JP4858308B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to an improvement of a control device for an internal combustion engine capable of switching a fuel combustion method during engine idle operation.

  A catalyst device for purifying exhaust gas discharged from the engine combustion chamber is provided in the exhaust passage of the internal combustion engine. The purification characteristic of the catalyst built in the catalyst device changes depending on the temperature, and normally, the original purification characteristic cannot be exhibited unless the temperature rises to the activation temperature. For this reason, there is a concern about deterioration of exhaust properties until a predetermined period has elapsed from the start of the engine and the temperature of the catalyst is sufficiently increased by exhaust heat. In response to such concerns, conventionally, for example, as seen in Patent Document 1, split injection that injects fuel in the compression stroke in addition to the intake stroke is performed for a period from when the engine is started until a predetermined period elapses. It has been proposed. By injecting fuel during the compression stroke in this way, the ignition timing can be set to the retard side as much as possible to raise the exhaust gas temperature, and the catalyst device using exhaust heat can be warmed up early. become able to. Then, the split injection is stopped at the time when it is determined that the warming-up of the catalyst device is completed, and the batch injection for collectively injecting all the fuel during the intake stroke is performed and the ignition timing is also advanced. I am doing so.

  As described above, when the fuel injection mode and the ignition timing are changed to switch the combustion method, the following situation may be caused. In other words, the intake air amount required for engine idle operation in each combustion method naturally differs, and therefore, when switching such a combustion method, the intake air amount is reduced to a target amount suitable for the combustion method after the switching. Need to change. However, even if, for example, the throttle valve opening is changed to change the intake air amount, there is a response delay until the intake air amount actually reaches the target amount. For this reason, if the change of the intake air amount and the change of the fuel injection mode and the ignition timing are simultaneously performed, the fuel injection mode and the ignition timing are adapted to the intake air amount at that time due to the response delay of the change of the intake air amount. The engine combustion state becomes unstable. In particular, during engine idle operation, the combustion state of the engine tends to be difficult to stabilize, and when the catalyst device has not been warmed up, the elapsed time since the start of the engine is short. Since the frictional resistance generated in the movable part is large, the tendency of the engine combustion state to become unstable becomes even more remarkable.

  Therefore, it is conceivable to change the fuel injection mode and the ignition timing in anticipation of such a response delay of the intake air amount change. That is, by changing the fuel injection mode and the ignition timing after a predetermined period of time has elapsed since the start of the change in the intake air amount, the fuel injection mode and the ignition timing are changed at an inappropriate timing with respect to the intake air amount at that time. As a result, the instability of the engine combustion state is suppressed as much as possible.

  By the way, during engine idling operation, it is desirable not only to stabilize the engine combustion state, but also to appropriately suppress fluctuations in engine output and, further, fluctuations in engine rotation speed resulting from the fluctuations. In other words, during engine idle operation, engine vibration and associated noise are relatively small, and when engine output and engine speed fluctuations occur, they are easily recognized as vibration and noise. For this reason, during engine idle operation, the engine output should not be changed, or even if the engine output changes with the switching of the combustion method, this should be changed as smoothly as possible. desirable. In response to such a request, as described above, simply providing a delay period between the start of change of the intake air amount and the start of change of the fuel injection mode and ignition timing depends on the length of the delay period. The engine output may increase unnecessarily or decrease. In response to such a fear, Patent Document 2 proposes and discloses a control apparatus for an internal combustion engine that can suppress as much as possible an engine output from fluctuating unnecessarily due to switching of a combustion method during engine idle operation. Has been. Specifically, during engine idle operation, the combustion mode and ignition timing are changed to switch the combustion method, and prior to the switching, the intake air amount is changed to an amount corresponding to each combustion method, and the switching timing is delayed. A torque step is eased by giving a period.

JP 2000-45843 A JP 2006-200516 A

  However, when such a control device for an internal combustion engine is put into production, in order to reduce the torque step, each internal combustion engine, that is, variation in intake air amount generated for each individual internal combustion engine, injection Optimization work for each internal combustion engine is indispensable in consideration of flow rate variation in the valve, sensor accuracy, and the like. In addition, when deposits are accumulated on the fuel injection valve, the fuel flow rate does not decrease, but the spray shape may collapse and affect the appropriate combustion. In particular, when so-called poor fuel is used, such a problem becomes significant. In this way, the state change of the internal combustion engine may affect the combustion in the process of using the internal combustion engine. Further, in the first idle significant retard control, since the stratified combustion is performed by the compression stroke, the dependence on the spray shape is high, and therefore it is required to improve the deterioration of torque fluctuation due to the spray shape abnormality. Conventional control devices for internal combustion engines do not deal with such problems and leave room for improvement.

  Therefore, the present invention provides an internal combustion engine control device capable of reducing torque fluctuations at the time of switching combustion modes as much as possible in response to variations in the internal combustion engine during production and changes in the state of the internal combustion engine during use. This is the issue.

