JP4240943B2 - Apparatus for determining the steady state of an internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an internal combustion engine steady operation state determination device that switches an engine combustion mode between a plurality of combustion modes.
[0002]
[Prior art]
2. Description of the Related Art An internal combustion engine in which the engine combustion mode is switched between a plurality of combustion modes based on the engine operating state, such as a direct injection internal combustion engine in which fuel is directly injected into a combustion chamber from a fuel injection valve, is known. It has been. In such an internal combustion engine, for example, the stratified combustion mode is selected as the engine combustion mode in the low load and low rotation region, and the engine thermal efficiency is improved and the fuel efficiency is improved. On the other hand, in the high-load high-rotation region, the homogeneous combustion mode is selected as the engine combustion mode, and a longer fuel injection time is secured to ensure a predetermined engine output.
[0003]
Further, in such an internal combustion engine that switches the engine combustion mode between a plurality of combustion modes, the parameter that most accurately indicates the magnitude of the engine load differs depending on the combustion mode. For example, in the homogeneous combustion mode, a parameter indicating the actual intake air amount (or the intake pressure having a correlation therewith) is used as the engine load. On the other hand, in the stratified combustion mode, the intake air amount has a low correlation with the engine load, and it is not appropriate to use a parameter indicating this as the engine load.
[0004]
For this reason, for example, in the device described in Japanese Patent Application Laid-Open No. 2000-297688, when the engine combustion mode is set to the homogeneous combustion mode, an intake air amount (or intake pressure) that can obtain an engine output equivalent to the stratified combustion mode is obtained. This is used as the virtual intake air amount (or virtual intake pressure) in the stratified combustion mode. In the stratified combustion mode, a parameter indicating this virtual intake air amount is used as the engine load.
[0005]
Here, for example, the accelerator operation amount of the internal combustion engine can be adopted as a parameter used as the engine load in the stratified combustion mode. In this case, however, the physical quantity is completely different between the homogeneous combustion mode and the stratified combustion mode. A certain parameter will be used as the engine load. For this reason, it becomes necessary to construct various engine controls when the engine combustion mode is the homogeneous combustion mode and various engine controls when the engine combustion mode is the stratified combustion mode.
[0006]
In this regard, as described above, the parameters used as the engine load in each combustion mode, whether actual or virtual, are unified to the same physical quantity such as the intake air amount (or intake pressure), It is possible to improve the efficiency of various adaptation work accompanying the construction of engine control.
[0007]
By the way, such switching of the engine combustion mode is basically performed based on the engine operating state, but there are cases where the switching is performed based on a predetermined condition being satisfied or a specific switching request.
[0008]
For example, in an internal combustion engine provided with a NOx occlusion reduction type catalyst device (NOx catalyst device) in the engine exhaust system, when it is determined that the NOx occlusion amount exceeds a predetermined amount and the NOx occlusion capacity is reduced, Processing for switching the engine combustion mode to the homogeneous combustion mode in which the air-fuel ratio is made richer than the stoichiometric air-fuel ratio, rich spike processing is performed. Incidentally, in an internal combustion engine that operates under an air-fuel ratio with a very lean fuel concentration with the engine combustion mode set to the stratified combustion mode, a large amount of NOx is generated during the stratified combustion mode. An exhaust gas recirculation mechanism for recirculating a part of the exhaust gas to the intake passage is provided. In this exhaust gas recirculation mechanism, the NOx emission amount is reduced by increasing the heat capacity of the air-fuel mixture by exhaust gas recirculation and lowering its combustion temperature. The NOx occlusion reduction type catalyst device is provided to purify NOx that is still exhausted by such exhaust gas recirculation.
[0009]
In addition, for example, a control device for an internal combustion engine monitors the temperature of a catalyst device provided in the engine exhaust system such as the NOx catalyst device. Then, when it is determined that the predetermined exhaust purification capacity cannot be secured if the temperature of the catalyst device decreases to a predetermined temperature or less and then further decreases in temperature, the engine combustion mode is increased to raise the temperature of the catalyst device. A switching request is output from the control device. If there is such a switching request, even if the engine combustion mode set based on the engine operating state is the stratified combustion mode, the engine combustion mode is changed to the homogeneous combustion mode in which the exhaust temperature is higher than that of the stratified combustion mode. It is forcibly switched.
[0010]
In addition, when the engine combustion mode is switched based on the temperature increase request of the catalyst device, it is usually determined whether the internal combustion engine is in a steady operation state, specifically, a state where the engine load is in a low load region. The engine combustion mode is switched on the condition that it is determined whether or not the predetermined time has elapsed. The condition that the engine is in the steady operation state as described above is that when the engine operation state is in the middle load region or the high load region, the exhaust gas temperature is high in the first place, so that the current temperature of the catalyst device is low. This is because the temperature rise can be expected thereafter. Further, when the engine combustion mode is switched, the engine output may slightly vary. For this reason, in order to avoid giving an unintentional shock to the driver, it is necessary to suppress unnecessary switching of the engine combustion mode as much as possible.
[0011]
As described above, in the conventional internal combustion engine, the engine combustion mode is basically switched based on the engine operating state, and when a predetermined condition is satisfied or when a specific switching request is generated. In addition, the engine combustion mode is appropriately switched.
[0012]
[Problems to be solved by the invention]
However, in the engine combustion mode, when the switching process associated with the rich spike process and the switching process based on the catalyst temperature increase request are performed in parallel, the following problems cannot be ignored.
[0013]
That is, when the engine combustion mode is switched from the stratified combustion mode to the homogeneous combustion mode along with the rich spike processing, the parameter used as the engine load is also switched from the virtual intake air amount to the actual intake air amount. Here, the virtual intake air amount indicating the engine load in the stratified combustion mode is set so that the same engine output can be obtained if the engine combustion mode is set to the homogeneous combustion mode. This is based on the output characteristics at the time of steady operation in and only simulates the characteristics.
[0014]
That is, when the engine combustion mode is switched from the stratified combustion mode to the homogeneous combustion mode, the engine output hardly fluctuates if a steady operation is performed immediately after the switching. However, in actuality, immediately after switching from the stratified combustion mode to the homogeneous combustion mode, there is a response delay mainly in the change in the intake air amount. There is a period that is temporarily larger than the one. If there is a response delay of such a change in intake air amount, the engine load temporarily increases. Therefore, in the above-described engine combustion mode switching process based on the temperature increase request of the catalyst device, the internal combustion engine is in steady operation. It is determined that there is no state. Therefore, if the temperature of the catalyst device should be raised originally, there is a disadvantage that the temperature raising process is not properly executed due to a temporary increase in the engine load accompanying the rich spike process.
[0015]
FIG. 7 is a timing chart showing temporal transition of the intake air amount and the like accompanying such rich spike processing. Hereinafter, the response delay of the intake air amount change will be described in more detail with reference to FIG.
[0016]
In the rich spike process, first, exhaust gas recirculation (FIG. 5B) by the exhaust gas recirculation mechanism is stopped (timing t71). Next, the throttle valve ((c) in the figure) is closed by a predetermined amount, the fuel injection timing is switched from the compression stroke injection to the intake stroke injection ((a) in the same figure), and the engine combustion mode is switched to the homogeneous combustion mode. It is done. However, even if the throttle valve is closed as the engine combustion mode is switched to the homogeneous combustion mode in this way, the intake air amount ((d) in the figure) only gradually decreases with a response delay. On the other hand, the parameter used as the engine load ((e) in the figure) is changed from the virtual intake air amount to the actual intake air amount as the engine combustion mode is switched to the homogeneous combustion mode. For this reason, the engine load temporarily increases during the period (timing t72 to t74) from when the change is made until the intake air amount decreases to the amount during steady operation.
[0017]
Then, when the engine load temporarily increases in this way, this exceeds a threshold value for determining whether or not the engine operating state is in the low load region, and as a result, the count indicating the period during which the internal combustion engine is in the steady operating state. The value ((f) in the figure) is reset to “0” (timing t72 to t73). Therefore, if reset processing of the counter value associated with such rich spike processing is frequently performed, it is possible to shift to execution of the temperature increase processing even though the temperature of the catalyst device is lowered and the temperature increase request is generated. Disappear.
[0018]
Here, in order to eliminate such inconvenience, for example, the engine combustion mode is changed until the time when the intake air amount is reduced to the amount during normal operation (for example, timing t74) in anticipation of the response delay of the intake air amount change. It is also conceivable to employ a control method such as delaying the timing for switching to the homogeneous combustion mode. However, in this case, the period during which the engine combustion mode is set to the stratified combustion mode with the exhaust gas recirculation stopped (for example, timings t71 to t74) becomes long, and a significant increase in the NOx emission cannot be avoided.
[0019]
Further, in order to avoid such an increase in the NOx emission amount, if the exhaust gas recirculation is continued until the time when the engine combustion mode is switched to the homogeneous combustion mode (for example, timing t74) in the above case, the exhaust gas recirculation is performed. However, the amount of intake air is further reduced. For this reason, in the stratified combustion mode, the air-fuel ratio of the air-fuel mixture, particularly the air-fuel ratio of the air-fuel mixture around the spark plug becomes extremely rich, leading to deterioration of the combustion state and eventually misfire.
[0020]
Therefore, in an internal combustion engine that performs processing to switch the engine combustion mode to the homogeneous combustion mode in order to raise the temperature of the catalyst device on the condition that the steady operation state continues for a predetermined time while performing such rich spike processing. The inconvenience as described above cannot be avoided.
[0021]
The inconvenience caused by the response delay of the intake air amount change includes the switching process associated with the rich spike process for the engine combustion mode as described above and the switching process based on the catalyst temperature increase request on condition that the engine is in a steady operation state. This is extremely remarkable in an internal combustion engine that executes the above in parallel. However, the same inconvenience is that the engine combustion mode can be switched between a combustion mode in which a parameter indicating the actual intake air amount is used as the engine load and other combustion modes, and the steady state of the internal combustion engine is determined based on the engine load. The determination apparatus for determining the driving state is generally common.
