JP4051261B2 - Control method for stoichiometric air-fuel ratio stratified combustion internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an internal combustion engine in which fuel is directly injected into a cylinder and burned mainly by ignition.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an internal combustion engine that directly injects fuel into a cylinder has been known to reduce harmful components in exhaust gas by introducing EGR gas (exhaust gas recirculation gas). Further, in that case, in order to effectively maintain the combustion performance, there is known one in which the mixing ratio of EGR gas is changed depending on the place. As an example of these, for example, there is a system as described in JP-A-2001-280140.
[0003]
This system mainly relates to a compression ignition engine. EGR gas passages with control valves are connected to two intake ports that open to one cylinder, and the shape of the intake port and the valve opening period of the intake valve are shifted. Thus, a layer with a large amount of EGR gas and a layer with a small amount of EGR gas are formed in the cylinder. Then, the intake air stratified in the longitudinal direction of the cylinder is stratified in the axial direction in the piston cavity by the squish flow in the compression stroke, and by injecting the fuel therein, NOx and soot (black smoke) are effectively produced. It is said that simultaneous reduction can be achieved.
[0004]
[Patent Document 1]
JP 2001-280140 A (Page 5-6, FIGS. 2 and 4)
[0005]
[Problems to be solved by the invention]
However, the above configuration has the following problems.
[0006]
That is, the independent intake pipe used in the conventional configuration is suitable for generating a swirl, but has a large ventilation resistance at high load due to the bending provided in the intake pipe. There is a problem that a sufficient amount of air cannot be sucked by the negative pressure generated when the piston descends, leading to a decrease in output. Also, the piston shape has a cavity, which inevitably leads to an increase in piston thickness, that is, an increase in weight, and there is a problem that it becomes an obstacle when the engine speed is increased to improve the output. . Furthermore, since the EGR gas is introduced into each of the independent intake pipes, there is a problem that piping and mechanisms for that are complicated, leading to an increase in cost and weight.
[0007]
In addition, the compression ignition engine described in the conventional configuration, that is, the diesel engine, has a problem that it is difficult to simultaneously reduce black smoke and NOx, and it is difficult to install the catalyst, and the black smoke combustion apparatus is also expensive. It has become. In addition, in the case of a gasoline engine, when stratified combustion is performed using a lean mixture as a whole, there is no effect even if a conventional three-way catalyst is used to reduce emissions (exhaust gas). In general, a NOx reduction catalyst is used to purify (nitrogen oxides). However, as a method of using this catalyst, the air-fuel ratio is enriched to about 13 at regular intervals and is adsorbed during lean operation. Therefore, it is necessary to perform an operation for reducing the NOx. This is called a rich spike, but not only stratified combustion is not possible during the rich spike, but also wastes fuel as energy for NOx reduction. However, since it is offset by the rich spike, there is a problem that the actual fuel efficiency improvement rate is lowered. At this time, in the current technology, the NOx purification rate of the NOx reduction catalyst is about 90% at the maximum, which is lower than the purification rate of 99% when the three-way catalyst is used, and the reduction of NOx generation amount due to lean combustion is considered. Even so, there is a problem that as a result, the amount of NOx exhausted from the tail pipe, that is, the exhaust pipe is increased.
[0008]
The present invention has been made in order to solve the above-described problems. The piston is light in weight suitable for realizing a high rotation, and the intake passage has a low resistance, so that a sufficient amount of air can be secured at a high load. A first object is to provide a system capable of performing stratified combustion while being configured. In addition, by effectively using a three-way catalyst with high exhaust purification efficiency, it is possible to suppress the deterioration of emissions at a low cost, and also to avoid rich spikes during stratified combustion or to reduce the number of times as much as possible. A second object is to provide a stratified combustion system that prevents deterioration.
[0009]
[Means for Solving the Problems]
  In order to solve the above problems, the present invention has the following means.
  That is, an intake valve that controls the amount of air introduced into the cylinder, fuel injection means that directly injects fuel into the cylinder, and exhaust gas after combustion is recirculated or retained in the cylinder EGR In a control method for an internal combustion engine comprising a control means,
  An air-fuel mixture near the stoichiometric air-fuel ratio in which air and fuel are mixed in the cylinder is formed near the spark plug by controlling the intake valve and the fuel injection valve. A control method is characterized in that the EGR control means is controlled to be introduced into the cylinder as EGR gas.