A control device for an internal combustion engine of the present invention for solving such a problem is a control device for an internal combustion engine that performs split injection during engine idle operation, and after the first split injection that performs a plurality of intake stroke injections, The second divided injection divided into the intake stroke injection and the compression stroke injection is performed, and the injection ratio between the intake stroke injection and the compression stroke injection in the second divided injection is variable . With such a configuration, it is possible to reduce the torque step even if the intake air amount varies when the combustion method is switched. In the second divided injection, it is possible to select an injection ratio that minimizes torque fluctuations by making the injection ratio between the intake stroke injection and the compression stroke injection variable. Moreover, it is also possible to acquire information that can be used for subsequent control by performing the first divided injection. It should be noted that the number of divisions in the first divided injection and the second divided injection is not limited to two, and the number of divisions can be further increased.

Such a control device for an internal combustion engine increases the ratio of the injection ratio of the compression stroke injection within a range in which the torque fluctuation due to the divided injection is within a predetermined value . For example, when performing the second split injection, the compression stroke injection is started from the minimum injection period of the fuel injection valve, and the injection ratio is gradually increased within a range where the torque fluctuation becomes a predetermined value. The injection ratio can be found. As a result, it is possible to suppress torque fluctuations caused by torque steps caused by switching the fuel system, deposits deposited on the fuel injection valve, and the like. The present invention can exhibit such a learning function.

Such a control device for an internal combustion engine can perform batch injection when the torque fluctuation due to the first divided injection exceeds a predetermined value . If the torque fluctuation exceeds a predetermined value when the first divided injection is performed, it is considered that the spray shape has collapsed due to the accumulation of deposits on the fuel injection valve. The collective injection in such a state is performed for the purpose of blowing away the deposited deposit. Such collective injection is desirably performed by increasing the fuel pressure in order to blow off the deposit .

Furthermore, the when the first split injection torque fluctuation due to the performed exceeds a predetermined value, it may be a configuration in which the fuel pressure increase control is performed in the subsequent high-speed and high load operation. During engine idle operation, it may be difficult to ensure the range of increase in fuel pressure, so the fuel pressure must be increased when the vehicle starts running and the internal combustion engine is operated at high speed and high load. Can effectively remove deposits.

When the torque fluctuation due to performing the first divided injection again after performing the fuel pressure increase control in spite of the batch injection for removing the deposit as described above exceeds a predetermined value It can be set as the structure which issues a warning .

Further, the injection amount of the divided injection in such a control device for an internal combustion engine can be corrected by a correction coefficient corresponding to the content in the fuel . For example, when alcohol as a content is contained in gasoline as fuel, there is a risk of misfire due to split injection, so that the corrected injection amount can be set to avoid this. Thereby, the lean misfire in the compression stroke injection can be avoided and the lean limit can be secured.

Although the present invention can reduce the torque step accompanying the switching of the combustion method when the engine is idling, the power transmission device is moved from the drive range (D range) as a case where the combustion method is switched. A case of switching to a neutral range (N range) or a parking range (P range) is assumed. Therefore, the control device for an internal combustion engine according to the present invention provides the first split injection and the above-described divided injection when the engine output of the internal combustion engine is not transmitted to a drive system of a vehicle on which the internal combustion engine is mounted as a drive source It can be set as the structure which performs 2nd division | segmentation injection.

  According to the present invention, after the first split injection for performing a plurality of intake stroke injections, the second split injection divided into the intake stroke injection and the compression stroke injection is performed, and the intake air in the second split injection is performed. Since the injection ratio between the stroke injection and the compression stroke injection is made variable, the torque fluctuation at the time of switching the combustion system is reduced as much as possible in response to variations in the internal combustion engine during production and changes in the state of the internal combustion engine during use. be able to.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an internal combustion engine and its control device. The control device includes a control unit 40 that controls the internal combustion engine 10 mounted on the vehicle in an integrated manner, and a detection unit 50 that detects an engine operating state such as an engine rotation speed. The intake passage 11 of the internal combustion engine 10 is provided with a throttle valve 12 for adjusting the amount of intake air and a motor 13 for opening and closing the throttle valve 12. The internal combustion engine 10 includes a plurality of cylinders, and each cylinder is provided with a fuel injection valve 15 in addition to a spark plug 14. The fuel injection valve 15 is an in-cylinder injection valve that directly injects fuel into the combustion chamber 16 of each cylinder. The exhaust passage 17 of the internal combustion engine 10 is provided with a catalyst device 18 for purifying exhaust exhausted from the combustion chamber 16. The engine output shaft of the internal combustion engine 10 is drivingly connected to a vehicle drive system such as a propeller shaft, a differential gear, a drive shaft, and drive wheels (all not shown) via an automatic transmission (not shown).