[0022]
The present invention has been made in view of these conventional situations, and its purpose is to eliminate the influence as much as possible even when a response delay of intake air amount change occurs due to switching of the engine combustion mode. It is another object of the present invention to provide a steady operation state determination device for an internal combustion engine that can make an appropriate determination.
[0023]
[Means for Solving the Problems]
  The configuration for achieving the above object and the effects thereof will be described below.
  (1) The invention described in claim 1 relates to an internal combustion engine in which the engine combustion mode can be switched between a plurality of combustion modes including at least a specific combustion mode using a parameter indicating an actual intake air amount as an engine load. In the steady operation state determination device for an internal combustion engine, the steady combustion state determination device includes determination means for determining that the load is in a stable state and determining that the internal combustion engine is in a steady operation state when the stable state is continued. When the engine combustion mode is switched from the combustion mode other than the specific combustion mode to the specific combustion modeIt is determined whether the fluctuations in engine load that occurred are due to a temporary response delay in the change in intake air amount due to switching of the engine combustion mode, and the response delay in the change in intake air amount When a determination result indicating that it is caused is obtained, based on this result,An internal combustion engine, comprising: suppression means for executing a process for suppressing the influence of fluctuations in engine load on the determination relating to the stable state of the engine load by the determination means, that is, making the result of the determination incorrect. The first combustion mode switching process for switching the engine combustion mode from the other combustion mode to the specific combustion mode under a predetermined condition, and when there is a switching request for the engine combustion mode, the determination means A second combustion mode switching process for switching the engine combustion mode to a combustion mode that meets the switching request among the plurality of combustion modes is performed on condition that it is determined that the internal combustion engine is in a steady operation state. In the first combustion mode switching process, the homogeneous combustion mode in which the air-fuel ratio is set richer than the stoichiometric air-fuel ratio is specified. In rich spike processing, the engine combustion mode is switched from the stratified combustion mode as the other combustion mode to the homogeneous combustion mode with a predetermined period set based on the NOx occlusion amount in the NOx catalyst device of the engine exhaust system. The gist of the present invention is that the suppression means executes the suppression process when the engine combustion mode is switched by the first combustion mode switching process.
[0024]
  The above inventionAccording to the above, when the engine combustion mode is switched from the combustion mode other than the specific combustion mode to the specific combustion mode, the engine load fluctuates due to a temporary response delay of the intake air amount change caused by the switching. Even in this case, the influence of the fluctuation of the engine load on the determination relating to the stable state is suppressed. Therefore, when there is a response delay of the change in the intake air amount due to the switching of the engine combustion mode, it is erroneously determined that the internal combustion engine is in an unsteady operation state even though it is in a steady operation state. This makes it possible to make an appropriate determination while avoiding as much as possible.The above parameters correlate with the intake air amount such as the actual intake air pressure as well as the actual intake air amount detected by the detection means such as the intake air amount sensor, and there is a similar response delay. If it is a thing, this can be employ | adopted as what shows the engine load in specific combustion mode.
[0025]
  Further, according to the above invention, when the engine combustion mode is switched through the first combustion mode switching process, the engine combustion mode is switched due to a response delay of the intake air amount change even though the internal combustion engine is in a steady operation state. An erroneous determination that the internal combustion engine is in an unsteady operation state is avoided as much as possible, and an appropriate steady operation state determination is made. As a result, the second combustion mode switching process that is performed on the condition that it is determined that the internal combustion engine is in the steady operation state can be performed at an appropriate time according to the switching request. It becomes like this.
[0026]
  Normally, in the homogeneous combustion mode, a parameter indicating the actual intake air amount is used as the engine load, whereas in the stratified combustion mode, a parameter indicating the virtual intake air amount is used as the engine load. Therefore, in the above invention, when executing the first combustion mode switching process, the stratified combustion mode is switched to the homogeneous combustion mode (rich homogeneous combustion mode) in which the air-fuel ratio is set richer than the stoichiometric air-fuel ratio. The parameter used as the engine load can be switched from the parameter indicating the virtual intake air amount to the parameter indicating the actual intake air amount. Also, when trying to obtain the same engine output in both combustion modes, the actual intake air is set when the homogeneous combustion mode is set rather than when the engine combustion mode is set to the stratified combustion mode. The amount is relatively small. Therefore, in the first combustion mode switching process, the actual intake air amount decreases, and the engine load temporarily increases due to the response delay.
In this regard, in the above-described invention, even when the engine load temporarily increases due to the response delay of the intake air amount change, erroneous determination due to this is avoided as much as possible, and determination of an appropriate steady state of operation is made. Is done. Therefore, even when the rich spike process as the first combustion mode switching process is frequently executed prior to the second combustion mode switching process, the second combustion mode switching process is used as the switching request. It will be possible to do it appropriately.
[0027]
  (2) The invention described in claim 2 relates to an internal combustion engine in which the engine combustion mode can be switched between a plurality of combustion modes including at least a specific combustion mode using a parameter indicating an actual intake air amount as an engine load. In the steady operation state determination device for an internal combustion engine, the steady combustion state determination device includes determination means for determining that the load is in a stable state and determining that the internal combustion engine is in a steady operation state when the stable state is continued. When the engine combustion mode is switched from the stratified combustion mode as the combustion mode other than the specific combustion mode among the modes to the homogeneous combustion mode as the specific combustion modeIt is determined whether the fluctuations in engine load that occurred are due to a temporary response delay in the change in intake air amount due to switching of the engine combustion mode, and the response delay in the change in intake air amount When a determination result indicating that it is caused is obtained, based on this result,And a suppression unit that executes a process of suppressing an influence of a change in the engine load on the determination on the stable state of the engine load by the determination unit. When the change in engine load that occurs after switching the mode is due to a temporary response delay in intake air amount change caused by switching the engine combustion mode, the engine load is not in a stable state due to the change in the engine load. The gist is to prohibit judgment.
[0028]
  (3) A third aspect of the present invention is the internal combustion engine steady state determination apparatus according to the second aspect, wherein the determination means is configured to detect fluctuations in the engine load generated after switching the engine combustion mode. Temporary intake air amount due to the change of engine load due to the change of engine combustion mode when it is determined whether it is due to operation and the determination result that it is not due to accelerator pedal operation is obtained The gist is to determine that the change is due to a delay in response.
[0029]
  (4) The invention described in claim 4 is the internal combustion engine steady state determination device according to claim 2 or 3, wherein the internal combustion engine sets the engine combustion mode to the other combustion under a predetermined condition. When the first combustion mode switching process for switching from the mode to the specific combustion mode and when there is a request for switching the engine combustion mode, the determination means determines that the internal combustion engine is in a steady operation state. As a condition, a second combustion mode switching process for switching the engine combustion mode to a combustion mode commensurate with the switching request among the plurality of combustion modes is executed, and the suppression means switches the first combustion mode switching. The gist is that the suppression process is executed when the engine combustion mode is switched by the process.
[0030]
  (5) The invention according to claim 5 is the steady operation state determination device for an internal combustion engine according to claim 4, wherein the first combustion mode switching process sets the air-fuel ratio to be richer than the stoichiometric air-fuel ratio. The homogeneous combustion mode is set as the specific combustion mode, and the engine combustion mode is changed from the stratified combustion mode as the other combustion mode to the homogeneous combustion mode with a predetermined period set based on the NOx occlusion amount in the NOx catalyst device of the engine exhaust system. The gist is that it is rich spike processing to switch to.
[0031]
  (6) The invention according to claim 6 is the steady operation state determination device for an internal combustion engine according to claim 1 or 5, wherein the second combustion mode switching process requires a temperature increase request of the NOx catalyst device. Sometimes, the gist is that the engine combustion mode is switched to the temperature rising combustion mode in which the exhaust temperature is relatively high among the plurality of combustion modes.
[0032]
  Usually, the NOx catalyst device (more precisely, the catalyst main body in the NOx) has temperature dependency with respect to the NOx storable amount, and the NOx storable amount tends to decrease as the temperature decreases. For this reason, if the engine operation in the combustion mode with a low exhaust temperature such as the stratified combustion mode is continued for a long period of time, the temperature of the NOx catalyst device is lowered and the NOx occlusion capability is lowered. For this reason, as described above, in an internal combustion engine equipped with such a NOx catalyst device, its temperature (catalyst bed temperature) is constantly monitored, and when this temperature falls below a predetermined temperature, a temperature increase request is issued. The engine combustion mode is set to the temperature rising combustion mode in which the exhaust temperature is relatively high, such as the homogeneous combustion mode.
[0033]
  According to the above invention, by avoiding the erroneous determination as much as possible, when the internal combustion engine is in a steady operation state based on such a temperature increase request, the engine combustion mode is quickly shifted to the temperature increase combustion mode. Thus, the NOx storage capacity of the NOx catalyst device can be suitably maintained. In addition, when the internal combustion engine is not in a steady operation state, the engine load shifts to a medium load or a high load, and the exhaust temperature is appropriately increased. Therefore, the temperature increase of the NOx catalyst device can be expected thereafter. In the above configuration, the engine combustion mode is shifted to the temperature rising combustion mode on condition that the internal combustion engine is in a steady operation state. Thus, when the temperature increase of the NOx catalyst device can be expected in this way, By avoiding switching of the engine combustion mode, it is possible to avoid the occurrence of a shock feeling associated therewith.
[0034]
  (7) The invention according to claim 7 is characterized in that, in the steady operation state determination device for an internal combustion engine according to claim 6, the temperature increase combustion mode is a homogeneous combustion mode.
According to the above invention, the temperature of the NOx catalyst device can be quickly raised by increasing the exhaust gas temperature.
