JP2684611B2 - Knock detection device - Google Patents

Description

The present invention relates to a knotting detection device.

[Conventional technology]

When knocking occurs in the engine, vibration with a unique resonance frequency component is generated. The presence or absence of occurrence of knocking is detected by separating and distinguishing from the engine vibration detected by the vibration sensor, the vibration due to the occurrence of knocking and the back ground vibration caused by other than the knocking. That is, the conventional knocking detection device is
For example, as described in JP-A-58-45520, a specific 1 or 2 within a range of 8 to 15 KHz is determined from engine vibration.
The resonance frequency component of the above was determined in advance, separated using a bandpass filter tuned to that frequency, and the presence or absence of knocking was determined by determining whether or not it exceeded a predetermined level.

[Problems to be solved by the invention]

In the above-mentioned conventional technology, since the presence or absence of knocking is determined by using only the specific frequency component included in the output of the vibration sensor, the fluctuation of the back ground vibration during the high load high speed operation in which the back ground vibration becomes large. Will be larger than the vibration due to the occurrence of knocking. Therefore, the vibration due to the occurrence of knocking and the background vibration cannot be separated from the output of the vibration sensor, and it is impossible to determine whether or not the knocking occurs.

An object of the present invention is to provide a knocking detection device capable of determining whether or not knocking has occurred even during high load and high speed operation.

[Means for solving the problem]

In the knocking detection device for determining whether knocking occurs by detecting engine vibration or cylinder pressure vibration, a vibration sensor for detecting engine vibration or cylinder pressure vibration, and a plurality of resonances from the output of the vibration sensor. The presence or absence of knocking is determined by obtaining a frequency component, creating a knocking index based on at least two resonance frequency components of the plurality of resonance frequency components, and comparing the knocking index with a predetermined value for determining knocking. And a determining means, or
A knocking detection device for detecting engine vibration or cylinder internal pressure to determine the presence or absence of knocking, a vibration sensor for detecting engine vibration or cylinder internal pressure, and a digital frequency by A / D converting the output of the vibration sensor. Performs analysis to find multiple frequency components, selects a frequency component for making a knocking determination index from the obtained multiple frequency components, creates a knocking index based on the selected frequency component, and then the knocking index And means for determining the presence or absence of knocking by comparing with a predetermined value for determining knocking.

[Action]

By frequency analysis, a knocking index is compositely created from a plurality of resonance frequency components included in the output of the vibration sensor or a plurality of selected frequency components, and the presence or absence of knocking is determined based on this knocking index. In this way, using a knocking index created in a complex way,
Even when it is difficult to separate and separate the background vibration from the individual frequency components (especially during high-load high-speed operation where the background vibration becomes large), it is possible to distinguish between vibration caused by knocking and background vibration, and knocking occurs. The presence or absence of can be determined.

[Example] First, the principle of the determination of the presence or absence of knocking in the present invention will be described. The vibration of the engine contains many vibration components. For example, there are vibration components due to piston friction, crankshaft rotation, valve operation, and the like. Further, these vibration components change depending on the engine condition.

When knocking occurs in the engine, vibration characteristic of knocking occurs. Whether or not the knocking has occurred is determined by separating the vibration characteristic of the knocking from the overall vibration of the engine detected by the vibration sensor.

FIGS. 8A and 8B are diagrams showing the output of the vibration sensor when no knocking occurs and the analysis result of the frequency component of the output of the vibration sensor. On the other hand, FIGS. 8C and 8D are diagrams showing the results of analysis of the output of the vibration sensor and the frequency component of the output of the vibration sensor when knocking occurs.

As shown in Table 1, when the resonance vibration mode is ρ _nm , where n is the order of the cylinder in the circumferential direction and m is the order of the radial direction, there is a resonance frequency _nm corresponding thereto.

Further, as can be seen by comparing (b) and (d) of FIG. 8, in the case where the knocking occurs, the resonance frequency components of the respective resonance frequencies are larger than those in the case where the knocking does not occur. ing.

The determination as to whether or not knocking has occurred using the knocking determination index will be described with reference to FIG. In order to explain the principle of operation, the resonance frequency ₁₀ (6.3 KHz)
_An explanation will be given using the frequency component of ₀₁ (13.0 KHz). However, the present invention is not limited to this, and the presence or absence of knocking can be determined using any two or more resonance frequency components.

