JP2002188504A - Knocking control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform proper control for keeping engine power constant regardless of change in signal intensity even in the case of performing knocking judgement based on the fact that the vibration intensity distribution detected through a knock sensor becomes normal distribution. SOLUTION: The intensity of the vibration generated in an internal combustion engine is detected through the detection signal (knock signal) from the knock sensor (S10), and a knock judging level is set based on the normal distribution presumed for the logarithmic conversion value (S70), and the presence and absence of the generation of knocking is judged based on this knock judging level (S80). When the logarithmic conversion value shows a value in a smaller intensity range in the dynamic range of an input circuit, the standard deviation is over-renewed according to the detection frequency in the low limit value of the dynamic range, and the center value is under-renewed (S40 and S50). When the logarithmic conversion value shows a value in a larger intensity range, an abnormality is judged according to the frequency of detecting upper limit values (S90), prohibiting the control of the ignition time of the internal combustion engine toward the spark advance range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a knocking control apparatus for an internal combustion engine that determines the occurrence of knocking of the internal combustion engine and performs necessary control such as ignition timing control and air-fuel ratio control.

[0002]

2. Description of the Related Art In an internal combustion engine, generally, when it is determined that knocking has occurred, the ignition timing is retarded, and when it is determined that knocking has not occurred, the ignition timing is gradually advanced. Ignition timing control for optimizing the ignition timing.

Conventionally, as a method for determining the occurrence of knocking of an internal combustion engine, for example, Japanese Patent Laid-Open No.
The following method described in Japanese Patent No. 1269 is known. That is, here, assuming that the intensity distribution of the vibration detected through the knock sensor (more precisely, its logarithmically converted value) is a normal distribution, the knock determination level is determined based on the standard deviation and the median obtained from the probability distribution. The knocking is determined based on the set knock determination level.

More specifically, as shown in FIG. 8, first, the standard deviation SGM and the median value Vm of the normal distribution in which the standard deviation SGM and the median value Vm are defined as initial values are used as the knock signal (signal Strength) Update based on KCS logarithmic conversion value IVpk.

[0005] That is, the standard deviation SGM is calculated as follows.
GM) <the logarithmic conversion value lVpk <the median value Vm ”(the range A in FIG. 8), the standard deviation SGM = the previously set standard deviation SGM′−2α (1) Conversely, the logarithmically transformed value lV
When pk is in a range other than the range A (range B in FIG. 8), the standard deviation SGM is updated as follows: standard deviation SGM = previously set standard deviation SGM ′ + α (2). On the other hand, when the logarithmic conversion value lVpk is in the range of “median value Vm <logarithmic conversion value lVpk”, the median value Vm = median value Vm = median value Vm ′ + β set last time (3) , And conversely, the logarithmically transformed value lV
When pk is in the range of “median value Vm ≧ logarithmically converted value 1Vpk”, the median value Vm is updated as follows: median value Vm = median value Vm′−β set last time (4).

As described above, the standard deviation SGM and the median value V
By updating m, the normal distribution determined by the standard deviation SGM and the median value Vm converges to a normal distribution corresponding to the distribution of the logarithmically converted value lVpk at that time.

The standard deviation SGM and the median V
The knock determination level Vkd is set based on m, and the occurrence of knocking is determined on the condition that the logarithmic conversion value lVpk becomes larger than the knock determination level Vkd.

By determining the occurrence of knocking in this manner, it is possible to determine knocking with higher accuracy according to the intensity distribution of the logarithmically converted value lVpk of knock signal KCS at that time. Then, by performing the above-described ignition timing control or the like based on such a knocking determination result, an appropriate engine output can be maintained.

[0009]

In the knocking determination, as described above, the vibration detected through the knock sensor, that is, the intensity distribution of the logarithmically converted value lVpk of the knock signal KCS is input to and processed by a circuit. It is a major premise that the distribution is normally distributed within the determined dynamic range. That is, as shown in FIG. 9, the characteristics of the knock signal KCS are substantially linear in accordance with the intensity of the detected vibration. Among them, the knock signal or the knock determination level is actually set. What is used is the vibration intensity W
This is a value corresponding to the range of 1 to W2 (a value from the lower limit value Vmn to the upper limit value Vmx for the logarithmic conversion value 1Vpk). Conventionally, the dynamic range of the circuit for inputting and processing the same matches the range of the vibration intensities W1 to W2, and the logarithmic conversion value lVpk of the knock signal KCS always changes from the lower limit value Vmn to the upper limit value Vmx. To take.

For this reason, if the strength of the knock signal KCS changes due to, for example, individual differences of the internal combustion engine or changes over time, the value of the knock signal KCS falls outside the above dynamic range.
The intensity distribution of the logarithmically converted value 1Vpk deviates from the assumed normal distribution, and it becomes impossible to perform a proper knocking determination.

