JP4591318B2 - Combustion switching control system for compression ignition internal combustion engine - Google Patents

Description

  The present invention relates to a combustion switching control system for a compression ignition internal combustion engine that controls switching of a combustion mode in a compression ignition internal combustion engine that selects either premixed combustion or normal combustion according to an operating state.

  In a compression ignition internal combustion engine (hereinafter simply referred to as an internal combustion engine), premixed combustion may be performed for the purpose of suppressing NOx and smoke. In premix combustion, premixed gas is formed by executing fuel injection at a time earlier than the time near the top dead center of the compression stroke. However, when combustion is performed while forming a premixed gas, the possibility of premature ignition increases as the engine load or engine speed of the internal combustion engine increases. Therefore, in the internal combustion engine, the combustion mode is switched from premixed combustion to normal combustion, or from normal combustion to premixed combustion, depending on the operating state. Here, the normal combustion is diffusion combustion performed by executing fuel injection at a time near the top dead center of the compression stroke.

  Further, the amount of exhaust gas (so-called EGR gas) introduced into the intake system into the cylinder differs greatly between the case of performing premixed combustion and the case of performing normal combustion in an internal combustion engine. That is, during premixed combustion, a larger amount of EGR gas is required than during normal combustion in order to suppress premature ignition.

  Here, when the combustion mode is switched by switching the fuel injection timing in the internal combustion engine, it is necessary to increase or decrease the amount of EGR gas in the cylinder, but the EGR gas amount in the cylinder is switched to the combustion mode after switching. It is difficult to immediately change to a suitable amount. Therefore, when the combustion mode is switched from normal combustion to premixed combustion, the amount of EGR gas in the cylinder may be insufficient. Further, when the combustion mode is switched from premixed combustion to normal combustion, the amount of EGR gas in the cylinder may become excessive.

  If the amount of EGR gas in the cylinder is excessive with respect to the combustion mode, there is a risk of misfire. Further, if the amount of EGR gas in the cylinder is insufficient with respect to the combustion mode, there is a risk of premature ignition.

Therefore, in an internal combustion engine, when the combustion mode is switched to premixed combustion or normal combustion, when the EGR gas rate in the intake air reaches a predetermined value between a value suitable for premixed combustion and a value suitable for normal combustion. A technique for switching the fuel injection timing is known (for example, see Patent Document 1).
JP 2003-286876 A JP 2003-286880 A

  In an internal combustion engine that selects either premixed combustion or normal combustion according to the operating state, one of the premixed combustion region in which premixed combustion is performed and the normal combustion region in which normal combustion is performed is changed from one to the other. When the operating state shifts to, the combustion mode is switched.

The combustion mode is switched by changing the fuel injection timing. Further, when the combustion mode is switched, it is necessary to increase or decrease the EGR gas amount in the cylinder accordingly. However, although the fuel injection timing can be changed immediately, it takes some time to change the amount of EGR gas in the cylinder. Therefore, in the combustion switching control for switching the combustion mode, the fuel injection timing may be changed over a certain amount of time depending on the change in the amount of EGR gas in the cylinder.

  In such a case, the operation state of the internal combustion engine is being changed while the operation mode of the internal combustion engine is shifted from one of the premixed combustion region and the normal combustion region to the other. May move to a different area again (that is, return to one area).

  The present invention relates to an internal combustion engine that selects either premixed combustion or normal combustion according to the operating state, and performs combustion when the operating state of the internal combustion engine returns to the original region during switching of the combustion mode. It is an object of the present invention to provide a technique capable of suitably returning the mode to the combustion mode in the original region.

  In the first aspect of the invention, when the combustion mode in the internal combustion engine is returned to one combustion mode while switching from one of the premixed combustion and normal combustion to the other, the EGR gas amount in the cylinder and the fuel injection timing Is once changed to the target value in the other combustion mode as usual, and then the EGR gas amount and the fuel injection timing are changed toward the target value in one combustion mode.

More specifically, the combustion switching control system for an internal combustion engine according to the first invention is:
An EGR passage communicating the exhaust system and the intake system of the compression ignition internal combustion engine;
EGR gas amount control means for controlling the flow rate of EGR gas in the EGR passage,
An exhaust gas recirculation device for introducing a part of the exhaust gas discharged from the compression ignition internal combustion engine into the intake system as EGR gas;
Command means for giving a command to the exhaust gas recirculation device to change the EGR gas amount in the cylinder by controlling the EGR gas amount control means;
A fuel injection valve for injecting fuel into a cylinder of the compression ignition internal combustion engine;
The operation state of the compression ignition internal combustion engine belongs to a premixed combustion region in which premixed combustion is performed in which premixed gas is formed by injecting fuel from the fuel injection valve at a time earlier than the time near the top dead center of the compression stroke. Or a determination means for determining whether it belongs to a normal combustion region in which normal combustion is performed by injecting fuel from the fuel injection valve at a time near the top dead center of the compression stroke,
Either one of the premixed combustion region and the normal combustion region is a first region and the other is a second region,
When it is determined by the determination means that the operation state of the compression ignition internal combustion engine has shifted from the first region to the second region, the EGR gas amount control means burns the EGR gas amount in the cylinder in the first region. The target EGR gas amount in the mode is changed to the target EGR gas amount in the combustion mode in the second region, and the fuel injection timing from the fuel injection valve is changed from the target fuel injection timing in the combustion mode in the first region to the second region. In a combustion switching control system for a compression ignition internal combustion engine that switches the combustion mode by changing the target fuel injection timing in the combustion mode at a predetermined pattern in
While the operation state of the compression ignition internal combustion engine has shifted from the first region to the second region and the combustion mode is being switched, the operation state of the compression ignition internal combustion engine is changed to the second region by the determination means. When it is determined that the transition has been made again from the first region to the first region, the EGR gas amount in the cylinder continues to be changed to the target EGR gas amount in the combustion mode in the second region, and in the second region of the fuel injection timing. The change to the target fuel injection timing in the combustion mode is continued according to the predetermined pattern, and the EGR gas amount in the cylinder becomes the target EGR gas amount in the combustion mode in the second region or an amount in the vicinity thereof, and the fuel injection timing Is the target fuel injection timing in the combustion mode in the second region, and then the EGR gas amount in the cylinder is changed to the target EGR gas amount in the combustion mode in the first region. A command is issued from the command means to the exhaust gas recirculation device, and a change to the target fuel injection timing in the combustion mode in the first region of the fuel injection timing is started in the predetermined pattern. And

  In the internal combustion engine according to the present invention, premixed combustion is performed when the operating state belongs to the premixed combustion region, and normal combustion is performed when the operating state belongs to the normal combustion region. The premixed combustion is performed by injecting fuel from the fuel injection valve at a time earlier than the time near the top dead center of the compression stroke to form a premixed gas, and this premixed gas is used for combustion. On the other hand, normal combustion is diffusion combustion performed by injecting fuel from a fuel injection valve at a time near the top dead center of the compression stroke. The target fuel injection timing in each combustion mode is set in advance.

  The present invention also includes an exhaust gas recirculation device having an EGR passage and an EGR gas amount control means. By this exhaust gas recirculation device, a part of the exhaust gas is introduced into the intake system as EGR gas, whereby the EGR gas flows into the cylinder together with the intake air. In each combustion mode, a different target EGR gas amount is set, and the target EGR gas amount in the premixed combustion is larger than the target EGR gas amount in the normal combustion.

  In the present invention, when one of the premixed combustion region and the normal combustion region is the first region and the other is the second region, when the operating state of the internal combustion engine has shifted from the first region to the second region, In order to switch the combustion mode, the fuel injection timing is changed from the target fuel injection timing (hereinafter referred to as the first target fuel injection timing) in the combustion mode in the first region (hereinafter referred to as the first combustion mode) to the second region. The target fuel injection timing (hereinafter referred to as the second target fuel injection timing) in the combustion mode (hereinafter referred to as the second combustion mode) is changed. Furthermore, in this case, the EGR gas amount in the cylinder is changed from the target EGR gas amount in the first combustion mode (hereinafter referred to as the first target EGR gas amount) to the target EGR gas amount in the second combustion mode (hereinafter referred to as the second target EGR). (Referred to as gas amount).

  The amount of EGR gas in the cylinder is changed when a command is issued from the command means to the exhaust gas recirculation device so as to change the flow rate of the EGR gas by the EGR gas amount control means (hereinafter, the command at this time is referred to as EGR). (Referred to as gas amount change command). At this time, since the EGR gas flows into the cylinder after passing through the EGR passage and the intake system, the EGR gas amount in the cylinder does not change immediately after the EGR gas amount change command is issued, It takes some time to reach the second target EGR gas amount after starting to change. On the other hand, the fuel injection timing from the fuel injection valve can be immediately changed to the second target fuel injection timing.

  Accordingly, when the region to which the operating state of the internal combustion engine belongs is changed, an EGR gas amount change command is issued from the command means to the exhaust gas recirculation device so as to change the EGR gas amount in the cylinder to the second target EGR gas amount. At the same time, when the combustion injection timing from the fuel injection valve is immediately changed to the second target fuel injection timing, the amount of EGR gas in the cylinder may be excessive or insufficient with respect to the fuel injection timing.

  Therefore, when changing the fuel injection timing from the first target fuel injection timing to the second target fuel injection timing in order to switch the combustion mode, the fuel injection timing is changed over a certain period of time to some extent. Here, the predetermined pattern is a pattern determined based on the actual change in the EGR gas amount in the cylinder after the command means changes the EGR gas amount change command.

When the region to which the operating state of the internal combustion engine belongs shifts from the first region to the second region, the command means issues an EGR gas amount change command, and at the same time, starts changing the fuel injection timing in a predetermined pattern. The timing when the EGR gas amount in the cylinder becomes the second target EGR gas amount or an amount in the vicinity thereof and the timing when the fuel injection timing becomes the second target fuel injection timing can be synchronized. As a result, when the combustion mode is switched, the EGR gas amount in the cylinder can be suppressed from being excessive or insufficient with respect to the fuel injection timing. The predetermined pattern can be determined in advance by experiments or the like.

  As described above, when the fuel injection timing is changed in a predetermined pattern, the combustion mode is switched over to some extent. In such a case, while the operating state of the internal combustion engine has shifted from the first region to the second region, the internal combustion engine is being switched from the first combustion mode to the second combustion mode. In some cases, the operating state of the second shifts from the second region to the first region again.

  At this time, when the EGR gas amount change command is issued again from the command means to the exhaust gas recirculation device at the time when the operating state of the internal combustion engine shifts again from the second region to the first region, the EGR gas amount change means The state is immediately changed from the state corresponding to the second target EGR gas amount to the state corresponding to the first target EGR gas amount. Therefore, the EGR gas amount in the cylinder starts to change toward the first target EGR gas amount while changing toward the second target EGR gas amount. Even in such a case, a certain amount of time is required until the EGR gas amount in the cylinder actually reaches the first target EGR gas amount after the command means changes the EGR gas amount change command again to the exhaust gas recirculation device. take time.

  Further, when the operating state of the internal combustion engine shifts again from the second region to the first region, if the fuel injection timing is changed from the second target fuel injection timing to the first target fuel injection timing in a predetermined pattern, the internal combustion engine The fuel injection timing is temporarily changed to the second target fuel injection timing when the engine operating state shifts again. In other words, while the fuel injection timing is gradually changing toward the second target fuel injection timing, the fuel injection timing is immediately changed at the time of the second target fuel injection, and then from there, in a predetermined pattern toward the first target fuel injection timing. Will be changed.

  That is, in the above case, when the operating state of the internal combustion engine shifts again from the second region to the first region, the actual EGR gas amount in the cylinder is equal to or equal to the second target EGR gas amount. In a state where the fuel injection is not performed, the fuel injection timing once becomes the second target fuel injection timing. Further, as described above, the predetermined pattern is determined based on a change when the EGR gas amount in the cylinder changes from the first target EGR gas amount to the second target EGR gas amount. Therefore, even if the fuel injection timing that has become the second target fuel injection timing at the above timing is changed in a predetermined pattern toward the first target fuel injection timing, the fuel injection timing in the middle of the change remains within the actual cylinder This is a time deviating from the time corresponding to the change in the EGR gas amount.

  Therefore, in the present invention, the operation state of the internal combustion engine is changed from the second region to the first region while the operation mode of the internal combustion engine is shifted from the first region to the second region and the combustion mode is being switched. Even when the transition is made again to the region, the EGR gas amount change command is not immediately issued from the command means when the transition is made again, and the change of the EGR gas amount in the cylinder to the second target EGR gas amount is continued. Further, the change of the fuel injection timing to the second target fuel injection timing by a predetermined pattern is continued. Then, after the EGR gas amount in the cylinder becomes the second target EGR gas amount or an amount close thereto, and the fuel injection timing becomes the second target fuel injection timing, the EGR gas amount in the cylinder is changed to the first target EGR gas amount. The EGR gas amount change command is issued from the command means to the exhaust gas recirculation device so as to change to, and the change of the fuel injection timing to the first target fuel injection timing in a predetermined pattern is started.

  According to this, when the fuel injection timing once becomes the second target fuel injection timing, the EGR gas amount in the cylinder can be set to the second target EGR gas amount or an amount in the vicinity thereof. In addition, the timing when the fuel injection timing becomes the first target fuel injection timing and the timing when the EGR gas amount in the cylinder becomes the first target EGR gas amount or an amount in the vicinity thereof can be synchronized. In addition, the fuel injection timing in the middle of the change to each target fuel injection timing can be set to a timing according to the actual amount of EGR gas in the cylinder.

  Therefore, according to the present invention, even when the operating state of the internal combustion engine returns to the original region during switching of the combustion mode, the amount of EGR gas in the cylinder is excessive or insufficient with respect to the fuel injection timing. While suppressing this, the combustion mode can be returned to the combustion mode in the original region. Thus, premature ignition and misfire can be suppressed.

  In the present invention, when the first region is the normal combustion region and the second region is the premixed combustion region, the region where the engine load of the internal combustion engine is higher than the predetermined load is defined as the first region, and the engine load is less than the predetermined load. A certain area may be the second area. In this case, the predetermined load is set to a value lower than the premix combustion upper limit load that is the upper limit value of the engine load of the internal combustion engine capable of performing premix combustion.

  In the present invention, in the above case, the engine load of the internal combustion engine is changed during the switching of the combustion mode toward the premixed combustion because the operating state of the internal combustion engine has shifted from the first region to the second region. Even when the operating state of the internal combustion engine shifts from the second region to the first region again, the EGR gas amount in the cylinder is once changed to the target EGR gas amount in the premixed combustion. The fuel injection timing is once changed in a predetermined pattern up to the target fuel injection timing in the premixed combustion.

  In other words, in the present invention, even when the engine load of the internal combustion engine becomes higher than the predetermined load, switching to the premixed combustion in the combustion mode is continued. However, if the engine load of the internal combustion engine further increases during the switching and becomes higher than the premix combustion upper limit load, the fuel injection amount becomes excessive with respect to the fuel injection timing at this time, and premature ignition may occur. is there.

  Therefore, in the above case, when the operating state of the internal combustion engine shifts again from the second region to the first region while switching the combustion mode toward premixed combustion, the amount of EGR gas in the cylinder is Fuel injection is performed so that the engine load of the internal combustion engine does not become higher than the premixed combustion upper limit load until the target EGR gas amount in the premixed combustion or an amount in the vicinity thereof and the fuel injection timing reaches the target fuel injection timing in the premixed combustion. The amount of fuel injection from the valve may be controlled.

  According to this, it is possible to suppress an excessive increase in the fuel injection amount with respect to the fuel injection timing during switching of the combustion mode toward the premixed combustion. Accordingly, it is possible to suppress the occurrence of premature ignition, thereby suppressing the exhaust emission and the deterioration of combustion noise.

  In the above case, if the operating state of the internal combustion engine shifts again from the second region to the first region while the combustion mode is switched to the premixed combustion, the amount of EGR gas in the cylinder is increased. The increase in the fuel injection amount from the fuel injection valve may be prohibited until the target EGR gas amount in the mixed combustion or an amount in the vicinity thereof and the fuel injection timing reaches the target fuel injection timing in the premixed combustion.

  According to this, the engine load of the internal combustion engine is predicted before the EGR gas amount in the cylinder becomes the target EGR gas amount in the premixed combustion or an amount close thereto and the fuel injection timing becomes the target fuel injection timing in the premixed combustion. It can suppress becoming higher than a mixed combustion upper limit load.

  Further, in the above case, when the operating state of the internal combustion engine shifts again from the second region to the first region while switching the combustion mode toward the premixed combustion, the amount of EGR gas in the cylinder Until the fuel injection timing reaches the target fuel injection timing in the premixed combustion, and the engine load of the internal combustion engine does not become higher than the premixed combustion upper limit load. The increase rate of the fuel injection amount from the injection valve may be limited.

  According to this, the engine load of the internal combustion engine is predicted before the EGR gas amount in the cylinder becomes the target EGR gas amount in the premixed combustion or an amount close thereto and the fuel injection timing becomes the target fuel injection timing in the premixed combustion. It is possible to suppress the increase from exceeding the mixed combustion upper limit load, and even during this time, the engine load of the internal combustion engine can be increased to some extent.

  In the present invention, when the first region is a normal combustion region and the second region is a premixed combustion region, a region where the engine speed of the internal combustion engine is higher than a predetermined upper limit engine speed is defined as the first region, and the engine speed is A region that is equal to or lower than the predetermined upper limit rotational speed may be set as the second region. In this case, the predetermined upper limit rotational speed is set to a value lower than the premixed combustion upper limit rotational speed that is the upper limit value of the engine rotational speed of the internal combustion engine capable of performing the premixed combustion.

  In the present invention, in the above-described case, the engine rotation of the internal combustion engine is switched during the switching of the combustion mode toward the premixed combustion because the operating state of the internal combustion engine has shifted from the first region to the second region. Even when the engine speed increases and becomes higher than the predetermined upper limit rotational speed, and the operating state of the internal combustion engine shifts again from the second region to the first region, the EGR gas amount in the cylinder is once changed to the target EGR in the premixed combustion. While changing to the gas amount, the fuel injection timing is once changed in a predetermined pattern up to the target fuel injection timing in the premixed combustion.

  That is, in the present invention, even when the engine speed of the internal combustion engine becomes higher than the predetermined upper limit speed, the switching to the premixed combustion in the combustion mode is continued. However, if the engine speed of the internal combustion engine further increases during the switching and becomes higher than the premix combustion upper limit engine speed, the engine speed becomes excessively high with respect to the fuel injection timing at this time, and premature ignition occurs. There is a fear.

  Therefore, in the above case, when the operation state of the internal combustion engine is shifted again from the second region to the first region while switching the combustion mode toward the premixed combustion, the EGR in the cylinder The engine speed of the internal combustion engine is higher than the premix combustion upper limit engine speed before the gas quantity reaches or near the target EGR gas quantity in the premixed combustion and the fuel injection timing reaches the target fuel injection timing in the premixed combustion. When this happens, fuel injection from the fuel injection valve may be stopped.

  According to this, it is possible to suppress the occurrence of premature ignition due to the engine speed becoming excessively high during switching of the combustion mode toward the premixed combustion. Therefore, it is possible to suppress the deterioration of exhaust emission and combustion noise.

  In the present invention, the first region is a normal combustion region, the second region is a premixed combustion region, and a region where the engine load of the internal combustion engine is higher than a predetermined upper limit rotational speed is defined as the first region, and the engine rotational speed is predetermined. A region that is equal to or lower than the upper limit rotational speed is set as the second region, and the predetermined upper limit rotational speed is a value lower than the premixed combustion upper limit rotational speed that is the upper limit value of the engine rotational speed of the internal combustion engine capable of performing premixed combustion And the engine speed of the internal combustion engine increases and the predetermined upper limit is being changed during the switching of the combustion mode because the operating state of the internal combustion engine has shifted from the first region to the second region. When the engine speed becomes higher than the rotational speed and the operating state shifts again from the second region to the first region, the EGR gas amount in the cylinder becomes the target EGR gas amount in the premixed combustion or an amount in the vicinity thereof, and the fuel injection timing is Target combustion in mixed combustion Until the injection timing may be the engine speed of the internal combustion engine controls the fuel injection amount from the fuel injection valve so as not to become higher than the premixed combustion limit speed.

According to this, it is possible to suppress the engine speed from becoming excessively high with respect to the fuel injection timing while switching the combustion mode toward premixed combustion. In addition, a rapid change in the engine speed can be suppressed by suppressing an excessive increase in the engine speed without stopping the fuel injection. Accordingly, it is possible to suppress the occurrence of premature ignition while suppressing the deterioration of drivability.

  In the above case, if the operating state of the internal combustion engine shifts again from the second region to the first region while the combustion mode is switched to the premixed combustion, the amount of EGR gas in the cylinder is increased. Until the fuel injection timing reaches the target fuel injection timing in the premixed combustion, the engine speed of the internal combustion engine is higher than the predetermined upper limit speed, and the premixed combustion upper limit speed is reached. The fuel injection amount from the fuel injection valve may be limited so as to be maintained at a lower predetermined rotational speed.

  According to this, it is possible to suppress an excessive increase in the engine speed during the switching of the combustion mode toward the premixed combustion without stopping the fuel injection.