The vibration sensor detects a combined vibration including knocking and background noise. It was but connexion, Notsukingu determination index I is an index I _b becomes defined in Batsukugurando vibration when Notsukingu has not occurred, Batsukugurando vibration I _b when Notsukingu occurs
And the index I is defined including the vibration I _k due to the occurrence of knocking.

The following expression is obtained by mathematically formulating the above-mentioned notching determination index I using the main resonance frequency components.

I = ω ₁₀ P ( ₁₀ ) + ω ₂₀ P ( ₂₀ ) + ω ₀₁ P ( ₀₁ ) + ω ₃₀ P ( ₃₀ ) + ω ₁₁ P ( ₁₁ ) ... (1) where ω is a real value determined by the engine speed. .
In addition, it can take two values of 1 or 0. P is the vibration intensity (power spectrum) of each resonance frequency component.

As shown in FIG. 9, the knock determination index I _b indicated by the resonance frequency component of the back ground vibration and the index indicated by the resonance frequency component of the vibration caused by the occurrence of knocking.
I _k is different in direction and size. This is because, as is clear from the human hearing test, the engine sound without knock is distinguished by the sound such as crisp when there is knock, and the timbre is different depending on whether there is knock. is there.

When the vibration due to the occurrence of knocking is added to the back ground vibration, the knock determination index I based on the ₀₁ and ₁₀ components included in the vibration sensor enters a region below the knock determination threshold I ₀₁ in the case of FIG. 9 (a), In addition, it is possible to determine the occurrence of knocking by going outside the threshold value I ₀₂ in FIG.

In the present specification, not only the five terms on the right side of the equation (1), but also a combination of a plurality of resonance frequency components included in the output of the vibration sensor is defined as a knocking determination index.

As described above, the use of the knocking determination index takes into account the configuration of the specific frequency component due to the occurrence of knocking with respect to the back ground vibration, so that it is possible to determine whether or not the back ground vibration has occurred even if the back ground vibration increases.

Further, the present invention is based on the knowledge described below obtained from the combustion experiment of the engine. That is, the first is that the resonance frequency of occurrence of knocking is peculiar to the resonance frequency determined by the model of the engine. Secondly, when knocking occurs, each resonance frequency component has its own intensity (power spectrum), but the energy generated by knocking can be grasped as the sum of these intensities (power spectrum). Third, as shown in FIG. 10, the frequency distribution of the energy vibrating in each combustion cycle and the component of the resonance frequency is observed as a non-central distribution with respect to the energy generated by the knocking.

A specific configuration will be described following the principle of determining whether knocking has occurred. FIG. 1 is a system configuration diagram. Air enters from the inlet of the air cleaner 1, and the duct 3,
It is sucked into the cylinder of the engine 7 through a throttle body 5 having a throttle valve and an intake pipe 6. Intake air volume is duct 3
Is detected by the hot-wire air flow meter 2 provided in the control unit 9 and the detection signal is input to the control unit 9.

On the other hand, fuel is injected from a fuel tank (not shown) through the injector 16, mixed with intake air in the intake passage and supplied into the cylinder of the engine 7. The air-fuel mixture is compressed by the engine 7, ignited by the spark plug 15 and discharged from the exhaust pipe 8 after explosion. The exhaust pipe 8 has an exhaust sensor 11
Is provided, and the detection signal is the control unit 9
Is input to

The high voltage generated in the ignition coil 13 is distributed to each cylinder by the distributor 14 and supplied to the ignition plug 15. The rotation state of the engine is detected by the crank angle sensor 12, and the crank angle sensor 12 indicates the Ref signal indicating the absolute position for each rotation and the position moved by a predetermined angle from the absolute position.
Output Pos signal. The Ref signal and Pos signal are input to the control unit 9. A vibration sensor 151 for detecting vibration is attached to the engine 7, and the detection signal is input to the control unit 9.

The control unit 9 calculates the fuel supply amount, the ignition timing, etc. based on the signals from the respective sensors, and
A control signal is output to 16 and the ignition coil 13.

FIG. 2 is a diagram showing the details of the control unit 9. Control nit 9 is CPU20, A / D converter 21, ROM2
2, Input I / O23, RAM24, DPRAM25, Output I / O 26 and Bus 37
Control block 34 consisting of, CPU 29, port 2
7, a timing circuit 28, an A / D converter 30, a ROM 31, a RAM 32, a clock 33, an operational circuit 38, and a block 35 for detecting a knocking composed of a bus 36. Here, data exchange between the CPU 20 and the CPU 29 is performed through the DPRAM 25 which is a dual port RAM.

