JP4123987B2 - Internal combustion engine knock determination device and knock control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique for determining knocking of an internal combustion engine, and more particularly, to a technique for improving determination accuracy by preventing erroneous determination of knocking due to combustion noise.
[0002]
[Prior art]
In general, knocking determination in an internal combustion engine is performed based on the intensity of these frequency bands by extracting a plurality of characteristic frequency bands of knocking from a vibration signal detected by a knock sensor using a filter.
[0003]
In the above general knocking determination method, erroneous determination of knocking due to noise generated during combustion (referred to as combustion noise) has been a problem. As a technique for preventing such erroneous determination, whether or not combustion noise has occurred A technique has been proposed in which a determination is made based on the difference in the knocking detection frequency for each and the filter is switched according to the determination result (see Patent Document 1).
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 2001-173508
[Problems to be solved by the invention]
However, the method for determining combustion noise based on the occurrence frequency of knocking as described above has the following problems.
[0006]
Since the engine does not always perform steady operation in the vehicle mounted state, it is not practical to perform statistical processing in real time. In other words, in order to reduce the dispersion of statistical results, it is sufficient to narrow the sampling condition and take a large number of parameters, but the determination frequency is extremely lowered and the determination of combustion noise is delayed, and the sampling data is saved. Requires a large memory capacity and computational load. On the contrary, if the determination frequency is increased, the dispersion of statistical results increases, and the determination accuracy of combustion noise deteriorates.
[0007]
The present invention has been made paying attention to such a conventional problem, and it is possible to determine the combustion noise with a relatively simple determination method with high accuracy and to prevent the knocking erroneous determination well. An object of the present invention is to provide a device and a knocking control device using the determination device.
[0008]
[Means for Solving the Problems]
For this reason, the present invention determines the presence or absence of combustion noise occurring at the time of combustion for at least one of a plurality of frequency bands indicating the characteristics of knocking extracted from the engine vibration detection signal, and the vibration intensity at the time of fuel supply and at the time of fuel cut. It is determined that there is combustion noise when there is a difference greater than or equal to a predetermined value . Alternatively, it is determined that there is combustion noise when there is a difference greater than or equal to a predetermined level by comparing the vibration intensities of the engine rotation speed region where the combustion noise generation tendency is large and the engine rotation speed region where the combustion noise generation tendency is small. When it is determined that there is combustion noise, the vibration intensity in this frequency band is excluded from the knocking determination.
[0009]
In this way, the combustion noise can be determined with high accuracy by comparing the vibration intensities in the operation region in which the tendency of occurrence of the combustion noise is known in advance, and the vibration intensity in this frequency band is excluded from the knock determination. By doing so, the erroneous determination of knocking due to combustion noise can be prevented well.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a system configuration of an embodiment of the present invention.
[0011]
The engine (internal combustion engine) 1 includes an electronically controlled throttle valve 2 that controls the amount of intake air, a fuel injection valve 3 that injects and supplies fuel, and an ignition plug 4 that performs ignition.
[0012]
As various sensors, an air flow meter 5 for detecting the intake air amount, a crank angle sensor 6 for outputting a pulse signal for each unit crank angle, a water temperature sensor 7 for detecting the engine coolant temperature, and for determining knocking. A knock sensor 8 for detecting engine vibration is provided. A sensor that detects the in-cylinder pressure may be used instead of the knock sensor.
[0013]
Detection signals from the various sensors are input to a control unit 9 including a microcomputer, and the control unit 9 drives the throttle valve 2, the fuel injection valve 3, and the spark plug 4 based on the signals from the sensors. Thus, the intake air amount, the fuel injection amount, and the ignition timing are controlled. In particular, the knocking control (ignition timing control) is performed while processing the signal from the knock sensor 8 and performing the knocking determination according to the present invention.
[0014]
FIG. 2 is a control block diagram of the knocking control. The signal from the knock sensor 8 is adjusted in gain by the gain adjusting circuit 12 via the input circuit 11 and then A / D converted by the A / D converter 13. Then, the microcomputer of the control unit 9 performs the following process.