  In the present invention, when the first region is a normal combustion region and the second region is a premixed combustion region, a region where the engine speed of the internal combustion engine is lower than a predetermined lower limit rotational speed is defined as the first region, and the engine speed is A region that is equal to or greater than the predetermined lower limit rotational speed may be set as the second region. In this case, the predetermined lower limit rotational speed is set to a value higher than the premixed combustion lower limit rotational speed that is the lower limit value of the engine rotational speed of the internal combustion engine capable of performing premixed combustion.

  In the present invention, in the above-described case, the engine rotation of the internal combustion engine is switched during the switching of the combustion mode toward the premixed combustion because the operating state of the internal combustion engine has shifted from the first region to the second region. Even when the engine speed decreases and becomes lower than the predetermined lower limit rotational speed, and the operating state of the internal combustion engine shifts again from the second region to the first region, the EGR gas amount in the cylinder is once changed to the target EGR in the premixed combustion. While changing to the gas amount, the fuel injection timing is once changed in a predetermined pattern up to the target fuel injection timing in the premixed combustion.

  That is, in the present invention, even when the engine speed of the internal combustion engine becomes lower than the predetermined lower limit speed, switching to the premixed combustion in the combustion mode is continued. However, if the engine speed of the internal combustion engine further decreases during the switching and becomes lower than the premix combustion lower limit engine speed, the engine speed becomes excessively lower than the fuel injection timing at this time, and misfire may occur. is there.

  Therefore, in the above case, when the operation state of the internal combustion engine is shifted again from the second region to the first region while switching the combustion mode toward the premixed combustion, the EGR in the cylinder The engine speed of the internal combustion engine is lower than the premixed combustion lower limit rotational speed before the gas amount becomes the target EGR gas amount in the premixed combustion or an amount close thereto and the fuel injection timing becomes the target fuel injection timing in the premixed combustion. When this happens, fuel injection from the fuel injection valve may be stopped.

  According to this, it is possible to suppress the occurrence of misfire due to an excessively low engine speed during switching of the combustion mode toward premixed combustion.

In the present invention, the first region is the normal combustion region, the second region is the premixed combustion region, and the region where the engine speed of the internal combustion engine is lower than the predetermined lower limit rotational speed is defined as the first region, and the engine speed is The region that is equal to or higher than the predetermined lower limit rotational speed is set as the second region, and the predetermined lower limit rotational speed is higher than the premixed combustion lower limit rotational speed that is the lower limit value of the engine speed of the internal combustion engine capable of performing premixed combustion. In this case, the premix lower limit rotational speed may be set to a lower value as the engine load of the internal combustion engine is lower. In such a case, while the operation state of the internal combustion engine has shifted from the first region to the second region and the combustion mode is being switched, the engine speed of the internal combustion engine is reduced to a predetermined value. If the engine speed is lower than the lower limit speed and the operating state shifts again from the second region to the first region, the EG in the cylinder
Until the R gas amount becomes the target EGR gas amount in the premixed combustion or an amount close thereto and the fuel injection timing becomes the target fuel injection timing in the premixed combustion, the engine speed of the internal combustion engine is higher than the premixed combustion lower limit rotational speed. The fuel injection amount from the fuel injection valve may be limited so as not to decrease.

  By limiting the fuel injection amount, the engine load of the internal combustion engine can be reduced. And in the above, when the engine load of the internal combustion engine decreases, the premixed combustion rotational speed decreases. Therefore, even when the engine speed of the internal combustion engine further decreases from the predetermined lower limit speed, the engine speed of the internal combustion engine is controlled so as not to become lower than the premixed combustion lower limit speed by limiting the fuel injection amount. I can do it.

  According to the above, it is possible to suppress the engine speed from becoming excessively low with respect to the fuel injection timing while switching the combustion mode toward premixed combustion. In addition, a rapid change in the engine speed can be suppressed by suppressing an excessive decrease in the engine speed without stopping the fuel injection. Therefore, the occurrence of misfire can be suppressed while the deterioration of drivability is suppressed.

  In the second aspect of the present invention, when the operating state of the internal combustion engine shifts again from the second region to the first region while switching the combustion mode in the internal combustion engine from the first combustion mode to the second combustion mode, EGR The gas amount control means is brought into a state corresponding to the first combustion mode, and the change of the fuel injection timing to the first target fuel injection timing is started. The fuel injection timing is changed to the first target fuel injection timing over a period of time from the start of switching the combustion mode to the second combustion mode until the operating state of the internal combustion engine shifts to the first region again. Change gradually.

More specifically, the combustion switching control system for an internal combustion engine according to the second invention is:
An EGR passage communicating the exhaust system and the intake system of the compression ignition internal combustion engine;
EGR gas amount control means for controlling the flow rate of EGR gas in the EGR passage,
An exhaust gas recirculation device for introducing a part of the exhaust gas discharged from the compression ignition internal combustion engine into the intake system as EGR gas;
Command means for giving a command to the exhaust gas recirculation device to change the EGR gas amount in the cylinder by controlling the EGR gas amount control means;
A fuel injection valve for injecting fuel into a cylinder of the compression ignition internal combustion engine;
The operation state of the compression ignition internal combustion engine belongs to a premixed combustion region in which premixed combustion is performed in which premixed gas is formed by injecting fuel from the fuel injection valve at a time earlier than the time near the top dead center of the compression stroke. Or a determination means for determining whether it belongs to a normal combustion region in which normal combustion is performed by injecting fuel from the fuel injection valve at a time near the top dead center of the compression stroke,
Either one of the premixed combustion region and the normal combustion region is a first region and the other is a second region,
When it is determined by the determination means that the operating state of the compression ignition internal combustion engine has shifted from the first region to the second region, the EGR gas amount control means determines the EGR gas amount in the cylinder in the first region. The target EGR gas amount in the combustion mode is changed to the target EGR gas amount in the combustion mode in the second region, and the fuel injection timing from the fuel injection valve is changed from the target fuel injection timing in the combustion mode in the first region to the second time. The combustion mode is switched by gradually changing the target fuel injection timing in the combustion mode in the region over the first predetermined time,
When it is determined by the determination means that the operation state of the compression ignition internal combustion engine has shifted from the second region to the first region, the EGR gas amount control means burns the EGR gas amount in the cylinder in the second region. The target EGR gas amount in the first region is changed to the target EGR gas amount in the combustion mode in the first region, and the fuel injection timing from the fuel injection valve is changed from the target fuel injection timing in the combustion mode in the second region to the first region. In the combustion switching control system for a compression ignition internal combustion engine that switches the combustion mode by gradually changing the target fuel injection timing in the combustion mode at a second over a predetermined time,
While the operation state of the compression ignition internal combustion engine has shifted from the first region to the second region and the combustion mode is being switched, the operation state of the compression ignition internal combustion engine is changed to the second region by the determination means. From the command means to change the EGR gas amount in the cylinder to the target EGR gas amount in the combustion mode in the first region at the time when the determination is made again. A command is issued to the exhaust gas recirculation device, a change to the target fuel injection timing in the combustion mode in the first region of the fuel injection timing is started, and a switch to the combustion mode in the second region is started. A switching progress ratio that is a ratio of the time until the time when it is determined that the operating state of the compression ignition internal combustion engine has transitioned again to the first region with respect to the first predetermined time is calculated. The and changes over time which is calculated by multiplying the second predetermined time the fuel injection timing to the target fuel injection timing in the combustion mode in the first region.

  In the present invention, when the combustion mode in the internal combustion engine is switched from the first combustion mode to the second combustion mode, the fuel injection timing is gradually increased from the first target fuel injection timing to the second target fuel injection timing over a first predetermined time. Change to Here, the first predetermined time is a time taken to change the EGR gas amount in the cylinder from the first target EGR gas amount to the second target EGR gas amount or an amount in the vicinity thereof. On the other hand, when switching the combustion mode in the internal combustion engine from the second combustion mode to the first combustion mode, the fuel injection timing is gradually changed from the second target fuel injection timing to the first target fuel injection timing over a second predetermined time. To do. Here, the second predetermined time is a time taken to change the EGR gas amount in the cylinder from the second target EGR gas amount to the first target EGR gas amount or an amount in the vicinity thereof.

  As described above, the EGR gas flows into the cylinder through the EGR passage and the intake system. Therefore, it takes longer time to increase the EGR gas amount in the cylinder than to reduce the EGR gas amount in the cylinder. Therefore, when switching the combustion mode of the internal combustion engine, the time taken to change the EGR gas amount in the cylinder from the first target EGR gas amount to the second target EGR gas amount or an amount in the vicinity thereof, and the EGR in the cylinder This time is different from the time taken to change the gas amount from the first target EGR gas amount to the second target EGR gas amount or an amount in the vicinity thereof. The first predetermined time and the second predetermined time are determined in advance by experiments or the like.

  In the present invention, when the region to which the operating state of the internal combustion engine belongs is shifted from the command means to the exhaust gas recirculation device, an EGR gas amount change command is issued and the combustion mode is switched as described above. The fuel injection timing is gradually changed over time or a second predetermined time. As a result, when the combustion mode is switched, the EGR gas amount in the cylinder can be suppressed from being excessive or insufficient with respect to the fuel injection timing.

  In the above case, as in the first invention, the combustion mode is switched from the first combustion mode to the second combustion mode because the operating state of the internal combustion engine has shifted from the first region to the second region. In the meantime, the operating state of the internal combustion engine may shift again from the second region to the first region.

  In such a case, according to the present invention, when the operating state of the internal combustion engine shifts again from the second region to the first region, the command means exhausts the EGR gas amount in the cylinder to the first target EGR gas amount. An EGR gas amount change command is issued to the recirculation device. Thereby, the EGR gas amount control means is changed to a state corresponding to the first target EGR gas amount. Therefore, the EGR gas amount in the cylinder starts to change toward the first target EGR gas amount while changing toward the second target EGR gas amount.

At this time, the switching progress of the ratio of the time from the start of the switching of the combustion mode from the first combustion mode to the second combustion mode to the time when the operating state of the internal combustion engine shifts again to the first region with respect to the first predetermined time is progressed. A percentage. When an EGR gas amount change command is issued at the timing as described above to change the EGR gas amount in the cylinder to the first target EGR gas amount, the EGR gas amount in the cylinder after the EGR gas amount change command is issued. Is approximately the same as the time obtained by multiplying the second predetermined time by the switching progress rate.

  Therefore, in the present invention, when the operating state of the internal combustion engine shifts again from the second region to the first region, the change of the fuel injection timing to the first target fuel injection timing is started. Then, the fuel injection timing is gradually changed to the first target fuel injection timing over time obtained by multiplying the second predetermined time by the switching progress rate.

  Thereby, the timing when the fuel injection timing becomes the first target fuel injection timing and the timing when the EGR gas amount in the cylinder becomes the first target EGR gas amount or an amount in the vicinity thereof can be synchronized. Further, the fuel injection timing in the middle of the change can be set to a timing according to the EGR gas amount in the cylinder.

  Therefore, according to the present invention, even when the operating state of the internal combustion engine returns to the original region during switching of the combustion mode, the amount of EGR gas in the cylinder is excessive or insufficient with respect to the fuel injection timing. While suppressing this, the combustion mode can be returned to the combustion mode in the original region.

  Further, the combustion mode can be returned to the combustion mode in the original region more quickly after the operating state of the internal combustion engine returns to the original region during the switching of the combustion mode. Therefore, the occurrence of premature ignition and misfire can be further suppressed. In addition, it is possible to further suppress the deterioration of exhaust emission at the time of switching the combustion mode.

  In the present invention, as described above, the command means changes the EGR gas amount in the cylinder to the first target EGR gas amount when the operating state of the internal combustion engine shifts again from the second region to the first region. An EGR gas amount change command is issued to the exhaust gas recirculation device. However, in this case as well, there is a response delay from when the EGR gas amount change command is issued until the actual EGR gas amount in the cylinder starts to change toward the first target EGR gas amount. The response delay time at this time is defined as an EGR gas amount change delay time. After the EGR gas amount change command is issued at the above timing, the EGR gas amount in the cylinder is directed toward the first target EGR gas amount until the EGR gas amount change delay time elapses. Will change.

  Accordingly, in the present invention, the operating state of the internal combustion engine again shifts from the second region to the first region, and the command means changes the EGR gas amount in the cylinder to the first target EGR gas amount from the command means to the exhaust gas recirculation device. The change of the fuel injection timing to the first target fuel injection timing may be started when the EGR gas amount change delay time elapses from the time when the EGR gas amount change command is issued. The EGR gas amount change delay time at this time is a value that changes according to the operating state of the internal combustion engine, and is determined in advance by experiments or the like.

According to this, from when the EGR gas amount change command is issued from the command means to change the EGR gas amount in the cylinder to the first target EGR gas amount, until the EGR gas amount change delay time elapses, The change of the fuel injection timing toward the second target fuel injection timing is continued. Therefore, the fuel injection timing during the elapse of the EGR gas amount change delay time can be set to a time corresponding to the actual EGR gas amount in the cylinder. Further, it is possible to synchronize the time when the EGR gas amount in the cylinder actually starts to change toward the first target EGR gas amount and the time when the fuel injection timing starts to change toward the first target fuel injection timing. . Furthermore, the timing when the fuel injection timing becomes the first target fuel injection timing and the timing when the EGR gas amount in the cylinder becomes the first target EGR gas amount or an amount in the vicinity thereof can be synchronized more accurately.

  Therefore, when the operating state of the internal combustion engine returns to the original region during switching of the combustion mode, the EGR gas amount in the cylinder is excessively or insufficiently suppressed with respect to the fuel injection timing, and more The combustion mode can be quickly returned to the combustion mode in the original region.

  In the present invention, from the point in time when the EGR gas amount change command is issued from the command means to the exhaust gas recirculation device so as to change the EGR gas amount in the cylinder to the first target EGR gas amount, Until the injection timing maintenance time, which is a long time, elapses, the fuel injection timing at the time when it is determined that the operating state of the internal combustion engine has shifted to the first region again is maintained. The change toward the target fuel injection timing may be started.

  The EGR gas amount change delay time can be determined in advance as a value corresponding to the operating state of the internal combustion engine. However, the EGR gas amount change delay time tends to vary due to the influence of intake pressure, exhaust pressure, and the like. Therefore, when the predetermined EGR gas amount change delay time has elapsed from the time when the command means changes the EGR gas amount in the cylinder to the first target EGR gas amount, Even when the change of the injection timing toward the first target fuel injection timing is started, the ERG gas amount in the cylinder that has changed toward the second target EGR gas amount becomes the first target EGR gas amount. It is possible to accurately synchronize the timing at which the fuel injection timing starts to change toward the second target fuel injection timing and the timing at which the fuel injection timing that has been changed toward the second target fuel injection timing starts to change toward the first target fuel injection timing. It can be difficult.

  Therefore, as described above, during the period from when the EGR gas amount change command is issued to change the EGR gas amount in the cylinder to the first target EGR gas amount until the injection timing maintenance time elapses, The fuel injection timing at the time when it is determined that the operating state has shifted to the first region again is maintained. Then, the change of the fuel injection timing toward the first target fuel injection timing is started after the injection timing maintenance time has elapsed.

  According to this, when the operating state of the internal combustion engine returns to the original region during the switching of the combustion mode, even if the EGR gas amount change delay time varies, the fuel injection timing is set in the actual cylinder. It is possible to set a time corresponding to a certain amount of EGR gas. Therefore, the combustion mode can be quickly returned to the combustion mode in the original region while suppressing the EGR gas amount in the cylinder from being excessive or insufficient with respect to the fuel injection timing.

  The injection timing maintenance time here may be twice as long as the EGR gas amount change delay time. In addition, after the time when the EGR gas amount change delay time has elapsed after the operating state of the internal combustion engine shifts again to the first region, the EGR gas amount in the cylinder is the same as the operating state of the internal combustion engine. It is good also as time until it becomes the amount equivalent to the time of transfer to one area again.

  In the present invention, after the EGR gas amount change command is issued from the command means to the exhaust gas recirculation device to change the EGR gas amount in the cylinder to the first target EGR gas amount, from the time when the command is issued. When the EGR gas amount change delay time elapses, the fuel injection timing is changed so that the change rate of the fuel injection timing becomes zero, and then the change of the fuel injection timing shifts toward the first target fuel injection timing. It may be changed.

As described above, the EGR gas amount in the cylinder starts to change toward the first target EGR gas amount after the EGR gas amount change delay time has elapsed from the time when the command means changes the EGR gas amount change command. . At this time, after the EGR gas amount change command is issued, the rate of change of the EGR gas amount in the cylinder toward the second target EGR gas amount gradually decreases, and when the EGR gas amount change delay time has elapsed. The rate of change becomes zero. The rate of change gradually increases after the EGR gas amount in the cylinder starts to change toward the first target EGR gas amount. Here, the rate of change of the EGR gas amount is the amount of change of the EGR gas amount per unit time.

  Therefore, as described above, when the EGR gas amount change delay time has elapsed from when the EGR gas amount change command is issued from the command means, the rate of change of the fuel injection timing becomes zero, and then the change of the fuel injection timing The fuel injection timing is changed so that changes to change toward the first target fuel injection timing. Here, the rate of change of the fuel injection timing is the amount of change in the fuel injection timing per unit time.

  According to this, from when the EGR gas amount change command is issued from the command means to change the EGR gas amount in the cylinder to the first target EGR gas amount, until the EGR gas amount change delay time elapses, The fuel injection timing is changed toward the second target fuel injection timing, and the rate of change gradually decreases. Then, after the EGR gas amount change delay time has elapsed from when the EGR gas amount change command is issued from the command means, the fuel injection timing is changed toward the first target fuel injection timing, and the rate of change gradually increases. To rise.

  Therefore, the fuel injection timing from when the EGR gas amount change command is issued until the EGR gas amount in the cylinder becomes the first target EGR gas amount or an amount in the vicinity thereof corresponds to the actual EGR gas amount in the cylinder. It can be the time when. Therefore, it is possible to further suppress the EGR gas amount in the cylinder from becoming excessive or insufficient with respect to the fuel injection timing.

  According to a third aspect of the present invention, when the operating state of the internal combustion engine shifts from the first region to the second region, an EGR gas amount change command is issued from the command means to the exhaust gas recirculation device, and the command is issued Thereafter, the combustion mode is switched by starting the change of the fuel injection timing after a predetermined time has elapsed. Then, after the EGR gas amount change command is issued from the command means because the operation state of the internal combustion engine has shifted from the first region to the second region, the operation state of the internal combustion engine is When the transition is made again from the region to the first region, the state of the EGR gas amount control means is returned to the state corresponding to the first combustion mode, and the fuel injection timing is changed to the first target fuel injection timing at the time of transition again and thereafter. maintain.

More specifically, the combustion switching control system for a compression ignition internal combustion engine according to the present invention is:
An EGR passage communicating the exhaust system and the intake system of the compression ignition internal combustion engine;
EGR gas amount control means for controlling the flow rate of EGR gas in the EGR passage,
An exhaust gas recirculation device for introducing a part of the exhaust gas discharged from the compression ignition internal combustion engine into the intake system as EGR gas;
Command means for giving a command to the exhaust gas recirculation device to change the EGR gas amount in the cylinder by controlling the EGR gas amount control means;
A fuel injection valve for injecting fuel into a cylinder of the compression ignition internal combustion engine;
The operation state of the compression ignition internal combustion engine belongs to a premixed combustion region in which premixed combustion is performed in which premixed gas is formed by injecting fuel from the fuel injection valve at a time earlier than the time near the top dead center of the compression stroke. Or a determination means for determining whether it belongs to a normal combustion region in which normal combustion is performed by injecting fuel from the fuel injection valve at a time near the top dead center of the compression stroke,
Either one of the premixed combustion region and the normal combustion region is a first region and the other is a second region,
When it is determined by the determination means that the operation state of the compression ignition internal combustion engine has shifted from the first region to the second region, the EGR gas amount control means burns the EGR gas amount in the cylinder in the first region. A command is issued from the command means to the exhaust gas recirculation device to change the target EGR gas amount in the mode to the target EGR gas amount in the combustion mode in the second region, and after the command is issued, The fuel injection timing from the fuel injection valve is changed from the target fuel injection timing in the combustion mode in the first region after a predetermined response delay time, which is the time until the EGR gas amount in the cylinder actually starts to change, elapses. In the combustion switching control system for a compression ignition internal combustion engine that switches the combustion mode by changing to the target fuel injection timing in the combustion mode in the second region,
When the operating state of the compression ignition internal combustion engine has shifted from the first region to the second region, a command is issued from the command means to the exhaust gas recirculation device to change the EGR gas amount in the cylinder. If the determination means determines that the operation state of the compression ignition internal combustion engine has shifted from the second region to the first region before the predetermined response delay time elapses, the state of the EGR gas amount control means Is restored to the state corresponding to the target EGR gas amount in the combustion mode in the first region, and the fuel injection timing is maintained at the target fuel injection timing in the combustion mode in the first region at and after the determination is made. It is characterized by that.

  When the EGR gas amount change command is issued from the command means to the exhaust gas recirculation device by shifting the operation state of the internal combustion engine from the first region to the second region, the state of the EGR gas amount control means is changed to the second target EGR. It changes to the state corresponding to the amount of gas. However, as described above, it takes some time from when the EGR gas amount change command is issued until the EGR gas amount in the cylinder actually starts to change. This time is defined as a predetermined response delay time. The predetermined response delay time can be determined in advance by experiments or the like.