For example, as shown in FIG. 10, when the signal intensity decreases due to a temporal change of the knock sensor and its installation environment, and the detected vibration value becomes smaller than the lower limit value Vmn, a range outside the lower limit value Vmn. The standard deviation SGM is updated to a small value as much as the detection value of C is not used, and the median value Vm is updated to the side where the logarithm conversion value lVpk becomes large.

In this case, particularly, the standard deviation SGM rapidly becomes a small value, so that the knock determination level Vkd set based on the value also becomes a small value, and it is erroneously determined that a signal of a normal vibration level is caused by knocking. Become like When the ignition timing control is performed based on such knocking determination, the engine torque is reduced due to excessive retardation of the ignition timing.

On the other hand, as shown in FIG. 11, when the signal intensity of the knock sensor increases and the detected vibration value becomes larger than the upper limit value Vmx, a signal of a normal vibration level and a signal at the time of knocking occur. Can not be distinguished. That is, for the circuit to input and process this,
The logarithm conversion value lVpk = upper limit value Vmx is recognized as a uniform value. Eventually, in this case, it becomes impossible to determine the occurrence of knocking based on the logarithmically converted value 1Vpk, and it becomes difficult to control the ignition timing and the like.

[0014] The present invention has been made in view of such circumstances, and its purpose is to make a knocking determination based on the fact that the intensity distribution of vibration detected through the knock sensor becomes a predetermined distribution. Another object of the present invention is to provide a knocking control device for an internal combustion engine that can perform appropriate control for maintaining engine output regardless of a change in the signal strength.

[0015]

The means for achieving the above object and the effects thereof will be described below. First, according to the first aspect of the present invention, a knock sensor detects vibration generated in an internal combustion engine, and sets a knock determination level based on an intensity distribution of the detected vibration. And a knock control device for an internal combustion engine that determines whether knocking has occurred based on a comparison with the set knock determination level and performs the required engine control. Deviates from the pre-estimated distribution of
The gist of the present invention is to provide a means for detecting the fact and performing a fail-safe process.

According to the above configuration, when the intensity of the vibration detected through the knock sensor deviates from the distribution presumed by the internal combustion engine due to individual differences or changes over time, that is, the same detection is performed. Even when the intensity of the vibration to be inputted is out of the dynamic range of the circuit that inputs and processes the vibration, the execution of an improper knocking judgment and the erroneous judgment due to this, and the improper engine based on this erroneous judgment Execution of control and the like can be avoided through fail-safe processing.

According to a second aspect of the present invention, in the knocking control apparatus for an internal combustion engine according to the first aspect, the means for performing the fail-safe processing includes a step of estimating the intensity of the detected vibration in advance based on the intensity distribution. The gist is that the knock determination level is corrected by detecting a deviation from the distribution to be performed on the side of the smaller intensity.

According to the above configuration, the intensity of the detected vibration deviates from the dynamic range to the side where the intensity is small,
Accordingly, it is possible to prevent the knock determination level from being set to an inappropriate value. That is,
It is possible to suppress a decrease in knocking determination accuracy based on the knock determination level.

According to a third aspect of the present invention, in the knocking control apparatus for an internal combustion engine according to the second aspect, the distribution estimated in advance for the intensity distribution is a normal distribution,
The gist is that the knock determination level is corrected by excessively updating the standard deviation according to the frequency at which the logarithmic conversion value of the detected vibration intensity deviates from the same distribution to the lower intensity side.

According to a fourth aspect of the present invention, in the knocking control apparatus for an internal combustion engine according to the second aspect, the distribution estimated in advance for the intensity distribution is a normal distribution,
The gist is that the correction of the knock determination level is performed by an over-update of the standard deviation and an under-update of the median according to the frequency at which the logarithmically converted value of the detected vibration intensity deviates from the same distribution to the lower intensity side. And

According to each of these configurations, even when the knock determination is made based on the fact that the intensity distribution of the vibration detected through the knock sensor becomes a normal distribution, the signal intensity deviates from the distribution to the side of smaller intensity. In this case, an appropriate engine output can be maintained.

In particular, according to the configuration of the third aspect of the present invention, the standard deviation is excessively updated according to the frequency at which the logarithmically converted value of the detected vibration intensity deviates from the normal distribution to the smaller side. Can be suppressed from suddenly becoming a small value, and the knock determination level can be suitably corrected. Therefore, it is possible to preferably suppress a decrease in the knocking determination accuracy.