(8) The invention according to claim 8 is the steady operation state determination device for an internal combustion engine according to any one of claims 1 to 7, wherein the determination means has an engine load within a first predetermined range. The gist is that the engine load is determined to be in a stable state at a certain time, and the internal combustion engine is determined to be in a steady operation state when the duration of the stable state exceeds a predetermined determination period.
[0035]
  (9) The invention according to claim 9 relates to an internal combustion engine in which the engine combustion mode can be switched between a plurality of combustion modes including at least a specific combustion mode using a parameter indicating an actual intake air amount as an engine load. In the steady operation state determination device for an internal combustion engine, the steady combustion state determination device includes determination means for determining that the load is in a stable state and determining that the internal combustion engine is in a steady operation state when the stable state is continued. When the engine combustion mode is switched from the combustion mode other than the specific combustion mode to the specific combustion modeIt is determined whether the fluctuations in engine load that occurred are due to a temporary response delay in the change in intake air amount due to switching of the engine combustion mode, and the response delay in the change in intake air amount When a determination result indicating that it is caused is obtained, based on this result,The determination means comprises a suppression means for executing a process for suppressing the influence of the fluctuation of the engine load on the determination on the stable state of the engine load by the determination means, that is, making the result of the determination incorrect. Determines that the engine load is in a stable state when the engine load is within the first predetermined range, and the internal combustion engine is in a steady operation state when the duration of the stable state exceeds a predetermined determination period. The gist is that it is to determine the effect.
[0036]
  (10) The invention according to claim 10 is the apparatus for determining the steady operating state of the internal combustion engine according to claim 9, wherein the internal combustion engine changes the engine combustion mode from the other combustion mode under a predetermined condition. On condition that the determination means determines that the internal combustion engine is in a steady operation state when there is a request for switching the first combustion mode to the specific combustion mode and the engine combustion mode. A second combustion mode switching process for switching the engine combustion mode to a combustion mode commensurate with the switching request among the plurality of combustion modes is performed, and the suppression means is based on the first combustion mode switching process. The gist is that the suppression process is executed when the engine combustion mode is switched.
[0037]
  (11) According to an eleventh aspect of the present invention, in the steady state determination device for an internal combustion engine according to the tenth aspect, the first combustion mode switching process sets the air-fuel ratio to be richer than the stoichiometric air-fuel ratio. The homogeneous combustion mode is set as the specific combustion mode, and the engine combustion mode is changed from the stratified combustion mode as the other combustion mode to the homogeneous combustion mode with a predetermined period set based on the NOx occlusion amount in the NOx catalyst device of the engine exhaust system. The gist is that it is rich spike processing to switch to.
[0038]
  (12) The invention according to claim 12 is the steady operation state determination device for an internal combustion engine according to claim 11, wherein the second combustion mode switching process is performed when there is a temperature increase request of the NOx catalyst device. The gist of the invention is that the engine combustion mode is switched to the temperature rising combustion mode in which the exhaust temperature is relatively high among the plurality of combustion modes.
(13) The invention according to claim 13 is characterized in that, in the steady operation state determination device for an internal combustion engine according to claim 12, the temperature-rise combustion mode is a homogeneous combustion mode.
[0039]
  (14) The invention according to claim 14 is the steady operation state determination apparatus for an internal combustion engine according to any one of claims 8 to 13, wherein the determination means is configured such that the engine load is less than a predetermined value. The gist is that the engine load is judged to be stable.
According to the above invention, it is possible to determine a state in which the engine load is maintained in the low load region, particularly in the steady operation state. Therefore, when the above invention is applied to the invention described in claim 6 or 7 or 12 or 13, the engine is maintained only when the exhaust gas temperature is maintained at a low temperature and the subsequent temperature rise of the NOx catalyst device cannot be expected. Processing to switch the combustion mode to the temperature rising combustion mode such as the homogeneous combustion mode is performed. Therefore, it is possible to suppress unnecessary execution of engine combustion mode switching as much as possible.
[0040]
  (15) The invention according to claim 15 is the steady operation state determination device for an internal combustion engine according to any one of claims 8 to 14, wherein the determination means is a counter for measuring the duration of the stable state. The control means determines that the internal combustion engine is in a steady operation state when the counter value obtained through the counter process exceeds a predetermined determination value, and the suppression means has the engine load as the first load. The gist of the invention is that a process for prohibiting the reset process of the counter value performed when the value falls outside the predetermined range is executed.
According to the above invention, the suppression process can be executed for the counter value corresponding to the duration of the stable state through the prohibition of the reset process.
[0041]
  (16) In the sixteenth aspect of the invention, in the steady operation state determination device for an internal combustion engine according to the fifteenth aspect, the suppressing means has a predetermined period after the engine load has deviated from the first predetermined range. The gist is that the execution condition of the prohibition process is that the time has not elapsed.
[0042]
  The response delay of the intake air amount change is greatest immediately after the engine combustion mode is switched from the other combustion mode to the specific combustion mode, and decreases as time elapses from the switching. Accordingly, the engine load caused by such a response delay is also the largest immediately after switching the engine combustion mode, and gradually decreases thereafter. Accordingly, even if the engine load deviates from the first predetermined range, the engine load decreases when the predetermined time elapses, and the engine load is the value at the time of steady operation, in other words, the engine load before switching the engine combustion mode. It will converge to the value. On the other hand, for example, when the engine load fluctuates based on the operation of the accelerator operation member and deviates from the first predetermined range, the engine load is not passed until the operation of the accelerator operation member is performed again. As a result, it does not converge to the original state.
[0043]
  The present invention pays attention to this point, and according to the configuration, even if the engine load fluctuates temporarily due to the response delay of the change in the intake air amount caused when the engine combustion mode is switched, the counter The possibility of the value reset process is reduced. For this reason, it is possible to suppress the temporary fluctuation of the engine load from affecting the counter processing of the counter value, and more accurately determine that the internal combustion engine is in the steady operation state based on the counter value. Will be able to do.
[0044]
  (17) The invention according to claim 17 is the steady operation state determination device for an internal combustion engine according to claim 16, wherein the suppression means shortens the predetermined period as the engine rotation speed increases based on the engine rotation speed. The gist is that it is to be set.
[0045]
  The time during which the response delay of the intake air amount change occurs varies depending on the flow velocity of the intake air flowing through the engine intake system, and this flow velocity increases as the engine rotational speed increases. Therefore, when the engine load temporarily fluctuates due to the response delay of the intake air amount change accompanying the switching of the engine combustion mode, the higher the engine speed, the more the engine load converges to the value before switching the engine combustion mode. The time until is shortened. For this reason, it is desirable to set the predetermined time shorter as the engine speed is higher.
The present invention focuses on this point, and according to the configuration, based on the engine speed during the predetermined period, the temporary fluctuation of the engine load is suppressed from affecting the counter processing of the counter value. In doing so, it can be set to a suitable length.
[0046]
  (18) The invention according to claim 18 is the steady operation state determination apparatus for an internal combustion engine according to any one of claims 15 to 17, wherein the suppression means is configured such that the engine load is in the first predetermined range. The gist is that the execution condition of the prohibition process is set to be within a second predetermined range that is set larger than that.
[0047]
  When the engine load temporarily fluctuates due to a response delay of the change in intake air amount that occurs when the engine combustion mode is switched, the fluctuation range is generally very likely to be smaller than the fluctuation range of the engine load caused by the operation of the accelerator operation member. high.
The present invention focuses on this point, and according to the configuration, the second predetermined range is appropriately set larger than the first predetermined range, thereby switching the engine combustion mode. Even if the engine load temporarily fluctuates due to the response delay of the change in the intake air amount that occurs, the possibility that the counter value reset process will be performed is thereby reduced. For this reason, it is possible to suppress the temporary fluctuation of the engine load from affecting the counter processing of the counter value, and more accurately determine that the internal combustion engine is in the steady operation state based on the counter value. Will be able to do.
[0048]
  (19) The invention according to claim 19 is the steady operation state determination device for an internal combustion engine according to any one of claims 1 to 18, wherein the other combustion mode is set to the specific combustion mode. The gist of the invention is that a parameter indicating a virtual intake air amount that is set to obtain an engine output equivalent to that in the other combustion modes in the same specific combustion mode is used as the engine load.
[0049]
  In the above invention, as the engine load, in the specific combustion mode, a parameter indicating an actual intake air amount including a response delay in the change is used, while in another combustion mode, a parameter indicating a virtual intake air amount is used. It is done. For this reason, the inconvenience due to the response delay of the intake air amount change as described above tends to become very remarkable. In the invention according to the second aspect, since the premise configuration is provided, it is possible to make the effect exerted by the invention according to the respective claims more meaningful. As described above, the parameter used as the engine load in the specific combustion mode can employ the correlation value such as the actual intake air pressure as well as the actual intake air pressure. In the above invention, when the actual intake pressure is employed as the parameter used as the engine load in the specific combustion mode, the virtual intake pressure is also employed as the parameter used as the engine load in the other combustion mode. Is done.
[0052]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
FIG. 1 schematically shows a configuration of a steady operation state determination device according to the present embodiment and a cylinder injection on-vehicle internal combustion engine (gasoline engine) which is a determination target of the device.
[0053]
As shown in FIG. 1, an intake passage 11 and an exhaust passage 13 are connected to a combustion chamber 12 of the internal combustion engine 10 (only one of them is shown in the figure). A throttle valve 26 that is opened and closed by a motor 27 is provided in the intake passage 11. The intake air metered by the throttle valve 26 is introduced into the combustion chamber 12 when the intake valve 21 is opened. The fuel directly injected from the fuel injection valve 20 into the combustion chamber 12 is mixed with the introduced intake air, ignited by the spark plug 22 and burned, and then the exhaust passage 23 is opened as the exhaust valve 23 is opened. 13 is discharged.