  The control unit 40 stores a drive circuit (not shown) for driving the motor 13, the spark plug 14, the fuel injection valve 15 and the like, execution programs and data necessary for various controls, and execution results of the control. The memory 41 is provided. The detection unit 50 also includes an air flow meter 51 that detects the intake air amount Q, a throttle sensor 52 that detects the opening degree TA of the throttle valve 12, a rotation phase (crank angle) of the engine output shaft, and a crank that detects the engine speed NE. A sensor 53, a water temperature sensor 54 for detecting the engine cooling water temperature THW, and the like are provided. The control unit 40 takes in the detection signals of the detection unit 50 including these various sensors 51 to 54, and executes various controls such as intake air amount control, fuel injection control, and ignition timing control based on the detection results. A warning light 60 is electrically connected to the control unit 40.

  Next, the catalyst warm-up control performed during engine idle operation after engine start will be described among various controls executed by the control unit 40. In this catalyst warm-up control, part of the fuel is injected into the intake stroke, and split injection is performed in which the remaining fuel is injected in the latter half of the compression stroke, and the ignition timing is set to a retarded timing (first timing). 2 combustion method). Thus, by performing the compression stroke injection together with the intake stroke injection and setting the ignition timing to the retard side, the exhaust temperature can be raised and the catalyst device 18 can be warmed up early. Further, after the warm-up of the catalyst device 18 is completed, a batch injection for injecting all the fuel in the intake stroke is executed and the ignition timing is advanced to such an extent that knocking does not occur (first combustion method). Even if the catalyst device 18 has not been warmed up, the shift range of the automatic transmission is set to a range other than the parking range (P range) and neutral range (N range), for example, the drive range (D range). If so, the combustion method is similarly set to the first combustion method. As described above, in the catalyst warm-up control, by appropriately switching the combustion method, the exhaust gas purification ability of the catalyst device 18 is increased early after the engine is started to suppress the deterioration of the exhaust properties, and the vehicle driving force is also reduced. I try to secure it.

Details of such catalyst warm-up control will be described below.
FIG. 2 is a flowchart showing a processing procedure for determining whether or not to execute the catalyst warm-up control. The processing shown in this flowchart is continuously executed after the engine is started regardless of whether or not the internal combustion engine 10 is in an idle operation state.

In this series of processes, it is first determined whether or not the intake air amount integrated value ΣQ from the start of the engine to the present time is below a predetermined value ΣQJ (step S21). Here, the intake air amount integrated value ΣQ has a correlation with the amount of heat generated in the combustion chamber 16 since the start of the engine. Therefore, based on the intake air amount integrated value ΣQ, it is possible to estimate the total amount of heat given from the exhaust to the catalyst device 18 from the start of the engine, and thus the temperature increase of the catalyst device 18 from the start of the engine. Further, the predetermined value ΣQJ indicates whether or not the catalyst of the catalyst device 18 has risen to the vicinity of its activation temperature, in other words, the warm-up of the catalyst device 18 is completed and the original exhaust purification characteristics can be exhibited. This is a determination value for determining whether or not the process has shifted to (1). This predetermined value ΣQJ is calculated based on the following equation (1).

ΣQJ ← ΣQJB · k (1)
k> 1.0

Here, “ΣQJB” is a basic value of the predetermined value ΣQJ, and is set in advance based on experiments or the like in consideration of an average temperature rise mode of the catalyst device 18 after the engine is started. In the above equation (1), “k” is a correction coefficient for correcting the basic value ΣQJB based on the engine cooling water temperature THW at the time of starting the engine, and the lower the engine cooling water temperature THW at the time of engine starting, the lower the value. The predetermined value ΣQJ is set to be larger. By performing the correction based on the correction coefficient k in this way, the predetermined value ΣQJ can be set to an appropriate value commensurate with the idle operation at that time, and the period of catalyst warm-up accompanying switching of the combustion method is unnecessary. Can be avoided.

  Therefore, by comparing the magnitude of the predetermined value ΣQJ thus set with the intake air amount integrated value ΣQ, it is determined whether or not the catalyst device 18 is in a state where it can exhibit its original exhaust purification characteristics. Can do.

  Thus, when the warming-up state of the catalyst device 18 is determined and it is determined that the warming-up of the catalyst device 18 is completed, that is, the intake air amount integrated value ΣQ is equal to or greater than the predetermined value ΣQJ (step S21). : NO), the warm-up request flag XC is set to “OFF” (step S24). Here, the warm-up request flag XC determines whether to give priority to securing the vehicle driving force or early warm-up of the catalyst device 18. That is, when the warm-up request flag XC is set to “ON”, the combustion method is set to the second combustion method in order to promote the warm-up of the catalyst device 18, and the warm-up request flag XC is set. If it is set to “OFF”, the combustion method is set to the first combustion method in order to give priority to securing the vehicle driving force.

  On the other hand, when it is determined that the warm-up of the catalyst device 18 is not completed (step S21: YES), it is next determined whether or not the engine output is transmitted to the vehicle drive system (step S21). S22). Specifically, it is determined whether or not the shift range of the automatic transmission is in the P range or the N range. When it is determined that the engine output is not transmitted to the vehicle drive system (step S22: YES), the warm-up request flag XC is set to “ON” (step S23).

