JP4364412B2 - Knock control device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a knock control device for an internal combustion engine that detects the presence or absence of knock in the internal combustion engine and controls the operating state of the internal combustion engine.
[0002]
[Prior art]
Conventionally, as a prior art document related to a knock control device for an internal combustion engine, one disclosed in JP-A-7-103856 is known. In this case, when switching the knock detection frequency of the switched capacitor filter, the latest background level VBG is multiplied by the adaptation constant K to obtain the knock determination level VJL, and this knock determination level VJL and the peak of the filtered signal by the switched capacitor filter A technique is shown in which the value VP is compared to determine the presence or absence of knocking in the internal combustion engine.
[0003]
[Problems to be solved by the invention]
By the way, when the knock detection frequency is switched, the noise amount of the detected frequency changes, and the background level also changes accordingly. Therefore, it has been found that there is a matching constant K corresponding to the knock detection frequency. That is, if the knock determination level obtained with the adaptation constant K as a fixed value is used, noise generation may be erroneously determined as knock generation. In this case, inappropriate retard control of the ignition timing is performed, and internal combustion A reduction in engine output occurs. In addition, when the occurrence of knocking cannot be properly detected, there has been a problem that the knocking sound is increased by the advance control of the ignition timing.
[0004]
Accordingly, the present invention has been made to solve such a problem, and provides a knock control device for an internal combustion engine that can accurately determine whether knock has occurred in the internal combustion engine and perform knock control even when the knock detection frequency is switched. Is an issue.
[0005]
[Means for Solving the Problems]
According to the knock control device for an internal combustion engine of claim 1, the filtering frequency band of the band-pass filter switched by the frequency switching means for filtering the signal of the frequency band peculiar to the knock from the vibration waveform signal from the signal detecting means, and the back Based on the background level corresponding to the level transition of the filtered signal by the band-pass filter calculated by the ground level calculation means, the knock determination level is switched by the determination level switching means. The knock determination level and the filtered signal by the band pass filter are compared by the knock determination means, so that the presence or absence of knock occurrence in the internal combustion engine is accurately determined. The knock control means appropriately controls the operating state of the internal combustion engine based on the determination result thus obtained.
[0006]
In the frequency switching means in the knock control device for an internal combustion engine according to claim 2, the presence or absence of knock occurrence in the internal combustion engine by the band pass filter is switched by switching the filtering frequency band of the band pass filter according to the engine speed of the internal combustion engine. Accurately determined.
[0007]
The frequency switching means in the knock control device for an internal combustion engine according to claim 3 switches the filtering frequency band of the band pass filter in accordance with the load of the internal combustion engine, so that the presence or absence of knock occurrence in the internal combustion engine by the band pass filter can be accurately determined. Determined.
[0008]
In the determination level switching means in the knock control device for an internal combustion engine according to claim 4, whether or not knock occurs in the internal combustion engine due to the band-pass filter is switched by switching the adaptation constant at the knock determination level to a value corresponding to the operating state of the internal combustion engine. Is accurately determined.
[0009]
In the determination level switching means in the knock control device for an internal combustion engine according to claim 5, the necessary storage capacity can be minimized by adding and subtracting a predetermined correction amount to and subtracting the base value from the base value, and the necessary storage capacity can be minimized. According to the knock determination level switched based on the above, it is accurately determined whether or not knock has occurred in the internal combustion engine due to the band pass filter.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described based on examples.
[0011]
FIG. 1 is a block diagram showing an overall configuration of a knock control apparatus for an internal combustion engine according to an example of an embodiment of the present invention.
[0012]
In FIG. 1, a knock sensor 1 that is attached to an internal combustion engine (not shown) and detects vibration generated in the internal combustion engine, and a switched capacitor filter that receives an output signal from the knock sensor 1 and filters a signal in a frequency band specific to knock ( Switched Capacitor Filter (hereinafter simply referred to as “SCF”) 2, a rotational speed sensor 3 for detecting the crankshaft rotational speed of the internal combustion engine, and a filter characteristic of the SCF 2 based on the engine rotational speed NE detected by the rotational speed sensor 3 Filter control circuit 4 to be controlled, knock detection circuit 5 to detect the presence or absence of knock occurrence in the internal combustion engine based on the filtered signal of SCF 2 to be controlled, and knock occurrence state is suppressed when knock occurrence is detected by this knock detection circuit 5 The knock suppression circuit 6 controls the ignition timing and the like as much as possible.