[0054]
A catalyst device 16 having an exhaust purification function is provided in the exhaust passage 13. The catalyst device 16 is composed of two catalyst devices such as a three-way catalyst device and a NOx storage reduction catalyst device (in FIG. 1, these catalyst devices are collectively shown as one). The three-way catalyst device has a function of mainly purifying hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) contained in the exhaust gas through its redox action. On the other hand, the NOx occlusion reduction catalyst device temporarily occludes NOx in the exhaust when combustion is performed under a lean air-fuel ratio such as in the stratified combustion mode. The stored NOx is reduced and purified by reducing components (HC and CO) contained in the exhaust when combustion is performed under a rich air-fuel ratio or stoichiometric air-fuel ratio.
[0055]
The fuel injection valve 20 is an in-cylinder injection type electromagnetic valve that directly injects fuel into the combustion chamber 12 of each cylinder, and high-pressure fuel is supplied from a delivery pipe 24. The delivery pipe 24 is sequentially connected to a feed pump and a fuel tank via a high pressure pump (not shown), and fuel pressurized by the high pressure pump is supplied.
[0056]
Further, the internal combustion engine 10 is provided with an exhaust gas recirculation mechanism 70 for suppressing NOx emission. The exhaust gas recirculation mechanism 70 includes a recirculation passage 71 that connects the exhaust passage 13 and the downstream portion of the throttle valve 26 in the intake passage 11, and a flow rate control valve 72 provided in the recirculation passage 71. Yes. The amount of exhaust gas that is returned to the intake passage 11 through the recirculation passage 71, that is, the exhaust gas recirculation amount is adjusted according to the opening degree of the flow control valve 72.
[0057]
In addition, the internal combustion engine 10 is provided with various sensors for detecting the engine operating state and the like. For example, an intake air amount sensor 42 that detects an intake air amount is provided in a portion upstream of the throttle valve 26 in the intake passage 11. A crank sensor 43 for detecting the rotational speed (engine rotational speed) and rotational phase (crank angle) is provided in the vicinity of a crankshaft (not shown) connected to the engine piston 14 via a connecting rod 18. . An accelerator sensor 44 that detects the amount of depression (accelerator opening) is provided in the vicinity of the accelerator pedal 60. A vehicle speed sensor 45 that detects the traveling speed of the vehicle is provided in the vicinity of a drive shaft (not shown) provided in the vehicle drive system.
[0058]
Detection signals from these sensors 42 to 45 are taken into an electronic control unit 50 that performs various controls of the internal combustion engine 10 in an integrated manner. Based on these detection signals, the electronic control unit 50 drives the actuator such as the fuel injection valve 20, the spark plug 22, the motor 27 that drives the throttle valve 26, the flow control valve 72, and the like, thereby controlling the switching of the engine combustion mode. Various controls such as are executed. The electronic control unit 50 includes a memory 52 for storing a control program related to these various controls, a function map necessary for executing the control program, and a control result based on the function map.
[0059]
Among the various controls described above, in engine combustion mode switching control, the engine combustion mode of the internal combustion engine 10 is switched between the stratified combustion mode and the homogeneous combustion mode.
For example, when the engine operating state is in the low load and low rotation region, the engine combustion mode is basically switched to the stratified combustion mode. In this stratified combustion mode, the air-fuel ratio is set to be leaner than the stoichiometric air-fuel ratio, and the fuel injection timing is set to the late stage of the compression stroke. Further, when compared under the condition where the engine output is the same, the opening degree of the throttle valve 26 is set larger in this stratified combustion mode than in the homogeneous combustion mode, and a relatively large amount of intake air is generated in the combustion chamber. 12 is introduced.
[0060]
Further, in this stratified combustion mode, the opening degree of the flow rate control valve 72 of the exhaust gas recirculation mechanism 70 is set to be relatively large, and a relatively large amount of exhaust gas passes through the recirculation passage 71 to the intake passage 11 according to the engine operating state. Recirculated. By performing such exhaust gas recirculation, the heat capacity of the air-fuel mixture in the combustion chamber 12 increases and the combustion becomes slow, and the combustion temperature decreases, so that the amount of NOx emission can be reduced.
[0061]
On the other hand, when the engine operating state is at the time of starting the engine or in a high load high rotation region, the engine combustion mode is basically switched to the homogeneous combustion mode. Therefore, for example, at the time of vehicle acceleration or the like, the engine combustion mode normally shifts to a high load region, so the engine combustion mode is set to the homogeneous combustion mode. In this homogeneous combustion mode, the air-fuel ratio is set near the stoichiometric air-fuel ratio or richer than that, and the fuel injection timing is set during the intake stroke. Further, since the intake air amount is smaller in the homogeneous combustion mode than in the stratified combustion mode, for example, when the engine combustion mode is switched from the stratified combustion mode to the homogeneous combustion mode, the throttle valve 26 is controlled to the closed side. Along with this, the intake air amount decreases with a response delay.
[0062]
Further, in the homogeneous combustion mode, the flow control valve 72 of the exhaust gas recirculation mechanism 70 is closed, the recirculation passage 71 is closed, and the exhaust gas recirculation is stopped. When the engine combustion mode is switched from the stratified combustion mode to the homogeneous combustion mode, the exhaust gas recirculation is stopped prior to the switching, that is, before the throttle valve 26 is closed or the fuel injection timing and the fuel injection amount are changed. The
[0063]
This is because, when exhaust gas remaining in the intake passage 11 flows into the combustion chamber 12 in the homogeneous combustion mode, particularly in the rich homogeneous combustion mode in which the air-fuel ratio is set richer than the stoichiometric air-fuel ratio, the combustion state deteriorates. Because. That is, in order to avoid such deterioration of the combustion state, exhaust gas recirculation is stopped in advance, and all the exhaust gas remaining in the intake passage 11 is scavenged until the combustion mode is switched.
[0064]
In each of these combustion modes, the engine load that is a basic amount for determining the combustion control state is determined as follows.
That is, when the engine combustion mode is the homogeneous combustion mode, the actual intake air amount (actual intake air amount) is used as a parameter used as the engine load. Therefore, although various corrections are made in accordance with the homogeneous combustion mode, various control amounts in the homogeneous combustion mode are basically calculated based on the actual intake air amount.
[0065]
On the other hand, when the engine combustion mode is the stratified combustion mode, a virtual intake air amount (virtual intake air amount) is used as a parameter used as the engine load. This virtual intake air amount is an intake air amount set so that an equivalent engine output can be obtained in both combustion modes, assuming that the engine combustion mode is set to the homogeneous combustion mode.
[0066]
Specifically, the engine output obtained when the accelerator opening is maintained at a predetermined opening in the stratified combustion mode, and the engine obtained when the engine combustion mode is switched to the homogeneous combustion mode with the same accelerator opening. The intake air amount when the output is equivalent is obtained, and this is set as the virtual intake air amount in the stratified combustion mode. Therefore, when the engine combustion mode is switched from the stratified combustion mode to the homogeneous combustion mode, the parameters used as the engine load under the same engine speed, that is, the actual intake air amount and the virtual intake air amount are before and after the switching. If they are equal, the engine output does not fluctuate when switching. In the stratified combustion mode, although various corrections are made in accordance with the mode, various control amounts are basically calculated based on the virtual intake air amount.
[0067]
In this way, the parameters used for the engine load in each combustion mode are unified to the same physical quantity such as the actual intake air quantity and the virtual intake air quantity, thereby improving the efficiency of various adaptation work associated with the construction of engine control. As described above, it is possible to perform the above.
[0068]
The engine combustion mode is basically switched based on the engine operating state, in other words, based on the accelerator operation by the driver, for example. In order to maintain the exhaust purification performance of the previous catalyst device 16, such accelerator operation is performed. The engine combustion mode may be switched regardless of the above.
[0069]
For example, when the NOx occlusion amount in the catalyst device 16 (NOx catalyst device) increases to a predetermined amount or more near the limit amount, rich spike processing for forcibly switching the engine combustion mode to the rich homogeneous combustion mode is executed. By executing such rich spike processing, the NOx occluded in the catalyst of the catalyst device 16 is reduced and released by the reducing components contained in the exhaust gas, that is, HC and CO. It gradually decreases.
[0070]
Further, the exhaust gas temperature tends to decrease during the stratified combustion mode, and when the operation in the combustion mode is performed for a long period of time, the catalyst bed temperature of the catalyst device 16 decreases and the NOx occlusion capability decreases. For this reason, the electronic control unit 50 monitors the catalyst bed temperature based on the engine operating state, and when the catalyst bed temperature falls below a predetermined temperature, the exhaust temperature is higher than that in the stratified combustion mode. A catalyst temperature raising process for forcibly switching the engine combustion mode to the homogeneous combustion mode is executed. Hereinafter, the rich spike process and the catalyst temperature raising process will be described sequentially.
[0071]
FIG. 2 is a flowchart showing the execution procedure of the rich spike process. A series of processing shown in this flowchart is repeatedly executed at predetermined time intervals as interruption processing by the electronic control unit 50.
[0072]
In this rich spike processing, first, it is determined whether or not the current engine combustion mode is set to the stratified combustion mode (step S100). Here, when the current engine combustion mode is the stratified combustion mode (step S100: YES), the increase value β (> 0) of the NOx occlusion amount ΣNOx is then set to the engine operating state (engine load and engine speed). ) Based on (step S125). The occlusion amount increase value β is basically set to a larger value as the engine is in an operating state where the amount of NOx contacting the catalyst body of the catalyst device 16 (NOx catalyst device) per unit time increases. In this setting, the exhaust gas recirculation amount by the exhaust gas recirculation mechanism 70 is also taken into consideration. The relationship between the occlusion amount increase value β and the engine operating state is obtained in advance through experiments or the like, and is stored in the memory 52 of the electronic control unit 50 as function data. The increase value β may be a constant value. In this case, it is desirable to set the storage amount increase value β based on the maximum amount of NOx that contacts the catalyst body of the catalyst device 16 (NOx catalyst device) per time.
