JPH0819890B2 - Knocking detection device and ignition timing correction device for internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a knocking detection device and an ignition timing correction device for an internal combustion engine, and more specifically, to a knocking detection device that can accurately detect knocking occurrence from a detection signal of engine vibration. And an ignition timing correction device using the device.

<Prior Art> When knocking at a predetermined level or higher occurs in an internal combustion engine, not only the output is reduced, but also impacts adversely affect intake and exhaust valves and pistons, so knocking is detected and ignition timing is corrected. Therefore, there is a device provided with an ignition timing control device which can avoid knocking promptly (see Japanese Patent Laid-Open No. 58-105036).

Knocking detection for correcting ignition timing due to occurrence of such knocking is performed as follows.

That is, as shown in FIG. 8, the knock sensor 11 that outputs a detection signal corresponding to the vibration level by the piezoelectric element is used in the engine.
This knock sensor 11 is attached to the cylinder block 12 etc.
Is input to the band-pass filter 13 to pass only signals near the center frequency specific to knocking,
After performing half-wave rectification, the integrator 14 integrates for a predetermined integration interval (for example, ATDC 10 ° to 60 °), and the peak value of the integrated value in the integrator 14 (accumulation of specific frequency component strength in the integration interval) is calculated. The A / D converter 15 performs A / D conversion and inputs to the microcomputer 16. In the microcomputer 16, the peak of the integrated value when knocking occurs,
Whether or not knocking has occurred is determined based on the difference between the integrated value and the peak when knocking has not occurred.

<Problems to be Solved by the Invention> By the way, in the configuration in which the occurrence of knocking is determined by the peak level of the integrated value as described above, it is desirable that there is a sufficient difference in the peak level of the integrated value depending on the presence or absence of knocking. Actually, depending on the shape of the engine or the mounting position of the knock sensor, it may not be possible to sufficiently secure the above difference especially in the region where the signal level is small.In this case, it is clear that the peak level of the integrated value depends on the occurrence of knocking. Since there is no significant difference, knocking may be erroneously detected.

Further, conventionally, since the presence / absence of knocking is determined on / off based on the integrated value, the ignition timing is advanced / retarded by a fixed angle regardless of the strength of knocking. Therefore, it is difficult to avoid excessive correction while avoiding knocking with good responsiveness.

The present invention has been made in view of the above problems, even if the signal level from the knocking sensor is small,
It is an object of the present invention to be able to detect knocking with high accuracy, determine the knocking strength, and appropriately perform ignition timing correction.

<Means for Solving the Problems> Therefore, the knocking detection device for an internal combustion engine according to the present invention is configured as shown in FIG.

In FIG. 1, a vibration sensor is attached to the engine body to detect engine vibration. The intensity detecting means detects the intensity of a specific frequency component of the detection signal of the vibration sensor,
The intensity change detection means detects the intensity change pattern of the specific frequency component.

Then, the knocking determination means determines the occurrence of knocking based on the intensity of the specific frequency component of the vibration sensor detected as described above and the intensity change pattern.

Here, the intensity detecting means and the intensity change detecting means may be configured to detect the intensity and the pattern of the intensity change for each of the plurality of types of specific frequency components.

In the ignition timing correction device according to the present invention using the knocking detection device according to the present invention configured as described above, the ignition timing correction means includes the ignition timing of the internal combustion engine based on the determination result of knocking occurrence by the knocking determination means. To advance or retard.

By the way, the knocking determination means may be configured to include each means shown in the first diagram.

Here, the first discriminant value setting means sets the first discriminant value indicating the degree of belonging to knocking occurrence by comparing the intensity detected by the intensity detecting means with a predetermined value, and the second discriminant value setting means. The means sets the second discriminating value indicating the degree of belonging to knocking occurrence by comparing the intensity change pattern detected by the intensity change detection means with a predetermined reference change characteristic.

The final discriminant value setting means sets a final discriminant value indicating the degree of belonging to knocking occurrence based on the first discriminant value and the second discriminant value set by the first discriminant value setting means and the second discriminant value setting means, respectively. Set.

The ignition timing correction amount setting means shown in FIG. 1 is a device for receiving the result of knocking detection in the knocking detection device according to the present invention configured as described above and correcting the ignition timing by the final determination value setting means. The advance / retard correction amount of the ignition timing is variably set according to the set final judgment value,
The ignition timing correction means based on the discriminant value level advances or retards the ignition timing based on the ignition timing advance or retard correction amount set by the ignition timing correction amount setting means.