  In the present invention, when the operating state of the internal combustion engine shifts from the first region to the second region, the fuel injection timing is determined after a predetermined response delay time has elapsed after the EGR gas amount change command is issued from the command means. The change toward the second target fuel injection timing is started.

  In such a case, the internal combustion engine shifts from the first region to the second region, so that the internal combustion engine before the predetermined response delay time elapses after the command means issues the EGR gas amount change command. There are cases where the engine operating state shifts again from the second region to the first region. At this time, when the operating state of the internal combustion engine shifts again, the state of the EGR gas amount control means is returned to the state corresponding to the first target EGR gas amount.

  When the state of the EGR gas amount control means is controlled in this way, a predetermined response delay time after the EGR gas amount change command is issued from the command means when the operating state of the internal combustion engine shifts from the first region to the second region. The EGR gas amount in the cylinder does not become the second target EGR gas amount even when the time elapses and thereafter. Therefore, as in the normal fuel injection timing control according to the present invention, when the fuel injection timing is changed toward the second target fuel injection timing after a predetermined response delay time has elapsed since the EGR gas amount change command is issued, The amount of EGR gas in the cylinder becomes excessive or insufficient with respect to the fuel injection timing.

  Therefore, when the operating state of the internal combustion engine shifts again from the second region to the first region at the timing as described above, the operating state of the internal combustion engine shifts from the first region to the second region, so that the EGR gas from the command means The fuel injection timing is maintained at the first target fuel injection timing even after a predetermined response delay time has elapsed since the amount change command was issued.

  According to this, it is possible to prevent the EGR gas amount in the cylinder from becoming excessive or insufficient with respect to the fuel injection timing.

As described above, in the present invention, before the predetermined response delay time elapses after the EGR gas amount change command is issued from the command means by the operating state of the internal combustion engine shifting from the first region to the second region, When the operating state of the internal combustion engine shifts again from the second region to the first region, the state of the EGR gas amount control means corresponds to the first target EGR gas amount when the operating state of the internal combustion engine shifts again Return to. Even in such a case, while the operating state of the internal combustion engine belongs to the second region, the EGR gas amount control means is temporarily in a state corresponding to the second combustion mode.
Therefore, after the operating state of the internal combustion engine shifts to the first region again, that is, after the EGR gas amount control means is returned to the state corresponding to the first target EGR gas amount, the EGR gas amount in the cylinder temporarily changes. Therefore, it changes to the second target EGR gas amount side.

  The change in the EGR gas amount in the cylinder at this time is instructed to change the EGR gas amount in the cylinder to the second target EGR gas amount when the operating state of the internal combustion engine shifts from the first region to the second region. Starts when a predetermined response delay time elapses from when the EGR gas amount change command is issued. Further, the time during which the EGR gas amount in the cylinder changes to the second target EGR gas amount side corresponds to the time when the EGR gas amount changing means has been in a state corresponding to the second target EGR gas amount. Become.

  Therefore, in the present invention, after the operating state of the internal combustion engine shifts again to the first region, the EGR gas amount changes during a period in which the EGR gas amount in the cylinder temporarily changes to the second target EGR gas amount side. The fuel injection timing may be changed according to the above. That is, the fuel injection timing may be changed to the second target fuel injection timing side only during a period in which the EGR gas amount in the cylinder changes to the second target EGR gas amount side.

  As a result, the fuel injection timing can be made to correspond to the actual amount of EGR gas in the cylinder. Therefore, it is possible to further suppress the EGR gas amount in the cylinder from becoming excessive or insufficient with respect to the fuel injection timing.

  In the present invention, when the combustion mode of the internal combustion engine is normal combustion, the fuel injection executed at the timing near the top dead center of the compression stroke is set as the main fuel injection, and the sub fuel is injected at a timing before the main fuel injection by the fuel injection valve. You may perform injection. In this case, when the combustion mode of the internal combustion engine is premixed combustion, the auxiliary fuel injection is stopped.

  In such a case, the operating state of the internal combustion engine shifts from the premixed combustion region to the normal combustion region, so that the predetermined response delay time elapses after the EGR gas amount change command is issued from the command means. When the operating state of the internal combustion engine shifts again from the normal combustion region to the premixed combustion region, the stop of the auxiliary fuel injection may be continued at the time of transition again and thereafter.

  When sub fuel injection is executed when the main fuel injection timing is the target fuel injection timing during premixed combustion, bore flushing is likely to occur due to the fuel injected by the sub fuel injection. According to the above, even if the operating state of the internal combustion engine temporarily shifts to the normal combustion region, the auxiliary fuel injection is not executed. Thereby, it is possible to suppress the sub fuel injection from being executed when the main fuel injection timing is the target fuel injection timing at the time of the premixed combustion. Therefore, the occurrence of bore flushing can be suppressed.

  Further, after the operating state of the internal combustion engine shifts again from the normal combustion region to the premixed combustion region, the period during which the EGR gas amount in the cylinder changes to the target EGR gas amount side during normal combustion (that is, the EGR gas in the cylinder) Only when the main fuel injection timing is changed to the target fuel injection timing side during normal combustion (that is, the main fuel injection timing is retarded). If the auxiliary fuel injection is executed when the injection timing is changed, the ignition delay period may be shortened and the amount of smoke generated may increase. In such a case, the amount of smoke generated can be reduced by continuing to stop the auxiliary fuel injection as described above.

  In the above case, the predetermined response delay time elapses after the EGR gas amount change command is issued from the command means because the operating state of the internal combustion engine shifts from the normal combustion region to the premixed combustion region. If the operating state of the internal combustion engine has shifted again from the premixed combustion region to the normal combustion region before, execution of the auxiliary fuel injection may be continued at the time of the transition again and thereafter.

  If sub fuel injection is stopped when the main fuel injection timing is the target fuel injection timing for normal combustion, combustion in the cylinder becomes unstable and combustion noise worsens or misfires occur. There is a fear. According to the above, the auxiliary fuel injection is not stopped even when the operating state of the internal combustion engine temporarily shifts to the premixed combustion region. Thereby, it is possible to suppress the sub fuel injection from being stopped when the main fuel injection timing is the target fuel injection timing during normal combustion. For this reason, it is possible to prevent the combustion in the cylinder from becoming unstable.

  Further, after the operating state of the internal combustion engine shifts again from the premixed combustion region to the normal combustion region, the period during which the EGR gas amount in the cylinder changes to the target EGR gas amount side during premixed combustion (that is, EGR in the cylinder) When the main fuel injection timing is changed to the target fuel injection timing side during premixed combustion (that is, the main fuel injection timing is advanced) only during the period when the gas amount increases) If the sub fuel injection is stopped when the target fuel injection timing is changed to, the ignition delay period becomes longer and the combustion noise may deteriorate. In such a case, the deterioration of the combustion noise can be suppressed by continuing the execution of the auxiliary fuel injection as described above.

  According to the combustion switching control system for a compression ignition internal combustion engine according to the present invention, in an internal combustion engine that selects either premixed combustion or normal combustion according to an operating state, the internal combustion engine is switched during combustion mode switching. When the operating state returns to the original region, the combustion mode can be preferably returned to the combustion mode in the original region.

  Hereinafter, specific embodiments of a combustion switching control system for a compression ignition internal combustion engine according to the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine and its intake / exhaust system according to the present embodiment. The internal combustion engine 1 is a compression ignition internal combustion engine for driving a vehicle. A piston 3 is slidably provided in the cylinder 2 of the internal combustion engine 1. An intake port 4 and an exhaust port 5 are connected to the combustion chamber 11 in the upper part of the cylinder 2.

  The openings of the intake port 4 and the exhaust port 5 to the combustion chamber 11 are opened and closed by the intake valve 6 and the exhaust valve 7, respectively. The intake port 4 and the exhaust port 5 are connected to an intake passage 8 and an exhaust passage 9, respectively. The cylinder 2 is provided with a fuel injection valve 10 that directly injects fuel into the combustion chamber 11.

  The internal combustion engine 1 also includes an exhaust gas recirculation device 25 (hereinafter referred to as an EGR device 25) that introduces a portion of the exhaust gas flowing through the exhaust passage 9 into the intake passage 8 as EGR gas. The EGR device 25 has an EGR passage 12 that connects the intake passage 8 and the exhaust passage 9. The EGR passage 12 is provided with an EGR valve 13 that controls the flow rate of EGR gas and an actuator 14 that drives the EGR valve 13.

  The internal combustion engine 1 configured as described above is provided with an ECU 20 for controlling the internal combustion engine 1. A crank position sensor 23 that detects the crank angle of the internal combustion engine 1 and an accelerator opening sensor 24 that detects the accelerator opening of a vehicle on which the internal combustion engine 1 is mounted are connected to the ECU 20 via electrical wiring. These detected values are input to the ECU 20.

  The ECU 20 estimates the engine speed of the internal combustion engine 1 based on the detected value of the crank position sensor 23. Further, the ECU 20 estimates the engine load of the internal combustion engine 1 based on the detection value of the accelerator opening sensor 24.

  In addition, the fuel injection valve 10 and the actuator 14 are electrically connected to the ECU 20. These are controlled by the ECU 20.

<Combustion mode>
In the internal combustion engine 1 according to the present embodiment, either premixed combustion or normal combustion is selected according to the operating state. FIG. 2 is a diagram showing the relationship between the operating state of the internal combustion engine 1 and the combustion mode in the internal combustion engine 1. In FIG. 2, the horizontal axis represents the engine speed of the internal combustion engine 1, and the vertical axis represents the engine load of the internal combustion engine 1. In FIG. 2, a region R1 surrounded by a solid line L1 is a premixed combustion region in which premixed combustion is performed. In FIG. 2, a region R2 other than the premixed combustion region R1 is a normal combustion region where normal combustion is performed. In FIG. 2, a region surrounded by a one-dotted line L2 represents a region where premixed combustion is possible. That is, the upper limit load of the premixed combustion region R1 is lower than the upper limit load capable of premixed combustion. On the high rotation speed side, the upper limit rotation speed of the premix combustion region R1 is lower than the upper limit rotation speed capable of premix combustion, and on the low rotation speed side, the lower limit rotation of the premix combustion region R1. The number is a value lower than the lower limit rotational speed at which premixed combustion is possible.

  As described above, when the operating state of the internal combustion engine 1 is in the premixed combustion region R1, premixed combustion is performed so as to suppress the generation of NOx and smoke. However, if the load of the internal combustion engine 1 increases and the amount of fuel injection increases, or if the rotational speed of the internal combustion engine 1 increases and the time required for one combustion cycle is shortened, the premix combustion is performed in advance. When an air-fuel mixture is formed, pre-ignition tends to occur. Therefore, when the operating state of the internal combustion engine 1 shifts from the premixed combustion region R1 to the normal combustion region R2, the combustion mode in the internal combustion engine 1 is switched from premixed combustion to normal combustion. Further, when the operating state of the internal combustion engine 1 shifts from the normal combustion region R2 to the premixed combustion region R1, the combustion mode in the internal combustion engine 1 is switched from normal combustion to premixed combustion.

  Normal combustion is performed by injecting fuel from the fuel injection valve 10 at a time near the top dead center of the compression stroke. Further, in the premixed combustion, fuel is injected from the fuel injection valve 10 at a time earlier than the time near the top dead center of the compression stroke, so that a premixed gas is formed in the combustion chamber 11 and the premixed gas is burned. It is done by being offered. Thus, the target fuel injection timing is determined in each combustion mode, and the combustion mode is switched by changing the fuel injection timing. Hereinafter, the target combustion injection timing during normal combustion (timing near the top dead center of the compression stroke) is referred to as normal combustion injection timing, and the target fuel injection timing during premixed combustion (prior to the timing near the top dead center of the compression stroke) Time) is referred to as premixed combustion injection timing.

  In this embodiment, part of the exhaust gas flowing through the exhaust passage 9 is introduced into the intake passage 8 by the EGR device 25 as EGR gas. This EGR gas flows into the cylinder 2 together with the intake air. When premixed combustion is performed in the internal combustion engine 1, it is necessary to supply more EGR gas into the cylinder 2 than during normal combustion in order to suppress premature ignition. Therefore, different target EGR gas amounts are determined according to the respective combustion modes, and the target EGR gas amount during premixed combustion is larger than the target EGR gas amount during normal combustion. Hereinafter, the target EGR gas amount during normal combustion is referred to as normal combustion EGR gas amount, and the target EGR gas amount during premixed combustion is referred to as premixed combustion EGR gas amount.

The amount of EGR gas is changed by changing the opening degree of the EGR valve 13. When changing the EGR gas amount, an EGR gas amount change command is issued from the ECU 20 to the actuator 14. Then, the EGR valve 13 is driven by the actuator 14 to change the opening degree of the EGR valve 13. At this time, the opening degree of the EGR valve 13 is changed to a target opening degree corresponding to the target EGR gas amount in each combustion mode. Hereinafter, the target opening of the EGR valve 13 corresponding to the normal combustion EGR gas amount is referred to as normal combustion opening, and the target opening of the EGR valve 13 corresponding to the premixed combustion EGR gas amount is referred to as premix combustion opening.

  Here, one of the premixed combustion region R1 and the normal combustion region R2 is set as the first region, and the other is set as the second region. Further, the combustion mode in the first region is the first combustion mode, and the combustion mode in the second region is the second combustion mode.

  As described above, when the operating state of the internal combustion engine 1 shifts from the first region to the second region, the fuel injection timing is changed to the target fuel injection timing in the second combustion mode in order to switch the combustion mode, It is necessary to change the EGR gas amount to the target EGR gas amount in the second combustion mode.

  However, although it is possible to change the fuel injection timing immediately, after the EGR gas amount change command is issued from the ECU 20 to the EGR valve 13, until the EGR gas amount in the cylinder 2 actually starts to change. Has a response delay. In addition, it takes some time to reach the target EGR gas amount in the second combustion mode after the EGR gas amount in the cylinder 2 starts to change.

<Combustion switching control>
For these reasons, when the amount of EGR gas in the cylinder 2 is excessive or insufficient with respect to the combustion mode in the internal combustion engine 1, misfire or premature ignition may occur. Therefore, in this embodiment, when the operating state of the internal combustion engine 1 shifts from the first region to the second region, combustion switching control described below is performed in order to suppress the occurrence of misfire and premature ignition. .

  Here, taking as an example a case where the operating state of the internal combustion engine 1 has shifted from the premixed combustion region R1 to the normal combustion region R2, the combustion switching control according to this embodiment will be described based on the time chart shown in FIG.

  (A) in FIG. 3 shows the time when the operating state of the internal combustion engine 1 has shifted from the premixed combustion region R1 to the normal combustion region R2. When the operating state of the internal combustion engine 1 shifts, the ECU 20 changes the EGR gas amount in the cylinder 2 from the premixed combustion EGR gas amount Qh to the normal combustion EGR gas amount Qd at time (a) from the ECU 20 to the actuator 14. An EGR gas amount change command is issued. That is, the ECU 20 issues a command to the actuator 14 to change the opening of the EGR valve 13 from the premixed combustion opening Vh to the normal combustion opening Vd.

  At this time, after the EGR gas amount change command is issued from the ECU 20 at the time point (a), there is a response delay until the opening of the EGR valve 13 actually reaches the normal combustion opening Vd. Hereinafter, the response delay time at this time is referred to as a valve response delay time Δtv.

  Further, since the EGR gas flows into the cylinder 2 after passing through the EGR passage 12 and the intake passage 8, the intake air whose EGR gas content has decreased after the opening degree of the EGR valve 13 becomes the normal combustion opening degree Vd. It takes some time to start flowing into the cylinder 2. That is, there is a response delay from when the opening degree of the EGR valve 13 becomes the normal combustion opening degree Vd until the EGR gas amount in the cylinder 2 actually starts to decrease.

For these reasons, after the EGR gas amount change command is issued from the ECU 20 to the actuator 14 at the time point (a), the first predetermined response delay time M12d has elapsed ((b in FIG. 3).
) The EGR gas amount in the cylinder 2 starts to decrease.

  Therefore, in the present embodiment, the normal combustion injection timing is changed from the premixed combustion injection timing of the fuel injection timing when the first predetermined response delay time M12d has elapsed since the EGR gas amount change command is issued from the ECU 20 to the actuator 14. Start changing to.

  In the present embodiment, the first predetermined response delay time M12d can be obtained in advance by experiments or the like. The first predetermined response delay time M12d corresponds to the respective operation states when the operation state of the internal combustion engine 1 belongs to the premixed combustion region R1 and when the operation state of the internal combustion engine 1 belongs to the normal combustion region R2. Determined.

  Further, the valve response delay time Δtv depends on the structure of the EGR valve 13 and the like. On the other hand, after the opening degree of the EGR valve 13 reaches the normal combustion opening degree Vd, the intake stroke and the exhaust stroke are repeated, so that the path volume from the EGR valve 13 to the cylinder 2, that is, along the flow of EGR gas. Thus, if the amount of gas equivalent to the volume of the EGR passage 12 downstream of the EGR valve 13 and the intake passage 8 downstream of the connection portion with the EGR passage 12 and the volume of the intake port 4 are replaced, the amount of EGR gas in the cylinder 2 is changed. It begins to decrease. Therefore, the response delay from when the opening degree of the EGR valve 13 becomes the normal combustion opening degree Vd to when the EGR gas amount in the cylinder 2 actually starts to change depends on the number of strokes. Hereinafter, the number of strokes corresponding to this response delay time is referred to as a first predetermined number of strokes. The valve response delay time Δtv and the first predetermined stroke number can be obtained by experiments or the like. Therefore, these may be determined separately in advance, and the sum thereof may be used as the first predetermined response delay time M12d.

  Further, the EGR gas flowing into the intake passage 8 from the EGR passage 12 diffuses in the intake passage 8 and the intake port 4 before reaching the cylinder 2. Therefore, even if the intake air whose EGR gas content has decreased at the time point (b) reaches the cylinder 2 and the EGR gas amount in the cylinder 2 starts to decrease, the EGR gas amount in the cylinder 2 immediately becomes normal combustion EGR. It does not become the gas amount Qd, but gradually changes toward the normal combustion EGR gas amount Qd.

  For this reason, the EGR gas amount in the cylinder 2 starts to decrease at the time point (b) until the EGR gas amount in the cylinder 2 reaches an amount in the vicinity of the normal combustion EGR gas amount Qd (in FIG. 3C). The first predetermined time M12h elapses until (time).

  Therefore, in this embodiment, the change of the fuel injection timing is started at the time (b), and the fuel injection timing is changed to the normal combustion injection timing Itd when the first predetermined time M12h has elapsed from the time (b). Thus, the fuel injection timing from the fuel injection valve 10 is gradually changed.

  In the present embodiment, the first predetermined time M12h is a time determined in advance by experiments or the like. The first predetermined time M12h is determined according to the operating state of the internal combustion engine 1 in the normal combustion region R2. Further, the amount in the vicinity of the normal combustion EGR gas amount Qd according to the present embodiment is an amount that can be determined that the amount of EGR gas in the cylinder 2 is not excessive even when the fuel injection timing becomes the normal combustion injection timing Itd. . The first predetermined time M12h may be a time from when the EGR gas amount in the cylinder 2 starts decreasing at the time point (b) until the normal combustion EGR gas amount Qd is reached.

  Further, during the first predetermined time M12h, the EGR in the cylinder 2 is the same as the response delay from when the opening of the EGR valve 13 becomes the normal combustion opening Vd until the EGR gas amount in the cylinder 2 actually starts to change. Depends on the number of strokes since the gas volume began to change. Here, the number of strokes corresponding to this response delay time is referred to as a second predetermined number of strokes. The second predetermined number of strokes can be obtained by experiments or the like. Therefore, the first predetermined time may be set as the second predetermined stroke number.

  At the time (c) when the first predetermined time M12h has elapsed from the time (b), the fuel injection timing becomes the normal combustion injection timing Itd, and the switching to the normal combustion in the combustion mode is completed, and the inside of the cylinder 2 The EGR gas amount becomes the normal combustion EGR gas amount Qd.

  At the time of switching from premixed combustion to normal combustion, by controlling the change start timing of the combustion injection timing as described above, the change start timing of the fuel injection timing and the time when the EGR gas amount in the cylinder 2 starts to decrease Can be synchronized. Further, by gradually changing the fuel injection timing as described above, the time when the fuel injection timing becomes the normal combustion injection timing Itd and the amount of EGR gas in the cylinder 2 become an amount near the normal combustion EGR gas amount Qd. The time can be synchronized.

  As a result, when the combustion mode in the internal combustion engine 1 is switched from premixed combustion to normal combustion, it is possible to suppress an excessive amount of EGR gas in the cylinder 2 with respect to the fuel injection timing.

  In the present embodiment, the combustion switching control is performed even when the combustion mode is switched from normal combustion to premixed combustion when the operating state of the internal combustion engine 1 shifts from the normal combustion region R2 to the premixed combustion region R1. Apply.

  That is, the EGR gas amount in the cylinder 2 actually increases after a command is issued from the ECU 20 to the actuator 14 to change the opening degree of the EGR valve 13 from the normal combustion opening degree Vd to the premixed combustion opening degree Vh. When the second predetermined response delay time, which is the time until the start of the operation, has elapsed, the change of the fuel injection timing from the normal combustion injection timing to the premixed combustion injection timing is started.

