JP2009293422A - Cylinder injection type spark ignition internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cylinder injection type spark ignition internal combustion engine enlarging a stable lean combustion operation region by adopting a collision injection method of allowing fuel to collide from mutually facing directions to retain a mixture near an ignition part. <P>SOLUTION: The cylinder injection type spark ignition internal combustion engine is provided with a fuel injection means 11 capable of injecting fuel by an indirect supply method, a direct supply method and a collision injection method of allowing the fuel to collide from the mutually facing directions; operating state detecting means 23, 24 each detecting the operating state of the internal combustion engine; and an ECU 20 switching the indirect supply method, the direct supply method and the collision injection method according to the operating state of the internal combustion engine. By this constitution, the operation region of lean combustion is enlarged by properly using the indirect supply method advantageous to stratified combustion in a low rotation region, the direct supply method advantageous in a region with a small fuel injection quantity in a medium rotation region, and the collision injection method advantageous in a medium load region with a large fuel injection quantity in a lean combustion time. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an in-cylinder injection spark ignition type internal combustion engine that performs combustion by forming a stratified mixture in a combustion chamber.

In-cylinder spark-ignition internal combustion engines that form fuel-air mixtures by directly injecting fuel into the combustion chamber, so-called direct-injection spark-ignition engines, have thermal efficiency at partial loads (low and medium loads) with large intake throttle loss Some perform stratified lean burn for improvement. There are various methods for stratifying the air-fuel mixture, and a method called spray guide method is well known.
In a spray guide type engine, for example, as disclosed in Patent Document 1, fuel is directly injected into the vicinity of an ignition portion of a spark plug in a compression stroke from a fuel injection valve provided in a combustion chamber. In the vicinity of the ignition part of the spark plug, an air-fuel mixture close to the stoichiometric ratio suitable for ignition is arranged (stratification of the air-fuel mixture) to establish lean combustion. Here, in the spray guide method, since the time interval from fuel injection to ignition is short, it is possible to prevent the diffusion of an excessive air-fuel mixture and to suppress the fuel collision to the piston, so that the amount of unburned HC is reduced, There is an advantage that high combustion efficiency can be realized.

On the other hand, in the spray guide method, combustion is not established unless ignition is performed during a period in which the spray passes near the ignition unit, that is, during a limited period immediately after fuel injection, so that the ignition timing and injection timing in the low rotation range Has the disadvantage of poor controllability.
To describe this drawback, the amount of fuel required per one stroke of the engine is largely determined by the engine load, and the influence of the engine speed is relatively small. Further, since the amount of fuel supplied to the engine is controlled by the opening period of the fuel injection valve (hereinafter abbreviated as the injection period), the injection period is long when the load is high, and the injection period is short when the load is low.

In general, the ignition timing and injection timing are often controlled in increments of crank angle (for example, the ignition timing is set to 30 ° before top dead center). When converted to time, the period of 1 ° is long at high revolutions. (For example, 1 ° corresponds to about 0.056 ms at 3000 rpm), and the period of 1 ° decreases as the rotation speed decreases (for example, 1 ° corresponds to about 0.278 ms at 600 rpm). (For example, at 600 rpm, the time resolution is 1/5 of 3000 rpm). For this reason, the degree of freedom in setting the ignition timing becomes smaller as the rotation speed becomes lower.
As described above, the spray guide system has a low degree of freedom in setting the ignition / injection control in the low rotation range, it is difficult to cope with disturbances, and misfire is likely to occur.

  That is why the spray guide system is not capable of stably dealing with a medium load operation region where the fuel injection amount is large, that is, the injection period is long. That is, in the spray guide system, fuel is directly injected into the vicinity of the ignition unit, and thus the flow rate of the air-fuel mixture in the vicinity of the ignition unit is increased. For this reason, in the operation region where the fuel injection amount is relatively large, there is a problem that the ignition discharge is easily blown out by the high-speed air flow, the stable ignition is not established, and the stratified lean combustion is difficult to be established.