[0013]
Next, the detailed configuration, function, and operation of each circuit described above will be described in detail.
[0014]
First, the SCF 2 that filters the knock-specific frequency band signal from the output signal of the knock sensor 1 has a configuration as shown in FIG. 2, for example, and uses a secondary SCF here. The SCF 2 includes capacitors 21a to 21g, for example, switching elements 22a to 22e made of FETs and operational amplifiers (operational amplifiers) 23 and 24. Then, by switching the switching elements 22a to 22e so as to switch between the state shown by the solid line and the state shown by the broken line in FIG. 2, the input terminal has a center frequency corresponding to the switching speed (switching cycle). It functions as a band-pass filter as a specific frequency band-pass filter that band-filters the signal input to Vin.
[0015]
In the SCF 2 shown in FIG. 2, it is assumed that the center frequency f0 is set by the following equation (1). Here, fCLK is the frequency of the switching drive signal output from the filter control circuit 4 for switching the switching elements 22a to 22e, that is, the switching frequency of these switching elements 22a to 22e.
[0016]
[Expression 1]
f0 = fCLK / 20 (1)
[0017]
Further, the filter control circuit 4 is configured to set the value n for determining the switching frequency fCLK based on the engine rotational speed NE detected by the rotational speed sensor 3 and the switching according to the set value n. A drive signal generator 42 is provided that generates a switching drive signal having a frequency fCLK and outputs it to the SCF 2.
[0018]
Among these, the n setting unit 41 automatically sets the value n according to the processing procedure of the flowchart shown in FIG. That is, assuming that the engine rotational speed NE is detected by the rotational speed sensor 3, the n setting unit 41 determines the engine rotational speed NE of the internal combustion engine, for example, every predetermined crank angle in step S101 of FIG. Read. Next, the process proceeds to step S102, where the engine speed NE read in step S101 is compared with a predetermined engine speed NEo set in advance. The predetermined engine speed NEo is set as an engine speed corresponding to a change in the operating state of the internal combustion engine in which the frequency band indicating the occurrence of knocking changes, and is usually an engine of, for example, 4000 [rpm]. A value corresponding to the rotation speed is selected.
[0019]
Then, when the determination condition of step S102 is satisfied, that is, when the engine speed NE is smaller than the predetermined engine speed NEo, the process proceeds to step S103, and after setting “3” as the value n, this routine is finished. On the other hand, if the determination condition in step S102 is not satisfied, that is, if the engine speed NE is greater than or equal to the predetermined engine speed NEo, the process proceeds to step S104, and after the value n is set to “2”, this routine is terminated. To do. The value n set in this way is given to the drive signal generator 42.
[0020]
The drive signal generation unit 42 has a configuration as shown in FIG. 4, for example, and generates a drive signal having a switching frequency fCLK corresponding to the value n given from the n setting unit 41. That is, as shown in FIG. 4, in the drive signal generator 42, the counter 421 receives, for example, a pulse signal having a frequency of 1 [MHz] oscillated from a crystal oscillator (not shown), and counts the rising edges of the pulse signal. The compare register 422 compares the count value of the counter 421 and the value n given from the n setting unit 41, and when both values match, the reset signal is sent to the counter 421 and the inverting latch circuit 423. Is a circuit that outputs. The inversion latch circuit 423 outputs a signal whose logic level is inverted every time a reset signal is applied, that is, every time the counter 421 is reset, as a drive signal (switching drive signal) of the SCF2.
[0021]
5 and 6 show the operation of the drive signal generator 42 when the value n set through the n setting unit 41 is “3” or “2”, respectively. For example, when the value n set through the n setting unit 41 is “3”, the drive signal generation unit 42 generates and outputs a drive signal as shown in FIG. That is, as shown in FIG. 5A, for the oscillation pulse oscillated from the crystal oscillator, the counter 421 counts 1 (time t1) as shown in FIG. ), Count 2 (time t2), count 3 (time t3), and when the count value reaches count 3, the compare register 422 resets the count value.