[0073]
When the storage amount increase value β is calculated in this way, the storage amount increase value β is added to the current NOx storage amount ΣNOx, and the added value (ΣNOx + β) is set as a new NOx storage amount ΣNOx. (Step S135). Incidentally, in this case, when the added value (ΣNOx + β) exceeds the limit amount that can be stored in the catalyst device 16, a so-called upper limit guard process is performed in which this is set equal to the limit amount.
[0074]
Next, the current NOx occlusion amount ΣNOx and its upper limit value ΣNOxMAX are compared (step S145). This upper limit value ΣNOxMAX is a value for determining that the NOx occlusion amount ΣNOx has increased to the vicinity of the limit amount that can be occluded in the catalyst device 16. That is, when the NOx occlusion amount ΣNOx exceeds the upper limit value ΣNOxMAX, the NOx occlusion amount ΣNOx is in the vicinity of the limit amount, and it is necessary to quickly reduce the NOx occlusion amount ΣNOx by executing the rich spike process. Judgment can be made. Therefore, when it is determined that the NOx occlusion amount ΣNOx exceeds the upper limit value ΣNOxMAX (step S145: YES), the request flag XRSP is set to “ON” to execute the rich spike processing. (Step S155).
[0075]
On the other hand, when it is determined in the previous step S100 that the current engine combustion mode is not the stratified combustion mode, that is, the homogeneous combustion mode (step S100: NO), whether or not the rich spike processing has already been executed. Is determined (step S110). If the rich spike process is being executed (step S110: YES), then the decrease value α (> 0) of the NOx occlusion amount ΣNOx is based on the engine operating state (engine load and engine speed). Calculated (step S120). This occlusion amount decrease value α is basically an engine operating state (for example, at high load or high) in which reducing components (HC and CO) that contact the catalyst body of the catalyst device 16 (NOx catalyst device) per unit time increase. It is set to a larger value when it is in rotation. The relationship between the occlusion amount decrease value α and the engine operating state is obtained in advance through experiments or the like, and is stored in the memory 52 of the electronic control unit 50 as function data. The decrease value α may be a constant value. In this case, it is desirable to set the occlusion amount decrease value α based on the minimum amount of the reducing component that contacts the catalyst body of the catalyst device 16 (NOx catalyst device) per time.
[0076]
When the storage amount decrease value α is calculated in this way, the storage amount decrease value α is subtracted from the current NOx storage amount ΣNOx, and the subtraction value (ΣNOx−α) is set as a new NOx storage amount ΣNOx. (Step S130). Incidentally, in this case, when the subtraction value (ΣNOx−α) is less than “0”, a so-called lower limit guard process for setting this equal to “0” is also executed.
[0077]
Next, the current NOx occlusion amount ΣNOx and its lower limit value ΣNOxMIN are compared (step S140). This lower limit value ΣNOxMIN is a value for determining that the NOx occlusion amount ΣNOx has decreased and has shifted to a state where the NOx occlusion capacity of the catalyst device 16 has a sufficient margin. That is, when the NOx occlusion amount ΣNOx falls below the lower limit value ΣNOxMIN, it is determined that the NOx occlusion amount ΣNOx has decreased through the rich spike process and the rich spike process need not be continued further. Can do. Accordingly, when it is determined that the NOx occlusion amount ΣNOx is below the lower limit value ΣNOxMIN (step S140: YES), the rich spike processing request flag XRSP is set to “off” (step S150). Incidentally, the lower limit value ΣNOxMIN is set to a value sufficiently smaller than the upper limit value ΣNOxMAX (ΣNOxMIN <ΣNOxMAX) in order to suppress the occurrence of the so-called hunting phenomenon in which the execution and stop of the rich spike processing are frequently repeated. Has been.
[0078]
When the rich spike processing request flag XRSP is turned on (step S150) or off (step S155) in this way, whether or not the rich spike processing request flag XRSP is set to “ON” next. Determination is made (step S160). Further, when it is determined that the NOx occlusion amount ΣNOx is in a range between the upper and lower limits ΣNOxMAX and ΣNOxMIN (ΣNOxMIN ≦ ΣNOx ≦ ΣNOxMAX) (steps S140 and 145: NO), a request flag for the rich spike process The above determination regarding XRSP is made.
[0079]
If the rich spike processing request flag XRSP is “ON” (step S160: YES), the rich spike processing described above is executed (step S170). On the other hand, when the rich spike processing request flag XRSP is “OFF” (step S160: NO), the rich spike processing is stopped and the engine combustion mode is switched to the combustion mode based on the engine operating state (step S175). . If it is determined in step S110 that the rich spike process is not being executed (step S110: NO), this series of processes is temporarily terminated.
[0080]
Next, the catalyst temperature raising process will be described with reference to FIGS.
FIG. 3 is a flowchart showing an execution procedure of the catalyst temperature raising process. A series of processing shown in this flowchart is repeatedly executed at predetermined time intervals as interruption processing by the electronic control unit 50. FIG. 4 is a timing chart showing an example of a control mode based on the processing procedure shown in this flowchart.
[0081]
In this catalyst temperature raising process, first, the catalyst bed temperature T during steady operation is calculated based on the current engine operating state (step S200). The catalyst bed temperature T is a temperature at which the catalyst bed temperature converges when the internal combustion engine 10 is continuously operated for a long time under the engine operation state. The catalyst bed temperature T is obtained in advance by experiments or the like and is stored in the memory 52 of the electronic control unit 50 as function data. In FIG. 4, the change in the catalyst bed temperature T is indicated by a solid line.
[0082]
Next, the actual catalyst bed temperature TS (i) in the current control cycle is calculated (estimated) based on the following equation (1) (step S210).
TS (i) ← {(n−1) TS (i−1) + T (i)} / n (1)
n: integer greater than or equal to 2
TS (i-1): Actual catalyst bed temperature in the previous control cycle
As shown in the above equation (1), here, by performing a weighted average process, a so-called annealing process, on the catalyst bed temperature T at the time of steady operation obtained based on the engine operation state as a gradual change process. The actual catalyst bed temperature TS (i) is obtained. Specifically, for the actual catalyst bed temperature TS (i-1) obtained in the previous control cycle, "(n-1) / n", for the catalyst bed temperature T (i) in the current control cycle. Weighting is performed by multiplying each by “1 / n”, and the added value is calculated as the actual catalyst bed temperature TS (i) in the current control cycle. The reason why such a process is performed is that the actual catalyst bed temperature changes with a predetermined response delay with respect to changes in the engine operating state. The coefficient n is obtained in advance based on experiments or the like according to the magnitude of the response delay of the catalyst bed temperature change. Generally, the coefficient n increases as the response delay amount increases. Set to a value. In FIG. 4, the change in the actual catalyst bed temperature TS (i) is indicated by a one-dot chain line.
[0083]
Next, the actual catalyst bed temperature TS (i) and the first determination temperature TSL are compared (step S220). The first determination temperature TSL is a value for determining that the NOx occlusion capability is decreasing due to a temperature decrease of the catalyst device 16 (NOx catalyst device). That is, as shown in FIG. 4, when the catalyst bed temperature T decreases with a decrease in engine load or the like, the actual catalyst bed temperature TS (i) gradually decreases with a predetermined response delay. (FIG. 4: For example, the period from timing t41 to t43). When the actual catalyst bed temperature TS (i) falls below the first determination temperature TSL (FIG. 4: timing t42), after that, when the state in which the exhaust gas temperature does not rise further continues, NOx in the catalyst device 16 It becomes impossible to secure the storage capacity. Therefore, if it is determined that the actual catalyst bed temperature TS (i) is lower than the first determination temperature TSL (step S220: YES), the temperature increase request flag XH is required to increase the temperature of the catalyst device 16. Is set to “ON” (step S230).
[0084]
On the other hand, when it is determined that the actual catalyst bed temperature TS (i) is equal to or higher than the first determination temperature TSL (step S220: NO), the actual catalyst bed temperature TS (i) is further set to the second determination temperature TSL. It is determined whether or not the temperature exceeds the determination temperature TSH (step S225). The second determination temperature TSH is a value for determining that the actual catalyst bed temperature TS (i) has sufficiently increased until a predetermined NOx storage capacity in the catalyst device 16 can be secured. Therefore, when it is determined that the actual catalyst bed temperature TS (i) is higher than the second determination temperature TSH (step S225: YES), the temperature increase request flag XH is set to “off”. (Step S235).
[0085]
As described above, when the temperature increase request flag XH is set to “ON” based on the comparison between the actual catalyst bed temperature TS (i) and the first determination temperature TSL, the temperature increase request flag XH is set to “ON”. Is determined (step S240). In addition, when it is determined that the actual catalyst bed temperature TS (i) is equal to or lower than the second determination temperature TSH (step S225: NO), the above determination regarding the temperature increase request flag XH is made. Here, when the temperature increase request flag XH is “OFF” (step S240: NO), it is not necessary to perform the temperature increase process on the catalyst device 16, and thus this series of processes is temporarily ended.
[0086]
On the other hand, when the temperature increase request flag XH is set to “ON” (step S240: YES), it is next determined whether or not the internal combustion engine 10 is in a steady operation state in a low load region ( Step S250). Specifically, it is determined whether or not the steady operation flag XST indicating that the internal combustion engine 10 is in the same state is set to “ON”. That is, through the processes of Step S240 and Step S250, the NOx occlusion capacity is decreasing due to the temperature decrease of the catalyst device 16, and the exhaust gas temperature is not expected to increase thereafter, the internal combustion engine 10 is in a situation that is not expected. Judgment is made. The control related to the steady operation state determination process of the internal combustion engine 10 such as the operation of the steady operation flag XST will be described later.