  On the other hand, when it is determined that the shift range of the automatic transmission is set to a range other than the P range or N range, for example, the D range, and the engine output is transmitted to the vehicle drive system (step S22: NO), the warm-up request flag XC is set to “OFF” (step S24). Thus, when the warm-up request flag XC is set to “OFF”, the combustion method is switched to the first combustion method in order to ensure the vehicle driving force.

  Incidentally, when the combustion method is set to the first combustion method in this way, although the exhaust temperature rise due to setting the ignition timing to the retarded timing cannot be expected, the accelerator operation member is operated thereafter. The engine load (fuel injection amount) is expected to increase. The exhaust temperature rises as the engine load increases, and as a result, there is a high possibility that the catalyst device 18 can be warmed up early. In addition, when the shift range is set to a range other than the P range and the N range as described above, the vehicle is likely to shift to an acceleration state after that, and the combustion method is switched after the shift. Then, there is a concern that the vehicle acceleration performance is lowered. For this reason, in this catalyst warm-up control, even if the warm-up of the catalyst device 18 is not completed, if the shift range is set to the D range or the like, the combustion method is set to the first combustion mode. The method is set. As a result, vehicle acceleration performance can be ensured.

After the warm-up request flag XC is set to “ON” or “OFF” in this way, this series of processes is temporarily ended.
FIG. 3 is a timing chart showing such an increase in the intake air amount integrated value ΣQ, a change in the shift range, and a state change of the warm-up request flag XC set based on these.

  Here, when the above-described combustion method is set to the second combustion method, the throttle opening degree TA is set larger and the intake air amount is larger than when the first combustion method is set. Increased. This is due to the following reason.

  That is, when the combustion method is set to the second combustion method, the ignition timing is set to a timing retarded from the ignition timing in the first combustion method, so that the engine output decreases, and the engine The amount of intake air required to maintain the rotational speed NE at the target engine rotational speed NET during idle operation increases.

  Thus, it is required to maintain the engine rotational speed NE at the target engine rotational speed NET when the combustion system is set to the first combustion system and when the combustion system is set to the second combustion system. The intake air amount is different, and when the combustion method is switched, the throttle opening degree TA is changed to ensure the required intake air amount.

Further, the target engine speed NET during engine idle operation is set mainly based on the following parameters.
1. Shift range: When the engine output is not transmitted to the vehicle drive system, such as when the shift range is set to the P range or N range, as when the D range or R range is set. The target engine speed NET is set higher than when the engine output is transmitted to the vehicle drive system.

2. Elapsed time after engine start: The shorter the elapsed time after engine start, the higher the target engine speed NET is set. This is because the engine combustion state becomes more unstable as the elapsed time after engine startup is shorter, so that the occurrence of engine stall is reliably suppressed.

3. Engine coolant temperature: The target engine speed NET is set higher as the engine coolant temperature is lower. This is because the engine combustion state becomes more unstable as the engine cooling water temperature is lower, as in the case where the elapsed time after engine startup is short, so that the occurrence of engine stall is reliably suppressed.

Further, the target value of the intake air amount Q, that is, the target intake air amount QT is set as follows mainly based on the combustion method, the target engine speed NET, and the like.
When the combustion method is set to the first combustion method, first, the target throttle opening degree TAT is calculated based on the following equation (2).

TAT ← TAB + K (NET-NE) (2)

In the above equation (2), the first term “TAB” on the right side is a prospective control amount and is a basic throttle opening set based on the target engine speed NET and the engine coolant temperature THW. The second term “K (NET−NE)” on the right side is a feedback control amount, and is set based on the gain K and the deviation (= NET−NE) between the current engine speed NE and the target engine speed NET. The Accordingly, when the current engine speed NE is higher than the target engine speed NET, the throttle opening degree TA is changed so as to increase the current intake air amount Q in accordance with the deviation. On the other hand, when the current engine speed NE is lower than the target engine speed NET, the throttle opening degree TA is changed so as to decrease the current intake air amount Q in accordance with the deviation. Here, the target intake air amount QT is set to an amount corresponding to the expected control amount (that is, the basic throttle opening degree TAB) and the target engine speed NET in the above equation (2). The relationship between the target intake air amount QT, the basic throttle opening degree TAB, and the target engine speed NET is obtained in advance through experiments or the like and stored in the memory 41.

  When the combustion method is set to the second fuel injection method, the target intake air amount QT is set based on the target engine speed NET. Similarly, the relationship between the target engine speed NET and the target intake air amount QT is obtained in advance through experiments and stored in the memory 41. Incidentally, in this case, the fuel injection amount is feedback-controlled so that the deviation between the current engine speed NE and the target engine speed NET becomes small.