[0022]
By repeating such an operation, the inversion latch circuit 423 outputs a drive signal whose logic level is inverted as shown in FIG. Here, when the value n is set to “3”, a drive signal having a frequency obtained by dividing the oscillation pulse by 6 is obtained. If the frequency of the oscillation pulse is 1 [MHz], the switching frequency is obtained. fCLK is obtained as a drive signal having a frequency set by the following equation (2).
[0023]
[Expression 2]
fCLK = 1 [MHz] / 6≈167 [kHz] (2)
[0024]
On the other hand, when the value n set through the n setting unit 41 is “2”, the drive signal generation unit 42 generates and outputs a drive signal as shown in FIG. That is, as shown in FIG. 6A, for the oscillation pulse oscillated from the crystal oscillator, the counter 421 counts 1 (time t1) as shown in FIG. ), The count is advanced like count 2 (time t2), and when the count value reaches count 2, the count value is reset by the compare register 422. By repeating such an operation, the inversion latch circuit 423 outputs a drive signal whose logic level is inverted as shown in FIG. Here, when the value n is set to “2”, a drive signal having a frequency obtained by dividing the oscillation pulse by 4 is obtained. If the frequency of the oscillation pulse is 1 [MHz], the switching frequency is obtained. fCLK is obtained as a drive signal having a frequency set by the following equation (3).
[0025]
[Equation 3]
fCLK = 1 [MHz] / 4 = 250 [kHz] (3)
[0026]
In the SCF 2 described above, the switching elements 22a to 22e are driven based on such a drive signal, and the center frequency f0 (filtering frequency band) is switched. As shown in FIG. 7, the frequency characteristic of the SCF 2 shows that when 167 [kHz] is selected as the frequency fCLK of the drive signal, that is, the engine rotational speed NE is less than a predetermined value NEo and the value n is set to “3”. When set, SCF2 becomes a specific frequency band pass filter having a center frequency f0 calculated by the following equation (4).
[0027]
[Expression 4]
f0 = 167 [kHz] /20≈8.3 [kHz] (4)
[0028]
Further, when 250 [kHz] is selected as the frequency fCLK of the drive signal, that is, when the engine speed NE is larger than the predetermined value NEo and the value n is set to “2”, the SCF 2 is A specific frequency bandpass filter having a center frequency f0 calculated by the following equation (5) is obtained.
[0029]
[Equation 5]
f0 = 250 [kHz] /20=12.5 [kHz] (5)
[0030]
The knock detection circuit 5 is a circuit that detects the presence or absence of occurrence of knock in the internal combustion engine based on the filtered signal of the SCF 2 that filters the output signal of the knock sensor 1 with the above-described frequency characteristics. As shown in FIG. A peak hold unit 51, a background level calculation unit 52, a gradual change table 53, an update amount calculation unit 54, a determination level calculation unit 55, and a determination unit 56 are provided. Here, the peak hold unit 51 is a part for peak-holding the inputted filtered signal every predetermined crank angle of the internal combustion engine. The peak value VP that is the peak-held signal corresponds to the knock intensity value and is output to the background level calculation unit 52 and the determination unit 56, respectively.
[0031]
The background level calculation unit 52 averages the peak value VP from the peak hold unit 51 for a predetermined number of times, for example, the ignition cycle of the internal combustion engine to obtain the background level VBG, and this background level VBG and each time When the peak value VP is larger than the background level VBG, a predetermined update amount ΔV is added and the background level VBG is updated (VBG ← VBG + ΔV). On the other hand, when the peak value VP is smaller than the background level VBG, the predetermined update amount ΔV is subtracted to update the background level VBG (VBG ← VBG−ΔV).
[0032]
The updated background level VBG is output to the determination level calculation unit 55, and the memory in the background level calculation unit 52 is compared with the next peak value VP as the latest background level VBG. (Not shown) is stored and held as appropriate.
[0033]
In addition, the background level calculation unit 52 monitors the setting of the value n by the filter control circuit 4 described above, and when the setting switching of the value n is performed, that is, when the operating state of the internal combustion engine changes ( In the present embodiment, when the engine speed NE rises or falls with the engine speed 4000 [rpm] as a boundary), it is further illustrated in cooperation with the gradual change table 53 and the update amount calculation unit 54. The processing is executed according to the flowchart shown in FIG.