The intake air amount Q _a detected by the hot wire type flow meter 2 is A /
It is converted into a digital value by the D converter 21 and taken into the CPU 20. Further, the Ref signal and the Pos signal detected by the crank angle sensor 12 are taken into the CPU 20 through the input I / O 23. The CPU 20 performs arithmetic processing according to the program stored in the ROM 22, and the arithmetic result is transmitted from the output I / O 26 to each actuator as a fuel injection time signal T _i which means a fuel injection amount and an ignition timing signal θ _ign. . The RAM 24 holds necessary data during arithmetic processing.

On the other hand, when the operation circuit 38 generates the TDC signal indicating the top dead center, the timing circuit 28 divides the periodic signal generated by the clock 33 according to the content input by the CPU 20 to the port 27. And generate a sampling signal. When a sampling signal is generated, A / D converter 3
0 converts the output signal of the vibration sensor 15 into a digital value.

A conventional vibration sensor for detecting knocking resonates in the vicinity of 13 KHz as shown in FIG. 3 (a), but in the present embodiment, in order to obtain a resonance frequency component of at least 18 to 20 KHz, 18KHz as shown in Fig. 3 (b)
What resonates above is used.

CPU29 stores the digital value sampled according to the program held in ROM31 in RAM32,
Frequency analysis is performed based on the stored data to determine whether knocking has occurred. The determination result of whether or not the knocking has occurred is transmitted to the CPU 20 via the DPRAM 25.

The CPU 20 will explain the calculation operation of the ignition timing for each ignition cycle using the flow chart of FIG. 4 (a). The operation of this flow chart is a fixed time period, for example 10msec
Fired every time. At step 201, the engine speed N and the intake air amount Q are read from the predetermined register set in the RAM 24.
Read in. In step 202, the intake air amount Q / N per unit rotational speed is calculated, the fuel injection time width T _i is calculated from Q / N, and is stored in the ROM 22 for fuel supply. As shown in FIG. The basic ignition timing θ _base is obtained in step 202 from the basic ignition timing map, and the basic ignition timing θ _adv obtained here is used as the ignition timing θ _adv used in the subsequent steps.
_Use the value of _base . In step 203, the knock flag (knock fl) determined by the flow chart of FIG.
Whether or not knocking has occurred is determined based on the contents of ag). If the knocking has occurred, at step 213, the predetermined retard angle amount Δθ _ret is subtracted from the ignition timing θ _adv . In addition,
Due to this subtraction, the ignition timing is retarded.
At step 214, the pace of recovery is determined by comparing the ignition timing retarded by the occurrence of knocking in the RAM 24 with a predetermined number of times, for example, 50 (step 205). If the count data A is larger than 50, the count data A is initialized in step 207 and then step 208
Proceed to.

Here, the calculation of the retard amount [Delta] [theta] _ret in step 213, in order to suppress the occurrence of sudden Notsukingu during high speed rotation, based on the rotational speed of the retard amount [Delta] [theta] _ret As shown in the flow chart of FIG. 4 (c) The variable case will be described. That is, if knocking has occurred in step 203, in step 231 the engine speed N
It is equal to or larger than the predetermined rotational speed N _2. If it is smaller than the predetermined rotation speed N ₂ , in step 232, the predetermined retard angle amount Δθ _ret 1 is set as the retard angle value Δθ _ret . Further, when the rotation speed is higher than the predetermined rotation speed N _2, in step 233, Δθ _ret2 larger than Δθ _ret 1 is _set as the retardation amount Δθ _ret , so that it is possible to set an appropriate retardation amount for suppressing the knocking.

If no knocking has occurred in step 203, one count data A is counted up in step 204. The count data A is used to determine whether it is time to recover the ignition timing θ _adv retarded by the occurrence of knocking by the advance amount Δθ _adv . Step 205
Then, it is determined whether the count data A has become equal to the predetermined value 50. Since the flow shown in FIG. 4 (a) is started every 10 msec, when the count data A becomes equal to 50, it means that 0.5 seconds has elapsed since the count data A was initialized, and 0.5 seconds has passed. It is recovered every time. If the count data A is 50 or less at step 205, the process proceeds to step 206. At step 206, a predetermined advance amount Δθ _{adv is} added to the ignition timing θ _adv . By this addition, the ignition timing is recovered. Further, in step 206, the amount of advance angle Δθ _adv may be variable according to the number of revolutions, as shown in the flow chart of FIG. 4 (b), in order to suppress the occurrence of sudden knocking by setting an appropriate amount of advance angle change. . That is, if A = 50 in step 205, step 2
At 21, it is determined whether the engine speed is higher than a predetermined speed N ₁ . If it is larger than the predetermined rotation speed N ₁ , the predetermined advance amount Δθ _adv 1 is set to the advance value Δ in step 222.
_Let θ _adv . If not greater than the predetermined rotation N _1, at step 223, the little by little the advance modify small amount of advance [Delta] [theta] _adv 2 than [Delta] [theta] _adv 1 as advance value [Delta] [theta] _adv.