[0087]
Here, when the steady operation flag XST is “OFF” (step S250: NO), the exhaust gas temperature is high when the engine load is equal to or higher than the medium load region, and a subsequent temperature increase of the catalyst device 16 can be expected. The execution of the 16 temperature raising processes is suspended, and this series of processes is temporarily terminated (FIG. 4: period from timing t42 to t43).
[0088]
On the other hand, here, when the steady operation flag XST is “ON” (step S250: YES), it is determined that the NOx occlusion capacity is lowered due to the temperature drop of the catalyst device 16, and the catalyst device 16 A temperature raising process is executed (step S260). That is, even if the engine combustion mode set based on the engine operating state is the stratified combustion mode, the engine combustion mode is forcibly switched to the homogeneous combustion mode.
[0089]
Further, when the temperature increase request flag XH is set to “off” based on the comparison between the actual catalyst bed temperature TS (i) and the second determination temperature TSH, the temperature increase control of the catalyst device 16 is stopped ( Step S265). That is, such a temperature raising process is executed until the actual catalyst bed temperature TS (i) rises to the second determination temperature TSH with the switching of the engine combustion mode (FIG. 4: period from timing t43 to t44). .
[0090]
Next, control related to the steady operation state determination process of the internal combustion engine 10 will be described with reference to FIGS. 5 and 6.
FIG. 5 is a flowchart showing an execution procedure of the steady operation state determination process. A series of processing shown in this flowchart is repeatedly executed at predetermined time intervals as interruption processing by the electronic control unit 50. FIG. 6 is a timing chart showing an example of a control mode based on the processing procedure shown in this flowchart.
[0091]
In this steady operation state determination process, first, a period in which the engine load is in a low load region is monitored, and when this period exceeds a predetermined determination period, it is determined that the internal combustion engine 10 is in a steady operation state. I am doing so. Specifically, the steady operation counter value CST is counted up when the engine load is in the low load region, while the steady operation counter value CST is set to “0” when the engine load deviates from the low load region. I try to reset it. Then, it is determined that the internal combustion engine 10 is in a steady operation state on the condition that the steady operation counter value CST exceeds a determination value CSJ corresponding to the determination period.
[0092]
In particular, in this counter process, even if a temporary engine load fluctuation occurs due to a response delay of the intake air amount change that occurs when the engine combustion mode is switched, the reset process is performed due to the fluctuation. I try to avoid doing as much as possible.
[0093]
In this series of processing, it is first determined whether or not the current engine load is less than a predetermined value QL (step S300). The parameter used as the engine load here is the virtual intake air amount when the engine combustion mode is set to the stratified combustion mode, and the actual intake air amount when the homogeneous combustion mode is set. It is done. Here, the predetermined value QL is for determining that the engine load is in a low load region. Therefore, when the engine load is less than the predetermined value QL, the difference between the predetermined value QL and the engine load value QIDL (idle engine load) during idle operation is maximum even if the fluctuation range of the engine load per hour is maximum. Does not exceed the range determined by. Therefore, when the engine load is less than the predetermined value QL, it can be determined that the engine load is in a low load region and is in a stable state.
[0094]
If it is determined that the engine load is not in the low load stable state (step S300: NO), then the elapsed time counter value CLP is counted up (CLP → CLP + 1) (step S310). The elapsed time counter value CLP is the elapsed time after the engine load increases to a predetermined value QL or more, in other words, the elapsed time after the engine load deviates from the predetermined range (predetermined value QL−idle engine load QIDL). It is equivalent.
[0095]
Here, the reason why the elapsed time counter value CLP corresponding to such elapsed time is calculated is as follows.
When the rich spike processing as described above (FIG. 6: period from timing t62 to t65) is executed, first, before switching the engine combustion mode, the flow rate control valve 72 of the exhaust gas recirculation mechanism 70 (FIG. 6C). ) Is closed (FIG. 6: timing t61). Then, after the flow rate control valve 72 is closed and exhaust gas recirculation is stopped, the throttle valve 26 (FIG. 6 (d)) is closed by a predetermined amount after a predetermined period, and the engine combustion mode (FIG. b)) is switched from the stratified combustion mode to the rich homogeneous combustion mode. In accordance with such switching of the engine combustion mode, the parameter used as the engine load (FIG. 6 (f)) is switched from the virtual intake air amount to the actual intake air amount (FIG. 6: timing t62).
[0096]
However, as described above, even if the throttle valve 26 is closed, the intake air amount (FIG. 6 (e)) changes with a predetermined response delay from the change of the throttle valve 26. There is a period in which the intake air amount temporarily increases compared to the amount corresponding to the opening (FIG. 6: period from timing t62 to t64). As a result, the engine load temporarily increases.
[0097]
Here, the response delay of such an intake air amount change is greatest immediately after the engine combustion mode is switched, and becomes smaller as time elapses from the switching. Accordingly, the fluctuation of the engine load caused by such a response delay is also the largest immediately after switching the engine combustion mode, and gradually decreases thereafter. Therefore, even if the engine load fluctuates and exceeds the predetermined value QL, the fluctuation is attenuated when a predetermined time elapses, and the engine load is a value at the time of steady operation, in other words, before switching the engine combustion mode. It will converge to the value of the engine load.
[0098]
On the other hand, for example, when the engine load fluctuates based on the operation of the accelerator pedal 60 and exceeds the predetermined value QL, the engine load increases with time unless the accelerator operation member is operated again. Will not converge to the original state.
[0099]
Therefore, in this steady operation state determination process, the elapsed time counter value CLP (FIG. 6 (g)) is calculated. Then, while the elapsed time counter value CLP is less than the predetermined determination value CLPJ, the engine load subsequently converges as the response delay amount decreases, and this may decrease to less than the predetermined value QL. The reset processing of the steady operation counter value CST is prohibited (FIG. 6: period from timing t62 to t63). On the other hand, when the state where the engine load exceeds the predetermined value QL continues beyond the period corresponding to the determination value CLPJ due to the operation of the accelerator pedal 60 or the like, the prohibition of such reset processing is canceled and the same operation is performed. The process is executed.
[0100]
On the other hand, when the engine load is less than the predetermined value QL in the previous step S300, it is determined that the engine load is stable in the low load region of the engine load (step S300: YES), and the elapsed time counter value CLP is determined. Is reset to “0” (step S315, FIG. 6: timing t63).
[0101]
Incidentally, as described above, when the engine combustion mode is switched from the stratified combustion mode to the rich homogeneous combustion mode during the execution of the rich spike processing, a temporary increase in engine load occurs due to a response delay of the intake air amount change. The increase in engine output resulting from this can be suppressed by retarding the ignition timing. Specifically, the increase amount of the engine output is calculated by the electronic control unit 50 based on the difference between the engine load immediately before switching the engine combustion mode and the engine load after the switch, and the increase amount of the engine output and the ignition timing are calculated. The amount of retardation is set so that the amount of decrease in engine output accompanying the retardation of is equal. Then, the ignition timing of the spark plug 22 set based on other engine operating states is set to the retard side by the retard amount. Accordingly, an increase in engine output caused by a temporary increase in engine load is suppressed. By suppressing the increase in engine output in this way, it is possible to suppress the occurrence of a shock caused by the engine output and the change (acceleration feeling) of the vehicle speed (FIG. 6A) unintended by the driver. Become.
[0102]
Next, it is determined whether or not any one of the conditions shown in the following equations (2) and (3) is satisfied (step S320).
CLP ≧ CLPJ (2)
Engine load ≧ QH (QH> QL) (3)
Here, the condition shown in the above equation (2) is for determining whether or not a predetermined determination period has elapsed after the engine load exceeds the predetermined value QL as described above. The determination value CLPJ can be set to a constant value. However, in the apparatus according to this embodiment, the determination value CLPJ is set to be smaller as the engine rotation speed is higher as a function of the engine rotation speed. Yes. This is mainly due to the following reasons.
[0103]
That is, the time when the response delay of the intake air amount change as described above (response delay time) occurs depends on the flow rate of the intake air flowing through the intake system in addition to the total volume of the engine intake system. The larger the value, the shorter the response delay time. Further, the flow velocity of the intake air flowing through the engine intake system increases as the engine rotational speed increases.
[0104]
Therefore, when the engine load temporarily fluctuates due to the response delay of the intake air amount change accompanying the switching of the engine combustion mode, the value before the engine load switches the engine combustion mode as the engine rotation speed at that time increases. The time until convergence is shortened. For this reason, whether the fluctuation of the engine load currently occurring is temporary due to the response delay of the change in the intake air amount accompanying the switching of the engine combustion mode, or due to the operation of the accelerator pedal 60, etc. In order to determine the accuracy more accurately, it is desirable to set the determination value CLPJ based on the engine speed. For this reason, in the apparatus according to the present embodiment, the determination value CLPJ is set to be smaller as the engine rotational speed is higher.
[0105]
On the other hand, with respect to the condition shown in the above equation (3), as shown below, whether the fluctuation of the engine load is caused by the response delay of the change in the intake air amount accompanying the switching of the engine combustion mode, or the accelerator pedal 60 It is for judging whether it is due to an operation or the like. That is, as described above, the engine load fluctuates due to the response delay of the intake air amount change accompanying switching of the engine combustion mode, but the fluctuation range can be smaller than the fluctuation range of the engine load caused by the operation of the accelerator pedal 60. The nature is extremely high.
[0106]
Therefore, when the condition expressed by the above equation (3) is satisfied, it can be determined that the fluctuation of the engine load is large and that the fluctuation is not caused by switching of the engine combustion mode. In order to make such a determination appropriately, the predetermined value QH shown in the above equation (3) is the maximum value of the engine load that fluctuates by switching the engine combustion mode, in other words, the response delay amount of the intake air amount change is the maximum. It is set to a value larger than the value of the engine load when
[0107]
If any one of the conditions shown in the above formulas (2) and (3) is satisfied (step S320: YES), the change in the intake air amount caused by the change in the engine combustion mode due to the change in the engine load. It is determined that it is not caused by response delay. In other words, it is determined that the engine load is not stable in the low load region. When such a determination is made, the steady operation counter value CST is reset (step S335), and the steady operation flag XST is set to “off” (step S355). Then, this series of processes is temporarily terminated.