[0034]
That is, assuming that the value n is switched by the filter control circuit 4, the background level calculation unit 52 determines whether the value n is switched by the filter control circuit 4 in step S201 of FIG. When the determination condition in step S201 is satisfied, that is, when the value n is switched, the process proceeds to step S202, and the value “10” is set in the built-in first counter C1. Next, the process proceeds to step S203, where it is determined whether the absolute value of the difference between the latest background level VBG and the peak value VP at this time exceeds a predetermined value α. The predetermined value α is a value for monitoring the presence or absence of an extreme level fluctuation of the filtered signal immediately after the value n is switched, that is, immediately after the filtering frequency band of the SCF 2 is changed.
[0035]
When the determination condition in step S203 is satisfied, that is, when the absolute value of the difference between the background level VBG and the peak value VP exceeds the predetermined value α, the process proceeds to step S204, and it is assumed that there is an extreme level fluctuation in the filtered signal. The value “1” is set in the second counter C2 incorporated in the background level calculation unit 52. Next, the process proceeds to step S205, where the value “1” is set to the knock determination prohibition flag FLAG, and the knock determination by the determination unit 56 is prohibited. This is transmitted to the determination unit 56 through the determination prohibition signal PB.
[0036]
On the other hand, if the determination condition in step S203 is not satisfied, that is, if the absolute value of the difference between the background level VBG and the peak value VP is smaller than the predetermined value α, the process proceeds to step S206, and the background level calculation unit 52 It is determined whether the absolute value of the difference between the background level VBG and the peak value VP is less than a predetermined value β described later. When the determination condition in step S206 is satisfied, that is, when the absolute value of the difference between the background level VBG and the peak value VP is smaller than the predetermined value β, the process proceeds to step S207, and the value set in the second counter C2 is “−1. Is changed. On the other hand, when the determination condition of step S206 is not satisfied, that is, when the absolute value of the difference between the background level VBG and the peak value VP is larger than the predetermined value β, the process proceeds to step S208, and the value set in the second counter C2 Is changed to “0”.
[0037]
Then, the process proceeds to step S209, where the background level calculation unit 52 resets the knock determination prohibition flag FLAG to “0” in any case. After the process of step S205 or step S209, the process proceeds to step S210, and the value set in the first counter C1 is decremented under the correction by the value set in the second counter C2 (C1 ← C1 + C2-1). ).
[0038]
Here, the predetermined value β is a value for determining whether or not the peak value VP is stable or close to the state compared to the latest background level VBG, and the background level VBG and the peak value are determined. When the absolute value of the difference from VP is as large as the predetermined value β or more and the value “0” is set in the second counter C2, the peak value VP is in a normal transient state, and the first counter C1 is decremented. It means that “1” is carried out normally. On the other hand, when the absolute value of the difference between the background level VBG and the peak value VP is so small as to be less than the predetermined value β and the value “−1” is set in the second counter C2, the peak value VP is stable or In this state, the first counter C1 is decremented by “2” at an accelerated speed.
[0039]
In this way, the background level calculation unit 52 that has decremented the first counter C1 accesses the gradual change table 53 according to the value of the decremented first counter C1, and the gradual change data T from the gradual change table 53. (C1) is read and output to the update amount calculation unit 54.
[0040]
For example, as shown in FIG. 9, the gradual change table 53 is a memory (for example, ROM) table in which gradual change data T (C1) corresponding to the value of the first counter C1 is stored in advance. That is, according to the gradual change table 53, the initial decrement in which the value of the first counter C1 to be decremented is "10" to "7", that is, the initial value in which the peak value VP of the filtered signal is in a transient state. Among them, as the gradually changing data T (C1), for example, a relatively large value such as “5” is read, but the value of the first counter C1 to be decremented is “6” to “4”. In the middle period of decrement, or later in the decrement period of “3” to “0”, the gradually changing data T (C1) is gradually small, for example, “3”, “1.5” or “1”. The value is read out.
[0041]
The update amount calculation unit 54 is a part that executes an extension calculation for the update amount ΔV based on the gradually changing data T (C1) read out in this way in step S211 of FIG. 8 [ΔV ← ΔV × T (C1) ], The calculated value of the extension update amount ΔV is returned to the background level calculation unit 52. As described above, the background level calculation unit 52 to which the extended update amount ΔV is returned compares the latest background level VBG with the peak value VP, and the peak value VP is higher than the background level VBG. When the peak value VP is smaller than the background level VBG, it is updated by subtracting the extension update amount ΔV from the background level VBG.
