JP4390939B2 - 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 controls an operating state of the internal combustion engine based on knock determination.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a knock control device for an internal combustion engine that performs knock determination on a knock signal extracted from a vibration signal waveform generated in the internal combustion engine and controls knock control factors such as ignition timing and fuel injection amount is known.
[0003]
[Problems to be solved by the invention]
As a knock detection system in the aforementioned knock control device for an internal combustion engine, a knock signal is extracted from a vibration signal waveform detected by a knock sensor by a band pass filter, and a peak output value of this knock signal is output as a lognormal distribution output distribution characteristic. The presence / absence of knock occurrence is determined by comparison with a predetermined knock determination level.
[0004]
By the way, for example, when the ignition timing is further retarded under specific operating conditions such as WOT (Wide Open Throttle: throttle valve fully open / full load), engine speed 2000 [rpm] and no knocking occurrence, A noise signal related to combustion (hereinafter referred to as a “pseudo knock signal”) as shown in FIG. 13B, which is different from the knock signal shown in FIG. .
[0005]
When these knock signals and the pseudo knock signal are compared, the knock signal has a feature that the peak output timing is early and the signal generation time is short, whereas the pseudo knock signal has a substantially constant output value and a long signal generation time. However, the frequencies of the knock signal and the pseudo knock signal are substantially the same. Therefore, if a false knock signal is erroneously detected as a knock signal during the transient retard control of the ignition timing, further retard control is performed, and appropriate feedback control at the time of knock occurrence becomes impossible. It was.
[0006]
Therefore, the present invention has been made to solve such a problem, and it is an object of the present invention to provide a knock control device for an internal combustion engine that can appropriately control the operating state of the internal combustion engine by distinguishing between a knock signal and a pseudo knock signal due to noise. It is said.
[0007]
[Means for Solving the Problems]
According to the knock control device for an internal combustion engine according to claim 1, the knock occurrence state based on the knock signal extracted by the signal extraction means is detected by the knock detection means, and noise different from that at the time of the knock occurrence is detected by the noise determination means based on the detection result. When it is determined that there is a pseudo-knock occurrence state due to, the filter characteristics of the signal extraction means are switched by the characteristic switching means in the specific characteristic switching operation area within the specific operation area. As a result, knock / pseudo knock occurrence is accurately determined, and the operating state of the internal combustion engine is appropriately controlled.
[0008]
Further, the noise determination means includesKnock / pseudo-knock occurrence is accurately determined by determining that there is a pseudo-knock occurrence based on the ratio of knock detection frequency obtained by dividing the maximum knock detection frequency of the cylinder group by the minimum knock detection frequency of the cylinder group .
[0009]
According to the knock control device for an internal combustion engine according to claim 2, the knock occurrence state based on the knock signal extracted by the signal extraction means is detected by the knock detection means, and noise different from that at the time of occurrence of the knock by the noise determination means based on the detection result. When it is determined that there is a pseudo-knock occurrence state due to, the filter characteristics of the signal extraction means are switched by the characteristic switching means in the specific characteristic switching operation area within the specific operation area. As a result, knock / pseudo knock occurrence is accurately determined, and the operating state of the internal combustion engine is appropriately controlled.
The noise determination meansCalculates the standard deviation value for each cylinder in the output distribution characteristic of the logarithmic normal distribution of the peak output value of the knock signal for each ignition of the internal combustion engine, and calculates the maximum standard deviation value of the cylinder group as the minimum standard deviation value of the cylinder group. Knock / pseudo-knock occurrence is accurately determined by determining that the pseudo-knock occurrence state is present based on the ratio of the standard deviation values divided by.
[0010]
Claim 3In the characteristic switching means in the internal combustion engine knock control apparatus, the switching of the filter characteristics in the signal extraction means is performed by at least one of the optimum center frequency or bandwidth for knock detection and pseudo knock determination. The occurrence of pseudo knock is accurately determined, and the operating state of the internal combustion engine is appropriately controlled.