  As described above, when the combustion method is switched between the two combustion methods described above, the change of the throttle opening TA and the change of the fuel injection mode and the ignition timing are executed together. Here, in the catalyst warm-up control, as shown in FIG. 3, the change timing of these throttle openings TA (FIG. 3: timing t31, t33, t35), the fuel injection mode and the ignition timing change timing ( FIG. 3: A predetermined delay period DT is provided between the timings t32, t34, and t36). That is, after the throttle opening degree TA is changed, the fuel injection mode and the ignition timing are changed after the change. The delay period DT is set so that the fuel injection mode and the ignition timing are changed at a time suitable for the intake air amount that changes with a response delay from the change in the throttle opening TA. In the present catalyst warm-up control, by setting the delay period DT in this way, it is possible to suppress fluctuations in the engine output that accompany switching of the combustion method.

  Hereinafter, the procedure for setting the delay period DT will be described with reference to the flowchart shown in FIG. This series of processing is executed on condition that the internal combustion engine 10 is in an idling state, that is, the accelerator operation amount is “0”.

  In this series of processing, it is first determined whether or not the warm-up request flag XC has been switched from “ON” to “OFF” or from “OFF” to “ON” (step S41). When the warm-up request flag XC is not switched and is maintained as “ON” or “OFF” (step S41: NO), this series of processes is temporarily ended.

  On the other hand, when the warm-up request flag XC is switched (step S41: YES), in other words, the combustion method is changed from the first combustion method to the second combustion method, or from the second combustion method to the first. When it is necessary to switch to the combustion method, the difference dQ (= | QT−Q |) between the current intake air amount Q and the target intake air amount QT corresponding to the combustion method after switching is calculated (step). S42).

  After the intake air amount difference dQ is calculated in this way, the difference dNE (= | NET−NE |) between the current engine speed NE and the target engine speed NET corresponding to the combustion method after switching is calculated. (Step S43).

  Next, the basic delay period DTB is calculated based on the intake air amount difference dQ and the engine coolant temperature THW (step S44). The basic delay period DTB can be set as a crank angle period, but here, time is taken as the dimension. FIG. 5 shows the relationship between the intake air amount difference dQ, the engine coolant temperature THW, and the basic delay period DTB. Such a relationship is obtained in advance through experiments or the like, and is stored as function data in the memory 41 of the control unit 40.

  As shown in FIG. 5, the basic delay period DTB is set to a longer period as the intake air amount difference dQ is larger. This is because the response delay of the intake air amount increases as the intake air amount difference dQ increases, and therefore it is preferable to switch the fuel injection mode and the ignition timing after the response delay amount decreases.

  The basic delay period DTB is set to a longer period as the engine coolant temperature THW is lower. This is because, when the engine coolant temperature THW is low, the effect of changing the fuel injection mode and the ignition timing, in particular, the instability of the engine combustion state by changing the ignition timing, and the fluctuation of the engine output due to this. This is because these tend to occur easily, and these are preferably suppressed.

Next, a correction coefficient α is calculated based on the engine speed difference dNE (step S45). FIG. 6 shows the relationship between the engine speed difference dNE and the correction coefficient α (≧ 1.0). This correction coefficient α is for correcting the basic delay period DTB obtained previously based on the engine speed difference dNE. Similar to the above-described relationship between the intake air amount difference dQ, the engine coolant temperature THW, and the basic delay period DTB, such a relationship is obtained in advance through experiments or the like, and is stored as function data in the memory 41 of the control unit 40. Yes.
After the basic delay period DTB and the correction coefficient α are calculated in this way, the final delay period DT is calculated based on the following equation (3) (step S46).

DT ← DTB ・ α ・ ・ ・ （3）

Here, as shown in FIG. 6, the delay period DT is set to a longer period because the correction coefficient α is set to a larger value as the engine speed difference dNE is larger. Become. The reason why the correction coefficient α is set in this way is as follows. That is, when the engine rotational speed difference dNE is large, the period from when the throttle opening degree TA is changed until the engine rotational speed NE converges to the target engine rotational speed NET becomes longer. The basic delay period DTB is corrected to determine the delay period DT.

  Next, an example of the combustion mode switching mode controlled through the above-described processes will be described with reference to FIG.

  FIG. 7 shows changes in the intake air amount Q and the engine rotational speed NE, and changes in the fuel injection mode and ignition timing when the shift range is switched from the D range to the N range (or P range). .

  As shown in FIG. 7, when the shift range is switched from the D range to the N range, the warm-up request flag XC that has been set to “OFF” is switched to “ON” (timing t71). When the warm-up request flag XC is switched in this way, first, the throttle opening TA increases to an opening corresponding to the target intake air amount QT after switching the combustion method. As a result, the intake air amount Q gradually increases, and the engine rotational speed NE increases accordingly.

  When the delay period DT elapses after the throttle opening degree TA is changed, the fuel injection mode is changed from batch injection to split injection, and the ignition timing is delayed from the current timing, that is, the exhaust temperature. Is set to a time when priority is given to the increase in the time (timing t72). As a result of the ignition timing being set to the retard side as described above, the engine output is reduced, and the engine rotational speed NE is gradually reduced accordingly and converges to the target engine rotational speed NET. Here, in the catalyst warm-up control, the delay period DT is set in consideration of the intake air amount difference dQ, the engine rotation speed difference dNE, and the engine cooling water temperature THW. Variations in the engine rotational speed NE are suppressed as much as possible and change smoothly.