On the other hand, there is also a direct-injection spark-ignition engine that generates a stratified mixture in a combustion chamber by a wall guide method as shown in Patent Document 2, for example, as opposed to a spray guide method.
In the wall guide system, in the compression stroke, fuel is injected toward the top surface of the ascending piston, and the spray is scooped up at the top surface of the piston and transported to the vicinity of the ignition part of the spark plug. Like the spray guide method, an air-fuel mixture close to the stoichiometric ratio is arranged in the vicinity of the ignition unit to realize stratified lean combustion.

  By the way, in the wall guide system, since the fuel is guided to the vicinity of the ignition part of the spark plug through the top surface of the piston, the flow rate of the spray is reduced, and an air-fuel mixture suitable for ignition stays in the vicinity of the ignition part of the spark plug. Thus, there is an advantage that the period during which ignition can be performed becomes long. In addition, the flow velocity of the airflow in the vicinity of the ignition unit is slower than that of the spray guide method, and stable ignition can be realized. However, if the engine speed increases and the flow in the cylinder increases, the diffusion of the air-fuel mixture is excessively promoted, resulting in an increase in unburned HC emission. In addition, if the engine speed increases or the load increases and the injection period becomes longer, the injection start timing is advanced, so that the piston position becomes far away so that the spray cannot be trapped in the piston cavity, and the air-fuel mixture is effectively placed near the ignition unit. There is a problem that it becomes impossible to transport.

For this reason, it is difficult to secure a wide range of lean combustion operation by adopting the spray guide method or the wall guide method alone. Therefore, as shown in Patent Document 2, a technique has been proposed in which two types of spray guide methods and wall guide methods are selectively used according to the operating state of the engine.
Japanese Patent Laid-Open No. 10-54246 JP 2004-353594 A

  However, even if the spray guide method and wall guide method are used properly, the range in which lean combustion can be performed is limited, so it is difficult to generate an air-fuel mixture suitable for ignition in the vicinity of the ignition unit under various operating conditions. . Particularly in the operation region where the fuel injection amount is large, both the spray guide method and the wall guide method have drawbacks, and in Patent Document 2, complicated control such as changing the fuel injection pressure or changing the valve closing timing. Means are taken. Nevertheless, it is difficult to expand the operating range of stable lean combustion.

  Accordingly, an object of the present invention is to adopt an in-cylinder injection spark capable of expanding a stable lean combustion operation region by adopting a collision injection method in which fuel is collided from opposite directions and an air-fuel mixture is retained in the vicinity of an ignition part. The object is to provide an ignition type internal combustion engine.

  In order to achieve the above object, the invention according to claim 1 is an indirect supply system in which fuel is indirectly injected to the vicinity of the ignition part during the compression stroke of the internal combustion engine, and also the fuel is directly injected to the vicinity of the ignition part. A fuel injection means capable of fuel injection is provided by a direct supply system, and a collision injection system in which fuel is caused to collide from opposite directions and stay in the vicinity of the ignition unit, and an operating state detecting means for detecting the operating state of the internal combustion engine is provided. In addition, a controller that switches between an indirect supply method, a direct supply method, and a collision injection method according to the operating state of the internal combustion engine is provided.

In other words, during lean burn operation, an indirect supply method with excellent controllability of ignition / injection timing is used in the low rotation range according to the operating state of the internal combustion engine, and unburned HC emissions are low in other regions and combustion is performed. Use an efficient direct supply system. However, the collision injection method is used in the middle load range where the characteristics of both indirect supply and direct supply deteriorate. In the collision injection method, the air-fuel mixture flows and stays in the vicinity of the ignition unit by causing the spray to collide in the vicinity of the ignition unit in the vicinity of the ignition unit. It has the feature that it does not increase, and good lean combustion characteristics can be realized even in a relatively high load region.
In this way, by properly using the three types of injection modes in accordance with the operating state of the internal combustion engine, the operating range of lean combustion can be expanded. Moreover, it does not require a lot of complicated control.