[0015]
First, the frequency analysis unit 14 calculates vibration intensities in a plurality of frequency bands indicating knock characteristics from the A / D converted digital value.
The knocking determination unit 15 determines the presence or absence of knocking based on the vibration intensity of the plurality of frequency bands. Here, the combustion noise is determined based on vibration intensity for a specific frequency band, and when it is determined that there is combustion noise, knocking determination is performed by excluding the vibration intensity of the specific frequency band.
[0016]
The knocking control unit 16 performs control to suppress knocking according to the knocking determination result.
Hereinafter, the details of the processing of each unit will be described with reference to the flowchart of FIG.
[0017]
FIG. 3 shows processing in the frequency analysis unit 14. As shown in FIG. 4, the processing of FIG. 3 is started by interrupting at a predetermined crank angle position which is the start timing of the knocking determination section for each cylinder by the pulse signal from the crank angle sensor 6.
[0018]
In step (denoted as S in the figure, the same applies hereinafter) 1, initialization processing is performed, and in step 2, the A / D converter 13 is driven to start A / D conversion.
In step 3, the A / D conversion value of the vibration intensity is sampled at regular intervals, and is sampled until the sampling number reaches a predetermined value (for example, 64) in the determination in step 4.
[0019]
When the number of samplings reaches a predetermined value, FFT processing is started in step 5 and the vibration is classified into frequency bands [i: i = 1 to 5] for different vibration strengths (hereinafter referred to as frequency-specific strengths). The intensity is integrated, and the process returns to step 3 and repeats this process until the number of FFTs reaches the upper limit in the determination of step 7. Note that other frequency analysis processing such as wavelet transform may be performed instead of the FFT processing.
[0020]
Here, a plurality of frequency bands [i: 1 to 5] indicating the characteristics of knocking separated by the FFT processing are a plurality (five) of vibration mode coefficients ρ _mn (ρ ₁₀ , ρ ₂₀ , ρ ₀₁ , ρ ₃₀ , ρ ₁₁ , the subscript m is the order of radial vibration, and n is the order of circumferential vibration). 5).
[0021]
f = C · ρ _mn / (π × B)
f: resonance frequency, C: speed of sound in the combustion atmosphere, B: cylinder bore diameter, ρ _mn : mode coefficient As shown in FIG. 4, the end of the knocking determination section for each cylinder by the pulse signal from the crank angle sensor 6 The process shown in the flowchart of FIG. 6 is performed by interrupting at a predetermined crank angle position that is a time.
[0022]
That is, in step 11, the driving of the A / D converter 13 is stopped and the A / D conversion is terminated.
In step 12, the frequency-based intensity integrated value [i] calculated in FIG. 4 is normalized and corrected by the following equation.
[0023]
Intensity integrated value correction value by frequency [i] = Intensity integrated value by frequency [i] x detection interval time / (total sampling number x sampling cycle)
In step 13, a knocking determination process is performed based on the frequency-based intensity integrated value correction value [i] (described in detail later), and an end process is performed in step 14 and the process ends.
[0024]
FIG. 7 shows knocking determination processing for each cylinder [j: for example, 4 = 1 for a 4-cylinder engine].
In step 21, the previous knocking determination result of the cylinder j currently in the knocking determination end timing is cleared.
[0025]
In step 22, an average intensity value for each frequency is calculated. Specifically, it is processed by a subroutine shown in FIG.
That is, in step 101, the frequency-specific intensity KDL [i] obtained by dividing the frequency-specific intensity integrated value correction value [i] calculated in step 12 by the engine speed as shown in the following equation is calculated.
[0026]
KDL [i] = Intensity integrated value correction value by frequency [i] / Engine rotation speed This is because the integrated value increases as the engine rotation speed increases as the intensity integration is executed in a time period. This is done to eliminate the effect of knocking on the knocking judgment accuracy.
[0027]
In step 102, in order to obtain a threshold value for knocking determination, the frequency-specific intensity integrated value correction value [i] is weighted and averaged according to the following equation to calculate the frequency-specific intensity average value KDLave.
