JP2013104323A - Device for controlling internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To determine possibility of preignition, before the preignition actually occurs (or before frequency of the actual preignition is increased) in a predetermined low-speed high-load region where preignition is likely to occur, when the low-speed high-load region is used.SOLUTION: In using an intermediate load region lower than the low-speed high-load region (hereinafter called a preignition region) or the preignition region, if eccentricity of frequency distribution of a combustion speed parameter toward a high combustion speed side, with respect to a reference frequency distribution of the combustion speed parameter, is at a predetermined level or more, an internal combustion engine is determined that the preignition is likely to occur in the preignition region.

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine suitable for use in a spark ignition type internal combustion engine.

  Conventionally, for example, Patent Literature 1 discloses a combustion diagnosis method for an internal combustion engine. This conventional combustion diagnosis method calculates the standard deviation of the change in the cylinder pressure at a predetermined crank angle before ignition of the engine, and the standard deviation is equal to or greater than the standard deviation threshold, and the cylinder at the reference crank angle and top dead center. Pre-ignition when the load ratio in-cylinder differential pressure, which is calculated by calculating the differential pressure of the internal pressure and dividing the differential pressure by the load factor on the driven machine driven by the engine, is equal to or greater than the load ratio in-cylinder differential pressure threshold It is determined that (pre-ignition) has occurred.

JP 2009-133284 A JP-A-2-136666 JP 2011-85098 A JP 2008-88826 A

  However, the method described in Patent Document 1 described above is to detect pre-ignition using a change in in-cylinder pressure caused by actual occurrence of pre-ignition, and pre-ignition may occur. The internal combustion engine is in a state where pre-ignition is likely to occur in the low rotation high load region before the predetermined low rotation high load region is actually used or during use of the low rotation high load region. It cannot be judged before pre-ignition starts to occur.

  The present invention has been made to solve the above-described problems, and before pre-ignition starts to actually occur (or actually occurs) in a predetermined low-rotation high-load region where pre-ignition may occur. An object of the present invention is to provide a control device for an internal combustion engine that can determine the ease of occurrence of pre-ignition when the low-rotation high-load region is used before the frequency of pre-ignition increases.

A first invention is a control device for an internal combustion engine,
Parameter acquisition means for acquiring a combustion rate parameter correlated with the combustion rate of the internal combustion engine;
With respect to a reference frequency distribution of the combustion speed parameter when using a load region lower than a predetermined low rotation high load region (hereinafter referred to as “preg region”) in which pre-ignition may occur or the pre-ignition region, A pre-ignition occurrence probability predicting means for determining the degree of ease of occurrence of the pre-ignition when the pre-ignition region is used according to the degree of bias of the frequency distribution of the combustion speed parameter to the faster combustion speed;
It is characterized by providing.

The second invention is the first invention, wherein
When the degree of bias of the frequency distribution of the combustion speed parameter toward the faster combustion speed with respect to the reference frequency distribution is equal to or higher than a predetermined level, the pre-ignition occurrence probability predicting means It is determined that an ignition is likely to occur.

The third invention is the second invention, wherein
When it is determined by the pre-ignition occurrence probability prediction means that the internal combustion engine is in a state where the pre-ignition is likely to occur in the pre-ignition region, the degree of bias of the frequency distribution of the combustion speed parameter toward the faster combustion speed is increased. In response, the apparatus further comprises a load area restriction amount determining means for determining a use restriction amount of the preg area.

Moreover, 4th invention is 2nd or 3rd invention,
Knock learning control means for learning the retard amount of the ignition timing for suppressing the occurrence of knock with respect to the basic ignition timing as a knock learning value;
When it is determined that the internal combustion engine is in a state where the pre-ignition is likely to occur in the pre-ignition region by the pre-occurrence occurrence probability predicting unit, the use time limit of the pre-region is determined according to the magnitude of the knock learning value. Load region time limit determining means for determining
Is further provided.

The fifth invention is the fourth invention, wherein
The load area limit time determining means, when the retard amount of the ignition timing as the knock learning value is larger than a predetermined value, executes use restriction of the plague area until the next refueling is performed. It is characterized by.