[0108]
On the other hand, when none of the conditions shown in the above equations (2) and (3) are satisfied, that is, the elapsed time counter value CLP is less than the determination value CLPJ, and the engine load is When it is less than the predetermined value QH (step S320: NO), the count-up process is executed without prohibiting the reset process of the steady operation counter value CST (FIG. 6 (h)) (step S330, FIG. 6: timing). (period from t62 to t63). That is, in the apparatus according to the present embodiment, the predetermined period has not elapsed since the engine load exceeds the predetermined value QL, and the engine load is less than the predetermined value QH set larger than the predetermined value QL. Both are conditions for prohibiting the reset processing of the elapsed time counter value CLP.
[0109]
After performing the count-up process of the steady operation counter value CST in this way, it is next determined whether or not the steady operation counter value CST exceeds the determination value CSJ (step S340). If the steady operation counter value CST exceeds the determination value CSJ (step S340: YES), the steady operation flag XST (FIG. 6 (i)) is set to “ON” (step S350 FIG. 6). : Timing t66). On the other hand, when the steady operation counter value CST is equal to or less than the determination value CSJ (step S340: NO), this series of processes is temporarily ended.
[0110]
According to the apparatus according to this embodiment in which the steady operation state of the internal combustion engine 10 is determined with the control mode described above, the following operational effects can be obtained.・ When the engine combustion mode is switched from the stratified combustion mode to the homogeneous combustion mode, even if the engine load fluctuates due to a temporary response delay of the intake air amount change due to the switching, the engine load fluctuates. The influence on the determination relating to the stable state is suppressed. Therefore, when there is a response delay of the intake air amount change accompanying the switching of the engine combustion mode, it is erroneously determined that the internal combustion engine 10 is in an unsteady operation state despite the steady operation state. This makes it possible to make an appropriate determination while avoiding the above.
[0111]
In addition, as a parameter used as an engine load, in the homogeneous combustion mode, an actual intake air amount including a response delay in the change is used, whereas in the stratified combustion mode, a virtual intake air amount is used. For this reason, there is a high possibility that an erroneous determination due to the response delay of the intake air amount change as described above is made. However, since the above-described effects can be achieved in such a device, this is more meaningful. Will be able to.
[0112]
In particular, in the apparatus according to the present embodiment, when the engine combustion mode is switched to the rich homogeneous combustion mode in accordance with the execution of the rich spike process, the fluctuation of the temporary engine load due to the response delay of the intake air amount change Therefore, it can be avoided that the internal combustion engine 10 is erroneously determined to be in an unsteady operation state. For this reason, it is possible to avoid as much as possible that such rich spike processing is frequently performed and it becomes impossible to shift to the catalyst temperature increase processing due to the erroneous determination caused by the rich spike processing. In this way, by performing the catalyst temperature raising process at an appropriate time, it is possible to suppress the exhaust gas purification capacity in the catalyst device 16, particularly the NOx storage capacity in the NOx catalyst device, and to ensure this. Become.
[0113]
Further, the condition that the internal combustion engine 10 is in a steady operation state is an execution condition of the catalyst bed temperature process. That is, there is a possibility that the engine load shifts to a medium load or a high load, and the exhaust gas purifying capability of the catalyst device 16, particularly the NOx occlusion capability in the NOx catalyst device, may be ensured by the accompanying increase in exhaust gas temperature. During operation, such a catalyst temperature raising process is not executed. For this reason, unnecessary switching of the engine combustion mode is avoided as much as possible, and the occurrence of a shock feeling associated therewith can be avoided in advance.
[0114]
Further, as the steady operation state, a state in which the engine load is maintained in the low load region is specified as the determination target. Therefore, it is possible to more suitably avoid the execution of the unnecessary switching of the engine combustion mode as described above and the generation of a shock feeling associated therewith.
[0115]
Further, on the condition that the predetermined period after the engine load exceeds the predetermined value QL has not elapsed, specifically, the elapsed time counter value CLP corresponding to the elapsed time has not reached the determination value CLPJ. The reset processing of the steady operation counter value CST is prohibited. For this reason, the possibility that the reset process is performed due to a temporary fluctuation of the engine load caused when the engine combustion mode is switched in the rich spike process is reduced. Therefore, it is possible to suppress such a temporary fluctuation of the engine load from affecting the counter processing of the steady operation counter value CST, and it is determined based on the counter value CST that the internal combustion engine 10 is in the steady operation state. Can be performed more accurately.
[0116]
Further, the determination value CLPJ corresponding to the predetermined period is used as a function of the engine rotation speed, and the determination value CLPJ is set smaller as the engine rotation speed increases. Accordingly, the magnitude of the determination value CLPJ is set to a magnitude suitable for suppressing the temporary fluctuation of the engine load caused by the response delay of the intake air amount change from affecting the counter processing of the steady operation counter value CST. Will be able to set.
[0117]
Further, reset processing of the steady operation counter value CST is prohibited on condition that the engine load is less than another predetermined value QH which is set to be larger than the predetermined value QL. For this reason, the possibility that the reset process is performed due to a temporary fluctuation of the engine load caused when the engine combustion mode is switched in the rich spike process is reduced. Therefore, it is possible to suppress such a temporary fluctuation of the engine load from affecting the counter processing of the steady operation counter value CST, and it is determined based on the counter value CST that the internal combustion engine 10 is in the steady operation state. Can be performed more accurately.
[0118]
The embodiment of the present invention has been described above, but the configuration of the embodiment can be changed as follows.
In the above embodiment, only the engine load is monitored, and whether the fluctuation is caused by the response delay of the intake air amount change accompanying switching of the engine combustion mode based on the change mode, or the operation of the accelerator pedal 60 Judgment whether it is due to etc. On the other hand, for example, by adding the following configuration, the determination can be made more accurately.
[0119]
(A) In the steady operation state determination process shown in the flowchart of FIG. 5, the engine combustion mode is actually switched between step S300 and step S310, such as the rich spike process being executed. Judgment processing for judging is added. If an affirmative determination is made in this determination process, the process proceeds to step S310, and to a negative determination step S315.
[0120]
(B) Similarly, in the steady operation state determination process shown in the flowchart of FIG. 5, the engine load such as that a predetermined period has elapsed between the step S300 and the step S310 after the depression operation of the accelerator pedal 60 is completed. A determination process is added to determine that the increase is not based on the driver's acceleration request. If an affirmative determination is made in this determination process, the process proceeds to step S310, and to a negative determination step S315.
[0121]
(C) Similarly, in the steady operation state determination process shown in the flowchart of FIG. 5, it is determined between step S300 and step S310 that the change width of the vehicle speed detected by the vehicle speed sensor 45 is within a predetermined value. Add decision processing. If an affirmative determination is made in this determination process, the process proceeds to step S310, and to a negative determination step S315.
[0122]
(D) Similarly, in the steady operation state determination process shown in the flowchart of FIG. 5, a determination process for determining that the ignition timing retardation process is not executed is added between step S300 and step S310. If an affirmative determination is made in this determination process, the process proceeds to step S310, and to a negative determination step S315.
[0123]
In the above embodiment, the internal combustion engine 10 in which the engine combustion mode is switched between the stratified combustion mode and the homogeneous combustion mode has been exemplified. For example, in addition to each of the combustion modes, the stratified strength is reduced as compared with the stratified combustion mode. The present invention can also be applied to the internal combustion engine 10 in which the substratified combustion mode is performed.
[0124]
In the above embodiment, the intake air amount is adopted as a parameter used as the engine load. However, for example, intake pressure can be adopted instead. That is, the virtual intake pressure is adopted as the parameter in the stratified combustion mode and the actual intake pressure is adopted in the homogeneous combustion mode. The virtual intake pressure can be obtained according to the same procedure as the virtual intake air amount.
[0125]
In the above embodiment, the steady operation state is determined in particular in a state where the engine load is stable in the low load region. For example, such an engine load is in the medium load region or the high load region. A stable state can also be determined as a steady operation state. Further, it can be determined that the internal combustion engine 10 is in a steady operation state only when the fluctuation range is small regardless of the magnitude of the engine load.
[0126]
In the above embodiment, an in-cylinder injection type gasoline engine is exemplified as the internal combustion engine. However, in the present invention, a parameter used as an engine load when the engine combustion mode is switched, such as an intake port injection type gasoline engine, a diesel engine, etc. Any device that can be changed to one that has a response delay of the intake air amount change can be applied.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an outline of a steady operation state determination device and an internal combustion engine that is a determination target according to the present invention.
FIG. 2 is a flowchart showing an execution procedure for rich spike processing;
FIG. 3 is a flowchart showing a procedure for executing the catalyst temperature raising process.
FIG. 4 is a timing chart showing changes in catalyst bed temperature and actual catalyst bed temperature during steady operation.
FIG. 5 is a flowchart showing an execution procedure for steady operation state determination processing;
FIG. 6 is a timing chart showing changes in intake air amount and steady operation counter value at the time of switching between engine combustion modes in the present embodiment.
FIG. 7 is a timing chart showing a transition of an intake air amount and a steady operation counter value at the time of switching between engine combustion modes in a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 11 ... Intake passage, 12 ... Combustion chamber, 13 ... Exhaust passage, 14 ... Engine piston, 16 ... Catalyst device, 18 ... Connecting rod, 20 ... Fuel injection valve, 21 ... Intake valve, 22 ... Spark plug , 23 ... exhaust valve, 24 ... delivery pipe, 26 ... throttle valve, 27 ... motor, 42 ... intake air amount sensor, 43 ... crank sensor, 44 ... accelerator sensor, 45 ... vehicle speed sensor, 50 ... electronic control device (determination means) , Suppression means), 52 ... memory, 60 ... accelerator pedal, 70 ... exhaust gas recirculation mechanism, 71 ... recirculation passage, 72 ... flow control valve.