[0011]
Claim4In the characteristic switching means in the internal combustion engine knock control apparatus, the switching of the filter characteristics in the signal extraction means is performed uniformly in all cylinders or in the noise determination cylinder, so that the knock / pseudo knock generation cylinder is accurately determined. The operating state of the engine is appropriately controlled.
[0012]
Claim 5In the characteristic switching means in the internal combustion engine knock control apparatus, since the switching of the filter characteristics in the signal extraction means is released when the characteristic switching operation region is out of range, discontinuity at the time of switching the filter characteristics may frequently occur. As a result, the operating state of the internal combustion engine is appropriately controlled.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described based on examples.
[0015]
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.
[0016]
In FIG. 1, reference numeral 10 denotes a knock sensor which is attached to a cylinder block (not shown) of the internal combustion engine and detects a vibration signal waveform generated in the internal combustion engine, and 11 is a knock from the vibration signal waveform of the knock sensor 10. The band frequency filter (Band Pass Filter: specific frequency band pass filter; hereinafter referred to as “BPF”) is capable of switching the center frequency for extracting the component related to the frequency in accordance with the switching signal from the microcomputer 20 according to the current operating condition. It is noted). The knock signal extracted by the BPF 11 is peak-held in accordance with the peak hold signal from the microcomputer 20 in the peak hold circuit 12, and then A / D converted (analog-digital conversion) by the A / D converter 21. The peak output value V is taken into the microcomputer 20.
[0017]
The microcomputer 20 receives a cylinder discrimination signal for specifying the knock detection cylinder from the cylinder discrimination sensor 15 of the internal combustion engine. In addition, the microcomputer 20 receives various sensor signals from, for example, a crank angle sensor, an intake air amount sensor, a water temperature sensor, and the like of the internal combustion engine. Based on these captured signals, the microcomputer 20 calculates the ignition timing, fuel injection amount, and the like. The calculation result is output from the microcomputer 20 to the igniter 30, the injector (fuel injection valve) 40, and the like. As the internal combustion engine of the present embodiment, a 4-cylinder configuration of # 1 cylinder to # 4 cylinder is assumed.
[0018]
Here, the microcomputer 20 includes a CPU as a central processing unit that executes various known arithmetic processes, a ROM that stores a control program, a RAM that stores various data, a B / U (backup) RAM, an input / output circuit, and the like. Is configured as a logical operation circuit including a bus line or the like for connecting the two.
[0019]
As described above, the knock signal is extracted from the vibration signal waveform generated in the internal combustion engine and knock determination is performed, and the center frequency of the BPF 11 is set to the basic knock frequency f0 as the filter characteristic corresponding to the switching signal from the microcomputer 20. The set state is referred to as “filter characteristic A”, and the state where the center frequency of the BPF 11 is set to the high frequency knock frequency f1 as the filter characteristic corresponding to the switching signal from the microcomputer 20 is referred to as “filter characteristic B”. To do.
[0020]
FIG. 2 is a characteristic diagram showing the above-described filter characteristics A and B in terms of knock detection using the engine speed Ne [rpm] as a parameter. As shown in FIG. 2, the knock detectability due to the filter characteristic A tends to increase to the left as the engine speed Ne decreases, and the knock detectability due to the filter characteristic B increases as the engine speed Ne increases. It has characteristics that contradict each other. That is, in the operating region α on the low speed side where the engine speed Ne is up to a predetermined engine speed N1, the knock detectability by the filter characteristic A exceeds the permissible detection level, and the engine speed Ne is a predetermined value. In the operating range β on the high speed side exceeding the engine speed N1, the knock detectability by the filter characteristic B exceeds the permissible detection level. For this reason, it is possible to improve the knock detectability over the entire engine speed Ne by selectively using the filter characteristic having better knock detectability before and after the engine speed N1. it can.