The sixth invention is the fourth or fifth invention, wherein
The load region limit time determining means uses the predetermined high load region on the higher rotation side than the preg region when the retard amount of the ignition timing as the knock learning value is equal to or less than a predetermined value. The restriction of use of the prey region is executed until the engine is operated for a predetermined time or longer.

According to a seventh invention, in any one of the first to sixth inventions,
The parameter acquisition means includes
Including a knock sensor for detecting knock based on pressure oscillation of combustion gas;
The difference between the knock generation timing detected by the knock sensor and the ignition timing is used as the combustion speed parameter, and the combustion speed parameter is treated as having changed to the faster combustion speed when the difference is small. It is a means.

Further, an eighth invention is any one of the first to sixth inventions,
The parameter acquisition means includes
In-cylinder pressure sensor that detects in-cylinder pressure,
The rate of heat generation calculated based on the in-cylinder pressure waveform at the time of combustion detected by the in-cylinder pressure sensor is used as the combustion rate parameter, and the combustion rate is increased on the higher combustion rate side due to the higher rate of heat generation. It is a means to treat the speed parameter as having changed.

  If post-ignition occurs frequently due to the presence of any ignition source in the cylinder, the frequency distribution of the combustion speed parameter is biased toward the higher combustion speed. In addition, the higher the occurrence frequency of the post-ignition, the more the frequency distribution of the combustion speed parameter is biased toward the higher combustion speed side. If post-ignition occurs frequently in a load region lower than the above-mentioned preg region, when the preload region on the high load side is to be used after that, the ignition delay is reduced and the pre-ignition is reduced. It is considered that ignition is likely to occur. Further, when post-ignition occurs frequently in the pre-ignition region, it is considered that pre-ignition is likely to occur due to the presence of an in-cylinder ignition source that generates such post-ignition. For this reason, according to the first aspect of the present invention, when these pre-ignition regions are used, the occurrence of post-ignition occurs according to the degree of deviation of the frequency distribution of the combustion speed parameter toward the faster combustion speed with respect to the reference frequency distribution. By determining the frequency, it is possible to satisfactorily determine the degree of ease of occurrence of pre-ignition when the pre-plug region is used.

  If the degree of deviation of the frequency distribution of the combustion speed parameter toward the faster combustion speed with respect to the reference frequency distribution is a predetermined level or more, it can be said that post-ignition occurs frequently. For this reason, according to the second aspect of the present invention, when the degree of bias of the frequency distribution of the combustion speed parameter toward the higher combustion speed is equal to or higher than a predetermined level, the internal combustion engine is likely to generate the pre-ignition in the pre-ignition region. It is possible to make a good determination that the

  According to the third invention, it is possible to prevent occurrence of pre-ignition by determining in advance that the probability of occurrence of pre-ignition is increased and by limiting the required minimum operating region.

  According to the fourth aspect of the present invention, it is possible to determine the cause of the retard of the ignition timing and appropriately set the use time limit of the pre-ignition region according to the factor.

  When the retard amount of the ignition timing as the knock learning value is large, it can be determined that the cause of the retard of the ignition timing is the influence of the fuel property. According to the fifth aspect of the present invention, by limiting the use period of the prag area to the time of the next refueling in such a case, it becomes possible to perform use restriction in an appropriate period.

  If the retard amount of the ignition timing as the knock learning value is not so large, it can be determined that the cause of the retard of the ignition timing is due to accumulation of deposits in the cylinder. The deposit accumulated in the cylinder is promoted to be removed by combustion by running using a high rotation and high load region. According to the sixth invention, in such a case, the period during which the use of the plague region is restricted is set to an appropriate period by operating the internal combustion engine using the high load region for a predetermined time or more. Can be restricted.

  According to the seventh aspect, it is possible to satisfactorily grasp the variation in the combustion speed by utilizing the difference between the knock generation timing detected by the knock sensor and the ignition timing.