[0028]
KDLave [i] [j] = (KDL [i] + 15 × KDLave ₋₁ [i] [j]) / 16
KDLave [i] [j]: Weighted average value KDL [i] of j cylinder frequency by frequency KDLave _-1 [i] [j]: Previous value of weighted average value KDLave [i] [j] Returning to FIG. In step 23, the combustion noise determination process according to the present invention is performed.
[0029]
Specifically, the two processes of FIGS. 9 and 11 are performed, and this determination is confirmed when it is determined that combustion noise is present in at least one of the processes.
By the way, it has been found that combustion noise is notably generated in the vibration mode ρ ₁₀ (the primary vibration mode in the radial direction) because the vibration level is not as great as knocking. Therefore, in this embodiment, the frequency band determined by the vibration mode [rho ₁₀ for [i = 1] only, and determining the presence or absence of combustion noise, when the combustion noise is present at this frequency band [1] as described later The vibration intensity in the frequency band [1] is excluded from the knocking determination. Although it may be configured to perform combustion noise determination for other frequency bands, control is simplified by configuring the combustion noise determination for only frequency band [1], and combustion noise compared to other frequency bands. Can be determined with high accuracy, and the influence on knocking determination accuracy due to erroneous determination can be sufficiently avoided.
[0030]
FIG. 9 shows a process for determining the presence or absence of combustion noise by comparing the vibration intensity of the vibration mode ρ ₁₀ at the time of fuel supply and at the time of fuel cut.
In step 41, it is determined whether the engine rotational speed NE is less than the lower limit rotational speed NESL where combustion noise determination is difficult. If it is less than NESL, the process proceeds to step 51 to prohibit new combustion noise determination. This is because if the rotational speed is too low, the signal from the knock sensor may fluctuate and combustion noise may be erroneously determined. Good determination accuracy can be ensured by prohibiting determination in the low-speed region. In addition, since combustion noise may be different from that after warm-up when the water temperature is low before warm-up, combustion noise determination may be prohibited. Also, when the intake / exhaust valve is seated on the valve, the average intensity value becomes large and it becomes difficult to judge combustion noise. When the valve seating timing overlaps with the noise determination section, the combustion noise determination may be prohibited.
[0031]
If it is determined in step 41 that the engine speed NE is equal to or higher than the lower limit speed NESL, it is determined in step 42 whether or not the cylinder j is fuel cut.
If it is determined that the fuel has been cut, the non-fuel cut continuation counter NFCcount [j] is cleared to 0 in step 43, and then the fuel cut continuation counter FCcount [j] is incremented in step 44.
[0032]
Then, in step 45, it is determined whether or not the value of FCcount [j] has reached a predetermined value (for example, 8 times). Before reaching the value, the process proceeds to step 51, and when it reaches, the latest KDLave [1] is determined in step 46. Is updated and set as FCLave [j] (KDLave during fuel cut).
[0033]
If it is determined in step 42 that the cylinder j is not under fuel cut, that is, fuel is being supplied, the fuel cut continuation counter FCcount [j] is cleared to 0 in step 47, and then non-fuel cut is continued in step 48. The number counter NFCcount [j] is incremented.
[0034]
In step 49, it is determined whether the value of the NFCcount [j] has reached a predetermined value (for example, 8 times). The process proceeds to step 51 as it is before reaching the value. If it has reached, the latest KDLave [1] is determined in step 40. Is updated and set as NFCLave [j] (KDLave at non-fuel cut).
[0035]
In this way, after switching to fuel cut or fuel supply, the intensity average value KDLave after the elapse of a predetermined period is updated as a value for determining combustion noise. In this way, by using the value after the lapse of a predetermined period after switching, a value that sufficiently reflects the state after switching can be used for the combustion noise determination excluding the influence of the state before switching in the weighted average calculation. , The determination accuracy is improved.
[0036]
In step 51, the presence or absence of combustion noise is determined using each of the above values. Specifically, it is determined whether the following equation holds.