  According to the second aspect of the present invention, the control unit is configured so that the internal combustion engine has a low load with a low rotational speed so that the advantages of the indirect supply system, the direct supply system, and the collision injection system are sufficiently exhibited in the operation region of the internal combustion engine. Switching to the indirect supply method when the engine is in the middle load range, switching to the direct supply method when the internal combustion engine is in the low load region of medium speed, and collision injection method when the internal combustion engine is in the medium load region of medium speed It was made to switch to.

  According to the third aspect of the present invention, in the middle injection upper limit region in which the fuel injection amount is particularly large and the in-cylinder air-fuel ratio is not sufficiently lean, the vicinity of the ignition unit is excessively concentrated. In order to increase CO and smoke emissions due to incomplete combustion, decrease combustion efficiency, or cause smoldering of spark plugs. Switch to.

  Preferably, the high diffusion mode is performed by indirect supply in which fuel is indirectly injected into the vicinity of the ignition unit during the compression stroke of the internal combustion engine so that particularly excellent diffusibility of the air-fuel mixture can be obtained. Similarly, in the high diffusion mode, after the fuel is injected from the intake stroke to the middle of the compression stroke of the internal combustion engine, the divided injection in which the fuel is directly injected into the vicinity of the ignition unit by direct supply or indirect supply during the subsequent compression stroke. To do.

  The invention according to claim 4 uses a system in which the fuel by the indirect supply system and the fuel by the direct supply system are collided as the collision injection system.

According to the first aspect of the present invention, an indirect supply method that is advantageous for stratified combustion in the low rotation region, a direct supply method that is advantageous in a region where the fuel injection amount in the middle rotation region is small, and a medium load region where the fuel injection amount is large. By properly using the three types of injection modes, such as an advantageous collision injection system, the operating range of stable lean combustion can be greatly expanded. Moreover, it does not require a lot of complicated control.
According to the invention of claim 2, the advantages of the indirect supply method, the direct supply method, and the collision injection method can be sufficiently exhibited in the operation region of the internal combustion engine.

According to the third aspect of the present invention, in the middle load upper limit region where the air-fuel ratio in the cylinder is likely not to be sufficiently lean, particularly in the region where the collision injection is performed, the diffusibility of the air-fuel mixture is enhanced and the discharge of harmful substances is performed. This suppresses the smoldering of the spark plug, and even when the fuel injection amount increases, it is possible to promise more stable lean combustion.
According to the invention of claim 4, in the collision injection method, since the indirect supply method fuel and the direct supply method fuel are caused to collide, it is necessary to design a new injection form for the collision injection method in the fuel injection means. There is no.

Hereinafter, the present invention will be described based on a first embodiment shown in FIGS.
FIG. 1 shows a combustion chamber structure per cylinder of an in-cylinder spark-ignition internal combustion engine, for example, a four-cycle direct injection gasoline engine (hereinafter simply referred to as an engine) mounted on an automobile (vehicle) for traveling. A cross-sectional view is shown.
The structure of the engine will be explained. In FIG. 1, 1 is a cylinder block constituting the engine body, 2 is a cylinder head mounted on the cylinder block 1, 3 is a cylinder liner formed on the cylinder block 1, and 4 is The piston is accommodated in the cylinder liner 3 so as to be able to reciprocate.

  Of these, a pent roof type combustion chamber 6 is formed on the lower surface of the cylinder head 2 facing the cylinder liner 3. On both sides of the combustion chamber 6, a pair of intake valves 8 (only one is shown: both are broken lines) for controlling intake air from the intake port 7 and a pair of exhaust valves 10 for controlling exhaust from the exhaust port 9. (Only one is shown: both are broken lines). Further, in the center of the combustion chamber 6, one fuel injection valve 11 (corresponding to the fuel injection means of the present application) is provided. The fuel injection valve 11 has an injection portion 12 that injects fuel at the tip, and this injection portion 12 is exposed into the combustion chamber 6.