  According to the eighth aspect of the present invention, the variation in the combustion speed can be satisfactorily grasped using the heat generation speed calculated based on the in-cylinder pressure waveform during combustion detected by the in-cylinder pressure sensor.

It is a figure for demonstrating the system configuration | structure of the internal combustion engine in Embodiment 1 of this invention. It is the conceptual diagram which represented by comparing the relationship of ignition timing and engine load by the time of normal combustion and the time of pre-ignition generation. It is a figure showing the frequency distribution of the combustion rate parameter at the time of normal time and the time of frequent poigs. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention.

Embodiment 1 FIG.
[System Configuration of Embodiment 1]
FIG. 1 is a diagram for explaining a system configuration of an internal combustion engine 10 according to Embodiment 1 of the present invention. The system shown in FIG. 1 includes a spark ignition type internal combustion engine (a gasoline engine as an example) 10. A piston 12 is provided in the cylinder of the internal combustion engine 10. A combustion chamber 14 is formed on the top side of the piston 12 in the cylinder. An intake passage 16 and an exhaust passage 18 communicate with the combustion chamber 14.

  An air flow meter 20 that outputs a signal corresponding to the flow rate of air sucked into the intake passage 16 is provided in the vicinity of the inlet of the intake passage 16. A compressor 22 a of the turbocharger 22 is disposed in the intake passage 16 on the downstream side of the air flow meter 20. Further, an electronically controlled throttle valve 24 is provided in the intake passage 16 on the downstream side of the compressor 22a.

  Each cylinder of the internal combustion engine 10 is provided with a fuel injection valve 26 for directly injecting fuel into the combustion chamber 14 (inside the cylinder) and an ignition plug 28 for igniting the air-fuel mixture. Further, a turbine 22 b of the turbocharger 22 is disposed in the exhaust passage 18.

  Further, the system shown in FIG. 1 includes an ECU (Electronic Control Unit) 30. In addition to the air flow meter 20 described above, a crank angle sensor 32 for detecting a crank angle and an engine speed, a knock sensor 34 for detecting a knock based on pressure vibration of combustion gas, Various sensors for detecting the operating state of the internal combustion engine 10 such as an in-cylinder pressure sensor 36 for detecting the in-cylinder pressure are connected. Further, a liquid level sensor 38 for detecting the liquid level of fuel in a fuel tank (not shown) is electrically connected to the input part of the ECU 30. Also, various actuators for controlling the operation of the internal combustion engine 10 such as the throttle valve 24, the fuel injection valve 26, and the spark plug 28 are connected to the output portion of the ECU 30. The ECU 30 controls the operating state of the internal combustion engine 10 by driving the various actuators according to a predetermined program based on the sensor outputs.

[Control of Embodiment 1]
In the internal combustion engine 10, the following knock learning control for the ignition timing is executed in order to suppress the occurrence of knock during operation. The memory of the ECU 30 stores a basic ignition timing map in which the basic ignition timing is determined according to the operating state of the internal combustion engine 10 (for example, specified by the load factor KL and the engine speed). The knock learning control is to suppress the occurrence of knock by retarding the ignition timing from the basic ignition timing when a knock is detected based on the output signal of the knock sensor 34. When knocking is not detected by the knock sensor 34, ignition timing control is performed in which the ignition timing is gradually advanced to optimize the ignition timing. In such knock learning control, the ignition timing retardation amount is learned as a “knock learning value” each time the ignition timing retardation control is executed. The retard amount is an amount learned so that the ignition timing is retarded when knock is detected, and is learned so that the ignition timing is gradually advanced when knock is not detected. .

  In addition to knocking, pre-ignition (hereinafter abbreviated as “Plaig”) and post-ignition (hereinafter abbreviated as “Posig”) are known as abnormal combustion occurring in a spark ignition type internal combustion engine. More specifically, in the knock, before the flame propagating in the combustion chamber after spark ignition by the spark plug arrives, the unburned mixture at a location far from the spark plug is compressed and becomes hot and self-ignition. It is a phenomenon. Plague is a phenomenon in which the air-fuel mixture self-ignites before spark ignition by the spark plug, using a hot spark plug or a deposit in the cylinder as an ignition source. Posig is a phenomenon of high temperature ignition source as described above. It is a phenomenon in which the air-fuel mixture self-ignites after spark ignition by the spark plug due to its existence.