[0010]
  further,An internal combustion engine capable of directly injecting fuel into a cylinder includes an independent intake pipe divided into at least two and a swirl control valve capable of closing one of them. Furthermore, an EGR (Exhaust Gas Recirculation) valve for recirculating the exhaust gas is provided, and the EGR passage is opened in the closed intake pipe portion. When the intake valve is opened, the gas flowing into the combustion chamber from one of the independent intake pipes is mainly air, and the gas flowing from the other of the independent intake pipes is mainly EGR gas.
[0011]
In addition, a variable valve timing mechanism is provided that makes the phase at the time of opening and closing different from the other intake valves for at least one intake valve.
[0012]
The top surface of the piston is configured as a flat surface or an uneven surface with a valve recess to reduce the weight. Furthermore, a three-way catalyst is provided in the exhaust passage.
[0013]
Further, in the in-cylinder direct fuel injection engine configured as described above, the fuel injection device is controlled so that fuel is injected in the latter half of the compression stroke during stratified combustion and in the intake stroke during homogeneous operation.
[0014]
Since it comprised as mentioned above, this invention has the following effects.
[0015]
In a low load region of the engine, the swirl control valve is closed, and the EGR gas from the EGR valve is allowed to flow into the closed independent intake pipe. Then, the intake valve on the side where EGR gas flows in the intake stroke is opened first, and only EGR gas flows into the combustion chamber. Then, in the latter half of the intake stroke, the intake valve on the side not blocked by the swirl control valve is opened, and combustion air is introduced. By flowing the EGR gas and the combustion air into the combustion chamber with a time difference, the intake air and the EGR gas are kept separated. In the subsequent compression stroke, fuel is injected toward the intake air. At this time, the fuel injection amount is controlled so that the air-fuel ratio of the air-fuel mixture becomes the stoichiometric air-fuel ratio. In this way, the exhausted EGR gas has the same composition as the exhaust gas burned at the stoichiometric air-fuel ratio. In this way, the air-fuel mixture is stratified to improve fuel efficiency by reducing pumping loss and cooling loss, and the air-fuel ratio of the gas as a whole is the stoichiometric air-fuel ratio that can be used by the three-way catalyst to simultaneously purify NOx and HC.
[0016]
Furthermore, when a higher load is required, the intake resistance is reduced by opening the swirl control valve to increase the intake air amount, and the fuel is injected into the intake stroke to achieve sufficient vaporization and air contact. Ensure mixing time, perform homogeneous combustion, and secure necessary output.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 and FIG. 2 show the configuration of the first embodiment of the present invention as viewed from above in FIG. 1 and as viewed from the horizontal direction in FIG. In the present embodiment, a multi-cylinder engine is mainly assumed, but for the sake of simplicity, one cylinder will be described.
[0018]
A swirl control valve 102 is attached to the intake pipe 101 so that 101b of the two independent intake pipes 101a and 101b can be opened and closed.
[0019]
The injector 122 is attached so as to inject fuel directly into the cylinder 123.
[0020]
The air sucked from the right side of the drawing passes through the air cleaner 106, measures the flow rate with the air flow meter 105, adjusts the flow rate with the electronic control throttle chamber 104, and then distributes it to each cylinder with the collector 103. Thereafter, the air passes through the intake pipes 101a and 101b, and flows into the cylinder 123 when the intake valves 111a and 111b are opened.
[0021]
The gas burned in the cylinder passes through the exhaust valve 112 and the exhaust pipe 110, is purified by the three-way catalyst 115, and is exhausted to the atmosphere through a silencer (not shown). At this time, a part of the gas is recirculated to the intake pipe 101 using the EGR passage 109 while adjusting the flow rate by the EGR control valve 108. The EGR passage 109 opens into the EGR side independent intake pipe 101b.