<Operation> According to this configuration, in addition to the intensity of the specific frequency component of the vibration sensor, the pattern of intensity change of the specific frequency component is used as information for knocking determination, and the pattern of intensity change is the detection signal. Since it does not relate to the absolute level, it is possible to improve the accuracy of knocking detection even when the detection signal level is generally low, compared to the case where knocking detection is performed only based on the intensity, and the ignition timing based on the detection result is used. The advance / retard correction will be appropriately performed.

Further, if the first discriminant value and the second discriminant value indicating the degree of occurrence of knocking are calculated from the intensity and intensity change patterns of the specific frequency component, respectively, and the final discriminant value is set using these. The ignition timing can be corrected by increasing or decreasing the ignition timing correction amount according to the degree of occurrence of knocking, and the responsiveness and accuracy of knocking avoidance control by ignition timing correction are further improved.

<Examples> Examples of the present invention will be described below.

In FIG. 2 showing one embodiment, a knock sensor (vibration sensor) 1 attached to a cylinder block of an internal combustion engine (not shown) has a built-in piezoelectric element and outputs a detection (voltage) signal having a waveform corresponding to engine vibration. To do.

The detection signal (analog signal) of the knock sensor 1 is
It is A / D converted by the A / D converter 2 and input to the comb filter 3.

The comb filter 3 includes a delay circuit 4 including a plurality of stages of unit delay elements, and an adder 5 that subtracts output data of the delay circuit 4 from data bypassing the delay circuit 4. To the filter 3, a circuit in which a number of resonators 6a to 6e corresponding to the number of frequencies to be extracted from the detection signal of the knock sensor 1 are connected in parallel is vertically connected.

The resonators 6a to 6e are arranged to resonate with mutually different frequency components, and in this embodiment, the resonance frequency is 7kHz, 8kHz according to the frequency range 7kHz to 9kHz in which knocking vibration is said to appear remarkably. , 9kHz, 10kHz, 11kHz.

In the comb filter 3, by subtracting the data delayed by the delay circuit 4 from the data bypassed by the delay circuit 4, the detection signal level is totally attenuated, and in particular, the frequency corresponding to the delay time is added. Bowl 5
, So that the frequency characteristics have a so-called comb shape.

As a result, the resonators 6a to 6e can be prevented from continuing to resonate based on the signals canceled by the adder 5, and the intensities of the respective frequency components can be sequentially obtained.

In this embodiment, the specific frequency component is extracted from the signal from the knock sensor 1 by the configuration of the comb filter 3 and the resonators 6a to 6e as described above, but an analog bandpass filter is required. The number of frequencies may be set so that the output of each band pass filter is A / D converted and read by the microcomputer 7.

The output of each of the resonators 6a to 6e, that is, the intensity signal of each frequency component is input to the microcomputer 7, and the microcomputer 7 is based on the detection signal from the crank angle sensor 8. On the basis of a specific frequency component of the knock sensor 1 input via the resonators 6a to 6e in a predetermined frequency analysis section to be detected, occurrence of knocking in an internal combustion engine (not shown) is detected, and based on the detection result. The ignition timing in the ignition device 9 is corrected and controlled.

The content of the knocking occurrence detection and the ignition timing correction control associated therewith will be described below with reference to the flowchart of FIG. In the present embodiment, the intensity detecting means, the intensity change detecting means, the knocking determining means, the first determining value setting means, the second determining value setting means, the final determining value setting means, the ignition timing correcting means, the ignition timing correction amount setting. The means and the function as the ignition timing correction means based on the discriminant value level are as shown in the flow chart of FIG.
Is equipped with software.

The knocking occurrence detection shown in the flowchart of FIG. 3 is performed in a predetermined frequency analysis section, and the predetermined frequency analysis section is a section in which combustion vibration of each cylinder can be sampled while avoiding ignition noise, for example. For example, in a 6-cylinder engine, ATDC is 10 ° to ATDC 60 °, and the predetermined frequency analysis section is detected based on the detection signal from the crank angle sensor 8.

First, when it is detected that the frequency analysis section is entered,
The intensity dB (amplitude) of each frequency component as shown in FIG. 5 input via each resonator 6a to 6e is stored as an initial value (S1).

Then, it is assumed that the initial values stored for each frequency component do not change, respectively, and that the intensity of a constant level continues in the frequency analysis section, and the time-axis change of the integrated value of the intensity at this time, the resonator 6a ~ Output interval from 6e (sampling period)
And the initial value, and this is used as the reference change characteristic when knocking does not occur (S2).

Next, the intensity of each frequency component that is to be input at each predetermined time in the frequency analysis section is stored, and the intensity temporal change (pattern of intensity change) for each frequency component.
Is detected (see FIG. 6). Then, based on such detection, the intensities are integrated for each sampling period on the time axis,
The intensity change pattern in the frequency analysis section is observed as the slope of the integrated value (S3).