[0021]
Further, FIG. 3 shows the false noise detection rate [%] using the engine speed Ne [rpm] as a parameter under a specific operating condition in which the above-described filter characteristics A and B are easily delayed by the ignition timing and pseudo knock is likely to occur. FIG. As shown in FIG. 3, as specific operating conditions of the internal combustion engine, for example, within a specific operating region γ in the vicinity of WOT, engine speed 2000 [rpm], in the filter characteristic A, many false errors caused by noise are mistaken for knocking. It can be seen that the noise false detection rate is high because of detection, but the filter characteristic B is not so false, so the noise false detection rate is low.
[0022]
FIG. 4 shows the above-described filter characteristics A and B within the specific operation region γ in which pseudo-knock is likely to occur, the knock determination rate [%] and the retard side when the advance side knock occurs at the ignition timing for each cylinder. It is a characteristic view which shows the judgment rate [%] which is mistaken for knock generation at the time of pseudo knock generation. As shown in FIG. 4, in the filter characteristic A, the determination rate at the time of knock occurrence when the ignition timing is advanced and the determination rate (false determination rate) that is mistaken for the occurrence of knock at the occurrence of pseudo knock that is further retarded from the time when no knock occurs are shown. In the filter characteristic B, the determination rate at the time of knock occurrence greatly exceeds the determination rate that is mistaken for the occurrence of knock at the occurrence of the pseudo knock.
[0023]
Next, a specific procedure for setting the center frequency of the BPF 11 for determining knock / pseudo knock in the microcomputer 20 used in the knock control apparatus for an internal combustion engine according to an example of the embodiment of the present invention will be described. FIG. 5 and the flowchart of FIG. 6 showing the processing procedure of the center frequency initial setting of the BPF 11 will be described with reference to FIG. 7 and FIG. This center frequency setting routine is repeatedly executed by the microcomputer 20.
[0024]
Here, FIG. 7 is a characteristic diagram showing a log (V) distribution characteristic as an output distribution characteristic of a lognormal distribution of the peak output value V of the knock output in each cylinder. Hereinafter, the output distribution characteristic of the logarithmic normal distribution of the peak output value V of the knock signal is simply referred to as “log (V) distribution characteristic”. FIG. 8 is an explanatory diagram showing a knock control region and a pseudo knock determination region using the engine speed [rpm] and the load of the internal combustion engine as parameters. In the knock control region shown in FIG. 8, Z1 and Z3 are regions where knock detection is performed using the basic knock frequency f0 as the center frequency of the BPF 11, Z4 is a region where knock detection is performed using the high frequency knock frequency f1 as the center frequency of the BPF 11, and Z2 is normal. Is a region where knock detection is performed using the basic knock frequency f0 and the high frequency knock frequency f1 as the center frequency of the BPF 11 at the time of noise determination, and Z5 is a region where pseudo knock is detected due to the occurrence of noise. Discontinuity frequently occurs when switching filter characteristics. The region Z5 is set to be less than the region Z2.
[0025]
In FIG. 5, at step S101, for example, the knock detection frequency Ci (i = 1, 2, 3, 4) for each cylinder for every 100 ignitions of the internal combustion engine, and the log (V) distribution characteristic for every 100 ignitions for the internal combustion engine. The standard deviation value Si (i = 1, 2, 3, 4) for each cylinder at is calculated. Next, the process proceeds to step S102, in which the # 3 cylinder and # 4 cylinder shown in FIG. 7 are set as cylinders where pseudo knock is likely to occur, and the # 1 cylinder and # 2 cylinder shown in FIG. B cylinder group as difficult cylinder, maximum knock detection frequency CWmax of W cylinder group, maximum knock detection frequency CBmax and minimum knock detection frequency CBmin of B cylinder group, maximum standard deviation value SWmax of W cylinder group, minimum standard of B cylinder group Deviation value SBmin is calculated. Further, the ratio HS (see FIG. 7) based on the standard deviation value obtained by dividing the maximum standard deviation value SWmax of the W cylinder group by the minimum standard deviation value SBmin of the B cylinder group, and the maximum knock detection frequency CWmax of the W cylinder group are represented by the B cylinder group. The ratio HC based on the knock detection frequency divided by the minimum knock detection frequency CBmin is calculated.