  The combustion chamber 6 is provided with a spark plug 14 along with the fuel injection valve 11. The spark plug 14 has an ignition portion 15 at the tip. The ignition unit 15 has a general electrode structure, specifically, a center electrode 16 and a side electrode 17 and a discharge unit (ignition position) formed between the tip of the center electrode 16 and the tip of the side electrode 17. It is. The ignition unit 15 protrudes into the combustion chamber 6 and is adjacent to the injection unit 11.

  The spark plug 14 and the fuel injection valve 11 are connected to a control unit, for example, an ECU 20 (for example, composed of a microcomputer), and enable lean combustion operation for burning the stratified mixture. That is, when fuel is injected from the injection unit 11 during the compression stroke in the engine cycle (intake stroke, compression stroke, expansion stroke, exhaust stroke) according to the command of the ECU 20, the entire combustion chamber 6 is in an excessive air state. In the vicinity of the ignition part 15 of the spark plug 14, an air-fuel mixture area close to the stoichiometric ratio suitable for ignition is formed (stratified air-fuel mixture), and stratified lean combustion is performed. Further, when fuel is injected from the injection unit 11 during the intake stroke, combustion (homogeneous combustion) is performed with the entire combustion chamber 6 as a uniform mixture.

  Of these, the fuel injection valve 11 is provided with three fuel injection modes for lean combustion operation. One is a wall guide system that is an indirect supply system, and for example, as shown in FIG. 1, fuel is indirectly injected into the vicinity of the ignition unit 15 during the compression stroke of the engine. Here, the fuel is injected from the injection unit 12 toward the top surface of the piston 4 that rises during the compression stroke. Then, the spray is scooped up at the top surface of the piston 4 and returns to the vicinity of the igniter 15, and a mixture (combustible mixture) suitable for ignition continues to be generated in the same portion. Of course, the fuel may be injected to the vicinity of the ignition unit 15 by reflection of other wall surfaces instead of the piston 4. As described in the “Background Art” section of the present application, this wall guide system has a characteristic of excellent controllability of ignition / injection timing in a low rotation range.

  The second is a spray guide method which is a direct supply method. In this system, as shown in FIG. 2, for example, fuel is directly injected into the vicinity of the ignition unit 15 during the compression stroke of the engine. Thereby, an air-fuel mixture suitable for ignition (combustible air-fuel mixture) is generated in the vicinity of the ignition unit 15 (immediately after the fuel injection period). As described in the “Background Art” section of this application, this spray guide system is easy to ensure stable combustion in a region where the fuel injection amount in the middle rotation region is small, and has little unburned HC, and combustion efficiency is low. It has the advantageous property of being high.

  The third is a collision injection system. In this method, fuel is caused to collide from opposite directions and the air-fuel mixture is retained in the vicinity of the ignition unit 15. This is performed by, for example, injecting fuel divided into two times in order at predetermined times in the compression stroke. Specifically, the first fuel injection is performed at the same timing (middle to late stage of the compression stroke) as in the wall guide system, and this first fuel injection flow passes through the top surface of the piston 4 and the ignition unit 15. The second fuel injection is performed at the timing immediately before and after reaching the vicinity (the latter stage of the compression stroke), and the wall guide airflow α generated by the first fuel injection and the second fuel injection as shown in FIG. The spray guide airflow β generated by the above causes collision with each other at a point near the ignition unit 15 so as to cancel each other, and an air-fuel mixture suitable for ignition (combustible air-fuel mixture) is generated in the vicinity of the ignition unit 15. In this fuel collision, the energy of both airflows cancel each other, so that the gas flow velocity in the igniter 15 is greatly reduced, and the combustible air-fuel mixture stagnates at a point near the igniter 15 for a long period. For this reason, the collision injection method has an advantage that the stable combustion region of the stratified lean combustion is markedly wider than the spray guide method indicated by the alternate long and short dash line, as shown by the solid line in FIG. In other words, the collision injection method has an advantageous characteristic that an air-fuel mixture suitable for ignition is easily stagnated in the vicinity of the ignition unit 15 even with a large amount of fuel injection. This collision injection method may be established in other ways.