Then, as described above, the reference change characteristic for each frequency component obtained assuming that the intensity is unchanged, and the characteristic of the change of the intensity integral value for each frequency component actually detected are compared,
The deviation amount of both is increased on the increasing side with respect to the normative change characteristic,
On the decreasing side, as a minus value, it is obtained at every intensity sampling interval and accumulated, and the accumulated value E represents the amount of deviation of the actual change from the reference change characteristic (S4).

Here, the reference change characteristic is linearly increased because it is premised that there is no change in intensity. On the other hand, when the change pattern of the intensity integrated value obtained based on the actual detection signal does not match. , It is estimated that the frequency component is not stable because the frequency component contains knocking vibration. However, the intensity integral value based on the actual detection signal is substantially the same as the reference change characteristic. In the case of linearly increasing change, it can be estimated that the frequency component is only mechanical vibration (see FIG. 4).

That is, as shown in FIG. 4, when knocking vibrations are included in the same frequency component, the knocking vibrations due to abnormal combustion are gradually attenuated. Therefore, the strength of the frequency component is also gradually gradually attenuated and the mechanical vibrations are gradually attenuated. When the knocking vibration is not included, the strength changes at a substantially constant mechanical vibration level. Therefore, when knocking vibration is not included, the initial strength of the analysis section is substantially maintained, and the integrated value of the strength rises substantially linearly.

Therefore, as described above, assuming that the initial intensity of the analysis section does not change thereafter, if the change over time of the integrated value of the intensity is estimated, this change characteristic (predetermined normative change characteristic) becomes
When the knocking is not occurring, the actual intensity is integrated on the time axis when the knocking is occurring, and as shown in FIG. 4, it is estimated to correspond to the time when the knocking is not occurring. The change pattern does not match the change characteristic, and the greater the knocking strength, the greater the difference in change characteristic. Therefore, the knocking strength can be detected by obtaining the integral value of the actual strength on the time axis, comparing it with that when the knocking is not occurring, and accumulating the difference.

In this way, since knocking can be detected based on the intensity change pattern of the specific frequency component, it is possible to identify even when the signal level is low, and even in the high rotation range where mechanical vibration becomes strong, It is possible to easily detect knocking by distinguishing between knocking vibration and mechanical vibration.

Depending on the frequency, there is a frequency range in which the strength becomes weaker than the engine vibration level due to occurrence of knocking, and returns to the engine vibration level as the knocking vibration attenuates. Knocking can be detected because it does not exhibit a linear change that is a change characteristic when it does not occur. In addition, the change characteristic when knocking is not generated is set by setting the strength in the initial stage of the frequency analysis section to be constant, but the strength change (decreasing change or increasing change) when knocking vibration is included for each frequency component in advance. In order to show the degree of non-knocking by comparing the intensity change characteristics expected to appear when knocking occurs with the intensity change pattern for each frequency component obtained from the actual detection signal. You may make it calculate | require the accumulation of the deviation amount of both.

For each frequency component corresponding to each of the resonators 6a to 6e, the cumulative value E of the deviation amount with respect to the reference change characteristic corresponding to the non-knock of the actual intensity change in the frequency analysis section is obtained as described above. The sum of absolute values of the cumulative value E obtained in step 1, or the average value, and further, the maximum value, etc., are calculated, and the finally set deviation amount cumulative value E is calculated from the deviation amount cumulative value E for each frequency. Based on the absolute value, the first determination value f ₁ indicating the degree of knocking occurrence is set (S5).

Since the cumulative value E of the deviation amount indicates the amount of deviation with respect to the characteristic when not knocking, it is generally estimated that the larger the cumulative value E, the higher the knocking strength, and conversely when the cumulative value E is small. That is, it is estimated that the frequency component shows a change characteristic close to that at the time of non-knock because it is close to the state where knocking does not occur.

Therefore, the smaller the cumulative value E is, the smaller the first determination value f ₁ is set, and conversely, the larger the cumulative value E is, the larger the first determination value f ₁ is set.
The strength of knocking that occurs is determined based on the level of the first determination value f ₁ .

The cumulative value E when converting the first determination value f ₁ may simply be that the first determination value f ₁ in proportion to the cumulative value E increases, but in fact the cumulative value E and knock Since it is not proportional to the strength, the actual knocking strength with respect to the cumulative value E is experimentally and empirically obtained in advance, and a membership function for converting the cumulative value E into the human subjective subjective accuracy is set. It is preferable that the first discriminant value f ₁ (membership value) representing the knocking strength is set by a so-called fuzzy set.