Here, the divided injection that is started from the timing t72 will be described with reference to FIGS. FIG. 8 is a flowchart illustrating an example of control for split injection.
When the control unit 40 issues a split injection command, first, the first split injection is performed (step S51). In the first split injection, a plurality of intake stroke injections are performed as shown in FIG. In this embodiment, the number of divisions is two. After performing such first divided injection, it is determined whether or not there is a spray shape abnormality in the first divided injection (step S52). In the first divided injection, the amount of fuel that is normally injected in a batch is divided into two injections. For this reason, normally, the torque fluctuation of the engine does not increase so much. However, if deposits are accumulated in the injection hole of the fuel injection valve 15, the spray shape changes, which may cause engine torque fluctuations. Therefore, when it is determined that the spray shape is abnormal, the process proceeds to step S53. On the other hand, when it is determined that there is no abnormality in the spray shape, the process proceeds to step S57. Here, a method for determining a spray shape abnormality will be described. Whether or not the spray shape is abnormal is determined based on the torque fluctuation of the engine. More specifically, the determination is made based on the fluctuation of the engine speed NE detected by the crank sensor 53. If the engine rotation speed NE exceeds the predetermined rotation speed lower limit by performing the first divided injection, it is determined that the spray shape is abnormal. It is also possible to determine whether or not there is an abnormality in the spray shape on the basis of the decrease width and decrease ratio of the engine speed NE. By performing the first divided injection in this way, it is possible to determine whether deposits are likely to be deposited.

  If YES is determined in step S52, that is, if it is determined that there is a spray abnormality, the process proceeds to step S53, and fuel pressure increase batch injection as shown in FIG. 10 is performed. The fuel pressure increase batch injection is a measure performed for the purpose of removing deposits accumulated in the nozzle hole of the fuel injection valve 15. For this reason, it is desirable that the fuel pressure is high, and in this embodiment, injection is performed at the maximum operating fuel pressure provided in the engine. After performing such fuel pressure increase batch injection, the process proceeds to step S54. The process in step S54 is the first divided injection similar to the process performed in step S51. In other words, the injection amount that is normally performed once is divided into two intake stroke injections for injection. Further, subsequently, the same processing as step S52 is performed in step S55. The process in step S55 is to confirm whether or not the deposit is removed and the spray shape abnormality is recovered by the fuel pressure increase batch injection in step S53.

  If YES is determined in the determination in step S55, that is, if it is determined that the abnormality in the spray shape has not yet been resolved, the process proceeds to step S56, the spray shape abnormality flag is turned ON, and the process is temporarily ended (END). ). In step S56, the warning lamp 60 is turned on by a command from the control unit 40. When such a spray shape abnormality flag is ON and the vehicle on which the internal combustion engine is mounted starts running and performs a high-speed high-load operation, fuel pressure increase control is performed. Thereby, it is expected that deposits that could not be removed even by the fuel pressure increase batch injection in step S53 are removed.

  If NO is determined in step S52, or if NO is determined in step S55, that is, if it is determined that there is no spray shape abnormality, the process proceeds to step S57. In step S57, the second divided injection is performed with the compression stroke injection as the minimum injection period τmin. As shown in FIG. 11, the second divided injection is performed by dividing the injection that is normally performed in a lump into the intake stroke injection and the compression stroke injection, and the compression ratio injection is set to the minimum injection period τmin. It is a thing. Here, the minimum injection period means the minimum injection period in which the fuel injection valve 15 included in the internal combustion engine can be realized. After performing such second divided injection, the process proceeds to step S58.

  In step S58, it is determined whether or not the torque fluctuation due to the second split injection in step S57 is within the target torque fluctuation value. The torque fluctuation is determined by the fluctuation of the engine rotational speed NE detected by the crank sensor 53 as in the processing in step S52 and step S55. However, a value different from the determination in step S52 or the like is adopted as the target torque fluctuation value.

  When it is determined YES in step S58, that is, when it is determined that the torque fluctuation is within the target torque fluctuation value, the process proceeds to step S59. In step S59, as shown in FIG. 12, the second divided injection in which the injection ratio of the compression stroke injection is increased is performed. After performing the process in step S59, the process proceeds to step S60, and it is confirmed whether or not the engine speed NE has reached the target engine speed TE. If the target engine speed TE has not been reached by performing the process in step S59 only once, the process in step S59 is repeated. Thus, by increasing the injection ratio of the compression stroke injection, the injection ratio is adjusted to a more appropriate injection ratio.

  If NO is determined in step S58, that is, if torque fluctuation has occurred exceeding the target torque fluctuation value, the second injection in step S57 is continued as it is.

  By performing the control as described above, an injection ratio suitable for each internal combustion engine is determined, and a torque step during engine idle operation is reduced.