[0022]
The fuel injection timing of the injector 122, the ignition timing of the spark plug 113, the opening of each of the swirl control valve 102, the electronic control throttle chamber 104, and the EGR control valve 108 are the intake air amount measured by the air flow meter 105, the accelerator opening Based on information such as temperature, engine water temperature, engine speed, and vehicle speed (all of which input sensors are not shown), the computer 201 sets and controls the optimum value and timing.
[0023]
When performing stratified combustion, first, the swirl control valve 102 is closed to close the EGR-side independent intake pipe 101b, and EGR gas is caused to flow into the EGR-side independent intake pipe 101b by using the EGR passage 109 and the EGR control valve 108. Keep it.
[0024]
The EGR side intake valve 111b is opened first in the second half of the exhaust stroke of the engine or in the intake stroke. Due to the negative pressure generated by the piston 107, EGR gas flows from the EGR-side independent intake pipe 101b, and is filled into the cylinder 123 while forming a swirl 121 clockwise as viewed from the upper side of the figure. It is desirable that the amount of change in the lift start and end crank angle of the EGR side intake valve 111b be 20 degrees CA (* CA is an abbreviation of the crank angle) or more so that mixing of EGR gas and intake air is minimized. In this way, in the conventional engine, the exhaust valve 112 and the EGR side intake valve 111b are opened simultaneously in the latter half of the exhaust stroke, so that the so-called overlap period becomes longer, and the EGR gas and air can be expected by blowing back to the intake pipe. However, in the present invention, the EGR side independent intake pipe 101b is closed by the swirl control valve 102, and the EGR side is obstructed. Since the independent intake pipe 101b is originally filled with EGR gas, there is no problem even if the exhaust valve 112 is open.
[0025]
Next, when the intake valve 111a is opened in the latter half of the intake stroke, air flows into the cylinder 123 through the independent intake pipe 101a and the intake valve 111a, forming a swirl 120 that is counterclockwise when viewed from the upper side of the figure. . Although the swirls 120 and 121 flow in opposite directions, the opening phases of the intake valves 111 a and 111 b are different, so that the EGR gas swirl 120 is located below the cylinder 123 and the intake air swirl 121 is located above the cylinder 123. The engine can be stratified without mixing for a short time between the intake and compression strokes of the engine.
[0026]
Subsequently, in the compression stroke, the intake valves 111a and 111b are closed, the piston 107 is raised, and the air in the cylinder 123 is compressed. Here, fuel is injected from the injector 122. At this time, as shown in FIG. 2, the spray pressure, that is, the penetration, is adjusted by adjusting the fuel pressure or the like so that the spray 125 is directed to the swirl 121 of the intake air and does not collide with the cylinder wall or the combustion chamber wall. Set it optimally. Further, the fuel spray 125 is a so-called deflected spray in which the upward component in the figure is larger than the downward component. By comprising in this way, mixing with the swirl 121 and the spray 125 is performed efficiently. Further, the mixing ratio of the intake air and the fuel, that is, the air-fuel ratio is adjusted so as to be close to the theoretical air-fuel ratio at which the exhaust purification can be efficiently performed by the three-way catalyst 115. In the latter half of the compression stroke, that is, when the optimum ignition timing is reached, the ignition plug 113 is ignited by a signal from the computer 201 to cause combustion.
[0027]
In this way, while forming a stoichiometric air-fuel mixture capable of good combustion in the vicinity of the spark plug, at the same time, the overall intake amount is increased, and pumping loss and cooling loss are reduced to improve fuel efficiency. Since it does not operate with a lean air-fuel mixture as in the prior art, there is no need to use a lean NOx catalyst, and there are no problems such as deterioration of fuel consumption due to rich spikes, low NOx removal rate and low exhaust purification effect. Further, since it is not necessary to use both the lean NOx catalyst and the three-way catalyst, the cost can be reduced.
[0028]
FIG. 3 shows the lift curve of the intake / exhaust valve in the first embodiment of the present invention. The operations of the intake valve 111a and the two exhaust valves 112 are not changed, and the operation of the EGR side intake valve 111b is accelerated only during stratified combustion. The amount of change in lift start and end crank angle is preferably 20 degrees CA (* CA is an abbreviation of crank angle) or more so that mixing of EGR gas and intake air is minimized. In this way, the exhaust valve 112 and the EGR side intake valve 111b open simultaneously in the latter half of the exhaust stroke, so-called overlap period becomes longer, but the independent intake pipe 101b is closed and filled with EGR gas. There is no problem of exhaust gas blowback. When the intake valve 111a reaches the fully opened lift amount, the EGR side intake valve 111b starts to close, and the operation of intake air as described in FIGS. 1 and 2 can be obtained.