  An operation region in which pre-ignition is likely to occur is a predetermined low-rotation high-load region (hereinafter simply referred to as “pre-plung region”) in the vicinity of the full load torque line. Conventionally-known pule suppression control is to take measures (such as fuel cut) to prevent the paging from occurring continuously after the occurrence of prags is actually detected. However, such a conventional method cannot determine whether or not the internal combustion engine is in a state where the pre-ignition is likely to occur in the pre-leg region before the pre-start of the actual occurrence of the pre-pre-ignition region. For this reason, when the internal combustion engine is actually in a state where the pre-ignition is likely to occur in the above-mentioned pre-gile region, the control for preventing the pre-ignition is frequently performed, thereby deteriorating the drivability of the internal combustion engine. And exhaust emissions will be worsened. Moreover, since a praig is generated with a loud sound, the sensory performance is also deteriorated.

  Therefore, in the present embodiment, the pragging area is not used (for example, when using an intermediate load area lower than the paging area) or during use of the paging area by the following method. In the region, it is determined whether or not the internal combustion engine 10 is in a state where pre-ignition is likely to occur (whether the occurrence probability of pre-ignition is increased). In addition, when it is determined that the internal combustion engine 10 is in the above state, the use of the plague region is restricted in order to avoid (prevent) the occurrence of the plague.

FIG. 2 is a conceptual diagram showing a comparison of the relationship between the ignition timing and the engine load at the time of normal combustion and at the time of occurrence of pre-ignition.
Possible causes of the occurrence of pre-ignition in the pre-ignition region include, for example, a situation where a large amount of deposit is deposited in the cylinder and a situation where a fuel having a low RON (research method octane number) is used. As shown in FIG. 2, when a prag is actually generated in a situation where the plow is likely to occur, as shown in FIG. 2, as the engine load increases, a pre-ignition that is earlier in ignition timing than the normal combustion is likely to occur. Become. More specifically, the solid line labeled “Pleig” in FIG. 2 represents the Pleig line with the earliest ignition timing among Pleigs that can occur at each engine load.

  On the other hand, the ignition delay of the air-fuel mixture increases as the engine load decreases. For this reason, when the internal combustion engine is in a state where pre-ignition is likely to occur, when the engine load is low, normal combustion is performed before the occurrence of abnormal ignition. As shown by the broken line in FIG. In other words, under conditions where pre-ignition is likely to occur, in the operating region on the low load side, as shown by the broken line in FIG. 2, pre-ignition does not occur, but there is no ignition source, and there is no ignition source. It is not only that, and it is considered that the poig is generated by the presence of the ignition source.

  Therefore, in the present embodiment, the variation in the combustion speed is grasped during the use of the predetermined medium load region on the lower load side than the preg region and the preg region, and the occurrence of multiple poigs from the variation in the combustion rate. Estimated. Specifically, by the method described with reference to FIG. 3 below, the deviation of the frequency distribution of the combustion rate parameter toward the faster combustion rate with respect to the frequency distribution of the predetermined combustion rate parameter (reference frequency distribution described later). When the degree is equal to or higher than the predetermined level, frequent posing has occurred, and as a result, it is determined that the internal combustion engine 10 is in a state where the pre-ignition is likely to occur in the plague region.

FIG. 3 is a diagram showing the frequency distribution of the combustion speed parameter in the normal time and in the frequent occurrence of the poig.
In the present embodiment, the difference X between the knock generation timing detected by the knock sensor 34 and the ignition timing is used as a combustion speed parameter correlated with the combustion speed. The difference X becomes smaller as the knock generation time is advanced. For this reason, here, the difference X is reduced, and the combustion speed parameter is treated as having changed to the higher combustion speed side.