FCLave [j] x SLnoize [j] [NE] <NFCLave [j]
Here, SLnoize [j] [NE] is a threshold coefficient set in a table for each cylinder and engine speed, and is set to a value of about 2 to 3, for example.
[0037]
If the above equation is satisfied, it is determined in step 52 that no combustion noise is generated in the cylinder j. If not, a determination result is determined in step 53 that combustion noise is generated in the cylinder j.
[0038]
In other words, combustion is not performed when fuel is cut, so no combustion noise is generated, and combustion is performed when no fuel is cut (when fuel is supplied), so the vibration intensity is greater than when fuel is cut even when there is no combustion noise. However, when combustion noise is generated, it becomes larger than that. Therefore, it is determined that the combustion noise is generated when the intensity average value NFCLave at the time of combustion is larger than the intensity average value FCLave at the time of fuel cut by a predetermined value or more. . In such a determination method, since a fuel cut time during which combustion noise is not generated is used as one comparison value, high determination accuracy can be ensured (see FIG. 10).
[0039]
Thus, the frequency band determined to have combustion noise is excluded from the knocking determination, thereby preventing erroneous determination of knocking due to combustion noise. Although combustion noise and knocking may occur simultaneously, it can be determined that knocking is present based on at least one of other frequency bands.
[0040]
However, if only combustion noise is generated and knocking is not detected, it is excluded from knocking determination only in this case, and if knocking is occurring at the same time, if this frequency band is used for knocking determination, It is possible to more accurately determine the occurrence of knocking while preventing erroneous determination that there is knocking due to combustion noise. To do this, for example, the combustion noise intensity level is higher than the knocking intensity level under low load conditions, and therefore the determination threshold (coefficient) is set lower than the combustion noise intensity level. What is necessary is just to comprise.
[0041]
In addition, in order to more accurately determine the occurrence of combustion noise, after the fuel cut is switched, the threshold coefficient SLnoize is increased after it has sufficiently converged, and the average intensity value is updated after switching. What is necessary is just to set the continuation number of times until it is large. If it is desired to obtain a determination result relatively quickly after switching, the number of continuations until the intensity average value is updated may be set to a small value while the threshold coefficient SLnoize is relatively small. Immediately after NFCLave and FCLave are calculated and updated, they are stored in the backup memory, and the combustion noise determination at step 51 is performed using the latest values up to that time other than at the time of updating. It is possible to prevent erroneous knocking determination due to combustion noise. Furthermore, by setting the threshold coefficient SLnoize [j] [NE] for each cylinder and for each engine rotation speed, it is possible to further improve the accuracy of determining combustion noise. The same applies to the following second combustion noise determination process.
[0042]
FIG. 11 shows a second determination process for determining the presence or absence of combustion noise by comparing the vibration intensity of the vibration mode ρ ₁₀ for each engine speed region. As described above, the determination method according to the presence / absence of fuel cut (non-combustion and combustion) has high accuracy, and this is sufficient. However, by performing the second combustion noise determination process in an auxiliary manner as in the present embodiment, it is possible to increase the determination frequency and prevent knocking misjudgment due to combustion noise earlier and improve knocking controllability. .
[0043]
In step 61, as in step 31 of FIG. 9, it is determined whether the engine rotational speed NE is less than the lower limit rotational speed NESL where combustion noise determination is difficult. If it is less than NESL, the process proceeds to step 71 and new combustion noise is determined. Cancel the judgment.
[0044]
When it is determined in step 61 that the engine rotational speed NE is equal to or higher than the lower limit rotational speed NESL, it is determined in step 62 whether or not the engine rotational speed region (hereinafter referred to as a noise region) in which combustion noise tends to be generated is high. Specifically, it is determined whether the engine rotational speed NE is higher than the lower limit rotational speed NEL in the region and lower than the upper limit rotational speed NEH.
[0045]
If it is determined that the area is outside the noise area, the noise area counter NAcount [j] is cleared to 0 in step 63, and then the non-noise area counter NNAcount [j] is incremented in step 64.
[0046]
In step 65, it is determined whether or not the value of the counter NNAcount [j] has reached a predetermined value (for example, 8 times), and the process proceeds directly to step 71 before reaching the value. ] Is updated and set as NNAave [j] (non-noise area KDLave).