On the other hand, according to the configuration of the present invention, the fact that the standard deviation rapidly decreases and the median value is updated to a large value indicates that the logarithmic conversion value of the vibration intensity is normal. It can be suppressed in a manner corresponding to the frequency of deviating from the distribution to the smaller side. For this reason, the knock determination level can be more suitably corrected as compared with the case where only the excessive update of the standard deviation is performed, so that a decrease in the knock determination accuracy can be more appropriately suppressed. become.

According to a fifth aspect of the present invention, in the knocking control apparatus for an internal combustion engine according to the first aspect, the means for performing the fail-safe processing includes a step of estimating the detected vibration intensity in advance with respect to the intensity distribution. The gist of the present invention is to detect a deviation from the distribution to be given to a side having a higher intensity and prohibit the determination relating to the occurrence of the knocking.

According to the above configuration, the intensity of the detected vibration deviates from the dynamic range to a higher intensity side,
Even when knocking cannot be determined, it is possible to prevent knocking determination and prevent erroneous determination, thereby suppressing a decrease in the accuracy of knocking determination.

According to a sixth aspect of the present invention, in the knocking control apparatus for an internal combustion engine according to the fifth aspect, the distribution estimated in advance for the intensity distribution is a normal distribution,
The gist of the present invention is to further include means for restricting the control of the ignition timing of the internal combustion engine to the advanced angle side in accordance with the frequency at which the logarithmic conversion value of the detected vibration intensity deviates from the same distribution to the higher intensity side. .

In an internal combustion engine, normally, an appropriate engine output is maintained by controlling the ignition timing based on the result of the knocking determination. Therefore, when knocking determination is prohibited, such ignition timing control cannot be performed.
In this regard, according to the above configuration, even when the logarithmic conversion value of the detected vibration intensity deviates from the estimated normal distribution to the side with the higher intensity, the progress in the ignition timing control is performed according to the frequency of the deviation. Control to the corner side is regulated. As a result, the engine output can be properly maintained even when the knocking determination is prohibited.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a knocking control device for an internal combustion engine according to the present invention will be described below.

FIG. 1 shows a schematic configuration of a multi-cylinder (for example, four cylinder, only one cylinder is shown in FIG. 1) internal combustion engine to which the knocking control device according to the present embodiment is applied. In the present embodiment, as this internal combustion engine,
It is assumed that fuel is injected in the intake passage, and a mixture of the injected fuel and intake air is sucked into the combustion chamber.

As shown in FIG. 1, a knock sensor 21 for outputting a knock signal KCS corresponding to the intensity of vibration generated in the internal combustion engine 10 is provided near the combustion chamber 12 in the internal combustion engine 10. Have been. In the vicinity of the crankshaft 13, a rotation speed sensor 22 that outputs a rotation speed signal NE corresponding to the rotation speed (engine rotation speed) is provided. On the other hand, a surge tank 14 provided in the intake passage 11 has an intake pressure sensor 2 that outputs an intake pressure signal PM corresponding to the pressure of intake air in the tank 14.
3 are provided. And the crankshaft 1
A cam angle for outputting an appropriate pulse signal (cam angle signal) CA corresponding to a predetermined cam angle (here, a cam angle corresponding to the compression top dead center) is provided near the camshaft 15 driven to be connected to the cam shaft 3. A sensor 24 is provided.

The internal combustion engine 10 is provided with a spark plug 16 for igniting the air-fuel mixture sucked into the combustion chamber 12. An ignition coil 17 and an igniter 18 are electrically connected to the ignition plug 16.

The knocking control device according to the present embodiment is provided with an electronic control device 30 composed of, for example, a microcomputer or the like. The electronic control device 30 has an input circuit 30a provided therein. , The respective detection signals KCS, NE, PM, and CA output from the sensors 21, 22, 23, and 24 are taken in.

The electronic control unit 30 includes the combustion chamber 12
The ignition timing for igniting the air-fuel mixture introduced into the engine (the amount of retardation from the compression top dead center) is calculated based on the rotational speed signal NE and the intake pressure signal PM. The electronic control unit 30 determines the occurrence of knocking in the internal combustion engine 10 based on a knock signal KCS detected by the knock sensor 21, and adjusts the ignition timing based on the determination result.

The electronic control unit 30 outputs a signal (ignition signal) indicating the calculated and adjusted ignition timing to the igniter 18. The igniter 18 is a device that drives the ignition coil 17 based on the input ignition signal to cause the ignition plug 16 to perform an ignition operation. As a result, the air-fuel mixture sucked into the combustion chamber 12 is ignited at the calculated ignition timing, exploded and burned, so that an appropriate engine output is maintained.