[0029]
4 and 5 show the operation when the engine load is small in the first embodiment.
[0030]
First, the opening degree of the electronic control throttle chamber 104 is set to be small by a signal from the computer 201. On the other hand, the opening degree of the EGR control valve 108 is set large. As a result, when the intake valves 111a and 111b are opened in the intake stroke of the engine, the gas sucked into the cylinder 123 is EGR that has passed through the EGR side independent intake pipe 101b rather than the intake air that has passed through the independent intake pipe 101a. The amount of gas increases, and the amount of the swirl 120 is larger than that of the swirl 121. Even in this case, the swirl 121 of the intake air is finally sucked into the cylinder 123 and is in the upper part of the cylinder 123, that is, in the vicinity of the plug 113, and the spray 125 is a deflected spray having a large component upward in FIG. The spray 125 is mainly mixed with the swirl 121 of the intake air and can form a stoichiometric air-fuel mixture around the plug 113. Most of the rest is a swirl 120 made of EGR gas. The swirl 120 flows under the cylinder 123 and maintains the air-fuel ratio in the entire cylinder 123 in the vicinity of the theoretical air-fuel ratio, while increasing the intake amount to reduce pumping loss and cooling loss. Can be reduced.
[0031]
6 and 7 show the operation when the engine load is medium in the first embodiment.
[0032]
First, the opening degree of the electronically controlled throttle chamber 104 is set to be slightly larger than that shown in FIGS. 4 and 5 by a signal from the computer 201. On the other hand, the opening degree of the EGR control valve 108 is set slightly smaller. As a result, when the intake valves 111a and 111b are opened during the intake stroke of the engine, the gas sucked into the cylinder 123 is the intake air passing through the independent intake pipe 101a and EGR passing through the EGR side independent intake pipe 101b. The amount of the swirl 121 of the intake air is larger than that of the swirl 120 of EGR gas. In this case as well, as in the case described with reference to FIGS. 4 and 5, the swirl 121 of the intake air is finally sucked into the cylinder 123 and is in the upper part of the cylinder 123, that is, in the vicinity of the plug 113. Therefore, the spray 125 is mainly mixed with the swirl 121 of the intake air and can form a stoichiometric air-fuel mixture around the plug 113. Most of the other is the swirl 120 made of EGR gas, which flows under the cylinder 123 and keeps the air-fuel ratio as a whole in the cylinder 123 in the vicinity of the theoretical air-fuel ratio, while increasing the intake amount to reduce pumping loss and cooling loss. Can be reduced.
[0033]
4 to 7, the ratio of the swirl 121 of the intake air or air-fuel mixture that rotates counterclockwise and the swirl 120 of the EGR gas that rotates clockwise varies depending on the operating state, but the intake air amount is a reference, that is, 100% For example, it can be set by changing from 10% to about 200%.
[0034]
8 and 9 show the operation when the engine load is large in the first embodiment.
[0035]
First, the swirl control valve 102 is set to be opened by a signal from the computer 201. The opening degree of the electronically controlled throttle chamber 104 is set to be larger (close to full opening) than the case shown in FIG. As a result, the intake resistance of the intake pipe 101 is reduced. Therefore, when the intake valves 111a and 111b are opened during the intake stroke of the engine, a large amount of fresh air is drawn from both the independent intake pipe 101a and the EGR side independent intake pipe 101b. Can be made.
[0036]
Further, the opening degree of the EGR control valve 108 is set small. The lift curve of the EGR side intake valve 111b is made equal to the lift curve of the intake valve 111a so that the intake valves 111a and 111b open and close simultaneously.
[0037]
At this time, a signal is sent from the computer 201 to the injector 122 during the intake stroke of the engine to perform fuel injection. Thereby, the vaporization time and the diffusion time of the spray can be lengthened to promote the mixing with the intake air, and the homogeneity of the air-fuel mixture can be increased. Since the intake air amount is large, if the fuel injection amount is increased, a large amount of air-fuel mixture can be formed, and a large torque can be obtained.