  In addition, after the start of the change of the fuel injection timing, the injection timing is premixed when a second predetermined time, which is the time until the EGR gas amount in the cylinder 2 reaches an amount in the vicinity of the premixed combustion EGR gas amount Qh, has elapsed. The fuel injection timing from the fuel injection valve 10 is gradually changed so that the combustion injection timing Ith is reached. The amount in the vicinity of the premixed combustion EGR gas amount Qh according to the present embodiment is an amount by which it can be determined that the EGR gas amount in the cylinder 2 is not insufficient even when the fuel injection timing becomes the premixed combustion injection timing Ith. It is. Here, the second predetermined time may be a time from when the EGR gas amount in the cylinder 2 starts to increase until the premixed combustion EGR gas amount Qh is reached.

  As a result, when the combustion mode in the internal combustion engine 1 is switched from normal combustion to premixed combustion, it is possible to suppress a shortage of the EGR gas amount in the cylinder 2 with respect to the fuel injection timing.

  Note that the second predetermined response delay time and the second predetermined time can be obtained in advance by experiments or the like, like the first predetermined response delay time M12d and the first predetermined time M12h. As described above, the EGR gas flows into the cylinder 2 through the EGR passage 12 and the intake passage 8. Therefore, it takes longer time to increase the amount of EGR gas in the cylinder 2 than to decrease the amount of EGR gas in the cylinder 2. Therefore, the second predetermined time is longer than the first predetermined time M12h.

  In the present embodiment, the change pattern of the fuel injection timing in the combustion switching control corresponds to the predetermined pattern according to the present invention.

<Re-switching during combustion mode switching>
When the operating state of the internal combustion engine 1 shifts from the first region to the second region, the combustion mode is switched when the combustion mode is switched from the first combustion mode to the second combustion mode by the combustion switching control as described above. In the meantime, the operating state of the internal combustion engine 1 may shift again from the second region to the first region.

  For example, the operating state of the internal combustion engine 1 is shifted from the premixed combustion region R1 to the normal combustion region R2, and the fuel injection timing is changed in order to switch the combustion mode from premixed combustion to normal combustion (in FIG. (b) to (c)), the operating state of the internal combustion engine 1 may return from the normal combustion region R2 to the premixed combustion region R1.

  At this time, when the operating state of the internal combustion engine 1 returns to the premixed combustion region R1, an EGR gas amount change command is issued again from the ECU 20 to the actuator 14, and the normal fuel injection timing in the combustion switching control is also issued. The relationship between the amount of EGR gas in the cylinder 2 and the fuel injection timing when the change from the combustion injection timing Itd to the premixed combustion injection timing Ith is started will be described based on the timing chart shown in FIG.

  In FIG. 4, the operating state of the internal combustion engine 1 shifts from the premixed combustion region R1 to the normal combustion region R2 at the time point (a), and the normal state from the premixed combustion injection timing Ith of the fuel injection timing at the time point (b). The change toward the combustion injection timing Itd is started. Then, at the time point (d) before the fuel injection timing reaches the normal combustion injection timing Itd, the operating state of the internal combustion engine 1 shifts again from the normal combustion region R2 to the premixed combustion region R1.

  At this time, when an EGR gas amount change command is issued from the ECU 20 to the actuator 14 to change the opening degree of the EGR valve 13 from the normal combustion opening degree Vd to the premixed combustion opening degree Vh at the time point (d), After the valve response delay time Δtv elapses, the opening degree of the EGR valve 13 becomes the premixed combustion opening degree Vh. Thereafter, the EGR gas amount in the cylinder 2 starts to change toward the premixed combustion EGR gas amount Qh while changing toward the normal combustion EGR gas amount Qd.

  Further, at the time of (d), when the change of the fuel injection timing similar to the switching from the normal combustion to the premixed combustion in the combustion switching control is started, the fuel injection timing gradually moves toward the normal combustion injection timing Itd. In the middle of the change, it is immediately changed to the normal combustion injection timing Itd. Then, the change of the fuel injection timing from the time when the second predetermined response delay time M21d has elapsed from the time of (d) (time of (e)) toward the premixed combustion injection timing Ith is started. The fuel injection timing returns to the premixed combustion injection timing Ith when the second predetermined time M21h has elapsed from the time (time (f)).

  In such a case, at the time point (d), the fuel injection timing is temporarily set to the normal combustion injection timing Itd while the actual EGR gas amount in the cylinder 2 is not in the vicinity of the premixed combustion EGR gas amount Qh. Will be. Further, the fuel injection timing from the normal combustion injection timing Itd to the premixed combustion injection timing Ith (between (d) and (f)) corresponds to the actual change in the EGR gas amount in the cylinder 2. It will be out of time.

  This is because the operating state of the internal combustion engine 1 shifts from the normal combustion region R2 to the premixed combustion region R1 and the fuel injection timing is changed in order to switch the combustion mode from normal combustion to premixed combustion. This is the same even when the operating state of the engine returns from the premixed combustion region R1 to the normal combustion region R2.

  In such a case, there is a possibility that misfire or premature ignition may occur due to an excessive or insufficient EGR gas amount in the cylinder 2 with respect to the fuel injection timing.

Therefore, in the present embodiment, the operation state of the internal combustion engine 1 is changed to the second region while the combustion mode is being switched because the operation state of the internal combustion engine 1 has shifted from the first region to the second region. When shifting from the first region to the first region again, the combustion switching control during re-transition described below is performed to suppress the occurrence of misfire or premature ignition.

(Premixed combustion region → Normal combustion region → Premixed combustion region)
First, the operating state of the internal combustion engine 1 shifts from the premixed combustion region R1 to the normal combustion region R2, and the fuel injection timing is changed in order to switch the combustion mode from normal combustion to premixed combustion. The transition switching combustion switching control when the operating state returns from the normal combustion region R2 to the premixed combustion region R1 will be described based on the time chart shown in FIG.

  In FIG. 5, as in FIG. 4, the operating state of the internal combustion engine 1 shifts from the premixed combustion region R1 to the normal combustion region R2 at the time point (a), and the premixed combustion at the fuel injection timing at the time point (b). The change from the injection timing Ith to the normal combustion injection timing Itd is started. The operating state of the internal combustion engine 1 again shifts from the normal combustion region R2 to the premixed combustion region R1 at the time (d) before the fuel injection timing reaches the normal combustion injection timing Itd.

  At this time, in the re-shift combustion switching control according to the present embodiment, at the time of (d), the ECU 20 does not immediately issue an EGR gas amount change command to the actuator 14, and the opening degree of the EGR valve 13 is normally set. The combustion opening degree Vd is maintained. That is, the change of the EGR gas amount in the cylinder 2 to the normal combustion EGR gas amount Qd is continued. At the time (d), the fuel injection timing is not immediately changed to the normal combustion injection timing Itd, but at the time when the first predetermined time M12h has elapsed from the time (b), the fuel injection timing is normal combustion injection. The change of the combustion injection timing so as to become the timing Itd is continued.

  As a result, when the first predetermined time M12h has elapsed from the time point (b) (the time point (g)), the EGR gas amount in the cylinder 2 becomes an amount near the normal combustion EGR gas amount Qd, and the fuel injection timing is The normal combustion injection timing Itd is reached. Then, from the time point (g), normal combustion switching control when switching from normal combustion to premixed combustion is started.

  That is, at the time of (g), the ECU 20 changes the opening degree of the EGR valve 13 to the premixed combustion opening degree Vh so as to change the EGR gas amount in the cylinder 2 to the premixed combustion EGR gas quantity Qh. In response, an EGR gas amount change command is issued. Furthermore, the fuel injection timing is maintained at the normal combustion injection timing Itd from the time (g) to the time when the second response delay time M21d elapses (time (h)), and the fuel injection timing from the time (h). The change toward the premixed combustion injection timing Ith is started. Then, the fuel injection timing is gradually changed so that the premixed combustion injection timing Ith is reached when the second predetermined time M21h elapses from the time (h) (time (i)).

  According to the re-shift combustion switching control as described above, the EGR gas amount in the cylinder 2 can be set to an amount in the vicinity of the normal combustion EGR gas amount Qd when the fuel injection timing once becomes the normal combustion injection timing Itd. . Further, the timing when the fuel injection timing becomes the premixed combustion injection timing Ith and the timing when the EGR gas amount in the cylinder 2 becomes an amount in the vicinity of the premixed combustion EGR gas amount Qh can be synchronized. Further, the fuel injection timing in the middle of the change to each target fuel injection timing can be set to a timing according to the actual EGR gas amount in the cylinder 2.

(Normal combustion region → Premixed combustion region → Normal combustion region)
Next, while the operating state of the internal combustion engine 1 shifts from the normal combustion region R2 to the premixed combustion region R1, the fuel injection timing is changed in order to switch the combustion mode from premixed combustion to normal combustion. 6 will be described based on the time chart shown in FIG. 6 when the operating state of the engine is returned from the premixed combustion region R1 to the normal combustion region R2.

In FIG. 6, when the operating state of the internal combustion engine 1 shifts from the normal combustion region R2 to the premixed combustion region R1 at the time point (a) and the second predetermined response delay time M21d has elapsed from the time point (a). At a certain point (b), the fuel injection timing is changed from the normal combustion injection timing Itd to the premixed combustion injection timing Ith. Then, at the time (d) before the fuel injection timing reaches the premixed combustion injection timing Ith, the operating state of the internal combustion engine 1 shifts again from the premixed combustion region R1 to the normal combustion region R2.

  At this time, in the re-shift combustion switching control according to this embodiment, at the time of (d), the EGR gas amount change command is not immediately issued from the ECU 20 to the actuator 14 at the time point (d), and the EGR valve 13 is The opening is maintained at the premixed combustion opening Vh. That is, the change of the EGR gas amount in the cylinder 2 to the premixed combustion EGR gas amount Qh is continued. At the time (d), the fuel injection timing is not immediately changed to the premixed combustion injection timing Ith, but at the time when the second predetermined time M21h has elapsed from the time (b), the fuel injection timing is premixed. The change of the combustion injection timing is continued so as to become the combustion injection timing Ith.

  As a result, when the second predetermined time M21d elapses from the time point (b) (time point (g)), the EGR gas amount in the cylinder 2 becomes an amount in the vicinity of the premixed combustion EGR gas amount Qh, and the fuel injection timing Is the premixed combustion injection timing Ith. Then, from the time point (g), normal combustion switching control when switching from premixed combustion to normal combustion is started.

  That is, at the time of (g), the ECU 20 controls the actuator 14 to change the opening degree of the EGR valve 13 to the normal combustion opening degree Vd so as to change the EGR gas amount in the cylinder 2 to the normal combustion EGR gas amount Qd. An EGR gas amount change command is issued. Furthermore, the fuel injection timing is maintained at the premixed combustion injection timing Ith from the time (g) to the time when the first response delay time M12d elapses (time (h)), and the fuel injection is started from the time (h). The change to the normal combustion injection timing Itd is started. Then, the fuel injection timing is gradually changed so that the normal combustion injection timing Itd is reached when the first predetermined time M12h has elapsed from the time (h) (time (i)).

  According to the above-described combustion switching control during re-transition, the EGR gas amount in the cylinder 2 is set to an amount in the vicinity of the premixed combustion EGR gas amount Qh when the fuel injection timing once becomes the premixed combustion injection timing Ith. I can do it. Further, the timing when the fuel injection timing becomes the normal combustion injection timing Itd and the timing when the EGR gas amount in the cylinder 2 becomes an amount in the vicinity of the normal combustion EGR gas amount Qd can be synchronized thereafter. Further, the fuel injection timing in the middle of the change to each target fuel injection timing can be set to a timing according to the actual EGR gas amount in the cylinder 2.

  Therefore, according to the present embodiment, the operation state of the internal combustion engine 1 is changed to the first while the operation mode of the internal combustion engine 1 is shifted from the first region to the second region and the combustion mode is switched. Even in the case of returning to the region, the combustion mode can be returned to the first combustion mode while suppressing the EGR gas amount in the cylinder 2 from being excessive or insufficient with respect to the fuel injection timing. Thereby, generation | occurrence | production of misfire and a combustion noise can be suppressed.

<Control routine for re-burning combustion switching control>
Here, the control routine of the re-shifting combustion switching control according to the present embodiment will be described based on the flowchart shown in FIG. Here, the combustion switching at the time of re-transition when the operating state of the internal combustion engine 1 returns to the premixed combustion region R1 in the middle of changing the fuel injection timing to switch the combustion mode from the normal combustion to the premixed combustion. Control will be described as an example. This routine is stored in advance in the ECU 20 and is executed at predetermined intervals during the operation of the internal combustion engine 1.

  In this routine, first in S101, the ECU 20 determines whether or not the operating state of the internal combustion engine 1 has shifted from the normal combustion region R2 to the premixed combustion region R1. If an affirmative determination is made in S101, the ECU 20 proceeds to S102, and if a negative determination is made, the ECU 20 ends the execution of this routine.

  In S102, the ECU 20 changes the combustion mode from the premixed combustion to the normal combustion, that is, the fuel injection timing is changed from the premixed combustion injection timing Ith to the normal combustion injection timing Itd. It is determined whether or not the process is in progress (between (b) and (g) in FIG. 5). If an affirmative determination is made in S102, the ECU 20 proceeds to S103, and if a negative determination is made, the ECU 20 ends the execution of this routine.

  In S103, the ECU 20 maintains the opening degree of the EGR valve 13 at the normal combustion opening degree Vd.

  Next, the ECU 20 proceeds to S104 and continues to gradually change the fuel injection timing from the premixed combustion injection timing Ith to the normal combustion injection timing Itd. That is, the fuel injection timing reaches the normal combustion injection timing Itd when the first predetermined time M12h elapses from the time when the fuel injection timing is changed from the premixed combustion injection timing Itth to the normal combustion injection timing Itd. Continue to change fuel injection timing.

  Next, the ECU 20 proceeds to S105, and determines whether or not the first predetermined time M12h has elapsed since the change of the fuel injection timing from the premixed combustion injection timing Ith to the normal combustion injection timing Itd was started. If an affirmative determination is made in S105, the ECU 02 proceeds to S106, and if a negative determination is made, the ECU 20 returns to S103.

  In S106, the ECU 20 starts execution of combustion switching control when switching the combustion mode from normal combustion to premixed combustion. Thereafter, the ECU 20 ends the execution of this routine.

  The schematic configuration of the internal combustion engine and its intake / exhaust system according to this embodiment is the same as that of the first embodiment. Also in this embodiment, the same combustion switching control and re-transition combustion switching control as in the first embodiment are performed.

  In this embodiment, the upper limit load of the premixed combustion region R1 indicated by the solid line L1 in FIG. Moreover, let the upper limit of the engine load which can perform the premix combustion shown by the dashed-dotted line L2 in FIG. 2 be a premix combustion upper limit load.

  While the operating state of the internal combustion engine 1 is shifted from the normal combustion region R2 to the premixed combustion region R1, the engine load of the internal combustion engine 1 is increased to a predetermined load while the combustion mode is switched to the premixed combustion. In some cases, the operating state of the internal combustion engine 1 shifts again from the premixed combustion region R1 to the normal combustion region R2. Even in such a case, according to the re-shift combustion switching control according to the present embodiment, the EGR gas amount in the cylinder 2 is temporarily changed to the premixed combustion EGR gas amount Qh as shown in FIG. At the same time, the fuel injection timing is once changed to the premixed combustion injection timing Ith in the same manner as in the normal combustion switching control.

  However, in the above case, the fuel injection timing is being changed toward the premixed combustion injection timing Ith, that is, while the combustion mode is being switched to the premixed combustion ((b in FIG. 6). ) To (g)), when the engine load of the internal combustion engine 1 further rises and becomes higher than the premix combustion upper limit load, the fuel injection amount becomes excessively large with respect to the fuel injection timing at this time point. There is a risk of ignition.

<Fuel injection amount control during re-transition>
Therefore, in this embodiment, when the operating state of the internal combustion engine 1 shifts again from the premixed combustion region R1 to the normal combustion region R2 while switching the combustion mode toward premixed combustion, the EGR in the cylinder 2 is changed. Until the gas amount reaches an amount near the premixed combustion EGR gas amount Qh and the fuel injection timing reaches the premixed combustion injection timing Ith, that is, after the change of the fuel injection timing to the premixed combustion injection timing Ith is started. Until the predetermined time M21h elapses (until time point (g) in FIG. 6), the fuel injection amount from the fuel injection valve 10 is controlled so that the engine load of the internal combustion engine 1 does not become higher than the premix combustion upper limit load. Re-transfer fuel injection amount control is executed.

<Control routine for reinjection fuel injection amount control>
Hereinafter, the control routine of the re-transfer fuel injection amount control according to this embodiment will be described based on the flowchart shown in FIG. This routine is stored in advance in the ECU 20 and is executed at a predetermined interval.

  In this routine, first in S201, the ECU 20 determines whether or not the operating state of the internal combustion engine 1 has shifted from the premixed combustion region R1 to the normal combustion region R2. If an affirmative determination is made in S201, the ECU 20 proceeds to S202, and if a negative determination is made, the ECU 20 ends the execution of this routine.

  In S202, the ECU 20 changes the combustion mode from the normal combustion to the premixed combustion, that is, the fuel injection timing is changed from the normal combustion injection timing Itd to the premixed combustion injection timing Ith. It is determined whether or not the process is in progress (between (b) and (g) in FIG. 6). If an affirmative determination is made in S202, the ECU 20 proceeds to S203, and if a negative determination is made, the ECU 20 ends the execution of this routine.

  In S203, the ECU 20 prohibits an increase in the fuel injection amount Qf from the fuel injection valve 10.

  Next, the ECU 20 proceeds to S204, and determines whether or not the second predetermined time M21h has elapsed from the time when the fuel injection timing is changed from the normal combustion injection timing Itd to the premixed combustion injection timing Ith. If an affirmative determination is made in S204, the ECU 02 proceeds to S205, and if a negative determination is made, the ECU 20 returns to S203.

  In S205, the ECU 20 cancels the prohibition of increasing the fuel injection amount Qf from the fuel injection valve 10. Thereafter, the ECU 20 ends the execution of this routine.

  According to the fuel injection amount control at the time of re-transition described above, the internal combustion engine before the EGR gas amount in the cylinder 2 becomes an amount near the premixed combustion EGR gas amount Qh and the fuel injection timing becomes the premixed combustion injection timing Ith. It can suppress that the engine load of 1 becomes higher than the premix combustion upper limit load. That is, it is possible to suppress an excessive increase in the fuel injection amount with respect to the fuel injection timing during switching of the combustion mode toward the premixed combustion. Accordingly, it is possible to suppress the occurrence of premature ignition, thereby suppressing the exhaust emission and the deterioration of combustion noise.

<Modification>
Next, a control routine of a modification of the fuel injection amount control at the time of re-transition according to the present embodiment will be described based on the flowchart shown in FIG. This routine is stored in advance in the ECU 20 and executed at predetermined intervals. Note that S201, S202, and S204 in this routine are the same as the control routine shown in FIG.

In this routine, if an affirmative determination is made in S202, the ECU 20 proceeds to S303. In S303, the ECU 20 limits the increase rate Qfr of the fuel injection amount from the fuel injection valve 10 to a predetermined increase rate Qfr0 or less. Here, the predetermined increase rate Qfr0 means that the second predetermined time M21h elapses from the time when the fuel injection timing is changed from the normal combustion injection timing Itd to the premixed combustion injection timing Ith, that is, in the cylinder 2. The increase rate is such that the engine load of the internal combustion engine 1 does not become higher than the premixed combustion upper limit load until the EGR gas amount becomes an amount in the vicinity of the premixed combustion EGR gas amount Qh and the fuel injection timing becomes the premixed combustion injection timing Ith. Is the upper limit. The predetermined increase rate Qfr0 may be determined in accordance with the fuel injection amount at the time when the operating state of the internal combustion engine 1 shifts again to the normal combustion region R2. After S303, the ECU 20 proceeds to S204.

  If an affirmative determination is made in S204, the ECU 20 proceeds to S305. In step S305, the ECU 20 releases the restriction on the fuel injection amount increase rate Qfr from the fuel injection valve 10. Thereafter, the ECU 20 ends the execution of this routine.

  Here, a change in the engine load of the internal combustion engine 1 when the re-transfer fuel injection amount control according to the modification of the present embodiment described above is applied will be described with reference to FIG. In FIG. 10, the vertical axis represents the engine load of the internal combustion engine 1, and the horizontal axis represents time. The alternate long and short dash line L1 represents a predetermined load, and the alternate long and short dash line L2 represents a premixed combustion upper limit load. A solid line represents a change in the engine load of the internal combustion engine 1.

  In FIG. 10, when the operating state of the internal combustion engine 1 shifts from the normal combustion region R2 to the premixed combustion region R1 at the time point (a) and the second predetermined response delay time M21d has elapsed from the time point (a). At a certain point (b), the fuel injection timing is changed from the normal combustion injection timing Itd to the premixed combustion injection timing Ith. Then, at the time (d) before the fuel injection timing reaches the premixed combustion injection timing Ith, the operating state of the internal combustion engine 1 shifts again from the premixed combustion region R1 to the normal combustion region R2.

  From the time point (d) until the time point (g) when the EGR gas amount in the cylinder 2 becomes an amount in the vicinity of the premixed combustion EGR gas amount Qh and the fuel injection timing becomes the premixed combustion injection timing Ith, fuel injection is performed. The amount increase rate Qfr is limited to a predetermined increase rate Qfr0 or less. Thereby, it is suppressed that the engine load of the internal combustion engine 1 becomes higher than the premix combustion upper limit load before the time point (g).