Also, in the knocking control device according to the present embodiment, as described above, the intensity distribution of vibration detected through knock sensor 21 (more precisely, its logarithmically converted value) becomes a normal distribution. , A knock determination level is set based on a standard deviation or a median obtained from the probability distribution, and occurrence of knocking is determined based on the set knock determination level. That is, the knock signal K
The standard deviation SGM and the median value Vm of the normal distribution estimated based on the logarithmic conversion value lVpk of CS are updated as in the above-described relational expressions (1) to (4), and the standard deviation SGM and the median value Vm are updated. The knock determination level Vkd is set based on the knock determination level, and the occurrence of knocking is determined based on the knock determination level Vkd.

In addition, in the knocking control device according to the present embodiment, the logarithmic conversion value lVpk is applied to the input circuit 30a.
Dynamic range (lower limit value Vmn to upper limit value Vmx)
If the logarithmic conversion value lVpk deviates to a side where the intensity is smaller than the lower limit value Vmn, it is detected based on the detection frequency Cmn of the lower limit value Vmn or the detection frequency Cmx of the upper limit value Vmx. Updates the standard deviation SGM excessively in accordance with the detection frequency Cmn, and updates the median value Vm excessively, thereby correcting the knock determination level Vkd upward. On the other hand, if the logarithmic conversion value lVpk deviates to a side where the intensity is higher than the upper limit value Vmx, control of the ignition timing to the advanced side based on knocking determination is prohibited in accordance with the detection frequency Cmx. Fail-safe processing.

The above detection frequencies Cmn and Cmx are
It is stored in the electronic control unit 30. In particular,
The electronic control unit 30 performs a predetermined number of samplings (for example, 1
0), the number of times the lower limit value Vmn is detected and the number of times the upper limit value Vmx is detected are counted, and the respective detection frequencies Cmn and Cmx are referred to as “detection frequency Cmn = lower limit value Vmn. The number of times of detection / the number of predetermined samplings "and the number of detections Cmx = the number of times of detection of the upper limit value Vmx / the number of predetermined samplings are calculated and stored.

By performing such fail-safe processing, knock signal K detected through knock sensor 21
Even when CS changes due to individual differences of the internal combustion engine 10 or changes over time, etc., and deviates from the dynamic range of the input circuit 30a, an improper knocking determination is performed, and an erroneous determination due to this is performed. Execution of improper engine control or the like based on the determination is avoided.

Hereinafter, a processing procedure for determining such knocking will be described with reference to flowcharts shown in FIGS. This processing is performed, for example, as an interrupt processing for each predetermined cam angle.
Is executed by

As shown in FIG. 2, in this process, first, a knock signal KCS is read through the knock sensor 21 (step S10). Specifically, the peak value of the output signal of knock sensor 21 is held during a predetermined period in which knocking, which is obtained in advance through experiments or the like, may occur, and this peak value is read as knock signal KCS.

After that, the knock signal KCS is expressed by a logarithmic conversion value lVpk = A × log (knock signal KCS /
a) is logarithmically converted by the relational expression (step S2).
0). The coefficients “A” and “a” are both arbitrary constants (for example, A = 64 / log (4), a = 4). Further, the logarithmic conversion may be performed by a normal function operation, but by realizing the logarithmic conversion by a map operation for linearly interpolating the map values, the realization is easier.

Then, through the processing described below (steps S30 to S50), the logarithmically converted value lVp
The standard deviation SGM and the median value Vm based on k are updated. Here, the knock signal KCS includes mechanical vibration, which is not related to vibration due to combustion in the internal combustion engine 10, that is, a noise component. Since the mechanical vibration component, which is a noise component, changes according to the engine operating state, when the standard deviation SGM and the median value Vm are updated based on the logarithmic conversion value lVpk of the knock signal KCS in all engine operating states. The standard deviation SGM and the median value Vm reflect the fluctuation of the mechanical vibration component. That is, in this case, the knock determination level set based on the standard deviation SGM and the median value Vm also changes, which is not preferable in determining the occurrence of knocking.

For this reason, in the present embodiment, when the mechanical vibration component contained in knock signal KCS is relatively small, the internal combustion engine 10 is set in a stable operation state, and when the internal combustion engine 10 is in such a stable operation state. , The standard deviation SGM is updated.

The reason why the updating of the median value Vm is permitted even when the internal combustion engine 10 is not in a stable operation state is as follows. In order to reduce the influence of the mechanical vibration component, when the internal combustion engine 10 is not in a stable operation state, the standard deviation SGM and the median value Vm
It is generally considered effective to prohibit both updating of the normal distribution, that is, prohibiting the updating of the normal distribution itself. However, in such a configuration, during the period in which the update of the normal distribution is prohibited, the normal distribution and the intensity distribution based on the actual logarithmically converted value lVpk gradually deviate, and the followability when the update is restarted is reduced. Become. For this reason, from the viewpoint of followability, it is desirable to keep updating the normal distribution even when the influence of the mechanical vibration component is large.

