diagram corresponding to claims.

FIG. 11 is a characteristic diagram showing respective NOx and HC emissions with respect to an air-fuel ratio.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Cylinder 3 ... P intake port (port for swirl generation) 4 ... S intake port 7 ... Intake valve of S intake port 8 ... Exhaust valve 14 ... Communication passage 14a, 14b ... Connection opening 16 ... Injector 17 ... SCV 18, 19 EGR control valve 20 VVT 40 CPU (control means) M1 first map (lean burn means)

Continuation of the front page (51) Int.Cl. ⁷ Identification code FI F02B 31/02 F02B 31/02 J F02D 13/02 F02D 13/02 H K F02M 25/07 510 F02M 25/07 510B 580 580C 69/00 360 69/00 360C (56) Reference JP-A-62-101829 (JP, A) JP-A-3-160113 (JP, A) JP-A-54-126817 (JP, A) JP-A-5-209531 (JP JP-A-5-86913 (JP, A) JP-A-5-215002 (JP, A) JP-A-1-176752 (JP, U) JP-A-59-119924 (JP, U) JP-A-59-19242 4-40158 (JP, U) Japanese Utility Model 4-47165 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02B 17/00 F02B 31/02 F01L 13/00 F02D 13 / 02 F02M 25/07 F02M 69/00

Claims (7)

(57) [Claims] 1. A primary intake port and a secondary intake port provided for a single cylinder, a communication passage for internal EGR communicating between the two intake ports, and at least a stoichiometric air passage on a lower load side than a full load region. A lean burn means operating at a leaner air-fuel ratio than the fuel ratio, wherein the air-fuel ratio is at least lower than the full load range of the lean side at least on the load side and the opening timing of the intake valve of the secondary intake port is reduced. An engine control device comprising a control means for controlling the intake valve of a secondary intake port to open and close quickly with respect to the intake valve of a primary intake port while overlapping with a closing timing of an exhaust valve. 2. The engine control device according to claim 1, wherein said primary intake port is configured as a swirl generation port. 3. An internal EGR at a secondary intake port.
The engine according to claim 1 or 2, further comprising a swirl control valve which is operated in a valve closing direction at least on a load side lower than the full load range to control the strength of the in-cylinder flow, on an upstream side of the communication passage connecting portion. Control device. 4. The engine control according to claim 1, further comprising a variable valve timing device for adjusting an internal EGR amount by changing an amount of overlap between an intake valve and an exhaust valve of the secondary intake port. apparatus. 5. The method according to claim 1, wherein the overlap amount is A / F = 16 to 20.
The engine control device according to claim 4, wherein the region is larger than other regions. 6. The engine control device according to claim 1, wherein a connection opening with the primary intake port in the communication path of the internal EGR is provided near the cylinder wall. 7. The engine control device according to claim 1, wherein a fuel injection valve is disposed upstream of a connection opening of the communication passage for the internal EGR of the primary intake port.