  The “normal distribution” shown in FIG. 3 is a situation in which the internal combustion engine 10 is not in a state where it is easy to generate plague (more specifically, for example, the internal combustion engine 10 is deposited in a cylinder. This is the frequency distribution of the difference X when knocking occurs under the condition that there is no new state and the fuel of the appropriate RON scheduled is used. Hereinafter, the frequency distribution in this case is referred to as “reference frequency distribution”.

  If a poist is generated due to the presence of any ignition source in the cylinder, combustion occurs at other locations due to the presence of the ignition source in addition to the combustion by the normal spark ignition. Therefore, the combustion speed is faster than normal, and the knock generation time when the knock is generated by the generation of the poig is advanced. For this reason, under the situation where the poig occurs frequently, the frequency distribution of the difference X is smaller on the side where the difference X is smaller than the reference frequency distribution (that is, on the side where the combustion speed is faster) as shown by the broken line in FIG. ).

  Therefore, when the frequency distribution of the difference X is biased toward the smaller side of the difference X with respect to the reference frequency distribution, it can be estimated that the poige is generated for some reason. Therefore, in the present embodiment, when the degree of deviation of the frequency distribution of the difference X toward the side where the difference X is small (the side where the combustion speed is fast) with respect to the reference frequency distribution is a predetermined level or more, the poig occurs frequently. As a result, it is determined that the internal combustion engine 10 is in a state where pre-ignition is likely to occur in the pre-gauge region.

  In the present embodiment, when it is determined that the internal combustion engine 10 is in a state in which the occurrence of pre-ignition is likely to occur in the pre-ignition region as described above, the use of the pre-reproduction region is used according to the degree of deviation of the frequency distribution of the difference X. The usage limit of the prag area is limited in such a manner that the limit amount is determined.

  Furthermore, in the present embodiment, the time for performing the use restriction of the prag area is determined according to the magnitude of the knock learning value. More specifically, when the retard amount of the ignition timing as the knock learning value is larger than a predetermined value, the use restriction of the plague region is executed until the next refueling is performed, When the retard amount of the ignition timing as the learning value is equal to or less than the predetermined value, the operation of the internal combustion engine 10 using the operation region on the high rotation / high load side (the region on the higher rotation side than the preg region) is predetermined. The restriction on the use of the plague area is executed until the time is exceeded (accumulated).

  FIG. 4 is a flowchart showing a control routine executed by the ECU 30 in order to realize the control for predicting the ease of occurrence of pre-age and avoiding the occurrence of pre-age in advance. This routine is repeatedly executed every predetermined control cycle.

  In the routine shown in FIG. 4, first, the current operating region of the internal combustion engine 10 (specified by the engine load and the engine speed) is slightly less than the abnormal combustion region (that is, the Preg region) and the abnormal combustion region. It is determined whether one of the light predetermined medium load regions is present (step 100). The current operating region of the internal combustion engine 10 is calculated based on the engine speed calculated using the output of the crank angle sensor 32, the intake air amount detected by the air flow meter 20, and the engine speed. Based on the load factor (an index indicating the engine load).

  Next, the calculation of the frequency distribution of the combustion rate parameter (the difference X in the present embodiment) is executed (step 102). Specifically, the frequency distribution of the difference X is obtained by collecting the data of the difference X for each predetermined load region in the abnormal combustion region (preg region) and the medium load region in step 100, and then collecting each difference X data. It is created for each load area. In this step 102, the current difference X (in the current operation region) is calculated, and then the frequency distribution of the latest difference X for the load region to which the current operation region belongs is calculated. The knock occurrence time for calculating the difference X is acquired by using the knock sensor 34 and the crank angle sensor 32, for example, by obtaining a crank angle position at which the output of the knock sensor 34 shows a peak value. Can do. If no knock is detected by the knock sensor 34, the frequency distribution of the difference X in this step 102 is not calculated (updated).