[0042]
The background level calculation unit 52 repeats the above-described processing after step S203 in the same manner when the determination condition of step S212 in FIG. 8 is not satisfied, that is, when the value of the first counter C1 is not “0”. The On the other hand, when the determination condition in step S212 is satisfied, that is, when the value of the first counter C1 is “0”, the process proceeds to step S213, and after the knock determination prohibition flag FLAG is reset to “0”, the update amount ΔV is set. The above-described processing for updating the background level VBG as a predetermined value is repeatedly executed.
[0043]
The determination level calculation unit 55 is adapted to the background level VBG updated through the background level calculation unit 52 according to, for example, the engine speed NE detected through the rotation speed sensor 3 as described later. This is a part for multiplying by K and calculating and setting a knock determination level VJL for determining whether knock has occurred or not by the following equation (6).
[0044]
[Formula 6]
VJL = K ・ VBG (6)
[0045]
The determination unit 56 is a part that determines whether or not knock has occurred in the internal combustion engine based on the comparison between the calculated and set knock determination level VJL and the peak value VP of the filtered signal at each time. Specifically, if the peak value VP exceeds the knock determination level VJL, it is determined that knocking has occurred, and if the peak value VP does not exceed the knock determination level VJL, it is determined that no knock has occurred.
[0046]
As described above, according to the knock detection circuit 5, even if the level of the filtered signal changes greatly with the setting change of the value n, that is, with the switching of the filtering frequency band of the SCF 2, the background level Through the calculation unit 52, the gradual change table 53 and the update amount calculation unit 54, as shown in FIG. 8, the update amount ΔV is first expanded for a predetermined period corresponding to the value initially set in the first counter C1, After that, since the control for gradually reducing the enlargement amount is performed, the knock determination level VJL is also a level at which the presence or absence of knocking can be properly determined according to the signal level of the greatly changed filtered signal. As a result of the rapid transition to, the knock detection accuracy as the knock detection circuit 5 is suitably maintained. The knock suppression circuit 6 is a well-known circuit that retards the ignition timing by a predetermined amount to suppress knock when a signal determined that knock has occurred is output from the determination unit 56 of the knock detection circuit 5.
[0047]
Next, the procedure of knock determination in the background level calculation unit 52, the determination level calculation unit 55, and the determination unit 56 of the knock detection circuit 5 of the knock control device for an internal combustion engine according to an example of the embodiment of the present invention will be described. Based on the flowchart of FIG. 10 shown, it demonstrates with reference to FIGS. FIG. 11 is a table for obtaining the base value KB of the adaptation constant K using the engine speed NE [rpm] in the process of FIG. 10 as a parameter. FIG. 12 is a table for obtaining a correction amount corresponding to the center frequency [kHz] of the SCF 2 in the processing of FIG. FIG. 13 is a characteristic diagram showing the adaptation constant K set with the engine speed NE [rpm] in the process of FIG. 10 as a parameter. This knock determination routine is repeatedly executed by the knock detection circuit 5 at every knock detection section end timing of each combustion cycle of the internal combustion engine.
[0048]
In FIG. 10, in step S301, the background level VBG calculation process is executed as described above. Next, the process proceeds to step S302, where it is determined whether the center frequency of SCF2 is 8.3 [kHz]. If the determination condition in step S302 is satisfied, that is, if the center frequency is 8.3 [kHz], the process proceeds to step S303, and a matching constant K that matches the center frequency 8.3 [kHz] is selected. On the other hand, if the determination condition in step S302 is not satisfied, that is, if the center frequency is not 8.3 [kHz], the process proceeds to step S304, and a matching constant K corresponding to the center frequency 12.5 [kHz] is selected.