Here, a piston cavity 21 is formed on the top surface of the piston 4 so that three types of fuel injection can be performed accurately.
Further, the ECU 20 has, for example, an engine speed sensor 23 that detects an engine speed sensor and an accelerator position sensor 24 that detects an accelerator position as sensors for detecting the operating state of the engine (both are the operating state detecting means of the present application). Equivalent) is connected. Further, the ECU 20 has a function for properly using the three types of injection modes in accordance with the engine operating state detected from the engine speed information from the engine speed sensor 23 and the accelerator position information from the accelerator position sensor 24. Is set. Specifically, the three types of injection modes are defined in an engine operating region where the best of each mode can be exhibited, for example, as shown in the operation map of FIG.

  That is, in the operation map (FIG. 5) in which the injection mode is selectively used during lean combustion operation (stratified combustion), the wall guide performs fuel injection by the wall guide method in the low load to medium load region in the low rotation speed region. When the operation mode T is set, the spray guide operation mode U in which fuel is injected by the spray guide method is set in the low load region of the medium rotation speed range, and the engine is in the medium load range of the medium rotation speed range, A collision lean operation mode S for performing fuel injection by the collision injection method is set. The premix operation mode V, which is set to a high load range in the remaining high engine speed range, injects fuel during the normal intake stroke and burns the entire combustion chamber 6 as a uniform mixture (homogeneous). (Combustion) area.

By using (switching) the wall guide method, spray method, and collision injection method, the lean combustion operation can be performed in a wide range. FIG. 6 shows a flowchart for performing control to selectively use such fuel injection.
With reference to the flowchart, the proper use (switching) of fuel injection during lean combustion operation will be described. Now, it is assumed that an automobile (vehicle) is running by operating the engine. During this travel, the ECU 20 detects the operating state of the engine from the engine information such as the engine speed and the accelerator opening detected by the engine speed sensor 23 and the accelerator opening sensor 24 in step S1.

  At this time, it is assumed that the operating state of the engine is a low / medium load region (including idle) in a low rotation region. Then, the ECU 20 proceeds to step S3 through step S2, selects the wall guide operation mode T in the operation map of FIG. 5, and controls the fuel injection valve 11 according to the wall guide operation mode T. Then, the fuel of the injection amount determined according to the low load or the medium load is injected from the injection unit 12 of the fuel injection valve 11 to the vicinity of the ignition unit 15 of the spark plug 14 by the wall guide method in the compression stroke of the engine. Be injected.

  Specifically, for example, as shown in FIG. 1, the fuel is injected from the injection unit 12 toward the piston cavity 21 on the top surface of the piston 4 at the middle to late timing of the compression stroke. Then, the jet flow is scooped up by the piston 4 and is directed to the vicinity of the ignition unit 15. The fuel diffuses during this time, and continues to generate an air-fuel mixture suitable for ignition (a combustible air-fuel mixture) in the vicinity of the ignition unit 15.

  In both the low and medium load ranges of the engine, stratified combustion is stably performed if ignition is performed by the ignition unit 15 of the spark plug 14 during the generation of the combustible mixture. In other words, by utilizing the characteristics of the wall guide system, ignition and fuel injection can be controlled without the lack of time resolution of ignition / injection control as in the spray guide system. As a result, the entire inside of the cylinder is in an excess air state, and the lean combustion operation is stably performed by disposing an air-fuel mixture near the stoichiometric ratio in the vicinity of the ignition unit 15.