  Next, it is determined whether or not the frequency distribution of the difference X calculated in step 102 is more than a predetermined level on the faster combustion speed side (smaller difference X side) than the reference frequency distribution (step 104). ). A reference frequency distribution as shown in FIG. 3 is stored in the ECU 30 as a reference value in each load region in which the frequency distribution of the difference X is calculated individually. Specifically, the process of step 104 is executed as follows, for example. That is, the difference between the average value of the reference frequency distribution and the average value of the frequency distribution of the difference X calculated in step 102 is calculated. Then, by determining whether or not this difference is equal to or greater than a predetermined threshold, it is determined whether or not the frequency distribution of the current determination target is biased to a predetermined level or more on the faster combustion speed side. Instead of the determination using the difference between the average values of the frequency distributions described above, for example, a method for evaluating the correlation between the shapes of the calculated frequency distribution of the difference X and the reference frequency distribution may be used. .

  If it is determined in step 104 that the frequency distribution of the difference X is biased to a predetermined level or more with respect to the reference frequency distribution on the side where the combustion speed is fast (the side where the difference X is small), the poig occurs frequently. It is determined that the internal combustion engine 10 is in a state where the pre-ignition is likely to occur in the pre-ignition region (step 106).

  Next, the use limit amount of the prag region is determined according to the degree of deviation of the frequency distribution of the difference X toward the faster combustion speed (step 108). It is determined that the degree of deviation of the frequency distribution of the difference X toward the faster combustion speed is larger as the difference between the average value of the reference frequency distribution and the average value of the frequency distribution of the difference X (calculated in step 104 above) is larger. be able to. In this step 106, the use limit amount of the load in the prag region is determined so that the use is limited to a higher load region in the praig region as the degree of bias is larger.

  Next, the load used by the internal combustion engine 10 is limited based on the load usage limit determined in step 108 (step 110). The load limitation in this step 110 can be executed by limiting the intake air amount by adjusting the opening of the throttle valve 24, for example.

  FIG. 5 is a flowchart showing a control routine executed by the ECU 30 in order to control the execution time of the load restriction for avoiding the paging. This routine is started when the process of step 110 of the routine shown in FIG. 4 is executed, and is repeatedly executed at predetermined control cycles until the load restriction is released.

  In the routine shown in FIG. 5, it is first determined whether or not the ignition timing retard amount (KCS (knock control system) retard amount) as a knock learning value is larger than a predetermined value (step 200). This KCS retardation amount increases in a situation where knocking is likely to occur.

  If it is determined in step 200 that the KCS retardation amount is larger than the predetermined value, it is determined whether or not fuel supply has been performed after the load restriction is performed in step 110 (step 202). ). Whether or not fuel has been supplied can be determined by detecting a change in the amount of fuel in the fuel tank using the liquid level sensor 38, for example.

  While it is determined in step 202 that fuel supply has not yet been performed, the load limitation in step 110 is continued (step 204). On the other hand, if it is determined in step 202 that the fuel supply has been executed after the load restriction is implemented, the load restriction of the internal combustion engine 10 in step 110 is released (step 206).

  On the other hand, if it is determined in step 200 that the KCS retardation amount is equal to or less than the predetermined value, after the load restriction in step 110 is performed, a predetermined high rotation high load on the high rotation side with respect to the plague region. It is determined whether or not the operation of the internal combustion engine 10 using the region has been performed for a predetermined integration time or longer (step 208). As a result, while the determination in step 208 is still not established, the load limitation in step 110 is continued (step 204). On the other hand, if the determination in step 208 is established, the load restriction on the internal combustion engine 10 in step 110 is released (step 206).

  According to the routine shown in FIG. 4 described above, the difference X is compared with the reference frequency distribution during use of the abnormal combustion region (preg region) and a predetermined medium load region that is slightly lighter than the abnormal combustion region. When it is determined that the frequency distribution is biased to a predetermined level or more on the fast combustion speed side, it is determined that multiple poig- ing has occurred, and as a result, the internal combustion engine 10 generates plague in the plague region. It is determined that it is easy to do. More specifically, when it is determined that the poisting occurs frequently while the medium load area is being used (that is, in a situation in which the praig area is not used), the high load side plag area thereafter Therefore, it can be determined that pre-ignition is likely to occur due to a small ignition delay. In addition, when it is determined that the poig occurs frequently while using the above-mentioned pre-gauge area, it is determined that the pre-ignition is likely to occur due to the presence of an in-cylinder ignition source that generates such po can do.