[0026]
Next, the process proceeds to step S103, and it is determined whether or not it is in a specific operation region in which a pseudo knock is likely to occur in the knock control region. When the determination condition of step S103 is satisfied, that is, when it is in the region Z2 shown in FIG. 8 as the specific operation region, the routine proceeds to step S104, where it is determined whether the maximum knock detection frequency CBmax of the B cylinder group is less than the predetermined value K0. The When the determination condition in step S104 is satisfied, that is, when the maximum knock detection frequency CBmax of the B cylinder group is less than the predetermined value K0, the process proceeds to step S105, and the BPF 11 extracts the component related to knock from the vibration signal waveform of the knock sensor 10. It is determined whether the frequency switching flag FF for switching the center frequency is set to “0”, that is, whether the center frequency of the BPF 11 is set to the basic knock frequency f0. When the ignition switch (not shown) of the internal combustion engine is turned on, the frequency switching flag FF is set to “0” in step S201 of FIG. 6 showing the center frequency initial setting routine of the BPF 11, and the center frequency of the BPF 11 is the basic frequency. The knock frequency f0 is initially set.
[0027]
When the determination condition of step S105 is satisfied, that is, when FF = 0 and the center frequency of the BPF 11 is set to the basic knock frequency f0, the process proceeds to step S106, and the ratio HC based on the knock detection frequency calculated in step S102 is predetermined. It is determined whether the value K1 is exceeded. When the determination condition in step S106 is satisfied, that is, when the ratio HC based on the knock detection frequency exceeds the predetermined value K1, the process proceeds to step S107, and the ratio HS based on the standard deviation value calculated in step S102 exceeds the predetermined value K2. Is determined. When the determination condition in step S107 is satisfied, that is, when the ratio HS based on the standard deviation value is larger than the predetermined value K2, it is considered that a pseudo knock has occurred, so the process proceeds to step S108, and the frequency switching flag FF is set to “1”. The center frequency of the BPF 11 is switched to the high frequency knock frequency f1 (see FIG. 8), and this routine is finished.
[0028]
On the other hand, when the determination condition of step S106 is not satisfied, that is, when the ratio HC based on the knock detection frequency is as small as the predetermined value K1 or less, or when the determination condition of step S107 is not satisfied, that is, the ratio HS based on the standard deviation value When is smaller than the predetermined value K2, the process proceeds to step S109. In step S109, the frequency switching flag FF is “0” and the center frequency of the BPF 11 remains the basic knock frequency f0 (see FIG. 8), and this routine ends.
[0029]
On the other hand, when the determination condition of step S103 is not satisfied, that is, when it is not in the area Z2 shown in FIG. 8 as the specific operation area, or the determination condition of step S104 is not satisfied, that is, the maximum knock detection frequency of the B cylinder group. When CBmax is larger than the predetermined value K0 or when the determination condition of step S105 is not satisfied, that is, when the frequency switching flag FF is "1" and the center frequency of the BPF 11 is switched to the high frequency knock frequency f1, nothing is done. This routine is finished without executing. An ignition timing advance / retard processing routine for avoiding knocking after the end of the center frequency setting routine is omitted.
[0030]
As described above, the knock control device for an internal combustion engine according to the present embodiment serves as a signal extraction unit that can switch a filter characteristic for extracting a knock signal from the knock sensor 10 that detects a vibration signal waveform generated in the internal combustion engine (not shown). The BPF (bandpass filter) 11 and the microcomputer 20 for detecting the knock occurrence state in the knock control regions Z1 to Z4 (see FIG. 8) as the specific operation region of the internal combustion engine based on the knock signal extracted by the BPF 11 Knock detection means, noise determination means achieved by the microcomputer 20 for determining the presence / absence of noise generation based on the detection result by the knock detection means, and the knock control region Z1 to Z1 based on the determination result by the noise determination means In the ZPF (see FIG. 8) as a specific characteristic switching operation area in Z4, Characteristic switching means achieved by the microcomputer 20 for switching the filter characteristics. In the knock control device for an internal combustion engine according to this embodiment, the noise determination means determines whether or not noise is generated based on a difference in knock detection frequency for each cylinder of the internal combustion engine. In the knock control device for the internal combustion engine of the present embodiment, the characteristic switching means switches the filter characteristics in the BPF 11 at the center frequency. Furthermore, in the knock control device for an internal combustion engine of the present embodiment, the characteristic switching means switches the filter characteristics in the BPF 11 uniformly for all cylinders. Further, in the knock control device for an internal combustion engine according to the present embodiment, when the characteristic switching means deviates the switching of the filter characteristic in the BPF 11 from the region Z2 (see FIG. 8) as a specific characteristic switching operation region in the knock control region. It is a thing to cancel.