  If the engine operating state is the low load region in the middle rotation range, the ECU 20 proceeds to step S3 through step S4, selects the spray guide operation mode U in the operation map of FIG. The fuel injection valve 11 is controlled according to the mode U. Then, a small amount of fuel determined in accordance with the low load is injected from the injection unit 12 of the fuel injection valve 11 directly into the vicinity of the ignition unit 15 by the spray guide method in the compression stroke of the engine.

Specifically, for example, as shown in FIG. 2, the fuel is injected from the injection unit 12 into the cylinder at a later stage of the compression stroke. As a result, an air-fuel mixture suitable for ignition is generated in the vicinity of the ignition portion 15 of the spark plug while the entire cylinder is in an excess air state. Then, the air-fuel mixture is ignited by the ignition unit 15 of the spark plug 14 in a short period substantially synchronized with the fuel injection period.
In the low load region of this engine, the fuel injection is small (because it is determined according to the load), and the gas flow velocity in the vicinity of the ignition unit 15 is slow. An air-fuel mixture suitable for ignition is generated while suppressing extinction. Moreover, in the middle rotation range, there is no shortage of time resolution of ignition / injection control, so that the control of ignition and fuel injection can be performed with a high degree of freedom by taking advantage of the characteristics of the spray guide system. As a result, the entire inside of the cylinder is in an excess air state, and the lean combustion operation is stably performed by disposing an air-fuel mixture near the stoichiometric ratio in the vicinity of the ignition unit 15.

  If the engine operating state is the middle load region in the middle rotation region, the ECU 20 proceeds to step S7 through step S6, selects the collision lean operation mode S in the operation map of FIG. According to mode S, the fuel injection valve 11 is controlled. Then, the fuel of the injection amount obtained from the injection unit 12 of the fuel injection valve 11 according to the medium load is ignited by the spark plug 14 by the collision injection method in two divided injections in the compression stroke of the engine. Injected near the portion 15.

  That is, the same injection method will be described. For example, when the piston 4 advances to the middle of the compression stroke, a part of the fuel injection amount determined by the medium load is used as the wall guide fuel from the injection unit 12 for the first time. It is injected toward the top surface of The wall guide fuel injected for the first time passes through the vicinity of the ignition part 15 of the spark plug 14 (the spark plug 14 is not activated) as shown in FIG. Is scooped up and heads away from the piston 4. The fuel is diffused during this period, and a wall guide mixture (a mixture suitable for ignition) is generated. The wall guide airflow α (jet) generated by the first fuel injection is directed to the vicinity of the ignition unit 15 from a direction opposite to the injection unit 12 as indicated by an arrow A.

  When the wall guide airflow α is in the latter half of the compression stroke immediately before and immediately after reaching the vicinity of the ignition unit 15, the remaining fuel injection amount is injected from the injection unit 12 of the fuel injection valve 11 as shown in FIG. The fuel is injected into the combustion chamber 6 from the section 12 as spray guide fuel β. The spray guide fuel β injected for the second time is directed to the vicinity of the ignition unit 15 as indicated by an arrow B. Then, while reaching the vicinity of the ignition unit 15, a spray guide air-fuel mixture (air mixture suitable for ignition) is generated.

At this time, the wall guide airflow α (jet flow) generated by the first fuel injection and the spray guide airflow β (jet flow) generated by the second fuel injection face each other in a direction facing each other in the vicinity of the ignition unit 15 ( Therefore, air currents collide at a point in the vicinity of the ignition unit 15 (FIG. 3).
Due to this collision, the energy of both airflows cancel each other, and the gas flow velocity in the igniter 15 is greatly reduced. Of course, the split injection has a small injection amount and the fuel flow rate is slow, and that alone contributes to the reduction of the air flow rate. Moreover, the air-fuel mixture suitable for ignition continues to stay at a point near the ignition unit 15 due to collision.