  Then, according to the routine shown in FIG. 4, when it is determined that the internal combustion engine 10 is in a state where the pre-ignition is likely to occur in the pre-ignition region, the load used by the internal combustion engine 10 to avoid the pre-ignition. The area is limited. According to such control, it is possible to determine in advance that the probability of occurrence of prag is increasing and prevent the occurrence of prag. In addition, by determining the load limit amount according to the degree of deviation of the frequency distribution of the difference X, it is possible to realize the prevention of the occurrence of such pregs by the minimum necessary limit of the operation region to be used.

  Further, according to the routine shown in FIG. 5 described later, when the KCS retardation amount of the ignition timing as the knock learning value is larger than a predetermined value, the load is applied until the refueling is performed after the load restriction is performed. The limit will be enforced. When the KCS retardation amount is large, that is, when the ignition timing needs to be greatly retarded with respect to the basic ignition timing because knocking is likely to occur, the influence of fuel properties (for example, use of low RON fuel) It can be determined that For this reason, in this case, the load restriction can be performed in an appropriate period by setting the execution time of the load restriction until the next refueling time.

  Further, according to the routine shown in FIG. 5, when the KCS retardation amount of the ignition timing as the knock learning value is equal to or less than a predetermined value, the high load area on the high rotation side with respect to the pre-age area is integrated for a predetermined time. Until this is done, load limiting is performed. If the KCS retard amount is not so large, it can be determined that the cause of the retard of the ignition timing is due to the accumulation of deposits in the cylinder. The deposit accumulated in the cylinder is promoted to be removed by combustion by running using a high rotation and high load region. For this reason, according to such a method, it is possible to appropriately set the execution time of the load restriction when the KCS retardation amount is equal to or less than a predetermined value.

  In the first embodiment described above, an example in which the difference X between the knock generation timing detected by the knock sensor 34 and the ignition timing is used as a combustion speed parameter correlated with the combustion speed has been described. However, the combustion speed parameter in the present invention is not limited to the above-described one. For example, when the in-cylinder pressure sensor 36 is provided as in the internal combustion engine 10, it is based on the in-cylinder pressure waveform during combustion. It may be a value indicating the rate of heat generation obtained. More specifically, as a value indicating the rate of heat generation, for example, a crank angle position when the combustion mass ratio (MFB) becomes a predetermined value (for example, 50%) can be used. The combustion mass ratio is an index value representing the ratio of the mass of the burned fuel to the mass of the fuel supplied into the cylinder. By using the in-cylinder pressure sensor 36 and the crank angle sensor 32 in combination, It is a value that can be calculated for each predetermined crank angle according to a known relational expression based on the pressure waveform. When the crank angle position calculated in this way is an advanced value, it can be determined that the combustion speed is fast. Therefore, using the frequency distribution of the crank angle position calculated in this way, the same determination as in the case of the frequency distribution of the difference X described above may be performed.

  In the first embodiment described above, the frequency distribution of the difference X (combustion rate parameter) with respect to the reference frequency distribution is higher than a predetermined level on the faster combustion rate during use of the abnormal combustion region (preg region) or the like. An example has been described in which it is determined that the internal combustion engine 10 is in a state where it is easy for the pre-ignition to occur in the pre-gauge region when it is determined that the bias is biased. However, the present invention is not limited to the above method. That is, according to the present invention, the degree of the ease of occurrence of the prig when the prag region is used is determined according to the degree of deviation of the frequency distribution of the combustion rate parameter toward the faster combustion rate with respect to the reference frequency distribution. For example, it may be determined that the higher the degree of bias is, the more likely the plag is to occur when the preg region is used.