[0031]
In other words, the occurrence of knocking in the knock control regions Z1 to Z4 of the internal combustion engine is detected, and among these, the region Z2 is considered to be a pseudo-knock occurrence due to noise different from knocking based on the difference in knock detection frequency for each cylinder. As a filter characteristic for all cylinders, the center frequency of the BPF 11 is switched from the basic knock frequency f0 for knock detection to the high frequency knock frequency f1 for pseudo knock determination. The switching state of the filter characteristics of the BPF 11 is canceled and restored by the initial setting when the ignition switch is turned on, and so-called hysteresis characteristics are provided so that discontinuities at the time of switching do not occur frequently. Thereby, knock / pseudo knock occurrence is accurately determined, and the operating state of the internal combustion engine can be appropriately controlled.
[0032]
Next, a modified example of the processing procedure for setting the center frequency of the BPF 11 for determining knock / pseudo knock in the microcomputer 20 used in the knock control device for an internal combustion engine according to an example of the embodiment of the present invention. Based on the flowchart of FIG. 9 shown, it demonstrates with reference to the above-mentioned FIG. The center frequency setting routine is repeatedly executed by the microcomputer 20. Further, the ignition timing advance / retard processing routine for avoiding knocking after the end of the center frequency setting routine is omitted.
[0033]
In FIG. 9, in step S301, it is determined whether or not the vehicle is in a specific operation region in which a pseudo knock is likely to occur in the knock control region. When the determination condition of step S301 is satisfied, that is, when it is in the region Z2 shown in FIG. 8 as the specific operation region, the process proceeds to step S302 and the center frequency of the BPF 11 that extracts the component related to knock from the vibration signal waveform of the knock sensor 10 Is set to “0”, and it is determined whether the center frequency of the BPF 11 is set to the basic knock frequency f0. As described above, when the ignition switch (not shown) of the internal combustion engine is turned on, the frequency switching flag FF is set to “0”, and the center frequency of the BPF 11 is initially set to the basic knock frequency f0.
[0034]
When the determination condition of step S302 is satisfied, that is, when FF = 0 and the center frequency of the BPF 11 is set to the basic knock frequency f0, the process proceeds to step S303, and whether the ignition timing retardation amount TRET is less than the predetermined value K3. Determined. When the determination condition of step S303 is satisfied, that is, when the ignition timing retardation amount TRET is smaller than the predetermined value K3, it is considered that a pseudo knock has occurred, so the process proceeds to step S304, and the frequency switching flag FF is “1”. The center frequency of the BPF 11 is switched to the high frequency knock frequency f1 (see FIG. 8), and this routine ends.
[0035]
On the other hand, when the determination condition of step S303 is not satisfied, that is, when the ignition timing retardation amount TRET is larger than the predetermined value K3, the process proceeds to step S305, where the frequency switching flag FF is “0” and the center frequency of the BPF 11 is the basic knock. This routine is terminated while the frequency f0 is maintained (see FIG. 8). On the other hand, when the determination condition of step S301 is not satisfied, that is, when it is not in the area Z2 shown in FIG. 8 as the specific operation area, or the determination condition of step S302 is not satisfied, that is, the frequency switching flag FF is “1”. When the center frequency of the BPF 11 is switched to the high frequency knock frequency f1, this routine is finished without doing anything.