  As described above, according to this modification, the EGR gas amount in the cylinder 2 becomes an amount in the vicinity of the premixed combustion EGR gas amount Qh and the fuel injection timing becomes the premixed combustion injection timing Ith. It is possible to suppress the engine load from becoming higher than the premixed combustion upper limit load. Further, even during this time, the engine load of the internal combustion engine 1 can be increased to some extent. Thereby, the acceleration of the vehicle can be improved as compared with the case where the increase in fuel injection is prohibited.

  The schematic configuration of the internal combustion engine and its intake / exhaust system according to this embodiment is the same as that of the first embodiment. Also in this embodiment, the same combustion switching control and re-transition combustion switching control as in the first embodiment are performed.

  In FIG. 2, in the high speed region, the solid line L1 represents the upper limit rotational speed of the premixed combustion region R1, and the alternate long and short dash line L2 represents the upper limit value of the engine speed of the internal combustion engine 1 capable of performing premixed combustion. Represents. In this region, the engine speed indicated by the solid line L1 is set as the predetermined upper limit speed, and the engine speed indicated by the alternate long and short dash line L2 is set as the premixed combustion upper limit speed. As shown in FIG. 2, the predetermined upper limit rotational speed is lower than the premixed combustion upper limit rotational speed.

  In FIG. 2, in the low engine speed region, the solid line L1 represents the lower limit engine speed of the premixed combustion region R1, and the alternate long and short dash line L2 represents the engine speed of the internal combustion engine 1 capable of performing premixed combustion. Represents the lower limit. In this region, the engine speed indicated by the solid line L1 is defined as the predetermined lower limit speed, and the engine speed indicated by the alternate long and short dash line L2 is defined as the premixed combustion lower limit speed. As shown in FIG. 2, the predetermined lower limit rotational speed is higher than the premixed combustion lower limit rotational speed.

  While the operating state of the internal combustion engine 1 is shifted from the normal combustion region R2 to the premixed combustion region R1, the engine speed of the internal combustion engine 1 is increased to a predetermined value while switching the combustion mode toward premixed combustion. The operating state of the internal combustion engine 1 is changed from the premixed combustion region R1 to the normal combustion region R2 again when it becomes higher than the upper limit rotational speed or when the engine rotational speed of the internal combustion engine 1 decreases and becomes lower than the predetermined lower limit rotational speed. May migrate. Even in such a case, according to the re-shift combustion switching control according to the present embodiment, the EGR gas amount in the cylinder 2 is temporarily changed to the premixed combustion EGR gas amount Qh as shown in FIG. At the same time, the fuel injection timing is once changed to the premixed combustion injection timing Ith in the same manner as in the normal combustion switching control.

  At this time, when the engine speed of the internal combustion engine 1 rises and becomes higher than the predetermined upper limit speed, the operating state of the internal combustion engine 1 shifts again from the premixed combustion region R1 to the normal combustion region R2, the fuel If the engine speed of the internal combustion engine 1 further increases and becomes higher than the premix combustion upper limit engine speed during the change of the injection timing toward the premixed combustion injection timing Ith, the engine is compared with the fuel injection timing at this time. There is a possibility that the rotational speed becomes excessively high and premature ignition occurs.

  Further, when the engine speed of the internal combustion engine 1 decreases and becomes lower than the predetermined lower limit speed, the operation state of the internal combustion engine 1 shifts again from the premixed combustion region R1 to the normal combustion region R2, fuel injection If the engine speed of the internal combustion engine 1 further decreases and becomes lower than the premix combustion lower limit engine speed while the timing is being changed toward the premixed combustion injection timing Ith, the engine speed is increased with respect to the fuel injection timing at this time. The number becomes excessively low and there is a risk of misfire.

<Fuel injection stop control during re-transition>
Therefore, in this embodiment, when the operating state of the internal combustion engine 1 shifts again from the premixed combustion region R1 to the normal combustion region R2 while switching the combustion mode toward premixed combustion, the EGR in the cylinder 2 is changed. Before the gas amount becomes the premixed combustion EGR gas amount Qh and the fuel injection timing becomes the premixed combustion injection timing Ith, that is, after the change of the fuel injection timing to the premixed combustion injection timing Ith is started. When the engine speed of the internal combustion engine 1 becomes higher than the premix combustion upper limit engine speed before the predetermined time M21h elapses (before the time point (g) in FIG. 6), or the engine speed of the internal combustion engine 1 When the engine speed becomes lower than the premix combustion lower limit rotational speed, re-transmission fuel injection stop control for stopping fuel injection from the fuel injection valve 10 is executed.

<Control routine for reinjection fuel injection stop control>
Hereinafter, the control routine of the re-transfer fuel injection stop control according to the present embodiment will be described based on the flowchart shown in FIG. This routine is stored in advance in the ECU 20 and executed at predetermined intervals. Note that S201, S202, and S204 in this routine are the same as the control routine shown in FIG.

  In this routine, if an affirmative determination is made in S202, the ECU 20 proceeds to S403. In S403, the ECU 20 determines whether or not the engine speed Ne of the internal combustion engine 1 has become higher than the premix combustion upper limit engine speed Nelimit1, or has become lower than the premix combustion lower limit engine speed Nelimit2. If an affirmative determination is made in S403, the ECU 20 proceeds to S404, and if a negative determination is made, the ECU 20 ends the execution of this routine.

  In S404, the ECU 02 stops fuel injection from the fuel injection valve 10. Thereafter, the ECU 20 proceeds to S204. If an affirmative determination is made in S204, the ECU 20 proceeds to S405, and if a negative determination is made, the ECU 20 returns to S404.

  In S <b> 405, the ECU 20 cancels the stop of fuel injection from the fuel injection valve 10. Thereafter, the ECU 20 ends the execution of this routine.

  According to the present embodiment, it is possible to suppress the occurrence of premature ignition due to the engine speed becoming excessively high during the switching of the combustion mode toward the premixed combustion. Thereby, exhaust emission and the deterioration of combustion noise can be suppressed. Further, it is possible to suppress the occurrence of misfire due to the engine speed becoming excessively low during the switching of the combustion mode toward the premixed combustion.

  The schematic configuration of the internal combustion engine and its intake / exhaust system according to this embodiment is the same as that of the first embodiment. Also in this embodiment, the same combustion switching control and re-transition combustion switching control as in the first embodiment are performed.

<Fuel injection amount control during re-transition>
As described above, the engine speed of the internal combustion engine 1 is switched during the switching of the combustion mode toward the premixed combustion by the operating state of the internal combustion engine 1 shifting from the normal combustion region R2 to the premixed combustion region R1. And the operating state of the internal combustion engine 1 may shift again from the premixed combustion region R1 to the normal combustion region R2 as the engine speed increases and becomes higher than the predetermined upper limit rotational speed. In such a case, when the engine speed of the internal combustion engine 1 further increases and becomes higher than the premix combustion upper limit engine speed while the fuel injection timing is being changed toward the premix combustion injection timing Ith, There is a possibility that the engine speed becomes excessively high with respect to the fuel injection timing and premature ignition occurs.

  Therefore, in this embodiment, in such a case, the EGR gas amount in the cylinder 2 becomes an amount in the vicinity of the premixed combustion EGR gas amount Qh and the fuel injection timing becomes the premixed combustion injection timing Ith, that is, the fuel injection. Until the second predetermined time M21h elapses after the change to the premixed combustion injection timing Ith is started (until time (g) in FIG. 6), the engine speed of the internal combustion engine 1 remains at the premixed combustion upper limit. The re-injection fuel injection amount control for controlling the fuel injection amount from the fuel injection valve 10 so as not to become higher than the rotational speed is executed.

<Control routine for reinjection fuel injection amount control>
Hereinafter, the control routine of the re-injection fuel injection amount control according to the present embodiment will be described based on the flowchart shown in FIG. This routine is stored in advance in the ECU 20 and executed at predetermined intervals. Note that S201, S202, and S204 in this routine are the same as the control routine shown in FIG.

  In this routine, first, the ECU 20 determines in S501 whether or not the engine speed of the internal combustion engine 1 has increased. If an affirmative determination is made in S501, the ECU 20 proceeds to S201, and if a negative determination is made, the ECU 20 ends the execution of this routine.

  If an affirmative determination is made in S202, the ECU 20 proceeds to S503. In S503, the ECU 20 limits the fuel injection amount from the fuel injection valve 10 to such an amount that the engine speed Ne of the internal combustion engine 1 is maintained at the predetermined speed Ne1. Here, the predetermined rotational speed Ne1 is a rotational speed that is higher than the predetermined upper limit rotational speed Nelimit1 and lower than the premix combustion upper limit rotational speed. The predetermined rotational speed Ne1 is determined in advance according to the engine load of the internal combustion engine 1.

  Next, the ECU 20 proceeds to S204. If an affirmative determination is made in S204, the ECU 20 proceeds to S505, and if a negative determination is made, the ECU 20 returns to S503.

  In step S <b> 505, the ECU 20 releases the restriction on the fuel injection amount from the fuel injection valve 10. Thereafter, the ECU 20 ends the execution of this routine.

  Here, the change in the engine load of the internal combustion engine 1 when the above-described fuel injection amount control at the time of re-transition is applied will be described with reference to FIG. In FIG. 13, as in FIG. 2, the vertical axis represents the engine load of the internal combustion engine 1, and the horizontal axis represents the engine speed of the internal combustion engine 1. Further, the alternate long and short dash line L1 on the high rotation side represents the predetermined upper limit rotation speed, and the alternate long and short dash line L2 on the high rotation side represents the premix combustion upper limit rotation speed. Furthermore, the alternate long and short dash line L3 represents a predetermined rotation speed. A solid line represents a change in the operating state of the internal combustion engine 1.

  In FIG. 13, when the operating state of the internal combustion engine 1 shifts from the normal combustion region R2 to the premixed combustion region R1 at the time point (a) and the second predetermined response delay time M21d has elapsed from the time point (a). At a certain point (b), the fuel injection timing is changed from the normal combustion injection timing Itd to the premixed combustion injection timing Ith. Then, at the time point (d) before the fuel injection timing reaches the premixed combustion injection timing Ith, the engine speed of the internal combustion engine 1 becomes higher than the predetermined upper limit speed, and the operating state of the internal combustion engine 1 is premixed. It shifts again from the combustion region R1 to the normal combustion region R2.

  From the time point (d) to the time point (g) when the EGR gas amount in the cylinder 2 becomes an amount in the vicinity of the premixed combustion EGR gas amount Qh and the fuel injection timing becomes the premixed combustion injection timing Ith, the internal combustion engine The fuel injection amount is limited so that the engine speed of 1 is maintained at a predetermined speed. Thereby, it is suppressed that the engine speed of the internal combustion engine 1 becomes higher than the premix combustion upper limit engine speed before the time (g).

  According to the fuel injection amount control at the time of re-transition described above, it is possible to suppress the engine speed from becoming excessively high with respect to the fuel injection timing while switching the combustion mode toward premixed combustion. . In addition, a rapid change in the engine speed can be suppressed by suppressing an excessive increase in the engine speed without stopping the fuel injection. Accordingly, it is possible to suppress the occurrence of premature ignition while suppressing the deterioration of drivability.

  Even when the re-injection fuel injection amount control according to this example is executed, for example, when the vehicle equipped with the internal combustion engine 1 is traveling on a downhill, the engine speed of the internal combustion engine 1 is May be difficult to maintain at a predetermined rotational speed. That is, the engine speed of the internal combustion engine 1 may reach the premix combustion upper limit engine speed while switching the combustion mode toward premix combustion. In such a case, the fuel injection from the fuel injection valve 10 may be stopped by the re-transfer fuel injection stop control according to the third embodiment described above.

  The schematic configuration of the internal combustion engine and its intake / exhaust system according to this embodiment is the same as that of the first embodiment. Also in this embodiment, the same combustion switching control and re-transition combustion switching control as in the first embodiment are performed.

<Fuel injection amount control during re-transition>
As described above, in FIG. 2, in the low speed region, the solid line L1 represents the predetermined lower limit speed, and the alternate long and short dash line L2 represents the premixed combustion lower limit speed. As shown in FIG. 2, the predetermined lower limit rotational speed and the premixed combustion lower limit rotational speed are lower as the engine load of the internal combustion engine 1 is lower.

  Further, when the operating state of the internal combustion engine 1 is shifted from the normal combustion region R2 to the premixed combustion region R1, the engine speed of the internal combustion engine 1 decreases while switching the combustion mode toward the premixed combustion. In some cases, the operating state of the internal combustion engine 1 shifts again from the premixed combustion region R1 to the normal combustion region R2 by being lower than the predetermined lower limit rotational speed. In such a case, when the engine speed of the internal combustion engine 1 further decreases and becomes lower than the premixed combustion lower limit speed during the change of the fuel injection timing toward the premixed combustion injection timing Ith, There is a possibility that the engine speed becomes excessively low with respect to the fuel injection timing and misfire occurs.

  Therefore, in this embodiment, in such a case, the EGR gas amount in the cylinder 2 becomes an amount in the vicinity of the premixed combustion EGR gas amount Qh and the fuel injection timing becomes the premixed combustion injection timing Ith, that is, the fuel injection. Until the second predetermined time M21h elapses after the start of the change to the premixed combustion injection timing Ith (until time (g) in FIG. 6), the engine speed of the internal combustion engine 1 remains at the lower limit of premixed combustion. The re-injection fuel injection amount control is executed to control the fuel injection amount from the fuel injection valve 10 so as not to become lower than the rotational speed.

<Control routine for reinjection fuel injection amount control>
Hereinafter, the control routine of the re-transfer fuel injection amount control according to the present embodiment will be described based on the flowchart shown in FIG. This routine is stored in advance in the ECU 20 and executed at predetermined intervals. Note that S201, S202, and S204 in this routine are the same as the control routine shown in FIG.

  In this routine, first, the ECU 20 determines in S601 whether or not the engine speed of the internal combustion engine 1 has decreased. If an affirmative determination is made in S601, the ECU 20 proceeds to S201, and if a negative determination is made, the ECU 20 ends the execution of this routine.

  If an affirmative determination is made in S202, the ECU 20 proceeds to S603. In step S603, the ECU 20 limits the fuel injection amount from the fuel injection valve 10 so that the engine speed Ne of the internal combustion engine 1 does not fall below the premix combustion lower limit rotation speed Nelimit2. By limiting the fuel injection amount, the engine load of the internal combustion engine 1 can be reduced. As described above, the lower the engine load, the lower the premixed combustion lower limit rotational speed Nelimit2. Therefore, by limiting the fuel injection amount, it is possible to control the engine speed so that it does not become lower than the premixed combustion speed Nelimit2.

  Next, the ECU 20 proceeds to S204. If an affirmative determination is made in S204, the ECU 20 proceeds to S506, and if a negative determination is made, the ECU 20 returns to S603.

  In step S <b> 605, the ECU 20 releases the restriction on the fuel injection amount from the fuel injection valve 10. Thereafter, the ECU 20 ends the execution of this routine.

  Here, changes in the engine load of the internal combustion engine 1 when the above-described fuel injection amount control at the time of re-transition is applied will be described with reference to FIG. In FIG. 15, as in FIG. 2, the vertical axis represents the engine load of the internal combustion engine 1, and the horizontal axis represents the engine speed of the internal combustion engine 1. Further, the alternate long and short dash line L1 on the high rotation side represents the predetermined upper limit rotation speed, and the alternate long and short dash line L2 on the high rotation side represents the premix combustion upper limit rotation speed. A solid line represents a change in the operating state of the internal combustion engine 1.

In FIG. 15, when the operating state of the internal combustion engine 1 shifts from the normal combustion region R2 to the premixed combustion region R1 at the time point (a) and the second predetermined response delay time M21d has elapsed from the time point (a). At a certain point (b), the fuel injection timing is changed from the normal combustion injection timing Itd to the premixed combustion injection timing Ith. And the fuel injection timing is premixed combustion injection timing Ith
At the time of (d) before reaching, the engine speed of the internal combustion engine 1 becomes lower than the predetermined lower limit speed, and the operating state of the internal combustion engine 1 shifts again from the premixed combustion region R1 to the normal combustion region R2. .

  From the time point (d) to the time point (g) when the EGR gas amount in the cylinder 2 becomes an amount in the vicinity of the premixed combustion EGR gas amount Qh and the fuel injection timing becomes the premixed combustion injection timing Ith, the internal combustion engine The fuel injection amount is limited so that the engine speed of 1 does not become lower than the premixed combustion lower limit speed. Thereby, the engine load of the internal combustion engine 1 is reduced, and the engine speed of the internal combustion engine 1 is suppressed from becoming lower than the premix combustion upper limit engine speed before the time point (g).

  According to the fuel injection amount control at the time of re-transition described above, it is possible to suppress the engine speed from becoming excessively low with respect to the fuel injection timing while switching the combustion mode toward premixed combustion. . In addition, a rapid change in the engine speed can be suppressed by suppressing an excessive decrease in the engine speed without stopping the fuel injection. Therefore, the occurrence of misfire can be suppressed while the deterioration of drivability is suppressed.

  Even when the fuel injection amount control at the time of re-transition according to this example is executed, depending on the operation state of the vehicle on which the internal combustion engine 1 is mounted, the combustion mode is being switched to the premixed combustion. The engine speed of the internal combustion engine 1 may reach the premixed combustion lower limit speed. In such a case, the fuel injection from the fuel injection valve 10 may be stopped by the re-transfer fuel injection stop control according to the third embodiment described above.

  The schematic configuration of the internal combustion engine and its intake / exhaust system according to this embodiment is the same as that of the first embodiment. Also in the present embodiment, the combustion switching control similar to that in the first embodiment is performed.

<Re-switching during combustion mode switching>
In the present embodiment, the operation state of the internal combustion engine 1 is changed from the second region to the first while the combustion mode is switched because the operation state of the internal combustion engine 1 has shifted from the first region to the second region. The re-combustion combustion switching control when re-entering the region will be described based on the time chart shown in FIG. In this case, the operating state of the internal combustion engine 1 shifts from the premixed combustion region R1 to the normal combustion region R2, and the internal combustion engine 1 changes during the fuel injection timing to change the combustion mode from normal combustion to premixed combustion. The case where the operating state of the engine 1 returns to the premixed combustion region R1 will be described as an example.

  The time points (a), (b), and (d) in FIG. 16 represent the same time points as the time points (a), (b), and (d) in FIG. 4, respectively. That is, the operating state of the internal combustion engine 1 again shifts from the normal combustion region R2 to the premixed combustion region R1 at the time (d) before the fuel injection timing reaches the normal combustion injection timing Itd.

  At this time, in the re-burning combustion switching control according to the present embodiment, at the time of (d), the EGR gas amount in the cylinder 2 is immediately changed to the premixed combustion EGR gas amount, that is, the EGR valve 13 is turned on. An EGR gas amount change command is issued from the ECU 20 to the actuator 14 so as to change the opening to the premixed combustion opening Vh. As a result, when the valve response delay time Δtv elapses from the time point (d), the opening degree of the EGR valve 13 becomes the premixed combustion opening degree Vh.

  Then, since the opening degree of the EGR valve 13 becomes the premixed combustion opening degree Vh, the EGR in the cylinder 2 from the time point when the EGR gas amount change delay time Δte has elapsed from the time point (d) (the time point (j)). The gas amount starts to change toward the premixed combustion EGR gas amount Qh. That is, the EGR gas amount in the cylinder 2 starts to change toward the premixed combustion EGR gas amount Qh while changing toward the normal combustion EGR gas amount Qd.

  At this time, from the time when the change of the fuel injection timing to the normal combustion injection timing Itd is started (time (b)), the time when the operation state of the internal combustion engine 1 is shifted again to the premixed combustion region R1 (at (d)). The ratio of the time M12hw to the first predetermined time M12h until the time) is the switching progress ratio α. That is, M12hw = M12h × α.

Here, the ECU is configured to change the opening degree of the EGR valve 13 to the premixed combustion opening degree Vh at the time point (d).
The time from when the EGR gas amount change command is issued from 20 to the actuator 14 until the EGR gas amount in the cylinder 2 becomes the amount near the premixed combustion EGR gas amount Qh (until time (k)) is the time M21hw And This time M21hw is calculated by the following formula (1).
M21hw = M21h × α × β (1)

  In the above equation (1), β is a correction coefficient determined based on the EGR gas amount change delay time Δte. The EGR gas amount change delay time Δte is a value that changes according to the operating state of the internal combustion engine 1, and can be obtained in advance by experiments or the like.

  When the time M12hw elapses from the time point (b), the EGR gas amount in the cylinder 2 at the time point (d) becomes the premixed combustion EGR gas amount Qh because the opening degree of the EGR valve 13 becomes the premixed combustion opening degree Vh. The time until returning to the amount in the vicinity is a time obtained by multiplying the second predetermined time M21h by the switching progress rate α. However, as described above, the EGR gas amount change delay time Δte is not changed from the time point (d) until the time point (j) at which the EGR gas amount in the cylinder 2 starts to change toward the premixed combustion EGR gas amount Qh. Elapse. That is, between the time point (d) and the time point (j), the EGR gas amount in the cylinder 2 further changes toward the normal combustion EGR gas amount Qd.