On the other hand, the knock signal KCS itself always has a large value by this mechanical vibration component. Therefore, when, for example, only the standard deviation SGM is continuously updated based on the logarithmic conversion value lVpk of the knock signal KCS, the logarithmic conversion value lVpk becomes a value within a range such as “median value Vm <logarithmic conversion value lVpk”. More often.
That is, the standard deviation SGM is frequently updated based on the relational expression (2). As a result, the standard deviation SGM
Suddenly becomes a large value, and accordingly, the knock determination level also rapidly changes. On the other hand, when only the median value Vm is updated based on the logarithmic conversion value lVpk, the median value Vm becomes a large value, but the knock determination level at this time becomes more abrupt as the standard deviation SGM changes. Does not change. In the present embodiment,
For this reason, even when the internal combustion engine 10 is not in a stable operation state, only the updating of the median value Vm is selectively permitted.

Hereinafter, such standard deviation SGM and median value V
The processing for updating m will be specifically described. In this process, first, the engine speed detected through the speed sensor 22 is within a predetermined range. The pressure of the intake air detected through the intake pressure sensor 23 is equal to or lower than a predetermined pressure. The amount of change in the pressure of the intake air per predetermined time is not more than a predetermined amount. It is determined whether or not the internal combustion engine 10 is in a stable operation state based on whether or not all the conditions are satisfied (step S30).

When it is determined that the internal combustion engine 10 is in a stable operation state (step S30; YES),
Thereafter, the standard deviation S is calculated based on the logarithmically converted value lVpk.
The GM and the median value Vm are updated (steps S40 and S50).

On the other hand, when it is determined that the vehicle is not in the stable operation state (step S30; NO), the update of the standard deviation SGM is prohibited (the processing of step S40 is jumped), and
Only the updating of the median value Vm based on the logarithmically converted value lVpk (step S50) is performed.

The updating of the standard deviation SGM is performed through the following processing. As shown in FIG. 3, in this process, first, the logarithmic conversion value lVpk at this time is set to “(median value V
m-standard deviation SGM) <logarithmically converted value lVpk <median V
It is determined whether it is within the range of “m” (step S41). If it is determined that the values are in the same range (step S41; YES), the standard deviation SGM is updated based on the relational expression (1) (step S42).

On the other hand, if it is determined that the value is outside the above range (step S41; NO), the logarithmically converted value l
It is determined whether or not Vpk is in the range of “(median value Vm−standard deviation SGM)> logarithmically converted value 1Vpk” (step S43).

If it is determined that the distance is outside the same range (step S43; NO), the standard deviation SGM is updated based on the relational expression (2) (step S44). Conversely, if it is determined that the value falls within the above range (step S43; YES), the correction coefficient K1
Is calculated (step S45), the standard deviation SGM is updated based on the relational expression (5) such as standard deviation SGM = standard deviation SGM ′ set last time + correction coefficient K1 × α (5) (step S45). S46). Note that the coefficient “α” is
A value calculated based on the deviation between the logarithmic conversion value lVpk and the median value Vm (for example, a value obtained by dividing the difference between the logarithmic conversion value lVpk and the median value Vm by 32) is used. Further, a map (map A) for calculating the correction coefficient K1 based on the detection frequency Cmn is stored in the electronic control device 30 in advance.

Here, in the normal distribution, the median value Vm
, The detection frequency tends to increase. For this reason, when the estimated normal distribution changes to the side where the intensity is small due to the change of the logarithmic conversion value lVpk of the knock signal KCS to a small value, as the degree of change increases, that is, the lower limit value Vmn becomes smaller. The detection frequency Cmn of the lower limit value Vmn increases as the value approaches the median value Vm.

The above map A is based on such a tendency, and FIG.
The correction coefficient K1 is set to “1” based on the map A when the detection frequency Cmn is a small value, and the detection frequency Cm is set based on the map A.
It is set so that the larger the value of n, the larger the value exponentially.

For this reason, in updating the standard deviation SGM based on the relational expression (5), if the logarithmically converted value lVpk has not changed or has not changed so much,
The correction coefficient K1 is set to “1” based on the map A.
That is, at this time, the relational expression (5) becomes equivalent to the relational expression (2), and the standard deviation SGM is updated to a larger value, but is not excessively updated. On the other hand, when the logarithmic conversion value 1Vpk changes relatively largely in the update, the correction coefficient K1 is set to a “large value” based on the map A in accordance with the degree of the change. At this time, the standard deviation S
The GM is also over-updated to a large value. As a result, the abrupt update of the standard deviation SGM to a small value is suppressed in accordance with the degree of change of the logarithmic conversion value lVpk.

After the standard deviation SGM is updated in each of the above-mentioned modes (steps S42, S44, S46) through the judgment based on the logarithmically converted value lVpk, the process is temporarily terminated.