[0049]
As the adaptation constant K, first, as shown in the table of FIG. 11, the base value KB of the adaptation constant K is determined according to the engine speed NE [rpm] representing the operating state of the internal combustion engine at this time. Next, as shown in the table of FIG. 12, when the center frequency [khz] is in the low frequency band fLc, the correction amount is “0”, and when the center frequency [khz] is in the high frequency band fHc, the correction amount is “VAL1”. Set to As a result, as shown in the characteristic diagram of FIG. 13, when the center frequency [kHz] is in the low frequency band fL, the base value KB remains, whereas when the center frequency [kHz] is in the high frequency band fH, it conforms. As for the constant K, the correction value VAL1 is added to the base value KB, and the adaptation constant K for the engine speed NE in each frequency band is set. In the mutual switching between the low frequency band fL and the high frequency band fH, as shown in the characteristic diagram of FIG. 13, a hysteresis having a predetermined width (NECH1 to NECH2) is provided with respect to the engine speed NE. Chattering of the adaptation constant K is prevented.
[0050]
After the matching constant K is selected in step S303 or step S304, the process proceeds to step S305, where knock determination is executed based on the knock determination level VJL calculated as described above, and this routine is terminated.
[0051]
As described above, the knock control device for an internal combustion engine according to the present embodiment includes a knock sensor 1 as signal detection means for detecting a vibration waveform signal generated in the internal combustion engine (not shown), and the vibration waveform detected by the knock sensor 1. Based on the filtered signal by SCF (switched capacitor filter) 2 and SCF 2 as a band pass filter that filters the signal in the frequency band peculiar to knock, and the background level VBG corresponding to the level transition of the filtered signal is calculated The background level calculation means achieved by the knock detection circuit 5, the rotational speed sensor 3 as the operating state detecting means for detecting the operating state of the internal combustion engine, and the filtering frequency band of the SCF 2 based on the operating state of the internal combustion engine Frequency switching means achieved by the filter control circuit 4 for switching and controlling the background level Determination level switching means achieved by the knock detection circuit 5 for switching the knock determination level VJL based on the background level VBG calculated in the stage and the filtering frequency band of the SCF 2 switched by the frequency switching means, and the filtered signal by the SCF 2 And a knock determination circuit 5 that determines whether or not knock has occurred in the internal combustion engine based on the knock determination level VJL, and controls the operating state of the internal combustion engine according to the determination result by the knock determination means. And a knock control means achieved by the knock suppression circuit 6.
[0052]
That is, the knock determination level VJL is switched based on the background level VBG corresponding to the level transition of the filtered signal by the SCF2 and the filtered frequency band of the SCF2. By comparing this knock determination level VJL with the peak value VP of the filtered signal by SCF2, the presence or absence of knock occurrence in the internal combustion engine is accurately determined. According to the determination result thus obtained, the operating state of the internal combustion engine can be appropriately controlled.
[0053]
Further, the frequency switching means achieved by the filter control circuit 4 of the knock control device for the internal combustion engine of the present embodiment switches the filtering frequency band of the SCF 2 in accordance with the engine rotational speed NE of the internal combustion engine. As a result, the center frequency of the filtering frequency band of the SCF 2 is automatically and appropriately switched according to the engine speed NE of the internal combustion engine, and as a result, it is possible to accurately determine whether or not knocking has occurred in the internal combustion engine due to the SCF 2. .
[0054]
The determination level switching means achieved by the knock detection circuit 5 of the knock control device for the internal combustion engine of the present embodiment switches the adaptation constant K at the knock determination level VJL according to the operating state of the internal combustion engine. As a result, the knock determination level VJL can be switched to that corresponding to the operating state of the internal combustion engine, and as a result, the presence or absence of knock occurrence in the internal combustion engine due to the SCF 2 can be accurately determined.
[0055]
Further, the determination level switching means achieved by the knock detection circuit 5 of the knock control device for the internal combustion engine of the present embodiment is a knock determination based on the adaptation constant K obtained by adding a predetermined correction amount VAL1 to the base value KB. The level VJL is switched. As a result, in order to set the knock determination level VJL, it is only necessary to store the base value KB and the predetermined correction amount VAL1 in advance, so that the necessary storage capacity can be minimized and set in this way. According to the determined knock determination level VJL, it is possible to accurately determine whether knock has occurred in the internal combustion engine due to SCF2.
[0056]
By the way, in the said Example, although the filtering frequency band of SCF2 was switched by the engine speed NE of the internal combustion engine, you may make it switch according to charge efficiency etc. as a load of an internal combustion engine, for example. The frequency switching means achieved in the filter control circuit 4 of such a knock control device for an internal combustion engine switches the filtering frequency band of the SCF 2 in accordance with the load of the internal combustion engine, and has the same effect as the above-described embodiment.・ Effects can be expected.