[0036]
As described above, the knock control device for the internal combustion engine of the present modification performs the switching of the filter characteristics in the BPF 11 by the characteristic switching means achieved by the microcomputer 20 when the ignition timing retardation amount TRET is less than the predetermined value K3. Is. In other words, when the ignition timing retardation amount TRET becomes smaller than the predetermined value K3, it can be considered that a pseudo knock has occurred. Therefore, the center frequency of the BPF 11 is determined from the basic knock frequency f0 for knock detection. Is switched to the high frequency knock frequency f1. Thereby, knock / pseudo knock occurrence is accurately determined, and the operating state of the internal combustion engine can be appropriately controlled.
[0037]
Next, another modification of the processing procedure for setting the center frequency of the BPF 11 for the knock / pseudo knock determination in the microcomputer 20 used in the knock control device for an internal combustion engine according to an example of the embodiment of the present invention. Based on the flowchart of FIG. 10 which shows an example, it demonstrates with reference to FIG. 11 and above-mentioned FIG. Here, FIG. 11 is a characteristic diagram showing knock / pseudo-knock determination using log (V) distribution characteristics of a cylinder without pseudo knock and a cylinder with pseudo knock. The center frequency setting routine is repeatedly executed by the microcomputer 20. Further, the ignition timing advance / retard processing routine for avoiding knocking after the end of the center frequency setting routine is omitted.
[0038]
In FIG. 10, in step S401, it is determined whether or not the vehicle is in a specific operation region in which a pseudo knock is likely to occur in the knock control region. When the determination condition of step S401 is satisfied, that is, when it is in the region Z2 shown in FIG. 8 as the specific operation region, the process proceeds to step S402 and the center frequency of the BPF 11 that extracts the component related to knock from the vibration signal waveform of the knock sensor 10 It is determined whether or not the frequency switching flag FF for switching is set to the basic knock frequency f0 of "0". As described above, when the ignition switch (not shown) of the internal combustion engine is turned on, the frequency switching flag FF is set to “0”, and the center frequency of the BPF 11 is initially set to the basic knock frequency f0.
[0039]
When the determination condition in step S402 is satisfied, that is, when FF = 0 and the center frequency of the BPF 11 is set to the basic knock frequency f0, the process proceeds to step S403, and the log (V) distribution characteristic is log as shown in FIG. (V) corresponds to the cumulative frequency 0σ, that is, from the width S of log (V) corresponding to 1σ [%] of the cumulative frequency before and after the median value VM of 50 [%], corresponding to −1σ [%] of the cumulative frequency. It is determined whether the absolute value obtained by subtracting the width S ′ of log (V) to be exceeded exceeds the predetermined value KS. The value of | S−S ′ | is ideally “0” when no pseudo knock occurs. It is also possible to determine whether or not a pseudo knock has occurred based on the linearity before and after the median value VM where log (V) has a cumulative frequency of 0σ, that is, 50 [%].
[0040]
When the determination condition of step S403 is satisfied, that is, when the value of | S−S ′ | exceeds the predetermined value KS, it is considered that a pseudo knock has occurred, so the process proceeds to step S404, and the frequency switching flag FF is set to “ 1 ", the center frequency of the BPF 11 is switched to the high frequency knock frequency f1 (see FIG. 8), and this routine ends.
[0041]
On the other hand, when the determination condition of step S403 is not satisfied, that is, when the value of | S−S ′ | is as small as the predetermined value KS or less, the process proceeds to step S405 and the frequency switching flag FF is set to “0” and the center of the BPF 11 The routine ends with the frequency kept at the basic knock frequency f0 (see FIG. 8). On the other hand, when the determination condition of step S401 is not satisfied, that is, when it is not in the area Z2 shown in FIG. 8 as the specific operation area, or the determination condition of step S402 is not satisfied, that is, the frequency switching flag FF is “1”. When the center frequency of the BPF 11 is switched to the high frequency knock frequency f1, this routine is terminated without doing anything.