On the other hand, the updating of the median value Vm is performed through the following processing. As shown in FIG. 5, in this process, first, the logarithmic conversion value lVpk at this time is set to “the median value V
It is determined whether or not the range is such that m <logarithmically converted value lVpk ”(step S51). When it is determined that the values are in the same range (step S51; YES), the median value Vm is updated based on the relational expression (3) (step S52).

On the contrary, when it is determined that the logarithmic conversion value lVpk is in the range of “median value Vm ≧ logarithmic conversion value lVpk” (step S51; NO), the correction coefficient K2 is calculated. (Step S53) The median value Vm is updated based on the relational expression (6) such as median value Vm = median value Vm ′ set last time−correction coefficient K2 × β (6) (step S54). Note that, similarly to the coefficient “α”, the coefficient “β” is a value calculated based on the deviation between the logarithmic conversion value lVpk and the median value Vm (for example, the difference between the logarithmic conversion value lVpk and the median value Vm is calculated as follows). 4). Further, a map (map B) for calculating the correction coefficient K2 based on the detection frequency Cmn is stored in the electronic control device 30 in advance.

The map B is also set in the manner illustrated in FIG. 6 based on the tendency of the normal distribution described above. Based on the map B, the correction coefficient K2 is such that the detection frequency Cmn is a small value. Sometimes, it is set to “1”, and is set such that the larger the detection frequency Cmn becomes, the larger the exponential function becomes.

For this reason, in updating the median value Vm based on the above relational expression (6), if the logarithmic conversion value 1Vpk has not changed or has not changed so much, the correction coefficient K2 is set to “ 1 ". That is, at this time, although the median value Vm is updated to a smaller value, it is not excessively updated. On the other hand, if the logarithmic conversion value lVpk changes relatively large in the update, the correction coefficient K2 is set to a “large value” based on the map B in accordance with the degree of the change. At this time, the median value Vm is updated to a smaller value, that is, too small. Accordingly, the updating of the median value Vm to a large value is suppressed in accordance with the degree of change of the logarithmically converted value 1Vpk.

In this way, the median value Vm is equal to the logarithm conversion value l
Through the determination based on Vpk, each of the above aspects (step S
52, S54), the process is temporarily terminated. In the knocking determination processing according to the present embodiment, after updating the standard deviation SGM and the median Vm in such a manner, the updated standard deviation SGM and the median Vm are updated.
The knock determination level Vkd is set based on the normal distribution defined by

That is, first, the u value for the normal distribution defined by the standard deviation SGM and the median value Vm is set (step S60 in FIG. 2). The u value is set in a range of “0 to 3” based on the engine speed detected by the rotation speed sensor 22 and the intake air pressure detected by the intake pressure sensor 23. As the combustion pressure of the air-fuel mixture in the combustion chamber 12 increases, a larger value is set.

Then, the knock determination level Vkd
Is based on the u value, the standard deviation SGM, and the median value Vm. Knock determination level Vkd = median value Vm + u value ×
It is calculated by a relational expression such as standard deviation SGM × k (step S70).
The coefficient “k” is a value calculated in the same manner as the u value, and is a coefficient for finely adjusting the knock determination level Vkd.

Thereafter, whether or not knocking has occurred in the internal combustion engine 10 is determined by comparing the knock determination level Vkd with the logarithmically converted value 1Vpk (step S80). That is, when the logarithmic conversion value lVpk is in the range of “knock determination level Vkd <logarithmic conversion value lVpk”, it is determined that knocking has occurred in internal combustion engine 10. Conversely, the logarithmic transformed value l
Vpk is “knock determination level Vkd ≧ logarithmic conversion value lVp
When it is within the range such as “k”, it is determined that knocking has not occurred in the internal combustion engine 10. By performing necessary engine control such as ignition timing control based on the knocking determination result, an appropriate engine output can be maintained.

Thereafter, in the present embodiment, it is determined that the logarithmic conversion value lVpk deviates from the upper limit value Vmx of the dynamic range of the input circuit 30a to the side where the intensity is large, that is, an abnormal input of the knock signal KCS. When it is determined that the ignition is abnormal, the control of the ignition timing to the advanced side based on the knocking determination described above is prohibited (step S90).

That is, as shown in FIG. 7, in this process, first, it is determined whether or not the detection frequency Cmx is smaller than a predetermined value Lmx (step S91). In addition,
The predetermined value Lmx is set so that the detection frequency Cmx is equal to the predetermined value Lmx.
A value at which knock determination level Vkd may become larger than upper limit value Vmx when mx or more is set is set, and a value obtained in advance by experiment or the like is stored in electronic control device 30. . If it is determined that the value is smaller than the predetermined value Lmx (step S91; Y
ES), after it is determined that the input of knock signal KCS is normal (step S92), the process is temporarily terminated.
At this time, control to the advance side by ignition timing control based on knocking determination is permitted.