  Such divided injection can be corrected by a correction coefficient (fuel property correction coefficient) according to the content in the fuel when determining the injection amount. Such a configuration will be described with reference to FIGS. FIG. 13 is a flowchart showing an example of control for split injection in consideration of the fuel property correction coefficient. In the flowchart shown in FIG. 13, the process of step S100 is incorporated immediately before step S57. In step S100, the fuel property is determined, and a fuel property correction coefficient corresponding to the fuel property is calculated. For example, when it is determined that alcohol is mixed in the fuel, a fuel property correction coefficient derived from the fuel property is calculated from a map prepared in advance. The fuel property correction coefficient calculated in this way is considered in the second divided injection in steps S57 and S58. That is, as shown in FIGS. 14 and 15, in the compression stroke injection, an injection amount that compensates for the amount of alcohol contained is provided. Thereby, even when a content such as alcohol is present in the fuel, the torque step can be reduced as much as possible.

  The case where the combustion method is switched from the first combustion method to the second combustion method has been described above. Next, the case where the combustion method is switched from the second combustion method to the first combustion method will be described.

  FIG. 16 shows changes in the intake air amount Q and the engine rotational speed NE, and changes in the fuel injection mode and ignition timing when the shift range is switched from the N range (or P range) to the D range. .

  As shown in FIG. 16, when the shift range is switched from the N range to the D range, the warm-up request flag XC that has been set to “ON” is switched to “OFF” (timing t81). When the warm-up request flag XC is switched in this way, first, the throttle opening degree TA is lowered to an opening degree corresponding to the target intake air amount QT after switching the combustion method. As a result, the intake air amount Q gradually decreases, and the engine rotational speed NE also decreases accordingly.

  When the delay period DT elapses after the throttle opening degree TA is changed, the fuel injection mode is changed from split injection to batch injection, and the ignition timing is advanced from the current timing, that is, engine output. Is set to a normal time in which priority is given (timing t82). As a result of the ignition timing being set to the advance timing in this way, the engine output is reduced, and the engine rotational speed NE is gradually reduced accordingly and converges to the target engine rotational speed NET. According to the present embodiment, the fluctuation of the engine rotational speed NE accompanying the switching of the combustion method is suppressed as much as possible, and the engine rotational speed changes smoothly.

  According to the present catalyst warm-up control, when the combustion method is switched from the second combustion method to the first combustion method, similarly to the case where the combustion method is switched from the first combustion method to the second combustion method. Even if it exists, the unnecessary fluctuation | variation of the engine speed NE can be suppressed as much as possible.

  When the shift range is not switched and the combustion method is switched, the following control is performed.

  FIG. 17 shows that the warm-up request flag XC that has been set to “ON” when the intake air amount integrated value ΣQ is equal to or greater than the predetermined value ΣQJ in a state where the shift range is maintained in the N range (or P range). Each transition of the intake air amount Q and the engine rotational speed NE and the change mode of the fuel injection mode and the ignition timing when switched to “OFF” are shown. FIG. 17 shows changes in the engine speed NE and changes in the fuel injection mode and ignition timing when the catalyst warm-up control is executed.

  In this case, since the shift range is not switched, the target engine speed NET is maintained at a substantially constant speed as shown in FIG. However, the intake air amount Q gradually decreases as the warm-up request flag XC is switched to “OFF” and the throttle opening degree TA decreases.

  According to the present catalyst warm-up control, as shown in FIG. 17, fuel injection is performed after the delay period DT has elapsed since the warm-up request flag XC is switched from “ON” to “OFF” (timing t91). The form is changed from split injection to batch injection (timing t92). At the same time, the ignition timing is set to a timing that is ahead of the current timing, that is, a timing that gives priority to securing the engine output. As described above, the delay period DT is set in consideration of the intake air amount difference dQ, the engine speed difference dNE, and the engine coolant temperature THW. The decrease in the engine output due to the decrease and the increase in the engine output caused by setting the ignition timing to the advance side are suitably offset. As a result, the fluctuation of the engine rotational speed NE accompanying the switching of the combustion system is suppressed as much as possible, and the engine rotational speed NE changes smoothly.

  As described above, according to the control device that performs the catalyst warm-up control, the engine accompanying the switching of the combustion system based on the target intake air amount before and after the combustion system switching, the target engine rotation speed, and the engine cooling water temperature. After grasping the transition of the combustion state, it is possible to set the fuel injection mode and the ignition timing change timing, that is, the combustion system switching timing. Accordingly, the switching time can be set to an appropriate time for suppressing the fluctuation of the engine output accompanying the switching. Further, by dividing the injection into the first divided injection and the second divided injection and making the injection ratio in the second divided injection variable, it is possible to further reduce the torque step for each engine. That is, it is possible to reduce torque fluctuations and torque steps when switching the combustion system as much as possible in response to variations in the internal combustion engine during production and changes in the state of the internal combustion engine during use.