[0042]
As described above, in the knock control device for the internal combustion engine of the present modification, each of the noise determination means achieved by the microcomputer 20 determines the presence or absence of noise generation from the lognormal distribution of the knock generation status for each cylinder of the internal combustion engine. The determination is based on the value of | S−S ′ | which is the difference between the positive standard deviation value + σ and the negative standard deviation value −σ with respect to the median value VM for each cylinder. That is, when there is no pseudo knock, the value of | S−S ′ | is small and almost “0”. Therefore, when the value of | S−S ′ | exceeds the predetermined value KS, it can be determined that a pseudo knock has occurred. is there. Thereby, knock / pseudo knock occurrence is accurately determined, and the operating state of the internal combustion engine can be appropriately controlled.
[0043]
FIG. 12 is a block diagram showing a modification of the overall configuration of the knock control device for an internal combustion engine according to an example of the embodiment of the present invention. In the figure, components having the same configuration or corresponding parts as those in the above-described embodiment are denoted by the same reference numerals and symbols, and detailed description thereof is omitted.
[0044]
In the above-described embodiment, the center frequency is switched and used internally as the filter characteristic of the BPF 11. However, as shown in FIG. 12, this modification has two knock sensors 10A and 10B having different center frequencies, A switch circuit 14 is provided in the middle of a signal transmission path from the sensors 10A and 10B to the BPF 11, and a signal transmission path in the switch circuit 14 is switched by a switching signal from the microcomputer 20. That is, the signal waveform from the knock sensors 10A and 10B is selectively input to the BPF 11 via the switch circuit 14, and the filter characteristics for extracting the knock signal by the knock sensors 10A, 10B and BPF 11 are switched.
[0045]
Even in such a configuration, as in the configuration in the above-described embodiment, the occurrence of knock / pseudo knock can be accurately determined, and the effect that the operating state of the internal combustion engine can be appropriately controlled can be expected.
[0046]
By the way, in the said Example, although the center frequency of BPF11 was switched corresponding to the driving | running condition of the internal combustion engine, when implementing this invention, it is not limited to this, The bandwidth (Q value of BPF) ) May be switched according to operating conditions. Further, the center frequency and bandwidth (Q value) of the BPF may be switched according to the combination operation condition.
[0047]
In the above embodiment, the filter characteristics are uniformly switched over in all the cylinders in the operation region where noise is generated. However, the present invention is not limited to this, and the noise generating cylinder is specified in advance. In an internal combustion engine, the filter characteristics of a noise generating cylinder may be switched in a noise generation region, and the filter characteristics of a cylinder without noise generation may not be switched.
[0048]
In the above embodiment, in order to prevent frequent switching of the return timing of the filter characteristics, the ignition switch is released at the initial setting when the ignition switch is turned on when the specific characteristic switching operation area in the knock control area is deviated. However, the present invention is not limited to this, and may be canceled and restored under specific operating conditions such as idling.
[0049]
Further, in the above-described embodiment, the knock / pseudo knock determination when the noise generation state differs for each cylinder has been described. However, the present invention is not limited to this, and is uniform for all cylinders. In the case of noise generation, knock / pseudo knock determination may be performed based on the difference between the cylinders.
[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 characteristic diagram showing a filter characteristic by a knock control device for an internal combustion engine according to an example of an embodiment of the present invention in terms of knock detection with the engine speed as a parameter.
FIG. 3 is a characteristic diagram showing a filter characteristic by a knock control device for an internal combustion engine according to an example of an embodiment of the present invention in terms of a false noise detection rate with an engine speed as a parameter.
FIG. 4 is a graph showing the filter characteristics of the knock control device for an internal combustion engine according to an embodiment of the present invention. The determination rate of knock / pseudo-knock with respect to the ignition timing in a specific operation region where pseudo-knock is likely to occur. It is a characteristic view shown by.
FIG. 5 is a flowchart showing a BPF center frequency setting process for determining knock / pseudo knock in a microcomputer used in a knock control apparatus for an internal combustion engine according to an embodiment of the present invention; It is a flowchart to show.
6 is a flowchart showing a processing procedure for initial setting of the center frequency of the BPF of FIG. 5. FIG.