When the first determination value f ₁ indicating the knocking intensity is set on the basis of the intensity change of the specific frequency component in the predetermined frequency analysis section as described above, knocking vibration is expected to appear particularly remarkably. It is also possible to extract only the frequency component from the detection signal and set the first discriminant value f ₁ only from the change in the intensity of the frequency component.

The first discriminant value f ₁ indicating the knocking intensity is set based on the intensity change pattern of each frequency component in the frequency analysis section, and the second discriminant value f ₂ indicating the knocking intensity is set in the same manner. The process of setting based on the intensity level of the frequency component is performed in parallel.

Since the resonators 6a to 6e output the frequency spectrum as shown in FIG.
The frequency spectra obtained in the frequency analysis section are sequentially stored (S6).

Then, the integral value of each frequency component of the intensity obtained in the frequency analysis section is obtained as shown in FIG. 7 (S7), and the intensity integral value of each frequency component is calculated and calculated for each frequency component. The background level BGL
8).

The background level BGL is a weighted average value of the intensity integral value of each frequency component obtained for each frequency analysis section, and weighted past data is weighted so as to be weighted averaged, and knocking is determined. Intensity integrals are not weighted averaged. Therefore, the background level BGL can be regarded as a level of the intensity integrated value indicating only the mechanical vibration in the non-knocking state, and the background level BGL is the intensity obtained in the frequency analysis section of this time. If the integrated value exceeds, it is estimated that knocking occurs.

Therefore, for each frequency component, the intensity integration value found in the frequency analysis section this time is the background level BGL
Is calculated, and the degree of belonging to knocking occurrence, in other words, based on the total sum, average value, or maximum value, in other words,
Setting a second determination value f ₂ showing the knock intensity (S9).

When a large knock occurs, the intensity of the frequency component in which knocking vibration appears correspondingly becomes higher than when no knock occurs, and it greatly exceeds the background level BGL, so the detected intensity integral value
The larger the BGL is greatly exceeded, the larger the second discriminant value f _{2 is.}
Is set, and this second discriminant value f ₂ is also the first
Similar to the discriminant value f _1, it is a value indicating knocking strength that can be compared to a level.

Also here, only the intensity integrated value of one frequency component is obtained, and this intensity integrated value is compared with the background level BGL obtained by weighted averaging of the intensity integrated value to determine the second discriminant value f. You can also set ₂ . Further, when the first discriminant value f ₁ is set using the fuzzy set as described above, the second discriminant value f ₂ is also set using the fuzzy set.

Whether or not knocking has occurred based on the respective discriminant values f ₁ and f ₂ set in this way, and more specifically, it is possible to detect the knocking intensity,
In particular, the second set based on the knocking strength level
The determination value f ₂ cannot accurately indicate the knocking intensity when the distance from the knocking occurrence cylinder to the knock sensor 1 is long and the signal level is low.
By estimating the final knocking intensity using both f ₁ and f ₂ , the detection accuracy is improved as compared with the case where the knocking determination is made based on only one detection result.

The estimation of the final knocking intensity (setting of the final discriminant value f) based on the discriminant values f ₁ and f ₂ is performed by
The discriminant value finally derived from the respective discriminant values f ₁ and f ₂ in this manner may be obtained by obtaining the added value of f ₁ and f ₂ , obtaining the average value, or selecting one by comparing the magnitudes. Based on f, it is possible to determine not only whether knocking has occurred but also the knocking strength with high accuracy.

When the discriminant values f ₁ and f ₂ that are the membership values are set by using the fuzzy set, the discriminant value indicating the degree finally belonging to knocking occurrence is determined from the respective discriminant values f ₁ and f _2. A fuzzy set may be used again when setting.

If the discriminant value f indicating the knocking strength is finally obtained as described above, the ignition timing can be corrected according to the knocking strength at that time. Therefore, for example, the flowchart shown in FIG. 3 is used. As described above, when the discriminant value f is equal to or more than the predetermined value, it is discriminated that knocking has occurred, the ignition timing retard correction amount is increased in accordance with the increase in the discriminant value, and the discriminant value f does not show a clear knocking occurrence. Is a level that cannot be said to be non-knocking, the correction amount of the ignition timing is set to zero so that the ignition timing is not corrected, and the level of the discriminant value f is sufficiently small that it is recognized as non-knocking. At this time, a larger advance correction amount is set as the discriminant value f becomes smaller in order to obtain the engine output (S10).

Here, based on the discriminant value f, for example, it is divided into three states of "knocking occurrence", "possibility of knocking occurrence", and "non-knocking occurrence", and the ignition timing is advanced or delayed according to the respective states. The correction amount may be selected.