[0057]
In the above embodiment, the SCF 2 is used as a band-pass filter for filtering a signal in a frequency band peculiar to knocks in an internal combustion engine. However, the present invention is not limited to this, and a plurality of filters are not limited. A band pass filter as a specific frequency band pass filter, a band elimination filter as a plurality of specific frequency band rejection filters, or the like can be used, and the same action and effect can be obtained by appropriately switching them.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an overall configuration of a knock control apparatus for an internal combustion engine according to an example of an embodiment of the present invention.
FIG. 2 is a block diagram showing a detailed configuration of the SCF of FIG.
FIG. 3 is a flowchart showing a processing procedure in an n setting unit of the filter control circuit of FIG. 1;
4 is a block diagram showing a detailed configuration of a drive signal generation unit of the filter control circuit of FIG. 1; FIG.
FIG. 5 is a timing chart showing the operation when n = 3 of the drive signal generator of the filter control circuit of FIG.
6 is a timing chart showing an operation when n = 2 of a drive signal generation unit of the filter control circuit of FIG. 4. FIG.
FIG. 7 is a characteristic diagram showing the relationship between frequency and gain in the SCF of FIG. 1;
FIG. 8 is a flowchart showing a processing procedure in the background level calculation unit and the update amount calculation unit of the knock detection circuit of FIG. 1;
FIG. 9 is a characteristic diagram showing the relationship between the first counter and the gradual change data in the gradual change table of the knock detection circuit of FIG. 1;
FIG. 10 is a flowchart showing a knock determination processing procedure in the background level calculation unit, determination level calculation unit, and determination unit of the knock detection circuit of FIG. 1;
FIG. 11 is a table for obtaining the base value of the adaptation constant using the engine speed in the process of FIG. 10 as a parameter.
FIG. 12 is a table for obtaining a correction amount corresponding to the center frequency of the SCF in the process of FIG.
FIG. 13 is a characteristic diagram showing an adaptation constant set with the engine speed in the process of FIG. 10 as a parameter.
[Explanation of symbols]
1 Knock sensor (signal detection means)
2 SCF (band pass filter)
3 Rotational speed sensor (Operating state detection means)
4 Filter control circuit
5 Knock detection circuit
6 Knock suppression circuit

Claims (5)

Signal detection means for detecting a vibration waveform signal generated in the internal combustion engine;
A band-pass filter that inputs the vibration waveform signal detected by the signal detection means and filters a signal in a frequency band specific to knock; and
Based on the filtered signal by the bandpass filter, a background level calculation means for calculating a background level corresponding to the level transition of the filtered signal;
An operating state detecting means for detecting an operating state of the internal combustion engine;
Determination level setting means for setting a knock determination level for determining the presence or absence of knocking from the filtered signal by the band pass filter based on the background level calculated by the background level calculation means and a predetermined adaptation constant When,
Based on the operating state of the internal combustion engine, frequency switching means for switching and controlling the filtering frequency band of the bandpass filter;
Determination level switching means for switching the adaptation constant based on the filtering frequency band of the bandpass filter switched by the frequency switching means ;
Knock determination means for determining the presence or absence of knock occurrence in the internal combustion engine based on the filtered signal by the band-pass filter and the determination level by the determination level setting means ;
A knock control device for an internal combustion engine, comprising: knock control means for controlling an operating state of the internal combustion engine in accordance with a determination result by the knock determination means. 2. The knock control device for an internal combustion engine according to claim 1, wherein the frequency switching unit switches a filtering frequency band of the band-pass filter in accordance with an engine rotational speed of the internal combustion engine. 2. The knock control device for an internal combustion engine according to claim 1, wherein the frequency switching unit switches a filtering frequency band of the band-pass filter in accordance with a load of the internal combustion engine. 2. The knock control device for an internal combustion engine according to claim 1, wherein the determination level switching means switches an adaptation constant at the knock determination level in accordance with an operating state of the internal combustion engine. 2. The knock control device for an internal combustion engine according to claim 1, wherein the determination level switching means switches the knock determination level based on an adaptation constant obtained by adding or subtracting a predetermined correction amount to or from a base value.

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