[0038]
FIG. 10 shows a control flowchart of the operations shown in FIGS.
[0039]
First, the computer 201 reads the engine speed, the accelerator opening, the water temperature, the intake pressure, the exhaust temperature, and the gear position from each sensor, and calculates a target torque based on the read values.
[0040]
Next, using this torque, an engine speed-target torque operation state map is referred to determine whether the EGR stratified operation region or the homogeneous operation region, and then an appropriate fuel injection amount, ignition timing Decide.
[0041]
Next, when the EGR stratified operation is performed, the swirl control valve 102 is closed and the fuel injection timing is set to the compression stroke of the engine. Then, the lift start crank angle of the EGR side intake valve 111b is set earlier.
[0042]
On the other hand, when the EGR stratified operation is not performed, that is, when the homogeneous operation is performed, the swirl control valve 102 is opened and the fuel injection timing is set to the intake stroke of the engine. The lift start of the EGR side intake valve 111b is made equal to the intake valve 111a.
[0043]
Next, when the engine enters the exhaust-intake stroke, intake valves 111a and 111b operate as determined above. That is, when performing the stratified operation, the intake valve 111b opens first, and the EGR gas flows into the cylinder 123 to form the swirl 120. Next, a swirl 121 of intake air is formed. Here, fuel injection is performed in the compression stroke toward the swirl 121 of the intake air. Thus, the air-fuel mixture can be formed around the plug 113, and the surroundings can be stratified with the EGR gas and burned.
[0044]
On the other hand, when performing a homogeneous operation, the swirl control valve 102 opens, the intake valves 111a and 111b open simultaneously, and air flows from both the independent intake pipe 101a and the EGR side independent intake pipe 101b. Because the passage cross-sectional area is large and resistance is low, a lot of air flows in. On the other hand, by performing fuel injection in the intake stroke, the vaporization time can be increased and the homogeneity of the air-fuel mixture can be improved.
[0045]
Next, ignition is performed according to the determined ignition timing. Here, combustion is performed and output is taken out, and then combustion gas is discharged to the exhaust pipe 110 in the exhaust stroke. The cycle is completed once as described above, and the engine is operated by repeating this cycle.
[0046]
FIG. 11 shows a lift curve of the intake / exhaust valve in the second embodiment of the present invention. Since the basic configuration of the second embodiment is the same as that of the first embodiment, description thereof is omitted. As for the variable mechanism of the intake valves 111a and 111b, a mechanism for reducing the lift amount of the intake valve 111a as well as speeding up the start of operation of the EGR side intake valve 111b as in the first embodiment is added. With this configuration, the amount of intake air can be reduced while increasing the amount of EGR gas swirl 120 flowing into the cylinder 123, and more EGR gas can be introduced compared to the amount of intake air. The pumping loss in the low load range can be reduced.
[0047]
FIG. 12 shows the lift curve of the intake / exhaust valve in the third embodiment of the present invention. Since the basic configuration of the third embodiment is the same as that of the first embodiment, description thereof is omitted. The variable operation mechanism for the intake valves 111a and 111b is provided with a mechanism for independently changing the valve operating angle. When performing EGR stratified combustion, the operating angle of the intake valves 111a and 111b is reduced, the operation of the EGR side intake valve 111b is accelerated, and at the same time, the operation of the intake air side intake valve 111a is delayed. With this configuration, the timing at which the EGR gas swirl 120 flows into the cylinder 123 and the timing at which the intake air swirl 121 flows in can be shifted, and the EGR gas and the air-fuel mixture can be well stratified. Since many EGR gases can be introduced, the pumping loss in the low load region can be reduced.