On the other hand, the detection frequency Cmx is equal to a predetermined value Lmx
If it is determined that this is the case (step S91; N
O) After it is determined that the input of knock signal KCS is abnormal (step S93), the process is temporarily terminated. At this time, the control of the ignition timing to the advanced side is prohibited.

That is, the knock signal KCS changes, and its logarithmically converted value lVpk becomes equal to the knock determination level Vk.
If it becomes larger than d and it becomes impossible to determine even the occurrence of knocking, the control of the ignition timing to the advanced side in the ignition timing control is prohibited. Therefore, it is possible to erroneously determine that knocking has not occurred even though knocking has occurred, and to suppress occurrence of excessive knocking due to excessive advance of the ignition timing based on the erroneous determination. become.

As described above, according to the present embodiment, the following effects can be obtained. (1) Even when the knocking determination is performed based on the fact that the intensity distribution of the vibration detected through the knock sensor becomes a normal distribution, appropriate control for maintaining the engine output is performed regardless of the change in the signal intensity. Will be able to do it.

(2) The logarithm conversion value lVpk is equal to the lower limit value Vmn.
If the internal combustion engine 10 is in a stable operation state, the standard deviation SGM is over-updated, and the median Vm is under-updated. Knock determination level Vkd
Was fixed. For this reason, the logarithmic conversion value lVpk
Deviates from the normal distribution to the side where the intensity is smaller, and accordingly, the knock determination level Vkd is set to an inappropriate value, and thus, the knock determination accuracy based on the knock determination level Vkd is suppressed from lowering. Will be able to

(3) The excessive update of the standard deviation SGM and the excessive update of the median value Vm are performed according to the detection frequency Cmn of the lower limit value Vmn. Therefore, the abrupt update of the standard deviation SGM to a small value and the update of the median value Vm to a large value can be suppressed in accordance with the degree of change of the logarithmically converted value lVpk. become. Therefore, it is possible to appropriately update the normal distribution estimated in advance, and it is possible to appropriately correct the knock determination level.

(4) When the logarithmically converted value lVpk deviates from the upper limit value Vmx of the dynamic range of the input circuit 30a to the side where the intensity is higher, the ignition timing in the ignition timing control according to the detection frequency Cmx of the upper limit value Vmx Control to the advance side is prohibited. Therefore, it is erroneously determined that knocking does not occur despite knocking, and the occurrence of excessive knocking due to excessive advance of the ignition timing based on the erroneous determination can be suppressed. Become like

The above embodiment may be modified and implemented as follows. In the above embodiment, the knock determination level Vkd is set to only one value, but a plurality of knock determination levels may be set in a stepwise manner. According to such a configuration, the occurrence of knocking can be determined stepwise according to the degree of knocking, and more detailed engine control is possible.

In the above-described embodiment, one normal distribution is estimated in advance for all engine speed ranges, and knocking is determined based on the distribution.
For each of a plurality of rotation speed ranges, a normal distribution may be estimated and knocking may be determined.

In this case, when it is determined that the input of knock signal KCS is abnormal, the control of the ignition timing to the advance side is prohibited, but the setting is made in another rotation speed range. The knocking determination may be performed based on the knock determination level.

In the above embodiment, the standard deviation SGM and the median value Vm are updated to be too large or too small according to the detection frequency Cmn of the lower limit value Vmn. Instead, the u value is corrected. You may do so. Even with such a configuration, knock signal KCS is detected based on detection frequency Cmn.
Can be determined, and the u value is corrected thereby, so that at least the knock determination level can be suitably corrected.

In the above embodiment, knock signal KCS
Deviates from the normal distribution to the side with lower intensity,
When the internal combustion engine 10 is in a stable operation state, the standard deviation SGM and the median value Vm are both updated to be too large or too small according to the detection frequency Cmn of the lower limit value Vmn. It may be updated. According to such a configuration, at least the abrupt update of the standard deviation SGM to a small value can be suppressed in a manner corresponding to the degree of change of the logarithmic conversion value lVpk, and the knock determination level can be appropriately corrected. . Therefore, it is possible to suppress a decrease in the knocking determination accuracy.

In the above embodiment, knock signal KCS
When it is determined that the input is abnormal, the control of the ignition timing to the advanced side is prohibited as the fail-safe process. Instead, the control of the ignition timing to the advanced side is restricted. You may do so. According to such a configuration, it is possible to suppress a decrease in engine torque due to the fail-safe processing.