  As a result, the collision injection type can keep a mixture (combustible mixture) suitable for ignition for a long period of time in the vicinity of the ignition unit 15 in a region where the fuel injection amount is large, particularly in a middle load region. There is. For this reason, in the middle load operation region where the fuel injection amount is large, the ignition plug 14 is ignited during or immediately after the second fuel injection, thereby making the entire cylinder in an excess air state and igniting. By disposing an air-fuel mixture near the stoichiometric ratio in the vicinity of the portion 15, the lean combustion operation can be performed stably.

  Thus, a wall guide method that is advantageous for stratified combustion in the low rotation region, a spray guide method that is advantageous in a region where the fuel injection amount in the middle rotation region is small, and a collision injection method that is advantageous in a medium load region where the fuel injection amount is large, By adopting three types of injection modes, the operating range of stable lean combustion can be greatly expanded. In addition, simply switching between the three injection modes greatly expands the lean combustion operating range, eliminating the need for complicated control.

In particular, when the engine is in the low load to medium load range in the low rotation speed range, it switches to the wall guide method, and when the engine is in the low load range in the medium rotation speed range, it switches to the spray guide method. By switching to the collision injection in the region, the advantages of the wall guide method, the spray method, and the collision injection method can be sufficiently exhibited in the engine operation region.
7 and 8 show a second embodiment of the present invention.

  The present embodiment will be described. Among the regions of the collision lean operation mode S, the middle load upper limit region has a particularly large fuel injection amount and the air-fuel ratio tends not to be sufficiently lean. Therefore, only the middle load upper limit region S1 of the collision lean operation mode S shown in the operation map of FIG. 7 is intended to be switched to the high diffusion mode excellent in the diffusibility of the air-fuel mixture suitable for the state. Specifically, in the present embodiment, as shown in the operation map shown in FIG. 7, a wall guide that can be expected to diffuse the air-fuel mixture at the upper limit region S1 of the collision lean operation mode S as a high diffusion mode even if the fuel injection amount is large. The injection mode of the method was set. In this high diffusion injection mode, as shown in the flowchart of FIG. 8, the routine of steps S8 and S9 for executing the mode is interposed between step S6 and step S12, and the medium load of the collision lean operation mode S When the upper limit area S1, the wall guide for high diffusion (high diffusion mode) is switched.

  In this manner, when the fuel injection amount is large and the air-fuel ratio in the cylinder is not in a sufficiently lean state, such as the middle load upper limit region of the medium rotation of the engine, the ignition unit 15 near the cylinder and the inside of the cylinder is prevented from becoming rich (increasing CO and smoke emissions due to incomplete combustion and lowering combustion efficiency), creating an environment that is easy to burn, reducing emissions of harmful substances, and igniting The smoldering of the plug 14 is prevented, and a more stable lean combustion operation can be performed.

However, in the operation map shown in FIG. 7 and the flowchart shown in FIG. 8, the same parts as those of the first embodiment are denoted by the same reference numerals and the description thereof is omitted.
9 and 10 show a third embodiment of the present invention.
This embodiment is a modification of the second embodiment, and uses a split lean mode performed by split injection as a high diffusion mode in the middle load upper limit region S1 of the collision lean operation mode S.

  Specifically, in the split lean mode, a part of the fuel injection amount determined by the load is injected from the fuel injection valve 11 as the first time during the intake stroke of the engine, and the intake stroke and the compression stroke are injected. The middle stage is used to diffuse the fuel and make the cylinder a uniform mixture. Thereafter, during the compression stroke following the intake stroke, for example, in the middle or later stage of the compression stroke, the remaining fuel is injected from the fuel injection valve 11 to the vicinity of the igniter 15 by the spray guide, and near the igniter 15 of the uniform mixture. The split injection is used to generate a gas mixture close to the stoichiometric ratio.