[0048]
FIG. 13 shows a lift curve of the intake / exhaust valve in the fourth embodiment of the present invention. Since the basic configuration of the fourth embodiment is the same as that of the first embodiment, description thereof is omitted. The exhaust valve 112 is provided with a variable operation mechanism for shifting the valve opening period, and the intake valve 111a is provided with a mechanism for changing the valve operating angle. In the present embodiment, the EGR side intake valve may not include the operation variable mechanism. When performing EGR stratified combustion, the closing timing of the exhaust valve 112 is delayed by 20 ° or more in crank angle. Further, the operating angle of the intake valve 111a is reduced by 20 ° or more, and at the same time, the valve opening is delayed by 20 ° or more compared to the EGR side intake valve 111b. With this configuration, the combustion gas that has returned from the exhaust valve 112 past the top dead center remains in the cylinder 123, and then the EGR gas from the EGR side intake valve 111b generates the swirl 120, and finally sucks it. Air flows as the swirl 121 through the intake valve 111a. Since EGR gas can also be introduced from the exhaust valve 112, a large amount of EGR can be introduced. Further, since it is not necessary to change the timing of the EGR side intake valve 111b, it is only necessary to provide one type of valve operation variable mechanism on each of the intake side and the exhaust side, which is a structure compared to the second embodiment or the third embodiment. Becomes easier.
[0049]
In FIG. 14, the figure of the stratification and the homogeneous operation area | region on the rotation speed-torque map in this invention is shown. At the same engine speed, a relatively large amount of EGR gas is introduced when the load is small, and the EGR gas decreases when the load increases. When the load further increases, it switches to homogeneous combustion.
[0050]
FIG. 15 shows a stratification and homogeneous operation region on the rotational speed-torque map in the prior art, and FIG. 16 shows a comparison of fuel consumption by load between the prior art and the present invention.
[0051]
In the prior art, stratification is performed mainly by air. However, since EGR gas is used in the present invention, the specific heat ratio of the in-cylinder gas increases in the expansion stroke of the engine, and the efficiency of the engine is improved. Further, since the mixing of the EGR gas and the combustible mixture is suppressed to the minimum, the combustion deterioration of the mixture can be prevented, and the combustion efficiency is improved. For this reason, when compared with the same engine speed and load, fuel consumption can be reduced.
[0052]
Further, in the conventional technique, in order to maintain the activity of the lean NOx catalyst, it is necessary to apply rich spikes at regular intervals, and fuel consumption during this period is deteriorated. For this reason, the total fuel consumption can be further reduced in the present invention.
[0053]
In the above embodiment, the basic concept of the stoichiometric mixture combustion by EGR stratification is described, and the scope of the present invention is not necessarily limited to this. For example, the number of intake passages or the shape of the intake passages Even if the air pressure changes, it has an intake control valve or swirl control valve that partially closes these passages, introduces EGR gas into the closed portion, and varies the valve timing to change EGR gas and combustible mixture Any structure that achieves stratification is clearly within the scope of the present invention.
[0054]
Furthermore, although the present embodiment describes a naturally aspirated engine, the same operation can be performed for an engine with a supercharger as long as stratified combustion using EGR gas can be performed. In this case, since the pressure of the intake air is higher than the atmospheric pressure, the amount of intake air can be increased even if EGR gas is added, and the stratified operation range can be widened compared to the case of natural intake.
[0055]
Further, although four examples of the variable valve operation mechanism have been shown, the same effect can be obtained even when two or more of these are used in combination, and these are clearly included in the scope of the present invention.
[0056]
【The invention's effect】
The effects of the present invention are listed as follows.
[0057]
First, because EGR gas is used, stratified combustion can be performed to reduce the pumping loss and improve the efficiency while constantly improving the air-fuel ratio in the vicinity of the stoichiometric air-fuel ratio, and the exhaust gas can be purified by effectively using the three-way catalyst. There is no need to use a lean NOx catalyst as in the prior art, and there is an effect that deterioration of fuel consumption due to rich spikes can be prevented. In addition, the NOx removal rate is high, and the effect of exhaust purification is great. Furthermore, since it is not necessary to use both the lean NOx catalyst and the three-way catalyst, there is an effect that the cost can be reduced.
[0058]
In addition, the stratification of the air-fuel mixture and EGR gas does not depend on the shape of the intake port or piston cavity, etc., so the air flow at high rotation and high load is not hindered, pumping at high output and low load There is an effect that it can be made an engine with low loss and good fuel efficiency.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a first embodiment of the present invention viewed from above a cylinder.