[0047]
If it is determined in step 62 that the cylinder j is in the noise region, the non-noise region continuation counter NNAcount [j] is cleared to 0 in step 67 and then the noise region continuation counter NAcount [j in step 68. ] Is incremented.
[0048]
Then, in step 69, it is determined whether or not the value of NAcount [j] has reached a predetermined value (for example, 8 times). The process proceeds to step 71 as it is before reaching the value, and when it reaches, the latest KDLave [1] is reached in step 70. Is updated and set as NAave [j] (noise region KDLave).
[0049]
Thus, after switching to the non-noise region or the noise region, the determination accuracy is improved by updating the intensity average value KDLave after the lapse of a predetermined period as a value for determining combustion noise. It is the same as the processing.
[0050]
In step 71, the presence or absence of combustion noise is determined using each of the above values. Specifically, it is determined whether the following equation holds.
NNAave [j] × SLnoize2 [j] [NE] <NAave [j]
Here, SLnoize2 [j] [NE] is a threshold coefficient set in a table for each cylinder and engine speed in this determination processing method.
[0051]
If the above equation is established, it is determined in step 72 that no combustion noise is generated in the cylinder j. If not, a determination result is determined in step 73 that combustion noise is generated in the cylinder j.
[0052]
As described above, this determination is confirmed when it is determined that there is combustion noise in at least one of the two combustion noise determination processes shown in FIGS. Returning to FIG. 7, in step 24, the combustion noise determination result of the cylinder j is determined, and when it is determined that there is no combustion noise, the process proceeds to step 25 and corresponds to the vibration mode ρ ₁₀ used for the combustion noise determination. I = 1 is set so that knocking determination is performed including the frequency band [1] to be performed.
[0053]
On the other hand, when it is determined that the combustion noise exists in the cylinder j, the routine proceeds to step 26 so as to perform knocking determination except for the frequency band [1] used for the combustion noise determination, and i = 2 is set.
[0054]
In step 27, the presence or absence of knocking is determined. Specifically, it is determined whether the following equation holds.
KDL [i] ≦ SL [i] [j] [NE] + KDLave [i]
Here, SL [i] [j] [NE] is a threshold value set in a table for each cylinder and each engine speed.
[0055]
When the above formula is established, it is temporarily determined in step 28 that knocking has not occurred in the cylinder j. Then, i is incremented in step 29, and the process proceeds to step 27 until i> 5 is determined in step 30. Returning to the incremented frequency band [i], the above determination is repeated. When i> 5 is determined in step 30, the knocking determination for cylinder j is terminated. When i> 5, since it is determined that knocking has not occurred in all frequency bands characteristic of knocking where i = 1 to 4, it is determined that knocking has not occurred in cylinder j in step 29. Confirm.
[0056]
On the other hand, when the above formula is not established in the determination of step 27 during the period from i = 1 to i = 5, that is, KDL [i]> SL [i] [j] [NE] + KDLave [ i], the routine proceeds to step 31 where it is determined that knocking has occurred in the cylinder j and the knocking determination of the cylinder j is terminated (the determination result of knocking is determined).
[0057]
That is, the latest intensity KDL [i] calculated in step 102 (FIG. 8) is equal to or greater than the value obtained by adding the predetermined threshold value SL [i] [j] [NE] to the intensity average value KDLave [i]. It is determined that knocking has occurred.
[0058]
The series of processes shown above are executed in the same manner for the remaining cylinders.
In this way, the frequency band [1] in which combustion noise is generated is not used for knocking determination, so that erroneous determination due to combustion noise can be prevented and knocking determination accuracy can be improved. Control accuracy can be improved and drivability, fuel consumption, etc. can be improved.
[0059]
Based on the knocking determination result thus obtained, knocking control is performed by a known method. In general, for a cylinder that has been determined not to knock, the ignition timing is advanced by a small amount, while when it is determined that knocking is present, the ignition timing is retarded by a predetermined amount to suppress the knocking and maximize the output. Although the control is performed so as to increase, other knocking control can be used.