  In the operation map shown in FIG. 9, the split lean mode is set in the upper limit region S1 of the collision lean operation mode S. Further, the flowchart shown in FIG. 10 is provided with step S10 for executing the split injection lean mode (fuel injection in the intake stroke and fuel injection in the compression stroke) instead of step S9 of the second embodiment. Thus, when the collision lean operation mode S is in the middle load upper limit region S1, the high-split split injection is switched.

  In this way, as in the second embodiment, when the fuel injection amount is large and the in-cylinder air-fuel ratio is not sufficiently lean, such as the middle load upper limit region of the medium rotation of the engine, the split injection is performed. In addition, the vicinity of the ignition unit 15 and the inside of the cylinder are prevented from being excessively concentrated, and an environment in which stratified combustion is easily performed is ensured, so that a more stable lean combustion operation can be performed. Moreover, since the split injection is not affected by the piston position unlike the wall guide, there is an advantage that it can be sufficiently exerted even in a region where the engine speed is high as shown in FIG.

However, in the operation map shown in FIG. 9 and the flowchart shown in FIG. 10, the same parts as those in the first embodiment are denoted by the same reference numerals and the description thereof is omitted.
The present invention is not limited to any of the above-described embodiments, and various modifications may be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the collision injection is realized by using one fuel injection valve. However, the collision injection may be realized by using a plurality of (for example, two) fuel injection valves.

1 is a cross-sectional view showing a combustion chamber structure of a direct injection spark ignition type internal combustion engine according to a first embodiment of the present invention, together with an injection flow of fuel supplied by an indirect supply system. Sectional drawing which shows the injection flow of the fuel supplied with the direct supply system. Sectional drawing explaining the injection flow of the fuel supplied by the collision injection system. The diagram explaining the combustion stability of the stratified lean combustion which a collision injection system brings. The diagram which shows the driving | operation map which switches an indirect supply system, a direct supply system, and a collision injection system. The flowchart explaining the control switched according to the driving | operation map. The diagram which shows the driving | operation map which employ | adopted high diffusion mode in the middle load upper limit area | region used as the principal part which concerns on the 2nd Embodiment of this invention. The flowchart explaining the control switched according to the driving | operation map. The diagram which shows the driving | operation map which employ | adopted high diffusion mode in the medium load upper limit area | region used as the principal part which concerns on the 3rd Embodiment of this invention. The flowchart explaining the control switched according to the driving | operation map.

Explanation of symbols

4 Piston 6 Combustion chamber 11 Fuel injection valve (fuel injection means)
20 ECU (control unit)
23, 24 Engine speed sensor, accelerator opening sensor (operating state detection means)

Claims (4)

An indirect supply method in which fuel is indirectly injected near the ignition unit during the compression stroke of the internal combustion engine, a direct supply method in which fuel is directly injected into the vicinity of the ignition unit, and an ignition unit by causing fuel to collide from opposite directions. A fuel injection means capable of injecting fuel in a collision injection system for staying in the vicinity;
An operating state detecting means for detecting an operating state of the internal combustion engine;
A direct injection spark ignition type internal combustion engine comprising: a control unit that switches between the indirect supply method, the direct supply method, and the collision injection method in accordance with an operating state of the internal combustion engine. The controller is
When the internal combustion engine is in the low load to medium load region at a low rotational speed, the indirect supply method is switched,
When the internal combustion engine is in a low load region of medium speed, switching to the direct supply system,
The in-cylinder injection type spark ignition type internal combustion engine according to claim 1, wherein the internal combustion engine is set so as to be switched to the collision injection method when the internal combustion engine is in a medium load region of medium speed. The in-cylinder injection spark ignition internal combustion engine according to claim 2, wherein only the middle load upper limit region of the region in which the collision injection method is performed is switched to the high diffusion mode.   The in-cylinder injection spark ignition type internal combustion engine according to any one of claims 1 to 3, wherein the collision injection method causes a fuel of an indirect supply method and a fuel of a direct supply method to collide with each other. .

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