FIG. 2 is a configuration diagram of the first embodiment of the present invention viewed from the side of a cylinder.
FIG. 3 is a lift curve of an intake / exhaust valve in the first embodiment.
FIG. 4 is a diagram showing an operating state at a low load when viewed from above in the first embodiment.
FIG. 5 is a side view of an operating state at a low load in the first embodiment.
FIG. 6 is a top view of an operating state at a medium load in the first embodiment.
FIG. 7 is a side view of an operating state at a medium load in the first embodiment.
FIG. 8 is a top view of the operating state at the time of high load in the first embodiment.
FIG. 9 is a side view of an operating state at a high load in the first embodiment.
FIG. 10 is an operation flowchart in the first embodiment.
FIG. 11 is a lift curve of an intake / exhaust valve according to a second embodiment of the present invention.
FIG. 12 is a lift curve of an intake / exhaust valve according to a third embodiment of the present invention.
FIG. 13 is a lift curve of an intake / exhaust valve according to a fourth embodiment of the present invention.
FIG. 14 is a diagram of stratification and homogeneous operation regions on a rotation-torque map in the present invention.
FIG. 15 is a diagram of stratification and homogeneous operation regions on a rotation-torque map in the prior art.
FIG. 16 is a comparison diagram of fuel consumption between the present invention and the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 101 ... Intake pipe, 101a ... Independent intake pipe, 101b ... EGR side independent intake pipe, 102 ... Swirl control valve, 103 ... Collector, 104 ... Electronically controlled throttle chamber, 105 ... Air flow meter, 106 ... Air cleaner, 107 ... Piston, 108 ... EGR control valve, 109 ... EGR passage, 110 ... exhaust pipe, 111a ... intake valve on the intake air side, 111b ... intake valve on the EGR side, 112 ... exhaust valve, 113 ... ignition plug, 115 ... three-way catalyst, 120 ... Swirl by EGR gas, 121... Swirl by intake air, 122... Injector, 123... Cylinder, 125.

Claims (6)

Two independent intake pipes for guiding the air flow introduced into the cylinder;
An intake valve provided in each of the independent intake pipes;
Fuel injection means for directly injecting fuel into the cylinder;
EGR control means provided on one of the independent intake pipes for recirculating or retaining exhaust gas after combustion in the cylinder;
In a control method for an internal combustion engine comprising an on-off valve for opening and closing an independent intake pipe provided with the EGR control means,
The on-off valve is closed, the intake valve provided with the EGR control means is opened, and the exhaust gas in which the air-fuel mixture near the stoichiometric air-fuel ratio is combusted by controlling the EGR control means is introduced into the cylinder as EGR gas. later,
Open the other of the intake valves, introduce air into the cylinder, form the introduced air near the spark plug,
A control method for forming an air-fuel mixture in the vicinity of a theoretical air-fuel ratio in the vicinity of a spark plug by controlling the fuel injection means in the latter half of a compression stroke and injecting fuel toward the introduced air.   2. The control method according to claim 1, wherein the spray direction and the spray penetration force are adjusted so that the spray from the injector is a deflected spray and is mixed with a swirl mainly composed of air.   The intake valve that opens and closes the independent intake pipe provided with the EGR control means opens faster than the other intake valve by 20 ° or more earlier than the other intake valve. The control method according to claim 1, wherein the control is performed.   Means for changing the opening timing and lift amount of the intake valve, and when the lift amount of the intake valve that opens and closes the independent intake pipe provided with the EGR control means is used as a reference, the lift amount of the other intake valve is 2. The control method according to claim 1, wherein the control method is less than this.   Means for changing the opening timing and lift amount of the intake valve, and the opening of the intake valve for opening and closing the independent intake pipe provided with the EGR control means is earlier than the opening start of the other intake valve, 2. The control method according to claim 1, wherein the valve opening period is longer than the valve opening period of the other intake valve.   In claim 5, based on the opening timing of the intake valve connected to the closed intake pipe, comprising one or more exhaust valves and means for changing the opening and closing valve timing and lift amount of the exhaust valve, A control method characterized by delaying the closing timing of the exhaust valve.

Images