[Brief description of the drawings]
FIG. 1 is a diagram showing a system configuration of an embodiment of the present invention.
FIG. 2 is a block diagram showing knocking control according to the embodiment.
FIG. 3 is a flowchart showing frequency analysis processing of the knocking control.
FIG. 4 is a time chart showing a knocking determination section and determination processing interrupt timing.
FIG. 5 is a diagram showing vibration mode coefficients and related contents in a draper equation.
FIG. 6 is a flowchart showing an interrupt process at the end of the knocking determination section of the knocking control.
FIG. 7 is a flowchart showing a knocking determination process of the knocking control.
FIG. 8 is a flowchart showing similarly frequency-specific intensity average value calculation processing;
FIG. 9 is a flowchart showing the first combustion noise determination process.
FIG. 10 is a time chart showing the operation and effect of the first combustion noise determination process.
FIG. 11 is a flowchart showing a second combustion noise determination process of the same knocking control.
[Explanation of symbols]
1 engine (internal combustion engine)
3 Fuel Injection Valve 4 Spark Plug 6 Crank Angle Sensor 7 Water Temperature Sensor 8 Knock Sensor 9 Control Unit

Claims (9)

A knock determination device for an internal combustion engine that determines the presence or absence of knocking based on vibration intensity in a plurality of frequency bands indicating characteristics of knocking from an engine vibration detection signal,
The presence or absence of combustion noise that occurs during combustion for at least one of the plurality of frequency bands is determined as having combustion noise when there is a predetermined difference or more by comparing the vibration intensity at the time of fuel supply and at the time of fuel cut ,
When it is determined that there is combustion noise, the vibration intensity in this frequency band is excluded from the knocking determination.
An internal combustion engine knock determination device. A knock determination device for an internal combustion engine that determines the presence or absence of knocking based on vibration intensity in a plurality of frequency bands indicating characteristics of knocking from an engine vibration detection signal,
The presence / absence of combustion noise occurring during combustion in at least one of the plurality of frequency bands is compared with the vibration intensity between an engine rotation speed region where combustion noise is likely to occur and an engine rotation speed region where combustion noise is less likely to occur. When there is a difference greater than the predetermined value, it is determined that there is combustion noise,
When it is determined that there is combustion noise, the vibration intensity in this frequency band is excluded from the knocking determination.
A device for determining knocking of the internal combustion engine you wherein a. The determination of the combustion noise, compares the vibration intensity between the occurrence tendency of the combustion noise is the weighted average processing after a predetermined period of time has elapsed since the beginning different respective operating state,
The knock determination device for an internal combustion engine according to claim 1 or 2, characterized in that Compare vibration intensity normalized by engine speed ,
The knock determination device for an internal combustion engine according to any one of claims 1 to 3, wherein: The determination of the combustion noise is performed based on the vibration intensity in the vibration frequency band f corresponding to the vibration mode coefficient ρ ₁₀ = 1.841 in the following draper equation .
The knock determination device for an internal combustion engine according to any one of claims 1 to 4, wherein:
f = C · ρ _mn / (π × B)
f: resonance frequency, C: speed of sound in a combustion atmosphere, B: cylinder bore diameter, ρ _mn : mode coefficient (m is vibration order in the cylinder bore diameter direction, n is vibration order in the cylinder bore circumferential direction) The determination of the combustion noise is performed at least for each cylinder and for each engine speed .
The knock determination device for an internal combustion engine according to any one of claims 1 to 5, wherein The determination of the combustion noise is prohibited in a low speed range below a predetermined engine rotation speed.
The knock determination device for an internal combustion engine according to any one of claims 1 to 6. The determination of the combustion noise is prohibited when the engine coolant temperature is below a predetermined value .
The knock determination device for an internal combustion engine according to any one of claims 1 to 7, wherein The ignition timing is advanced / retarded based on a knocking determination result using the knocking determination device for an internal combustion engine according to any one of claims 1 to 8.
Knock control apparatus for internal combustion engine you wherein a.

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