FIG. 7 is a characteristic diagram showing a log (V) distribution characteristic for each cylinder in the knock control device for an internal combustion engine according to an example of the embodiment of the present invention;
FIG. 8 shows a knock control region and a pseudo knock determination region in which the engine speed and load of the internal combustion engine used in the knock control device for an internal combustion engine according to an example of the embodiment of the present invention are parameters. It is explanatory drawing shown.
FIG. 9 is a flowchart showing a procedure for setting the center frequency of the BPF for knock / pseudo knock determination in the microcomputer used in the knock control apparatus for an internal combustion engine according to an embodiment of the present invention; It is a flowchart which shows a modification.
FIG. 10 is a flowchart showing the procedure for setting the center frequency of the BPF for knock / pseudo knock determination in the microcomputer used in the knock control apparatus for an internal combustion engine according to an embodiment of the present invention; It is a flowchart which shows another modification.
FIG. 11 is a knock / pseudo-knock using log (V) distribution characteristics of a cylinder without pseudo knock and a cylinder with pseudo knock in the knock control apparatus for an internal combustion engine according to an embodiment of the present invention; It is a characteristic view which shows determination.
FIG. 12 is a block diagram showing a modification of the overall configuration of the knock control device for an internal combustion engine according to an example of an embodiment of the present invention.
FIG. 13 is a diagram showing a difference between a knock signal and a pseudo knock signal under a specific operating condition.
[Explanation of symbols]
10 Knock sensor
11 BPF (band pass filter)
12 Peak hold circuit
15 cylinder discrimination sensor
20 Microcomputer

Claims (5)

A signal extracting means capable of switching a filter characteristic for extracting a knock signal from a vibration signal waveform generated in an internal combustion engine;
Knock detecting means for detecting a knock occurrence state in a specific operation region of the internal combustion engine based on the knock signal extracted by the signal extracting means;
Noise determination means for determining the presence or absence of noise generation based on the detection result by the knock detection means;
Characteristic switching means for switching a filter characteristic in the signal extraction means in a specific characteristic switching operation region in the specific operation region based on a determination result by the noise determination unit ;
The noise determination means is a ratio of the knock detection frequency obtained by dividing the maximum knock detection frequency of the first cylinder group in which pseudo knock is likely to occur by the minimum knock detection frequency of the second cylinder group in which pseudo knock is difficult to occur. A knock control apparatus for an internal combustion engine, wherein the knock control apparatus determines that the pseudo-knock occurrence state is present . A signal extracting means capable of switching a filter characteristic for extracting a knock signal from a vibration signal waveform generated in an internal combustion engine;
Knock detecting means for detecting a knock occurrence state in a specific operation region of the internal combustion engine based on the knock signal extracted by the signal extracting means;
Noise determination means for determining the presence or absence of noise generation based on the detection result by the knock detection means;
Characteristic switching means for switching a filter characteristic in the signal extraction means in a specific characteristic switching operation region in the specific operation region based on a determination result by the noise determination unit;
The noise determining means calculates a standard deviation value for each cylinder in the logarithmic normal distribution output distribution characteristic of the peak output value of the knock signal for each ignition of the internal combustion engine, and the first cylinder in which pseudo knock is likely to occur. An internal combustion engine characterized in that it is determined that the pseudo-knock occurrence state is present based on a ratio of standard deviation values obtained by dividing the maximum standard deviation value of the group by the minimum standard deviation value of the second cylinder group in which the pseudo-knock is difficult to occur. Engine knock control device. The knock control device for an internal combustion engine according to claim 1 or 2, wherein the characteristic switching means performs switching of the filter characteristic in the signal extraction means by at least one of a center frequency and a bandwidth. . 3. The knock control device for an internal combustion engine according to claim 1 , wherein the characteristic switching unit performs the switching of the filter characteristic in the signal extraction unit in all cylinders uniformly or in a noise determination cylinder. 3. The knock control device for an internal combustion engine according to claim 1 , wherein the characteristic switching unit cancels switching of the filter characteristic in the signal extraction unit when the characteristic switching operation region is out of range.

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