Further, the abnormality in the input of knock signal KCS may be determined stepwise, and based on the result of the determination, inhibition and restriction of the control of the ignition timing to the advanced side may be appropriately switched and performed. .

Further, instead of prohibiting or restricting the control of the ignition timing to the advanced side, the determination relating to the occurrence of knocking may be prohibited. According to such a configuration, even when knock signal KCS deviates from the dynamic range of input circuit 30a to the side of higher strength and knock determination cannot be determined, it is possible to inhibit the knock determination and prevent erroneous determination. As a result, it is possible to suppress a decrease in the accuracy of the knocking determination.

At this time, prohibition or restriction of the control to the advance side may be performed together. According to such a configuration, even when the knocking determination is prohibited, the control to the advanced angle side where knocking is likely to occur is restricted, but the shape according to the degree of change of the logarithmic conversion value lVpk is controlled. The ignition timing can be controlled at the time.

In the above embodiment, the knocking control device according to the present invention is applied to a device for estimating a normal distribution as a distribution to be estimated in advance. However, the present invention is not limited to this. Even in a device for estimating another distribution in advance, a knock determination level is set based on the distribution, and the presence or absence of knocking is determined based on the knock determination level to perform necessary engine control. If it is a device, the knocking control device according to the present invention can be applied.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a knocking control device for an internal combustion engine according to the present invention.

FIG. 2 is a flowchart illustrating a procedure for determining knocking;

FIG. 3 is a flowchart showing a processing procedure when updating a standard deviation.

FIG. 4 is a schematic diagram showing a map structure of a map A used for calculating a correction coefficient K1.

FIG. 5 is a flowchart showing a processing procedure when updating a median value.

FIG. 6 is a schematic diagram showing a map structure of a map B used for calculating a correction coefficient K2.

FIG. 7 is a flowchart showing a processing procedure when determining an input abnormality.

FIG. 8 is a diagram showing a normal distribution estimated in advance.

FIG. 9 is a diagram showing characteristics of a knock signal.

FIG. 10 is a diagram showing a state in which a logarithmic conversion value of a knock signal deviates from a normal distribution estimated in advance.

FIG. 11 is a diagram showing a state in which a logarithmic conversion value of a knock signal deviates from a normal distribution estimated in advance.

[Explanation of symbols]

10 internal combustion engine, 11 intake passage, 12 combustion chamber, 13
... Crankshaft, 14 ... Surge tank, 15 ... Camshaft, 16 ... Spark plug, 17 ... Ignition coil, 18
.. Igniter, 21 knock sensor, 22 rotational speed sensor, 23 intake pressure sensor, 24 cam angle sensor, 30
... Electronic control device, 30a ... Input circuit.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02P 5/153

Claims (6)

[Claims] A knock sensor detects vibration generated in an internal combustion engine, and sets a knock determination level based on a detected intensity distribution of the vibration. The detected vibration intensity and the set knock determination are determined. A knocking control device for an internal combustion engine that determines whether knocking has occurred based on a comparison with the level and performs the required engine control, wherein the detected vibration intensity is a distribution in which the intensity distribution is estimated in advance. A knocking control device for an internal combustion engine, comprising means for detecting the fact when the vehicle deviates from the condition and performing a fail-safe process. 2. The means for performing the fail-safe processing detects that the intensity of the detected vibration deviates from a distribution estimated in advance with respect to the intensity distribution to a smaller intensity side and corrects the knock determination level. 2. The knocking control device for an internal combustion engine according to claim 1, wherein 3. A method according to claim 1, wherein the estimated distribution of the intensity distribution is a normal distribution, and the modification of the knock determination level is
3. The knocking control device for an internal combustion engine according to claim 2, wherein the logarithmic conversion value of the detected vibration intensity is performed by excessively updating the standard deviation according to the frequency of deviating from the same distribution to the lower intensity side. 4. A method according to claim 1, wherein the estimated distribution of the intensity distribution is a normal distribution, and the modification of the knock determination level includes:
3. The knocking control apparatus for an internal combustion engine according to claim 2, wherein the detected logarithmic converted value of the vibration intensity is performed by an excessive update of the standard deviation and an underupdate of the median according to the frequency of deviating from the distribution to the lower intensity side. 5. A means for performing the fail-safe process detects the magnitude of the detected vibration deviating from a pre-estimated distribution of the intensity distribution to a side having a higher magnitude and starts the knocking. The knocking control device for an internal combustion engine according to claim 1, wherein the determination is prohibited. 6. The ignition system according to claim 1, wherein the estimated distribution of the intensity distribution is a normal distribution, and the logarithmic conversion value of the detected vibration intensity deviates from the distribution to a higher intensity side. 6. The knocking control device for an internal combustion engine according to claim 5, further comprising means for restricting the control of the timing to an advanced side.