In addition, the said embodiment can also change the structure and control aspect as follows.
Regardless of whether the warm-up request flag XC is ON / OFF, the second combustion method, that is, when split injection is performed, the split injection is distinguished into the first split injection and the second split injection, The injection ratio in the two split injections can be made variable.
・ When the shift range is set to the N range or P range, and when the shift range is set to the R range, the warm-up request flag XC is set to “ON” and the combustion method is set to the second combustion mode. You may make it set to a system.

  -Judgment is made based on the shift range whether or not the engine output is transmitted to the vehicle drive system, and the combustion system is switched to the second combustion system on condition that the engine output is not transmitted. However, the combustion mode may always be maintained at the second combustion mode until it is determined that the warm-up of the catalyst device 18 has been completed after the engine is started, regardless of the shift range setting state.

1 is a schematic configuration diagram of an internal combustion engine to which an embodiment of the present invention is applied. The flowchart which shows the process sequence at the time of determining the decision | availability of execution of catalyst warm-up control. The timing chart which shows the state change of a warm-up request flag. The flowchart which shows the process sequence at the time of setting a delay period. 6 is a schematic diagram showing a relationship between a difference in intake air amount, engine coolant temperature, and a basic delay period. 6 is a schematic diagram showing a relationship between an engine rotation speed difference and a correction coefficient. The timing chart which shows an example of each transition of intake air amount and engine rotational speed, and the change aspect of a fuel injection form and ignition timing. The flowchart which shows an example of the control with respect to division | segmentation injection. Explanatory drawing which shows the mode of 1st division | segmentation injection. Explanatory drawing which shows the mode of the collective injection made into the highest operating fuel pressure. Explanatory drawing which shows the mode of the 2nd division | segmentation injection which made compression stroke injection the minimum injection period. Explanatory drawing explaining the mode of the 2nd division | segmentation injection which increased the injection ratio of compression stroke injection. The flowchart which shows an example of the control with respect to the division | segmentation injection which considered the fuel property correction coefficient. Explanatory drawing which shows the mode of the 2nd division | segmentation injection which considered the fuel property correction coefficient and made compression stroke injection into the minimum injection period. Explanatory drawing which shows the mode of the 2nd division | segmentation injection which considered the fuel property correction coefficient and made compression stroke injection into the minimum injection period. The timing chart which shows an example of each transition of intake air amount and engine rotational speed, and the change aspect of a fuel injection form and ignition timing. The timing chart which shows an example of each transition of intake air amount and engine rotational speed, and the change aspect of a fuel injection form and ignition timing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 11 ... Intake passage, 12 ... Throttle valve, 13 ... Motor, 14 ... Spark plug, 15 ... Fuel injection valve, 16 ... Combustion chamber, 17 ... Exhaust passage, 18 ... Catalyst device, 40 ... Control part, 41 ... Memory, 50 ... Detection part, 51 ... Air flow meter, 52 ... Throttle sensor, 53 ... -Crank sensor, 54 ... water temperature sensor, 60 ... warning light.

Claims (7)

A control device for an internal combustion engine that performs split injection during engine idle operation,
After the first split injection that performs a plurality of intake stroke injections, perform a second split injection that is split into intake stroke injection and compression stroke injection,
The injection ratio between the intake stroke injection and the compression stroke injection in the second split injection is variable,
The first compression stroke injection after switching to engine idle operation is the injection of the minimum injection period , which is the minimum injection period that can be realized by the fuel injection valve provided in the internal combustion engine , and then the divided injection is performed. A control apparatus for an internal combustion engine, wherein a ratio of an injection ratio of the compression stroke injection is increased within a range in which a torque fluctuation is within a predetermined value. The control apparatus for an internal combustion engine according to claim 1,
A control apparatus for an internal combustion engine, characterized in that collective injection is performed when torque fluctuation due to the first divided injection exceeds a predetermined value. The control apparatus for an internal combustion engine according to claim 1,
A control apparatus for an internal combustion engine, characterized in that when the torque fluctuation due to the first divided injection exceeds a predetermined value, the batch injection is performed by increasing the fuel pressure. The control apparatus for an internal combustion engine according to claim 1,
A control apparatus for an internal combustion engine, characterized in that when the torque fluctuation caused by performing the first split injection exceeds a predetermined value, fuel pressure increase control is performed during a subsequent high-rotation and high-load operation. The control apparatus for an internal combustion engine according to claim 4,
A control device for an internal combustion engine, wherein a warning is issued when a torque fluctuation resulting from performing the first divided injection again after performing the fuel pressure increase control exceeds a predetermined value. The control apparatus for an internal combustion engine according to claim 1,
The control apparatus for an internal combustion engine, wherein the injection amount of the divided injection is corrected by a correction coefficient according to the content in the fuel. The control apparatus for an internal combustion engine according to claim 1,
The internal combustion engine that performs the first split injection and the second split injection when the engine output of the internal combustion engine is not transmitted to a drive system of a vehicle in which the internal combustion engine is mounted as a drive source. Engine control device.

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