Further, the EGR gas amount in the cylinder 2 that started to change toward the premixed combustion EGR gas amount Qh at the time (j) is the same as the EGR gas amount in the cylinder 2 at the time (d). It takes some time to reach the quantity. Therefore, the correction coefficient β is determined based on the EGR gas amount change delay time Δte, and the time M21hw is calculated by the above equation (1).

  In this embodiment, the change of the fuel injection timing to the premixed fuel injection timing Ith is started from the time point (d). Thereafter, the fuel injection timing is gradually changed to the premixed combustion injection timing Ith over time M21hw. Thereby, at the time point (k), the EGR gas amount in the cylinder 2 becomes an amount in the vicinity of the premixed combustion EGR gas amount Qh, and the fuel injection timing becomes the premixed fuel injection timing Ith.

  According to the re-transition combustion switching control as described above, the timing when the fuel injection timing becomes the premixed combustion injection timing Ith and the timing when the EGR gas amount in the cylinder 2 becomes an amount in the vicinity of the premixed combustion EGR gas amount Qh. Can be synchronized. Further, the fuel injection timing in the middle of the change can be set to a timing according to the EGR gas amount in the cylinder 2.

  Further, the combustion mode can be returned to the premixed combustion more rapidly after the operating state of the internal combustion engine returns to the premixed combustion region R1 during the switching of the combustion mode.

  In the re-shift combustion switching control, the operating state of the internal combustion engine 1 shifts from the normal combustion region R2 to the premixed combustion region R1, and the fuel injection timing is changed to switch the combustion mode from normal combustion to premixed combustion. The present invention can also be applied when the operating state of the internal combustion engine 1 returns to the normal combustion region R2 on the way.

In this case, the timing when the fuel injection timing becomes the normal combustion injection timing Itd and the timing when the EGR gas amount in the cylinder 2 becomes an amount in the vicinity of the normal combustion EGR gas amount Qd can be synchronized. Also,
The combustion mode can be returned to the normal combustion more quickly after the operating state of the internal combustion engine returns to the normal combustion region R2 during the switching of the combustion mode.

  Therefore, according to the present embodiment, even when the operating state of the internal combustion engine returns to the original region during switching of the combustion mode, the amount of EGR gas in the cylinder is excessive with respect to the fuel injection timing or The combustion mode can be returned to the combustion mode in the original region while suppressing the shortage.

  In addition, since the combustion mode can be returned to the combustion mode in the original region more quickly after the operating state of the internal combustion engine returns to the original region during the switching of the combustion mode, premature ignition or misfire can be prevented. It can be further suppressed. In addition, it is possible to further suppress the deterioration of exhaust emission at the time of switching the combustion mode.

<Control routine for re-burning combustion switching control>
Here, the control routine of the re-transfer combustion switching control according to this embodiment will be described based on the flowchart shown in FIG. Here, as described above, in the middle of changing the fuel injection timing in order to switch the combustion mode from normal combustion to premixed combustion, the operation is resumed when the operating state of the internal combustion engine 1 returns to the premixed combustion region R1. The transition combustion switching control will be described as an example. Further, S101 and S102 in this routine are the same as the control routine shown in FIG. This routine is stored in advance in the ECU 20 and is executed at predetermined intervals during the operation of the internal combustion engine 1.

  In this routine, if an affirmative determination is made in S102, the ECU 20 proceeds to S703. In S703, the ECU 20 issues an EGR gas amount change command to the actuator 14 so that the opening degree of the EGR valve 13 is set to the premixed combustion opening degree Vh.

  Next, the ECU 20 proceeds to S704, and calculates the time M21hw based on the above equation (1).

  Next, the ECU 20 proceeds to S705 and starts changing the fuel injection timing toward the premixed combustion injection timing Ith. That is, the advance of the fuel injection timing is started.

  Next, the ECU 20 proceeds to S706 and gradually advances the fuel injection timing so that the fuel injection timing becomes the premixed combustion injection timing Ith when the time M21hw has elapsed since the start of the advance of the fuel injection timing. Horn.

  Next, the ECU 20 proceeds to S707 and determines whether or not the time M21hw has elapsed since the advance of the fuel injection timing was started. If an affirmative determination is made in S707, the ECU 20 proceeds to S708, and if a negative determination is made, the ECU 20 returns to S706.

  In step S708, the ECU 20 finishes changing the fuel injection timing. At this time, the fuel injection timing is the premixed combustion injection timing Ith. That is, the combustion mode returns to premixed combustion. Further, the EGR gas amount in the cylinder 2 returns to the premixed combustion EGR gas amount Qh. Thereafter, the ECU 20 once terminates execution of this routine.

  The schematic configuration of the internal combustion engine and its intake / exhaust system according to this embodiment is the same as that of the first embodiment. Also in the present embodiment, the combustion switching control similar to that in the first embodiment is performed.

<Re-switching during combustion mode switching>
Here, the re-combustion combustion switching control according to the present embodiment will be described based on the time chart shown in FIG. In this case, the operating state of the internal combustion engine 1 shifts from the premixed combustion region R1 to the normal combustion region R2, and the internal combustion engine 1 changes during the fuel injection timing to change the combustion mode from normal combustion to premixed combustion. The case where the operating state of the engine 1 returns to the premixed combustion region R1 will be described as an example.

  The time points (a), (b), and (d) in FIG. 18 represent the same time points as the time points (a), (b), and (d) in FIG. 4, respectively. That is, the operating state of the internal combustion engine 1 again shifts from the normal combustion region R2 to the premixed combustion region R1 at the time (d) before the fuel injection timing reaches the normal combustion injection timing Itd.

  Further, in the re-shift combustion switching control according to this embodiment, as in the sixth embodiment, at the time of (d), the ECU 20 immediately changes the opening of the EGR valve 13 to the premixed combustion opening Vh. 14, an EGR gas amount change command is issued. Thereby, the EGR gas amount in the cylinder 2 starts to change toward the premixed combustion EGR gas amount Qh from the time (j) when the EGR gas amount change delay time Δte has elapsed from the time (d).

Here, after the EGR gas amount in the cylinder 2 starts to change toward the premixed combustion EGR gas amount Qh at the time (j), the EGR gas amount in the cylinder 2 becomes an amount in the vicinity of the premixed combustion EGR gas amount Qh. The time until (until (k)) is set as a time M21hx. This time M21hx is calculated by the following equation (2).
M21hx = M21h × α × γ (2)

  In the above equation (2), γ is a correction coefficient determined based on the EGR gas amount change delay time Δte, similar to β in the above equation (1), but is a value different from β.

  In the transition switching combustion switching control according to the present embodiment, the change of the fuel injection timing toward the normal combustion injection timing Itd is continued until the time point (j). And the change from the time of (j) toward the premixed combustion injection timing Ith of the fuel injection timing is started. Thereafter, the fuel injection timing is gradually changed to the premixed combustion injection timing Ith over time M21hx. Thereby, at the time point (k), the EGR gas amount in the cylinder 2 becomes an amount in the vicinity of the premixed combustion EGR gas amount Qh, and the fuel injection timing becomes the premixed fuel injection timing Ith.

  According to the re-transition combustion switching control as described above, the EGR gas amount change from the time point when the EGR gas amount change command is issued from the ECU 20 to change the EGR gas amount in the cylinder 2 to the premixed combustion EGR gas amount Qh. Until the delay time Δte elapses, the change of the fuel injection timing toward the normal combustion injection timing Itd is continued. Accordingly, the fuel injection timing during the elapse of the EGR gas amount change delay time Δte can be set to a time corresponding to the actual EGR gas amount in the cylinder 2. Also, the time when the EGR gas amount in the cylinder 2 actually starts to change toward the premixed combustion EGR gas amount Qh is synchronized with the time when the fuel injection timing starts to change toward the premixed combustion injection timing Ith. I can do it. Furthermore, the timing when the fuel injection timing becomes the premixed combustion injection timing Ith and the timing when the EGR gas amount in the cylinder 2 becomes an amount in the vicinity of the premixed combustion EGR gas amount Qh can be more accurately synchronized.

  In the re-transition combustion switching control, as in the sixth embodiment, the operating state of the internal combustion engine 1 is shifted from the normal combustion region R2 to the premixed combustion region R1, and fuel injection is performed to switch the combustion mode from normal combustion to premixed combustion. The present invention can also be applied when the operating state of the internal combustion engine 1 returns to the normal combustion region R2 while the timing is being changed.

In this case, the time when the EGR gas amount in the cylinder 2 actually starts to change toward the normal combustion EGR gas amount Qd and the time when the fuel injection timing starts to change toward the normal combustion injection timing Itd can be synchronized. I can do it. Furthermore, the timing when the fuel injection timing becomes the normal combustion injection timing Itd and the timing when the EGR gas amount in the cylinder 2 becomes an amount in the vicinity of the normal combustion EGR gas amount Qd can be synchronized more accurately.

  Therefore, according to this embodiment, when the operating state of the internal combustion engine 1 returns to the original region during switching of the combustion mode, the amount of EGR gas in the cylinder 2 becomes excessive or insufficient with respect to the fuel injection timing. It is possible to return the combustion mode to the combustion mode in the original region more quickly while further suppressing this.

<Control routine for re-burning combustion switching control>
Hereinafter, the control routine of the re-transfer combustion switching control according to this embodiment will be described based on the flowchart shown in FIG. Here, as described above, in the middle of changing the fuel injection timing in order to switch the combustion mode from normal combustion to premixed combustion, the operation is resumed when the operating state of the internal combustion engine 1 returns to the premixed combustion region R1. The transition combustion switching control will be described as an example. Further, S101, S102, S703, and S708 in this routine are the same as the control routine shown in FIG. This routine is stored in advance in the ECU 20 and is executed at predetermined intervals during the operation of the internal combustion engine 1.

  In this routine, after S703, the ECU 20 proceeds to S804. In S804, the ECU 20 determines whether or not the EGR gas amount change delay time Δte has elapsed since the EGR gas amount change command was issued in S703. If an affirmative determination is made in S804, the ECU 20 proceeds to S805, and if a negative determination is made, the ECU 20 returns to S804.

  In S805, the ECU 20 calculates the time M21hx based on the above equation (2).

  Next, the ECU 20 proceeds to S806 and starts changing the fuel injection timing toward the premixed combustion injection timing Ith. That is, the advance of the fuel injection timing is started. In the present embodiment, the change of the fuel injection timing toward the normal combustion injection timing Itd is continued until this point.

  Next, the ECU 20 proceeds to S807 and gradually advances the fuel injection timing so that the fuel injection timing becomes the premixed combustion injection timing Ith when the time M21hx has elapsed since the advance of the fuel injection timing was started. Horn.

  Next, the ECU 20 proceeds to S808, and determines whether or not the time M21hx has elapsed since the advance of the fuel injection timing was started. If an affirmative determination is made in S808, the ECU 20 proceeds to S708, and if a negative determination is made, the ECU 20 returns to S807.

  Also in the present embodiment, in S708, the ECU 20 ends the change of the fuel injection timing. At this time, the fuel injection timing is the premixed combustion injection timing Ith. That is, the combustion mode returns to premixed combustion. Further, the EGR gas amount in the cylinder 2 returns to the premixed combustion EGR gas amount Qh. Thereafter, the ECU 20 once terminates execution of this routine.

  The schematic configuration of the internal combustion engine and its intake / exhaust system according to this embodiment is the same as that of the first embodiment. Also in the present embodiment, the combustion switching control similar to that in the first embodiment is performed.

<Re-switching during combustion mode switching>
Here, re-burning combustion switching control according to this embodiment will be described based on the time chart shown in FIG. In this case, the operating state of the internal combustion engine 1 shifts from the premixed combustion region R1 to the normal combustion region R2, and the internal combustion engine 1 changes during the fuel injection timing to change the combustion mode from normal combustion to premixed combustion. The case where the operating state of the engine 1 returns to the premixed combustion region R1 will be described as an example.

  The time points (a), (b), and (d) in FIG. 20 represent the same time points as the time points (a), (b), and (d) in FIG. 4, respectively. That is, the operating state of the internal combustion engine 1 again shifts from the normal combustion region R2 to the premixed combustion region R1 at the time (d) before the fuel injection timing reaches the normal combustion injection timing Itd.

  In the re-shift combustion switching control according to the present embodiment, as in the sixth and seventh embodiments, the ECU 20 immediately changes the opening degree of the EGR valve 13 to the premixed combustion opening degree Vh at the time point (d). The EGR gas amount change command is issued to the actuator 14. Thereby, the EGR gas amount in the cylinder 2 starts to change toward the premixed combustion EGR gas amount Qh from the time (j) when the EGR gas amount change delay time Δte has elapsed from the time (d).

  At this time, in the re-shift combustion switching control according to the present embodiment, the change of the fuel injection timing is stopped at the time point (d) when the operation state of the internal combustion engine 1 is shifted again. Then, the fuel injection timing at the time point (d) is maintained from the time point (d) to the time point (time point (l)) when the injection timing maintaining time M121d elapses. The injection timing maintenance time M121d here is a time twice as long as the EGR gas amount change delay time Δte.

Here, the time until the EGR gas amount in the cylinder 2 at the time (l) reaches an amount in the vicinity of the premixed combustion EGR gas amount Qh (until the time (k)) is defined as time M21hy. This time M21hy is calculated by the following equation (3).
M21hy = M21h × α × ε (3)

  In the above equation (3), ε is a correction coefficient determined based on the injection timing maintaining time M121d.

  In the re-shift combustion switching control according to the present embodiment, the change of the fuel injection timing from the time (l) toward the premixed combustion injection timing Ith is started. Thereafter, the fuel injection timing is gradually changed to the premixed combustion injection timing Ith over time M21hy. Thereby, at the time point (k), the EGR gas amount in the cylinder 2 becomes an amount in the vicinity of the premixed combustion EGR gas amount Qh, and the fuel injection timing becomes the premixed fuel injection timing Ith.

  In the above-described sixth embodiment, the timing at which the EGR gas amount in the cylinder 2 starts to change toward the premixed combustion EGR gas amount Qh is synchronized with the timing at which the fuel injection timing starts to change toward the premixed combustion injection timing Ith. Therefore, the fuel injection timing is changed toward the normal combustion injection timing Itd from the time point (d) until the EGR gas amount change delay time Δte elapses (time point (j)), and the time point (j) The fuel injection timing is started to change toward the premixed combustion injection timing Ith.

  At this time, the EGR gas amount change delay time Δte can be determined in advance as a value corresponding to the operating state of the internal combustion engine 1. However, the EGR gas amount change delay time Δte is likely to vary due to the influence of intake pressure, exhaust pressure, and the like. Therefore, even when the fuel injection timing is controlled as described above, the timing when the EGR gas amount in the cylinder 2 starts to change toward the premixed combustion EGR gas amount Qh and the fuel injection timing are set toward the premixed combustion injection timing Ith. In some cases, it is difficult to accurately synchronize the start time of the change.

Therefore, in this embodiment, as described above, the fuel injection timing is maintained from the time point (d) to the time point (l). Then, the change of the fuel injection timing from the time (l) toward the premixed combustion injection timing Ith is started. Thereafter, the fuel injection timing is gradually changed to the premixed combustion injection timing Ith over time M21hy. Thereby, at the time point (k), the EGR gas amount in the cylinder 2 becomes an amount in the vicinity of the premixed combustion EGR gas amount Qh, and the fuel injection timing becomes the premixed fuel injection timing Ith.

  According to the re-transition combustion switching control, even when the operating state of the internal combustion engine 1 returns to the premixed combustion region during switching of the combustion mode, even when the EGR gas amount change delay time Δte varies. The fuel injection timing can be made to correspond to the actual amount of EGR gas in the cylinder 2 to some extent.

  In the re-shift combustion switching control, the operating state of the internal combustion engine 1 is shifted from the normal combustion region R2 to the premixed combustion region R1, and the combustion mode is switched from normal combustion to premixed combustion, as in the sixth and seventh embodiments. This can also be applied to the case where the operating state of the internal combustion engine 1 returns to the normal combustion region R2 while the fuel injection timing is being changed.

  In this case, when the operating state of the internal combustion engine 1 returns to the normal combustion region during the switching of the combustion mode, the fuel injection timing is set to the actual cylinder 2 even if the EGR gas amount change delay time Δte varies. It is possible to set a time corresponding to a certain amount of EGR gas.

  Therefore, according to the present embodiment, the combustion mode is quickly returned to the combustion mode in the original region while suppressing the EGR gas amount in the cylinder 2 from being excessive or insufficient with respect to the fuel injection timing. I can do it.

  The injection timing maintaining time M121d according to this embodiment is set to the time when the EGR gas amount change delay time Δte has elapsed after the operating state of the internal combustion engine 1 has shifted to the first region again (time (j) in FIG. 20). ) Thereafter, the amount of time until the EGR gas amount in the cylinder 2 becomes equal to the amount at the time when the operating state of the internal combustion engine 1 shifts to the first region again (time point (d) in FIG. 20) is also obtained. good. Also in this case, the correction coefficient ε in the above equation (3) is determined based on the injection timing maintaining time M121d.

<Control routine for re-burning combustion switching control>
Hereinafter, the control routine of the re-transfer combustion switching control according to the present embodiment will be described based on the flowchart shown in FIG. Here, as described above, in the middle of changing the fuel injection timing in order to switch the combustion mode from normal combustion to premixed combustion, the operation is resumed when the operating state of the internal combustion engine 1 returns to the premixed combustion region R1. The transition combustion switching control will be described as an example. Further, S101, S102, S703, and S708 in this routine are the same as the control routine shown in FIG. This routine is stored in advance in the ECU 20 and is executed at predetermined intervals during the operation of the internal combustion engine 1.

  In this routine, after S703, the ECU 20 proceeds to S904. In step S904, the ECU 20 stops changing the fuel injection timing from the fuel injection valve 10. That is, the current fuel injection timing is maintained.

  Next, the ECU 20 proceeds to S905, and determines whether or not the injection timing maintaining time M121d has elapsed since the change of the fuel injection timing was stopped in S904. If an affirmative determination is made in S905, the ECU 20 proceeds to S906, and if a negative determination is made, the ECU 20 returns to S904.

In S906, the ECU 20 calculates the time M21hy based on the above equation (3).

  Next, the ECU 20 proceeds to S907 and starts changing the fuel injection timing toward the premixed combustion injection timing Ith. That is, the advance of the fuel injection timing is started.

  Next, the ECU 20 proceeds to S908, and gradually advances the fuel injection timing so that the fuel injection timing becomes the premixed combustion injection timing Ith when the time M21hy elapses after starting the advance of the fuel injection timing. Horn.

  Next, the ECU 20 proceeds to S909 and determines whether or not the time M21hy has elapsed since the advance of the fuel injection timing was started. If an affirmative determination is made in S909, the ECU 20 proceeds to S708, and if a negative determination is made, the ECU 20 returns to S908.

  Also in the present embodiment, in S708, the ECU 20 ends the change of the fuel injection timing. At this time, the fuel injection timing is the premixed combustion injection timing Ith. That is, the combustion mode returns to premixed combustion. Further, the EGR gas amount in the cylinder 2 returns to the premixed combustion EGR gas amount Qh. Thereafter, the ECU 20 once terminates execution of this routine.

  The schematic configuration of the internal combustion engine and its intake / exhaust system according to this embodiment is the same as that of the first embodiment. Also in the present embodiment, the combustion switching control similar to that in the first embodiment is performed.

<Combustion switching control during re-transition>
Here, the re-burning combustion switching control according to the present embodiment will be described based on the time chart shown in FIG. In this case, the operating state of the internal combustion engine 1 shifts from the premixed combustion region R1 to the normal combustion region R2, and the internal combustion engine 1 changes during the fuel injection timing to change the combustion mode from normal combustion to premixed combustion. The case where the operating state of the engine 1 returns to the premixed combustion region R1 will be described as an example.

  The time points (a), (b), and (d) in FIG. 22 represent the same time points as the time points (a), (b), and (d) in FIG. 4, respectively. That is, the operating state of the internal combustion engine 1 again shifts from the normal combustion region R2 to the premixed combustion region R1 at the time (d) before the fuel injection timing reaches the normal combustion injection timing Itd.

  Further, in the re-transition combustion switching control according to the present embodiment, the opening degree of the EGR valve 13 is immediately changed to the premixed combustion opening degree Vh at the time point (d) as in the sixth, seventh, and eighth embodiments. Thus, an EGR gas amount change command is issued from the ECU 20 to the actuator 14. Thereby, the EGR gas amount in the cylinder 2 starts to change toward the premixed combustion EGR gas amount Qh from the time (j) when the EGR gas amount change delay time Δte has elapsed from the time (d).

  When the EGR gas amount in the cylinder 2 changes as described above, the EGR gas amount in the cylinder 2 from the time point (d) toward the normal combustion EGR gas amount Qd as shown in FIG. The decrease rate gradually decreases, and the decrease rate becomes zero at the time point (j) when the EGR gas amount change delay time Δte has elapsed. The rate of increase gradually increases after the EGR gas amount in the cylinder 2 starts to increase toward the premixed combustion EGR gas amount Qh at the time (j). Here, the decreasing rate and increasing rate of the EGR gas amount are the increasing amount and decreasing amount of the EGR gas amount per unit time, respectively.