When the discriminant values f ₁ and f ₂ are set using a fuzzy set, the discriminant values f ₁ and f ₂ are defuzzified to be converted into the ignition timing correction amount, and the discriminant values are changed.
The center of gravity of the ignition timing correction amount obtained from f ₁ and f ₂ can be set as the final ignition timing correction amount.

When the correction amount of the ignition timing is set based on the knocking strength level as described above, the microcomputer 7 advances the basic ignition timing stored in advance corresponding to the operating condition based on the correction amount. Retard correction, and output an ignition signal to the ignition device 9 based on the corrected ignition timing,
Ignition processing based on the corrected ignition timing is executed. Here, the knocking intensity is accurately detected from the intensity level and the intensity change pattern of the specific frequency component of the detection signal of the knock sensor 1, and the ignition timing correction amount is set according to the knocking intensity. Knocking control is possible, quick knocking avoidance and MBT (Min
Ignition in the vicinity of imum Spark Advance for Best Torque) can be secured.

In the present embodiment, 7k from the detection signal of the knock sensor 1
Although five kinds of frequency components of Hz, 8kHz, 9kHz, 10kHz, and 11kHz are extracted, the frequencies to be extracted are not limited, and the number of frequencies is not limited.

<Effects of the Invention> As described above, according to the present invention, the accuracy of knocking detection is improved by determining the occurrence of knocking based on the intensity of a specific frequency component of the detection signal from the vibration sensor and the intensity change pattern. Therefore, by performing the ignition timing correction control for avoiding knocking based on the detection result, knocking can be favorably avoided, and in particular, if the determination value indicating the degree of knocking occurrence is set, The correction amount of the ignition timing can be set according to the knocking strength at that time, and there is an effect that the knocking control can be performed more accurately.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a system block diagram showing an embodiment of the present invention, and FIG. 3 is a flowchart showing the control contents of knocking detection and ignition timing correction in the same embodiment. FIG. 4 is a time chart for explaining knocking discrimination based on the intensity change pattern of a specific frequency, and FIGS. 5 to 7 are line diagrams showing the state of data for each specific frequency in the above-mentioned embodiment, respectively.
FIG. 1 is a block diagram showing an example of a conventional knocking detection device. 1 ... Knock sensor (vibration sensor), 2 ... A / D converter, 3
... comb filter, 4 delay circuit, 5 adder, 6a to 6e
... Resonator, 7 ... Microcomputer, 8 ... Crank angle sensor, 9 ... Ignition device

Claims (5)

[Claims] 1. A vibration sensor attached to an engine body for detecting engine vibration, intensity detection means for detecting the intensity of a specific frequency component of a detection signal of the vibration sensor, and a specific frequency component of the detection signal of the vibration sensor. Of the internal combustion engine configured to include an intensity change detection unit that detects a pattern of intensity change of, and a knocking determination unit that determines the occurrence of knocking based on the intensity of the detected specific frequency component and the pattern of intensity change. Knocking detection device. 2. The internal combustion engine according to claim 1, wherein the intensity detecting means and the intensity change detecting means are configured to detect an intensity and an intensity change pattern for each of a plurality of types of specific frequency components. Knocking detection device. 3. A first discriminant value setting means for setting the first discriminant value indicating the degree of belonging to knocking by comparing the intensity detected by the intensity detector with a predetermined value. A second discriminant value indicating a degree of belonging to knocking occurrence is set by comparing the intensity change pattern detected by the intensity change detection means with a predetermined reference change characteristic;
The discriminant value setting means, and the final discriminant value indicating the degree of belonging to knocking occurrence are set based on the first discriminant value and the second discriminant set by the first discriminant value setting means and the second discriminant value setting means, respectively. The knocking detection device for an internal combustion engine according to claim 1 or 2, further comprising: final discriminant value setting means. 4. An ignition timing correction for advancing / retarding the ignition timing of the internal combustion engine based on the determination result of knocking occurrence by the knocking determination means in the knocking detection device for an internal combustion engine according to claim 1. An ignition timing correction device for an internal combustion engine, characterized in that it comprises means. 5. An ignition timing correction amount setting for variably setting an ignition timing advance / retard correction amount according to the final determination value set by the final determination value setting means in the internal combustion engine knocking detection device according to claim 3. Means for advancing the ignition timing set by the ignition timing correction amount setting means.
An ignition timing correction device for an internal combustion engine, comprising: an ignition timing correction means based on a discriminant value level for advancing / retarding the ignition timing of the internal combustion engine based on a retard correction amount.