In the first embodiment described above, the ECU 30 executes the process of step 102, so that the “parameter acquisition means” in the first invention executes the series of processes of steps 100 to 106. Thus, the “pre-ignition occurrence probability predicting means” according to the first aspect of the present invention is realized.
Further, in the first embodiment described above, the “load region limit amount determining means” in the third aspect of the present invention is realized by the ECU 30 executing the process of step 108.
In the first embodiment described above, the ECU 30 performs the knock learning control using the knock sensor 34, whereby the “knock learning control means” in the fourth aspect of the present invention is the step 200 to 206. By executing a series of processes, the “load region time limit determining means” according to the fourth aspect of the present invention is realized.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Piston 14 Combustion chamber 16 Intake passage 18 Exhaust passage 20 Air flow meter 22 Turbocharger 24 Throttle valve 26 Fuel injection valve 28 Spark plug 30 ECU (Electronic Control Unit)
32 Crank angle sensor 34 Knock sensor 36 In-cylinder pressure sensor 38 Liquid level sensor

Claims (8)

Parameter acquisition means for acquiring a combustion rate parameter correlated with the combustion rate of the internal combustion engine;
With respect to a reference frequency distribution of the combustion speed parameter when using a load region lower than a predetermined low rotation high load region (hereinafter referred to as “preg region”) in which pre-ignition may occur or the pre-ignition region, A pre-ignition occurrence probability predicting means for determining the degree of ease of occurrence of the pre-ignition when the pre-ignition region is used according to the degree of bias of the frequency distribution of the combustion speed parameter to the faster combustion speed;
A control device for an internal combustion engine, comprising:   When the degree of bias of the frequency distribution of the combustion speed parameter toward the faster combustion speed with respect to the reference frequency distribution is equal to or higher than a predetermined level, the pre-ignition occurrence probability predicting means 2. The control apparatus for an internal combustion engine according to claim 1, wherein it is determined that an ignition is likely to occur.   When it is determined by the pre-ignition occurrence probability prediction means that the internal combustion engine is in a state where the pre-ignition is likely to occur in the pre-ignition region, the degree of bias of the frequency distribution of the combustion speed parameter toward the faster combustion speed is increased. 3. The control apparatus for an internal combustion engine according to claim 2, further comprising a load region limit amount determining means for determining a use limit amount of the preg region. Knock learning control means for learning the retard amount of the ignition timing for suppressing the occurrence of knock with respect to the basic ignition timing as a knock learning value;
When it is determined that the internal combustion engine is in a state where the pre-ignition is likely to occur in the pre-ignition region by the pre-occurrence occurrence probability predicting unit, the use time limit of the pre-region is determined according to the magnitude of the knock learning value. Load region time limit determining means for determining
The control apparatus for an internal combustion engine according to claim 2 or 3, further comprising:   The load area limit time determining means, when the retard amount of the ignition timing as the knock learning value is larger than a predetermined value, executes use restriction of the plague area until the next refueling is performed. The control device for an internal combustion engine according to claim 4.   The load region limit time determining means uses the predetermined high load region on the higher rotation side than the preg region when the retard amount of the ignition timing as the knock learning value is equal to or less than a predetermined value. 6. The control device for an internal combustion engine according to claim 4 or 5, wherein the use restriction of the plague region is executed until the engine is operated for a predetermined time or more. The parameter acquisition means includes
Including a knock sensor for detecting knock based on pressure oscillation of combustion gas;
The difference between the knock generation timing detected by the knock sensor and the ignition timing is used as the combustion speed parameter, and the combustion speed parameter is treated as having changed to the faster combustion speed when the difference is small. The control device for an internal combustion engine according to any one of claims 1 to 6, wherein the control device is a means. The parameter acquisition means includes
In-cylinder pressure sensor that detects in-cylinder pressure,
The rate of heat generation calculated based on the in-cylinder pressure waveform at the time of combustion detected by the in-cylinder pressure sensor is used as the combustion rate parameter, and the combustion rate is increased on the higher combustion rate side due to the higher rate of heat generation. 7. The control device for an internal combustion engine according to claim 1, wherein the control device treats the speed parameter as having changed.

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