That is, the direction of change in the EGR gas amount in the cylinder 2 does not change at an acute angle at the time point (j), but changes so as to draw a curve from decrease to increase. However, in the seventh embodiment, the control is such that the direction of change of the fuel injection timing changes from a retarded angle to an advanced angle at the time point (j).

  Therefore, in the re-transition combustion switching control according to the present embodiment, as shown in FIG. 22, the fuel injection timing is from the time point (d) to the time point (time point (m)) when the change time M121dw elapses. The fuel injection timing is controlled so that the change direction changes in a curve from a retard angle to an advance angle. That is, as in the seventh embodiment, the fuel injection timing is retarded from the time (d) to the time (j) and advanced from the time (j), but from the time (d) (j) The rate of change in the fuel injection timing is gradually reduced until the time point (j), the rate of change is made zero at the time point (j), and the rate of change is gradually increased from the time point (j) to the time point (m). . Here, the rate of change of the fuel injection timing is the amount of retardation or advance of the fuel injection timing per unit time.

At this time, the change time M121dw is longer than the EGR gas amount change delay time Δte. The change time M121dw may be twice the EGR gas amount change delay time Δte, similarly to the injection timing maintenance time M121d according to the eighth embodiment, and the EGR gas amount in the cylinder 2 after time (j). (D) It is good also as time until it becomes the quantity equivalent to the quantity at the time. The change time M121dw and how to change the change rate of the fuel injection timing between the time point (d) and the time point (m) are the same as the fuel time between the time point (b) and the time point (d). You may determine based on the change rate of injection timing, etc.

Here, the time until the EGR gas amount in the cylinder 2 at the time (m) reaches an amount in the vicinity of the premixed combustion EGR gas amount Qh (until the time (k)) is defined as a time M21hz. This time M21hz is calculated by the following equation (4).
M21hz = M21h × α × ζ Expression (4)

  In the above equation (4), ζ is a correction coefficient determined based on the change time M121dw.

  From time (m), the fuel injection timing is gradually changed to the premixed combustion injection timing Ith over time M21hz. Thereby, at the time point (k), the EGR gas amount in the cylinder 2 becomes an amount in the vicinity of the premixed combustion EGR gas amount Qh, and the fuel injection timing becomes the premixed fuel injection timing Ith.

  According to the re-shift combustion switching control, the actual fuel injection timing from when the EGR gas amount change command is issued until the EGR gas amount in the cylinder 2 reaches an amount in the vicinity of the premixed combustion EGR gas amount Qh is actually The time corresponding to the amount of EGR gas in the cylinder 2 can be set.

  In the re-transition combustion switching control, the operating state of the internal combustion engine 1 is shifted from the normal combustion region R2 to the premixed combustion region R1 and the combustion mode is changed from normal combustion to premixed combustion, as in the sixth, seventh, and eighth embodiments. The present invention can also be applied when the operating state of the internal combustion engine 1 returns to the normal combustion region R2 while changing the fuel injection timing to be switched.

  In this case, the fuel injection timing from when the EGR gas amount change command is issued until the EGR gas amount in the cylinder 2 reaches the amount in the vicinity of the normal combustion EGR gas amount Qd is determined by the actual EGR gas amount in the cylinder 2. It can be a corresponding time.

  Therefore, according to the present embodiment, it is possible to further suppress the EGR gas amount in the cylinder 2 from being excessive or insufficient with respect to the fuel injection timing.

  The schematic configuration of the internal combustion engine and its intake / exhaust system according to this embodiment is the same as that of the first embodiment. Also in the present embodiment, the combustion switching control similar to that in the first embodiment is performed.

<Control during re-transition before starting change>
In the combustion switching control according to the present embodiment, as described above, when the operating state of the internal combustion engine 1 shifts from the first region to the second region, the first predetermined response delay time M12d or the first (2) The change of the fuel injection timing is started after a predetermined response delay time M21d has elapsed.

  In such a case, the operating state of the internal combustion engine 1 may shift again from the second region to the first region before the first predetermined response delay time M12d or the second predetermined response delay time M21d elapses. In this case, in the present embodiment, re-migration control before start of change described below is performed. Here, before the first predetermined response delay time M12d elapses from the time when the operating state of the internal combustion engine 1 shifts from the premixed combustion region R1 to the normal combustion region R2, the operating state of the internal combustion engine 1 is changed to the normal combustion region. An explanation will be given based on the time chart shown in FIG. 23 by taking as an example the control at the time of re-transition before start of change when the transition is made again from R2 to the premixed combustion region R1.

  In FIG. 23, at (a), the operating state of the internal combustion engine 1 shifts from the premixed combustion region R1 to the normal combustion region R2. At this time, an EGR gas amount change command is issued from the ECU 20, and after the valve response delay time Δtv has elapsed, the opening of the EGR valve 13 changes from the premixed combustion opening Vh to the normal combustion opening Vd.

  Then, before the first predetermined response delay time M12d elapses from the time point (a) (before the time point (b)), the operation state of the internal combustion engine 1 is predicted from the normal combustion region R2 at the time point (d). It moves again to the mixed combustion region R1.

  In the re-transition control before the start of change according to the present embodiment, at the time of (d), an EGR gas amount change command is issued from the ECU 20 to the actuator 14 so as to return the opening of the EGR valve 13 to the premixed combustion opening Vh. Is issued. As a result, the opening degree of the EGR valve 13 changes from the normal combustion opening degree Vd to the premixed combustion opening degree Vh after the valve response delay time Δtv has elapsed from the time point (d).

  Even in such a case, since the EGR valve 13 once becomes the normal combustion opening degree Vd, the cylinder 2 is detected at the time point (b) when the first predetermined response delay time M12d has elapsed from the time point (a). The EGR gas amount in the inside changes toward the normal combustion EGR gas amount Qd. That is, the amount of EGR gas in the cylinder 2 decreases. However, since the opening degree of the EG valve 13 is returned to the premixed combustion opening degree Vh, the EGR gas amount in the cylinder 2 does not reach the normal combustion EGR gas amount Qd and is premixed at the time point (n). It returns to the combustion EGR gas amount Qh.

  At this time, when the operating state of the internal combustion engine 1 again shifts from the normal combustion region R2 to the premixed combustion region R1 at the time (d), it is the same as the switching from the normal combustion to the premixed combustion in the normal combustion switching control. When the change of the fuel injection timing is started, as shown by the broken line in the fuel injection timing of FIG. 23, the fuel injection timing is immediately changed to the normal combustion injection timing Itd at the time of (d). From there, the change of the fuel injection timing in the normal combustion switching control from the normal combustion injection timing Itd to the premixed combustion injection timing Ith is started.

  However, when the operating state of the internal combustion engine 1 shifts again from the normal combustion region R2 to the premixed combustion region R1 at the time as in the present embodiment, as described above, the amount of EGR gas in the cylinder 2 is (b) From time point (d) onward, the premixed combustion EGR gas amount Qh is almost the same. Therefore, when the fuel injection timing is controlled as described above, the EGR gas amount in the cylinder 2 may be excessive with respect to the fuel injection timing.

  Therefore, in the re-transition control before the start of change according to the present embodiment, the fuel injection timing is maintained at the premixed combustion injection timing Ith at the time (d) and thereafter.

  According to this, it is possible to suppress an excessive amount of EGR gas in the cylinder 2 with respect to the fuel injection timing.

  The re-transition control before starting change as described above is performed before the second predetermined response delay time M21d elapses from the time when the operating state of the internal combustion engine 1 shifts from the normal combustion region R2 to the premixed combustion region R1. This can also be applied to the case where the operation state 1 shifts again from the premixed combustion region R1 to the normal combustion region R2.

  In this case, the fuel injection timing is maintained at the normal combustion injection timing Itd at the time when the operating state of the internal combustion engine 1 again shifts from the premixed combustion region R1 to the normal combustion region R2, and thereafter. Thereby, it can suppress that the amount of EGR gas in the cylinder 2 is insufficient with respect to the fuel injection timing.

<Control routine for re-transition control before change start>
Here, the control routine of the re-migration control before the start of change according to the present embodiment will be described based on the flowchart shown in FIG. Here, similarly to the above, the operating state of the internal combustion engine 1 before the first predetermined response delay time M12d elapses from the time when the operating state of the internal combustion engine 1 shifts from the premixed combustion region R1 to the normal combustion region R2. Will be described by taking as an example the case where the fuel gas is transferred again from the normal combustion region R2 to the premixed combustion region R1. This routine is stored in advance in the ECU 20 and is executed at predetermined intervals during the operation of the internal combustion engine 1.

  In this routine, first, in S1001, the ECU 20 determines whether or not the operating state of the internal combustion engine 1 has shifted from the premixed combustion region R1 to the normal combustion region R2. If an affirmative determination is made in S1001, the ECU 20 proceeds to S1002, and if a negative determination is made, the ECU 20 ends the execution of this routine.

  In S1002, the ECU 20 determines whether or not the operating state of the internal combustion engine 1 has shifted again from the normal combustion region R2 to the premixed combustion region R1. If an affirmative determination is made in S1002, the ECU 20 proceeds to S1003, and if a negative determination is made, the ECU 20 repeats S1002.

  In S1003, the ECU 20 determines whether or not the first predetermined response delay time M12d has elapsed since it was determined in S1001 that the operating state of the internal combustion engine 1 has shifted from the premixed combustion region R1 to the normal combustion region R2. If an affirmative determination is made in S1003, the ECU 20 ends the execution of this routine. If a negative determination is made, the ECU 20 proceeds to S1004.

  In S1004, the ECU 20 issues an EGR gas amount change command to the actuator 14 so as to change the opening of the EGR valve 13 to the premixed combustion opening Vh.

  Next, the ECU 20 proceeds to S1005 and maintains the fuel injection timing at the premixed combustion injection timing Ith. Thereafter, the ECU 20 ends the execution of this routine.

  The schematic configuration of the internal combustion engine and its intake / exhaust system according to this embodiment is the same as that of the first embodiment. Also in the present embodiment, the combustion switching control similar to that in the first embodiment is performed.

<Control during re-transition before starting change>
Here, the re-migration control before the start of change according to the present embodiment will be described based on the time chart shown in FIG. Here, before the first predetermined response delay time M12d elapses from the time when the operating state of the internal combustion engine 1 shifts from the premixed combustion region R1 to the normal combustion region R2, the operating state of the internal combustion engine 1 is changed to the normal combustion region. The case where the transition is made again from R2 to the premixed combustion region R1 will be described as an example.

  The time points (a), (b), (d), and (n) in FIG. 25 represent the same timing as the time points (a), (b), (d), and (n) in FIG. 23, respectively. ing. Also in this embodiment, at the time of (d), an EGR gas amount change command is issued from the ECU 20 to the actuator 14 so as to return the opening degree of the EGR valve 13 to the premixed combustion opening degree Vh.

  In such a case, as described above, the EGR gas amount in the cylinder 2 temporarily decreases from the time point (b) to the time point (n). In the re-transition control before the start of change according to the present embodiment, the fuel injection timing is set to the premixed combustion injection in accordance with the decrease in the EGR gas amount in the cylinder 2 from the time point (b) to the time point (n). The normal combustion injection timing Itd is changed from the timing Ith. That is, the fuel injection timing is temporarily retarded from the premixed combustion injection timing Ith.

  At this time, the time during which the EGR gas amount in the cylinder 2 temporarily decreases, that is, the time from the time point (b) to the time point (n) is defined as an EGR gas amount decrease time Δtgd. The EGR gas amount decrease time Δtgd can be obtained based on the time during which the opening degree of the EGR valve 13 is the normal combustion opening degree Vd. The time during which the opening degree of the EGR valve 13 is the normal combustion opening degree Vd is equivalent to the time Δtvd from the time point (a) to the time point (d).

  Therefore, the fuel injection timing is retarded from the time point (d) until the EGR gas amount decrease time Δtgd elapses. At this time, the fuel injection timing is not delayed until the normal combustion injection timing Itd, but is delayed according to the amount of decrease in the EGR gas amount in the cylinder 2.

  According to the re-transition control before the start of change as described above, the fuel injection timing can be set to a timing corresponding to the actual EGR gas amount in the cylinder 2. That is, even when the EGR gas amount in the cylinder 2 temporarily decreases, it is possible to further suppress the shortage of the EGR gas amount in the cylinder 2 with respect to the fuel injection timing.

  In the re-transition control before the start of the change, the operation of the internal combustion engine 1 is performed before the second predetermined response delay time M21d has elapsed from the time when the operation state of the internal combustion engine 1 has shifted from the normal combustion region R2 to the premixed combustion region R1. The present invention can also be applied to a case where the state again shifts from the premixed combustion region R1 to the normal combustion region R2.

  In this case, the fuel injection timing is temporarily changed from the normal combustion injection timing Itd from the time when the second predetermined response delay time M21d has elapsed from the time when the operating state of the internal combustion engine 1 has shifted from the normal combustion region R2 to the premixed combustion region R1. Is also changed to the premixed combustion injection timing Ith side. That is, the fuel injection timing is temporarily advanced from the normal combustion injection timing Itd. Thereby, even when the amount of EGR gas in the cylinder 2 temporarily increases, it is possible to further suppress the amount of EGR gas in the cylinder 2 from being excessive with respect to the fuel injection timing.

<Control routine for re-transition control before change start>
Here, the control routine of the re-transition control before the start of change according to the present embodiment will be described based on the flowchart shown in FIG. Here, similarly to the above, the first predetermined response delay time M from the time when the operating state of the internal combustion engine 1 shifts from the premixed combustion region R1 to the normal combustion region R2.
An example will be described in which the operating state of the internal combustion engine 1 is shifted again from the normal combustion region R2 to the premixed combustion region R1 before 12d elapses. Also, S1001 to S1005 in this routine are the same as the control routine shown in FIG. This routine is stored in advance in the ECU 20 and is executed at predetermined intervals during the operation of the internal combustion engine 1.

  In this routine, the ECU 20 proceeds to S1106 after S1005. In S1106, the ECU 20 determines again whether or not the first predetermined response delay time M12d has elapsed since it was determined in S1001 that the operating state of the internal combustion engine 1 has shifted from the premixed combustion region R1 to the normal combustion region R2. . If an affirmative determination is made in S1106, the ECU 20 proceeds to S1107, and if a negative determination is made, the ECU 20 returns to S1005.

  In S1107, the ECU 20 calculates the EGR gas amount decrease time Δtgd based on the time Δtvd from the time point (a) to the time point (d).

  Next, the ECU 20 proceeds to S1108, and the EGR gas amount from the time when the first predetermined response delay time M12d has elapsed since it was determined that the operating state of the internal combustion engine 1 has shifted from the premixed combustion region R1 to the normal combustion region R2. The fuel injection timing is advanced from the premixed combustion injection timing Ith until the decrease time Δtgd elapses.

  Next, the ECU 20 proceeds to S1109 and maintains the fuel injection timing at the premixed combustion injection timing Ith. Thereafter, the ECU 20 ends the execution of this routine.

  The schematic configuration of the internal combustion engine and its intake / exhaust system according to this embodiment is the same as that of the first embodiment.

  In the present embodiment, when the combustion mode of the internal combustion engine 1 is normal combustion, the fuel injection to be executed at the timing near the top dead center of the compression stroke is set as the main fuel injection, and the fuel injection valve 10 is used before the main fuel injection. A secondary fuel injection is performed at the timing. When the combustion mode of the internal combustion engine 1 is premixed combustion, this auxiliary fuel injection is stopped. In the combustion switching control according to the present embodiment, the main fuel injection timing is controlled similarly to the control of the fuel injection timing in the combustion switching control according to the first embodiment.

<Control during re-transition before starting change>
Here, the re-migration control before the start of change according to the present embodiment will be described based on the time chart shown in FIG. Here, before the first predetermined response delay time M12d elapses from the time when the operating state of the internal combustion engine 1 shifts from the premixed combustion region R1 to the normal combustion region R2, the operating state of the internal combustion engine 1 is changed to the normal combustion region. The case where the transition is made again from R2 to the premixed combustion region R1 will be described as an example.

  The time points (a), (b), (d), and (n) in FIG. 27 represent the same timing as the time points (a), (b), (d), and (n) in FIG. 23, respectively. ing. As shown in FIG. 27, the opening degree of the EGR valve 13 is controlled in the same manner as in the eleventh embodiment. Further, the main fuel injection timing is controlled in the same manner as the fuel injection timing control in the eleventh embodiment.

At this time, when the operating state of the internal combustion engine 1 again shifts from the normal combustion region R2 to the premixed combustion region R1 at the time point (d), as shown by the broken line in the auxiliary fuel injection in FIG. As in the case of execution, when the execution of the auxiliary fuel injection is started at the time point (d), the auxiliary fuel injection is executed in a state where the main fuel injection timing is the premixed combustion injection timing Ith or a timing close thereto. Will be. In this case, bore flushing is likely to occur due to the fuel injected by the auxiliary fuel injection.

  Therefore, in the re-transition control before the start of change according to the present embodiment, the stop of the auxiliary fuel injection is continued at the time point (d) and thereafter.

  According to this, it is possible to suppress the sub fuel injection from being executed when the main fuel injection timing is the premixed combustion injection timing Ith or a timing in the vicinity thereof. Therefore, the occurrence of bore flushing can be suppressed.

  Further, if the auxiliary fuel injection is executed when the main fuel injection timing is temporarily advanced from the premixed combustion injection timing Ith (between (b) and (n) in FIG. 27), the ignition delay is delayed. There is a risk that the amount of smoke generated will increase due to the shortening of the period. According to the re-transition control before the start of the change, the amount of smoke generated can be reduced by continuing to stop the auxiliary fuel injection even in such a period.

  In the re-transition control before the start of the change, the operation of the internal combustion engine 1 is performed before the second predetermined response delay time M21d has elapsed from the time when the operation state of the internal combustion engine 1 has shifted from the normal combustion region R2 to the premixed combustion region R1. The present invention can also be applied to a case where the state again shifts from the premixed combustion region R1 to the normal combustion region R2.

  If the sub fuel injection is stopped when the main fuel injection timing is at or near the normal combustion injection timing Itd, combustion in the cylinder 2 becomes unstable and combustion noise worsens or misfire occurs. There is a risk of doing.

  Therefore, in the re-transition control before the start of change according to the present embodiment, the auxiliary fuel injection timing is executed at the time when the operating state of the internal combustion engine 1 shifts again from the premixed combustion region R1 to the normal combustion region R2 and thereafter. continue.

  As a result, it is possible to suppress the sub fuel injection from being stopped when the main fuel injection timing is the normal combustion injection timing Itd or a timing in the vicinity thereof. Therefore, it is possible to suppress the combustion in the cylinder 2 from becoming unstable.

  Further, if the auxiliary fuel injection is stopped when the main fuel injection timing is temporarily delayed from the normal combustion injection timing Itd, there is a possibility that the ignition delay period becomes longer and the combustion noise is deteriorated. According to the re-transition control before starting the change, the deterioration of the combustion noise can be suppressed by continuing the execution of the auxiliary fuel injection even in such a period.

BRIEF DESCRIPTION OF THE DRAWINGS The figure which shows schematic structure of the internal combustion engine which concerns on Example 1, and its intake / exhaust system. The figure which shows the relationship between the driving | running state of an internal combustion engine, and the combustion mode in this internal combustion engine. 3 is a time chart showing combustion switching control according to the first embodiment. When the operating state of the internal combustion engine returns to the premixed combustion region, the EGR gas amount change command is issued again from the ECU, and the fuel injection timing in the combustion switching control is changed from the normal combustion injection timing to the premixed combustion injection timing. 6 is a time chart showing the relationship between the amount of EGR gas in the cylinder and the fuel injection timing when starting is started. FIG. 3 is a first time chart showing re-transition combustion switching control according to Embodiment 1. FIG. FIG. 6 is a second time chart showing the re-combustion combustion switching control according to Embodiment 1. FIG. 3 is a flowchart illustrating a control routine of re-burning combustion switching control according to the first embodiment. 9 is a flowchart showing a control routine of re-transfer fuel injection amount control according to Embodiment 2. 9 is a flowchart showing a control routine for re-transmission fuel injection amount control according to a modification of the second embodiment. The figure which shows the change of the engine load of an internal combustion engine at the time of applying the fuel injection amount control at the time of re-transfer concerning the modification of Example 2. FIG. 9 is a flowchart showing a control routine of re-transmission fuel injection stop control according to Embodiment 3. 10 is a flowchart showing a control routine for re-transmission fuel injection amount control according to Embodiment 4; The figure which shows the change of the driving | running state of an internal combustion engine at the time of applying the fuel injection amount control at the time of re-transition which concerns on Example 4. FIG. 10 is a flowchart showing a control routine of re-transfer fuel injection amount control according to Embodiment 5. The figure which shows the change of the driving | running state of an internal combustion engine at the time of applying the fuel injection amount control at the time of re-transition which concerns on Example 5. FIG. FIG. 10 is a time chart illustrating combustion switching control during re-transition according to Embodiment 6. FIG. 10 is a flowchart showing a control routine of re-burning combustion switching control according to Embodiment 6. FIG. 10 is a time chart illustrating combustion switching control during re-transition according to Embodiment 7. FIG. 10 is a flowchart showing a control routine of re-burning combustion switching control according to a seventh embodiment. FIG. 10 is a time chart showing combustion transition control during re-transition according to an eighth embodiment. FIG. 10 is a flowchart showing a control routine of combustion switching control at the time of retransfer according to an eighth embodiment. FIG. 10 is a time chart showing combustion transition control during re-transition according to Embodiment 9. FIG. The time chart showing the control at the time of re-migration before the start of a change which concerns on Example 10. FIG. 18 is a flowchart illustrating a control routine for re-migration control before start of change according to a tenth embodiment. The time chart showing the control at the time of re-transfer before the change which concerns on Example 11. FIG. 18 is a flowchart showing a control routine for re-shift control before start of change according to Embodiment 11. FIG. 19 is a time chart showing re-migration control before start of change according to Embodiment 12. FIG.