Claims (19)

It is determined that the engine load is stable for an internal combustion engine in which the engine combustion mode can be switched between a plurality of combustion modes including at least a specific combustion mode using a parameter indicating the actual intake air amount as the engine load. In a steady operation state determination device for an internal combustion engine comprising determination means for determining that the internal combustion engine is in a steady operation state when the stable state continues.
Of the plurality of combustion modes, fluctuations in the engine load that occur when the engine combustion mode is switched from the combustion mode other than the specific combustion mode to the specific combustion mode are temporarily associated with the switching of the engine combustion mode. It is determined whether or not it is caused by a response delay of a change in intake air amount, and when a determination result indicating that it is caused by a response delay in change of intake air amount is obtained, based on this result, comprising a suppression means for performing processing to suppress that those variations in the engine load is the wrong result of the engine load according to a stable state on respect determining influence that same determination of by the determining means,
The internal combustion engine has a first combustion mode switching process for switching the engine combustion mode from the other combustion mode to the specific combustion mode under a predetermined condition, and when there is a switching request for the engine combustion mode, A second combustion mode switching process for switching the engine combustion mode to a combustion mode that meets the switching request among the plurality of combustion modes on the condition that the determination means determines that the internal combustion engine is in a steady operation state. Are executed respectively.
In the first combustion mode switching process, the homogeneous combustion mode in which the air-fuel ratio is set to be richer than the stoichiometric air-fuel ratio is set as the specific combustion mode, and a predetermined value set based on the NOx occlusion amount in the NOx catalyst device of the engine exhaust system. Rich spike processing for switching the engine combustion mode from the stratified combustion mode as the other combustion mode to the homogeneous combustion mode with a period of
The said suppression means performs the said suppression process at the time of switching of the engine combustion mode by the said 1st combustion mode switching process. The steady operation state determination apparatus of the internal combustion engine characterized by the above-mentioned. It is determined that the engine load is stable for an internal combustion engine in which the engine combustion mode can be switched between a plurality of combustion modes including at least a specific combustion mode using a parameter indicating the actual intake air amount as the engine load. In a steady operation state determination device for an internal combustion engine comprising determination means for determining that the internal combustion engine is in a steady operation state when the stable state continues.
Regarding engine load fluctuations that occur when the engine combustion mode is switched from the stratified combustion mode as the combustion mode other than the specific combustion mode to the homogeneous combustion mode as the specific combustion mode among the plurality of combustion modes. Judgment result of whether or not it is caused by a response delay of a change in the intake air amount temporarily due to switching of the engine combustion mode, and a determination result that it is caused by a response delay of a change in the intake air amount Is obtained based on this result, the suppression means for executing a process for suppressing the influence of the fluctuation of the engine load on the determination on the stable state of the engine load by the determination means,
The suppression means, as a process of suppressing the influence, when the fluctuation of the engine load caused after switching the engine combustion mode is due to a response delay of a temporary intake air amount change caused by switching the engine combustion mode And determining that the engine load is not in a stable state due to fluctuations in the engine load. In the internal combustion engine steady state determination device according to claim 2,
The determination means determines whether or not a change in engine load caused after switching the engine combustion mode is due to an operation of an accelerator pedal, and a determination result indicating that the change is not due to an operation of an accelerator pedal has been obtained. And determining that the fluctuation of the engine load is due to a response delay of a temporary intake air amount change caused by switching of the engine combustion mode. In the steady operation state determination device for an internal combustion engine according to claim 2 or 3,
The internal combustion engine has a first combustion mode switching process for switching the engine combustion mode from the other combustion mode to the specific combustion mode under a predetermined condition, and when there is a switching request for the engine combustion mode, A second combustion mode switching process for switching the engine combustion mode to a combustion mode that meets the switching request among the plurality of combustion modes on the condition that the determination means determines that the internal combustion engine is in a steady operation state. Are executed respectively.
The apparatus for determining a steady operating state of an internal combustion engine, wherein the suppression means executes the suppression process when the engine combustion mode is switched by the first combustion mode switching process. In the steady operation state determination device for an internal combustion engine according to claim 4,
In the first combustion mode switching process, the homogeneous combustion mode in which the air-fuel ratio is set to be richer than the stoichiometric air-fuel ratio is set as the specific combustion mode, and a predetermined value set based on the NOx occlusion amount in the NOx catalyst device of the engine exhaust system A rich spike process for switching the engine combustion mode from the stratified combustion mode as the other combustion mode to the homogeneous combustion mode with a period of. In the internal combustion engine steady operation state determination device according to claim 1 or 5,
The second combustion mode switching process switches the engine combustion mode to the temperature rising combustion mode in which the exhaust gas temperature becomes relatively higher among the plurality of combustion modes when there is a temperature rising request of the NOx catalyst device. An apparatus for determining a steady operating state of an internal combustion engine, comprising: The steady state determination device for an internal combustion engine according to claim 6,
The temperature rising combustion mode is a homogeneous combustion mode. In the steady operation state determination device for an internal combustion engine according to any one of claims 1 to 7,
The determination means determines that the engine load is in a stable state when the engine load is within a first predetermined range, and the internal combustion engine is in steady operation when the duration of the stable state exceeds a predetermined determination period. An apparatus for determining a steady operating state of an internal combustion engine, characterized in that it is determined that the engine is in a state. It is determined that the engine load is stable for an internal combustion engine in which the engine combustion mode can be switched between a plurality of combustion modes including at least a specific combustion mode using a parameter indicating the actual intake air amount as the engine load. In a steady operation state determination device for an internal combustion engine comprising determination means for determining that the internal combustion engine is in a steady operation state when the stable state continues.
Of the plurality of combustion modes, fluctuations in the engine load that occur when the engine combustion mode is switched from the combustion mode other than the specific combustion mode to the specific combustion mode are temporarily associated with the switching of the engine combustion mode. It is determined whether or not it is caused by a response delay of a change in intake air amount, and when a determination result indicating that it is caused by a response delay in change of intake air amount is obtained, based on this result, comprising a suppression means for performing processing to suppress that those variations in the engine load is the wrong result of the engine load according to a stable state on respect determining influence that same determination of by the determining means,
The determination means determines that the engine load is in a stable state when the engine load is within a first predetermined range, and the internal combustion engine is in steady operation when the duration of the stable state exceeds a predetermined determination period. An apparatus for determining a steady operating state of an internal combustion engine, characterized in that it is determined that the engine is in a state. In the steady operation state determination device for an internal combustion engine according to claim 9,
The internal combustion engine has a first combustion mode switching process for switching the engine combustion mode from the other combustion mode to the specific combustion mode under a predetermined condition, and when there is a switching request for the engine combustion mode, A second combustion mode switching process for switching the engine combustion mode to a combustion mode that meets the switching request among the plurality of combustion modes on the condition that the determination means determines that the internal combustion engine is in a steady operation state. Are executed respectively.
The apparatus for determining a steady operating state of an internal combustion engine, wherein the suppression means executes the suppression process when the engine combustion mode is switched by the first combustion mode switching process. In the internal-combustion-engine steady operation state determination device according to claim 10,
In the first combustion mode switching process, the homogeneous combustion mode in which the air-fuel ratio is set to be richer than the stoichiometric air-fuel ratio is set as the specific combustion mode, and a predetermined value set based on the NOx occlusion amount in the NOx catalyst device of the engine exhaust system A rich spike process for switching the engine combustion mode from the stratified combustion mode as the other combustion mode to the homogeneous combustion mode with a period of. In the internal combustion engine steady state determination device according to claim 11,
The second combustion mode switching process switches the engine combustion mode to the temperature rising combustion mode in which the exhaust gas temperature becomes relatively higher among the plurality of combustion modes when there is a temperature rising request of the NOx catalyst device. An apparatus for determining a steady operating state of an internal combustion engine, comprising: In the steady operation state determination device for an internal combustion engine according to claim 12,
The temperature rising combustion mode is a homogeneous combustion mode. In the steady operation state determination device for an internal combustion engine according to any one of claims 8 to 13,
The determination means is for determining that the engine load is in a stable state when the engine load is less than a predetermined value. In the steady operation state determination device for an internal combustion engine according to any one of claims 8 to 14,
The determination means performs a counter process for measuring the duration of the stable state, and determines that the internal combustion engine is in a steady operation state when a counter value obtained through the counter process exceeds a predetermined determination value. Yes,
The suppression means executes a process for prohibiting a reset process of the counter value that is performed when the engine load deviates from the first predetermined range. apparatus. The steady state determination device for an internal combustion engine according to claim 15,
The suppression means uses the prohibition process as an execution condition that a predetermined period of time has not elapsed since the engine load deviated from the first predetermined range. Judgment device. The internal combustion engine steady operation state determination device according to claim 16,
The said suppression means sets the said predetermined period short, so that the engine rotational speed becomes high based on an engine rotational speed. The steady operation state determination apparatus of the internal combustion engine characterized by the above-mentioned. In the steady operation state determination device for an internal combustion engine according to any one of claims 15 to 17,
The internal combustion engine characterized in that the suppression means sets the engine load within a second predetermined range set to be larger than the first predetermined range as an execution condition of the prohibition process. Steady operation state determination device. In the internal combustion engine steady operation state determination device according to any one of claims 1 to 18,
The other combustion mode is a parameter indicating a virtual intake air amount that is set so that an engine output equivalent to that of the other combustion mode can be obtained in the specific combustion mode when the engine combustion mode is set to the specific combustion mode. The engine is used as an engine load. A steady operation state determination device for an internal combustion engine.

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