Explanation of symbols

1. Compression ignition internal combustion engine (internal combustion engine)
2 ... Cylinder 3 ... Piston 8 ... Intake passage 9 ... Exhaust passage 10 ... Fuel injection valve 11 ... Combustion chamber 12 ... EGR passage 13 ... EGR valve 14 ... Actuator 20 ... ECU
23 .... Crank position sensor 24..Accelerator opening sensor 25..Exhaust gas recirculation device (EGR device)

Claims (17)

An EGR passage communicating the exhaust system and the intake system of the compression ignition internal combustion engine;
EGR gas amount control means for controlling the flow rate of EGR gas in the EGR passage,
An exhaust gas recirculation device for introducing a part of the exhaust gas discharged from the compression ignition internal combustion engine into the intake system as EGR gas;
Command means for giving a command to the exhaust gas recirculation device to change the EGR gas amount in the cylinder by controlling the EGR gas amount control means;
A fuel injection valve for injecting fuel into a cylinder of the compression ignition internal combustion engine;
The operation state of the compression ignition internal combustion engine belongs to a premixed combustion region in which premixed combustion is performed in which premixed gas is formed by injecting fuel from the fuel injection valve at a time earlier than the time near the top dead center of the compression stroke. Or a determination means for determining whether it belongs to a normal combustion region in which normal combustion is performed by injecting fuel from the fuel injection valve at a time near the top dead center of the compression stroke,
Either one of the premixed combustion region and the normal combustion region is a first region and the other is a second region,
When it is determined by the determination means that the operation state of the compression ignition internal combustion engine has shifted from the first region to the second region, the EGR gas amount control means burns the EGR gas amount in the cylinder in the first region. The target EGR gas amount in the mode is changed to the target EGR gas amount in the combustion mode in the second region, and the fuel injection timing from the fuel injection valve is changed from the target fuel injection timing in the combustion mode in the first region to the second region. In a combustion switching control system for a compression ignition internal combustion engine that switches the combustion mode by changing the target fuel injection timing in the combustion mode at a predetermined pattern in
While the operation state of the compression ignition internal combustion engine has shifted from the first region to the second region and the combustion mode is being switched, the operation state of the compression ignition internal combustion engine is changed to the second region by the determination means. When it is determined that the transition has been made again from the first region to the first region, the EGR gas amount in the cylinder continues to be changed to the target EGR gas amount in the combustion mode in the second region, and in the second region of the fuel injection timing. The change to the target fuel injection timing in the combustion mode is continued according to the predetermined pattern, and the EGR gas amount in the cylinder becomes the target EGR gas amount in the combustion mode in the second region or an amount in the vicinity thereof, and the fuel injection timing Is the target fuel injection timing in the combustion mode in the second region, and then the EGR gas amount in the cylinder is changed to the target EGR gas amount in the combustion mode in the first region. A command is issued from the command means to the exhaust gas recirculation device, and a change to the target fuel injection timing in the combustion mode in the first region of the fuel injection timing is started in the predetermined pattern. A combustion switching control system for a compression ignition internal combustion engine. A first region is the normal combustion region and a second region is the premixed combustion region;
A region where the engine load of the compression ignition internal combustion engine is higher than a predetermined load is a first region, and a region where the engine load is equal to or less than the predetermined load is a second region,
In the case where the predetermined load is a value lower than a premix combustion upper limit load that is an upper limit value of the engine load of the compression ignition internal combustion engine capable of performing premix combustion,
The engine load of the compression ignition internal combustion engine rises from the predetermined load while the combustion mode is being switched because the operation state of the compression ignition internal combustion engine has shifted from the first region to the second region. And when it is determined by the determination means that the operation state of the compression ignition internal combustion engine has shifted from the second region to the first region again,
The compression is performed until the EGR gas amount in the cylinder becomes the target EGR gas amount in the combustion mode in the second region or an amount in the vicinity thereof and the fuel injection timing becomes the target fuel injection timing in the combustion mode in the second region. The combustion switching control system for a compression ignition internal combustion engine according to claim 1, wherein the fuel injection amount from the fuel injection valve is controlled so that the engine load of the ignition internal combustion engine does not become higher than the premix combustion upper limit load.   When it is determined by the determination means that the operation state of the compression ignition internal combustion engine has shifted again from the second region to the first region, the EGR gas amount in the cylinder is the target EGR gas in the combustion mode in the second region The fuel injection amount from the fuel injection valve is prohibited until the fuel injection timing reaches the target fuel injection timing in the combustion mode in the second region. 3. A combustion switching control system for a compression ignition internal combustion engine according to 2.   When the engine load of the compression ignition internal combustion engine rises to be higher than the predetermined load, and the determination means determines that the operation state of the compression ignition internal combustion engine has shifted again from the second region to the first region, The compression ignition is performed until the EGR gas amount in the cylinder becomes the target EGR gas amount in the combustion mode in the second region or an amount in the vicinity thereof and the fuel injection timing becomes the target fuel injection timing in the combustion mode in the second region. 3. The combustion switching control of a compression ignition internal combustion engine according to claim 2, wherein an increase rate of the fuel injection amount from the fuel injection valve is limited so that an engine load of the internal combustion engine does not become higher than the premixed combustion upper limit load. system. A first region is the normal combustion region and a second region is the premixed combustion region;
A region where the engine speed of the compression ignition internal combustion engine is higher than a predetermined upper limit speed is the first region, and a region where the engine speed is equal to or less than the predetermined upper limit speed is the second region,
In the case where the predetermined upper limit rotational speed is a value lower than a premix combustion upper limit rotational speed that is an upper limit value of the engine rotational speed of the compression ignition internal combustion engine capable of performing premix combustion,
While the operation state of the compression ignition internal combustion engine has shifted from the first region to the second region and the combustion mode is being switched, the engine speed of the compression ignition internal combustion engine increases and the predetermined upper limit is reached. And the determination means determines that the operation state of the compression ignition internal combustion engine has shifted again from the second region to the first region, and the amount of EGR gas in the cylinder is in the second region. The engine speed of the compression ignition internal combustion engine becomes the premixed combustion before the fuel injection timing becomes the target fuel injection timing in the combustion mode in the second region. 2. The combustion switching control system for a compression ignition internal combustion engine according to claim 1, wherein when the engine speed becomes higher than an upper limit rotational speed, fuel injection from the fuel injection valve is stopped. A first region is the normal combustion region and a second region is the premixed combustion region;
A region where the engine speed of the compression ignition internal combustion engine is higher than a predetermined upper limit speed is the first region, and a region where the engine speed is equal to or less than the predetermined upper limit speed is the second region,
In the case where the predetermined upper limit rotational speed is a value lower than a premix combustion upper limit rotational speed that is an upper limit value of the engine rotational speed of the compression ignition internal combustion engine capable of performing premix combustion,
While the operation state of the compression ignition internal combustion engine has shifted from the first region to the second region and the combustion mode is being switched, the engine speed of the compression ignition internal combustion engine increases and the predetermined upper limit is reached. When the engine speed is higher than the engine speed and the determination means determines that the operation state of the compression ignition internal combustion engine has shifted again from the second region to the first region, the amount of EGR gas in the cylinder burns in the second region. Until the fuel injection timing reaches the target fuel injection timing in the combustion mode in the second region, the engine speed of the compression ignition internal combustion engine is the premixed combustion upper limit rotation. 2. The combustion switching control system for a compression ignition internal combustion engine according to claim 1, wherein a fuel injection amount from the fuel injection valve is controlled so as not to exceed a number. The engine speed of the compression ignition internal combustion engine increases to be higher than the predetermined upper limit engine speed, and the determination means determines that the operation state of the compression ignition internal combustion engine has shifted from the second region to the first region again. In this case, until the EGR gas amount in the cylinder is equal to or near the target EGR gas amount in the combustion mode in the second region and the fuel injection timing becomes the target fuel injection timing in the combustion mode in the second region, The fuel injection amount from the fuel injection valve is limited so that the engine speed of the compression ignition internal combustion engine is maintained at a predetermined speed higher than the predetermined upper limit speed and lower than the premix combustion upper limit speed. A combustion switching control system for a compression ignition internal combustion engine according to claim 6. A first region is the normal combustion region and a second region is the premixed combustion region;
A region where the engine speed of the compression ignition internal combustion engine is lower than a predetermined lower limit speed is a first region, and a region where the engine speed is equal to or higher than the predetermined lower limit speed is a second region,
In the case where the predetermined lower limit rotational speed is a value higher than a premixed combustion lower limit rotational speed that is a lower limit value of the engine speed of the compression ignition internal combustion engine capable of performing premixed combustion,
While the operation state of the compression ignition internal combustion engine has shifted from the first region to the second region and the combustion mode is being switched, the engine speed of the compression ignition internal combustion engine decreases and the predetermined lower limit is reached. And the determination means determines that the operation state of the compression ignition internal combustion engine has shifted again from the second region to the first region, and the EGR gas amount in the cylinder is determined to be in the second region. The engine speed of the compression ignition internal combustion engine becomes the premixed combustion before the fuel injection timing becomes the target fuel injection timing in the combustion mode in the second region. 2. The combustion switching control system for a compression ignition internal combustion engine according to claim 1, wherein when the engine speed becomes lower than a lower limit rotational speed, fuel injection from the fuel injection valve is stopped. A first region is the normal combustion region and a second region is the premixed combustion region;
A region where the engine speed of the compression ignition internal combustion engine is lower than a predetermined lower limit speed is a first region, and a region where the engine speed is equal to or higher than the predetermined lower limit speed is a second region,
The predetermined lower limit rotational speed is higher than a premix combustion lower limit rotational speed that is a lower limit value of the engine speed of the compression ignition internal combustion engine capable of performing premix combustion, and the premix combustion lower limit When the engine speed of the compression ignition internal combustion engine is lower as the engine speed is lower,
While the operation state of the compression ignition internal combustion engine has shifted from the first region to the second region and the combustion mode is being switched, the engine speed of the compression ignition internal combustion engine decreases and the predetermined lower limit is reached. When the engine speed is lower than the rotational speed and the determination means determines that the operation state of the compression ignition internal combustion engine has shifted again from the second region to the first region, the amount of EGR gas in the cylinder burns in the second region. Until the fuel injection timing reaches the target fuel injection timing in the combustion mode in the second region, the engine speed of the compression ignition internal combustion engine is the premixed combustion lower limit rotation. 2. The combustion switching control system for a compression ignition internal combustion engine according to claim 1, wherein the fuel injection amount from the fuel injection valve is limited so as not to be lower than the number. An EGR passage communicating the exhaust system and the intake system of the compression ignition internal combustion engine;
EGR gas amount control means for controlling the flow rate of EGR gas in the EGR passage,
An exhaust gas recirculation device for introducing a part of the exhaust gas discharged from the compression ignition internal combustion engine into the intake system as EGR gas;
Command means for giving a command to the exhaust gas recirculation device to change the EGR gas amount in the cylinder by controlling the EGR gas amount control means;
A fuel injection valve for injecting fuel into a cylinder of the compression ignition internal combustion engine;
The operation state of the compression ignition internal combustion engine belongs to a premixed combustion region in which premixed combustion is performed in which premixed gas is formed by injecting fuel from the fuel injection valve at a time earlier than the time near the top dead center of the compression stroke. Or a determination means for determining whether it belongs to a normal combustion region in which normal combustion is performed by injecting fuel from the fuel injection valve at a time near the top dead center of the compression stroke,
Either one of the premixed combustion region and the normal combustion region is a first region and the other is a second region,
When it is determined by the determination means that the operating state of the compression ignition internal combustion engine has shifted from the first region to the second region, the EGR gas amount control means determines the EGR gas amount in the cylinder in the first region. The target EGR gas amount in the combustion mode is changed to the target EGR gas amount in the combustion mode in the second region, and the fuel injection timing from the fuel injection valve is changed from the target fuel injection timing in the combustion mode in the first region to the second time. The combustion mode is switched by gradually changing the target fuel injection timing in the combustion mode in the region over the first predetermined time,
When it is determined by the determination means that the operation state of the compression ignition internal combustion engine has shifted from the second region to the first region, the EGR gas amount control means burns the EGR gas amount in the cylinder in the second region. The target EGR gas amount in the first region is changed to the target EGR gas amount in the combustion mode in the first region, and the fuel injection timing from the fuel injection valve is changed from the target fuel injection timing in the combustion mode in the second region to the first region. In the combustion switching control system for a compression ignition internal combustion engine that switches the combustion mode by gradually changing the target fuel injection timing in the combustion mode at a second over a predetermined time,
While the operation state of the compression ignition internal combustion engine has shifted from the first region to the second region and the combustion mode is being switched, the operation state of the compression ignition internal combustion engine is changed to the second region by the determination means. From the command means to change the EGR gas amount in the cylinder to the target EGR gas amount in the combustion mode in the first region at the time when the determination is made again. A command is issued to the exhaust gas recirculation device, a change to the target fuel injection timing in the combustion mode in the first region of the fuel injection timing is started, and a switch to the combustion mode in the second region is started. A switching progress ratio that is a ratio of the time until the time when it is determined that the operating state of the compression ignition internal combustion engine has transitioned again to the first region with respect to the first predetermined time is calculated. The combustion switching control of the compression ignition internal combustion engine, wherein the fuel injection timing is changed to the target fuel injection timing in the combustion mode in the first region over time calculated by multiplying the second predetermined time by system.   When it is determined by the determination means that the operation state of the compression ignition internal combustion engine has shifted again from the second region to the first region, the amount of EGR gas in the cylinder is changed to the target EGR gas in the combustion mode in the first region. A command is issued from the command means to the exhaust gas recirculation device so as to change to an amount, and from the time when the command is issued, the EGR gas amount in the cylinder is the target EGR gas in the combustion mode in the first region. When the EGR gas amount change delay time, which is the time until the actual change starts toward the amount, has elapsed, a change toward the target fuel injection timing in the combustion mode in the first region of the fuel injection timing is started. The combustion switching control system for a compression ignition internal combustion engine according to claim 10.   When it is determined by the determination means that the operation state of the compression ignition internal combustion engine has shifted again from the second region to the first region, the amount of EGR gas in the cylinder is changed to the target EGR gas in the combustion mode in the first region. A command is issued from the command means to the exhaust gas recirculation device so as to change to an amount, and from the time when the command is issued, the EGR gas amount in the cylinder is the target EGR gas in the combustion mode in the first region. It is determined that the operation state of the compression ignition internal combustion engine has shifted to the first region again until the injection timing maintenance time, which is a longer time than the time until the actual start of the change to the quantity, elapses. 11. The compression according to claim 10, wherein the current fuel injection timing is maintained, and thereafter, a change toward the target fuel injection timing in the combustion mode in the first region of the fuel injection timing is started. Combustion switching control system of fire internal combustion engine.   When it is determined by the determination means that the operation state of the compression ignition internal combustion engine has shifted again from the second region to the first region, the EGR gas amount in the cylinder is changed to the target EGR gas in the combustion mode in the first region. A command is issued from the command means to the exhaust gas recirculation device so as to change to an amount, and from the time when the command is issued, the EGR gas amount in the cylinder is the target EGR gas in the combustion mode in the first region. When the EGR gas amount change delay time, which is the time until the actual change starts toward the amount, elapses, the rate of change of the fuel injection timing becomes zero, and then the change of the fuel injection timing is combusted in the first region. The combustion switching control system for a compression ignition internal combustion engine according to claim 10, wherein the fuel injection timing is changed so as to shift to a change toward the target fuel injection timing in the mode. An EGR passage communicating the exhaust system and the intake system of the compression ignition internal combustion engine;
EGR gas amount control means for controlling the flow rate of EGR gas in the EGR passage,
An exhaust gas recirculation device for introducing a part of the exhaust gas discharged from the compression ignition internal combustion engine into the intake system as EGR gas;
Command means for giving a command to the exhaust gas recirculation device to change the EGR gas amount in the cylinder by controlling the EGR gas amount control means;
A fuel injection valve for injecting fuel into a cylinder of the compression ignition internal combustion engine;
The operation state of the compression ignition internal combustion engine belongs to a premixed combustion region in which premixed combustion is performed in which premixed gas is formed by injecting fuel from the fuel injection valve at a time earlier than the time near the top dead center of the compression stroke. Or a determination means for determining whether it belongs to a normal combustion region in which normal combustion is performed by injecting fuel from the fuel injection valve at a time near the top dead center of the compression stroke,
Either one of the premixed combustion region and the normal combustion region is a first region and the other is a second region,
When it is determined by the determination means that the operation state of the compression ignition internal combustion engine has shifted from the first region to the second region, the EGR gas amount control means burns the EGR gas amount in the cylinder in the first region. A command is issued from the command means to the exhaust gas recirculation device to change the target EGR gas amount in the mode to the target EGR gas amount in the combustion mode in the second region, and after the command is issued, The fuel injection timing from the fuel injection valve is changed from the target fuel injection timing in the combustion mode in the first region after a predetermined response delay time, which is the time until the EGR gas amount in the cylinder actually starts to change, elapses. In the combustion switching control system for a compression ignition internal combustion engine that switches the combustion mode by changing to the target fuel injection timing in the combustion mode in the second region,
After the operation state of the compression ignition internal combustion engine has shifted from the first region to the second region, the command means issues a command to change the EGR gas amount in the cylinder to the exhaust gas recirculation device. If the determination means determines that the operation state of the compression ignition internal combustion engine has shifted again from the second region to the first region before the predetermined response delay time elapses, the state of the EGR gas amount control unit is changed. To return to the state corresponding to the target EGR gas amount in the combustion mode in the first region, and maintain the fuel injection timing at the target fuel injection timing in the combustion mode in the first region at and after the determination is made. A combustion switching control system for a compression ignition internal combustion engine.   The state of the EGR gas amount control means is the target in the combustion mode in the second region until the operation state of the compression ignition internal combustion engine transitions from the first region to the second region and again to the first region. When the operation state of the compression ignition internal combustion engine shifts again to the first region by being in a state corresponding to the EGR gas amount, the EGR gas amount in the cylinder is the target EGR gas amount side in the fuel mode of the second region 15. The combustion switching control system for a compression ignition internal combustion engine according to claim 14, wherein the fuel injection timing is changed in accordance with the change in the EGR gas amount during the period of change. A first region is the premixed combustion region and a second region is the normal combustion region;
At the time of normal combustion, fuel injection executed at a timing near the top dead center of the compression stroke is set as the main fuel injection, and the sub fuel injection is executed at a timing before the main fuel injection by the fuel injection valve. Is to stop
When it is determined by the determination means that the operation state of the compression ignition internal combustion engine has shifted from the first region to the second region, the EGR gas amount control means burns the EGR gas amount in the cylinder in the second region. A command is issued from the command means to the exhaust gas recirculation device to change to the target EGR gas amount in the mode, and after the command is issued, until the EGR gas amount in the cylinder actually starts to change. Combustion after changing the main fuel injection timing from the target fuel injection timing in the combustion mode in the first region to the target fuel injection timing in the combustion mode in the second region In a combustion switching control system for a compression ignition internal combustion engine for switching modes,
After the operation state of the compression ignition internal combustion engine has shifted from the first region to the second region, the command means issues a command to change the EGR gas amount in the cylinder to the exhaust gas recirculation device. If it is determined by the determination means that the operation state of the compression ignition internal combustion engine has shifted again from the second region to the first region before the predetermined response delay time elapses, and thereafter 16. The combustion switching control system for a compression ignition internal combustion engine according to claim 14, wherein the sub fuel injection is continuously stopped. A first region is the normal combustion region and a second region is the premixed combustion region;
At the time of normal combustion, fuel injection executed at a timing near the top dead center of the compression stroke is set as the main fuel injection, and the sub fuel injection is executed at a timing before the main fuel injection by the fuel injection valve. Is to stop
When it is determined by the determination means that the operation state of the compression ignition internal combustion engine has shifted from the first region to the second region, the EGR gas amount control means burns the EGR gas amount in the cylinder in the second region. A command is issued from the command means to the exhaust gas recirculation device to change to the target EGR gas amount in the mode, and after the command is issued, until the EGR gas amount in the cylinder actually starts to change. Combustion after changing the main fuel injection timing from the target fuel injection timing in the combustion mode in the first region to the target fuel injection timing in the combustion mode in the second region In a combustion switching control system for a compression ignition internal combustion engine for switching modes,
When the operating state of the compression ignition internal combustion engine has shifted from the first region to the second region, a command is issued from the command means to the exhaust gas recirculation device to change the EGR gas amount in the cylinder. If the determination means determines that the operation state of the compression ignition internal combustion engine has shifted from the second region to the first region before the predetermined response delay time elapses, the time when the determination is made and 16. The combustion switching control system for a compression ignition internal combustion engine according to claim 14, wherein the execution of the auxiliary fuel injection is continued thereafter.

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