Therefore, it is possible to prevent the occurrence of knocking due to a sudden change in the advance angle.

In this way, the ignition timing θ _ign is calculated by adding the ignition timing θ _adv obtained as described above to the basic ignition timing θ _base in step 208. In step 209, the maximum advance value θ _res is obtained according to the engine speed N and the intake air amount Q / N per unit speed. The maximum advance value θ _res is RO
This is done by reading from the maximum advance value map stored in M31. At step 210, it is judged whether the ignition timing θ _ign exceeds the maximum advance value θ _res . If not, proceed to step 212. If the maximum advance angle value θ _res is exceeded, the advance angle is too _large, and therefore the maximum advance angle value θ _res is set as the ignition timing θ _ign in step 211.

In addition, here, before executing step 202, as shown in the flow chart of FIG. 4 (d), after the rotation speed N and the intake air amount Q are acquired, the vibration is detected based on the output of the vibration sensor. A case will be described in which the reliability of the vibration sensor is improved by determining the abnormality of the sensor. If the vibration sensor is abnormal, the abnormality is processed.

After the rotational speed N and the intake air amount Q are taken in at step 201, it is judged at step 231 whether the engine rotational speed N is higher than a predetermined rotational speed N ₃ . If the rotation speed is lower than the predetermined rotation speed N ₃ , the output of the vibration sensor has not increased enough to detect an abnormality, and therefore the process proceeds to step 202.

If the engine speed is higher than the predetermined speed N _{3 in} step 231, it is determined in step 232 whether the vibration sensor is higher than the predetermined level K or not. If it is larger, the vibration sensor is judged to be normal and the process proceeds to step 202. If the output of the vibration sensor is smaller than the predetermined level, it is determined that the vibration sensor is abnormal, and in step 234, the ignition timing for the abnormality of the vibration sensor is obtained. At step 234, the ignition timing θ at the time of abnormality according to the rotation speed N and the intake air amount per unit rotation
Search _irr from the map stored in ROM22. It should be noted that the retrieved abnormal point ignition timing θ _irr is a value that is sufficiently retarded from the value stored in the map of the basic ignition timing, so that knocking does not occur. At step 235, θ _irr is set as the basic ignition timing θ _base, and the flow is terminated without calculating the ignition timing by the notking detection.

After the ignition timing θ _ign is set as described above, the delay time t _d , the number of sampling points n _s , and the frequency division ratio t _s are output to the port 27 in step 212 according to the engine state. In step 213, the main comparison resonance frequency is set in the DPRAM 25 according to the engine state, and the flow is ended.

Note that the frequency division ratio t _s determines the sampling cycle of the digital value of the output of the vibration sensor, and the number of sampling points n _s
Determines the number of sampling points.

Note that the number of sampling points is 32 and the sampling cycle is
DMRAM25 with 25μsec, 26.4μsec and 25.9μsec
Table 2 shows the frequency components that can be set and analyzed.

To obtain a frequency component that matches the main resonance frequency in Table 1 above, such as the frequency marked with * in this table, for example, if ₁₁ = 18.1 KHz, set the sampling timing to 25.9 as shown in this table. If it is μsec, 18.098KHz is obtained in the wave number 15, and accurate frequency analysis at 18.1KHz becomes possible.

Thus, the resolution of frequency analysis is determined by the sampling period and the number of sampling points. The t _d , t _s , and n _{s set} in step 212 depend on the operating condition of the engine.
It is determined and set so that the resonance frequency component necessary for determining the occurrence of knocking is obtained.

FIG. 6 is a timing circuit 28 and its operation diagram.
The timing circuit 28 includes a delay counter 41, a sample rate count 42, a sample counter 44, and an AND gate 43 having an inverter at its input terminal. The TDC signal is the set terminal of the delay counter 41 and the sample counter.
Input to 44 set terminals. The output of the clock 33 is input to the enable terminal of the delay counter 41 and the terminal of the AND gate 43 including the inverter. The output of the AND gate 43 is input to the enable terminal of the sample rate counter 42. The zero output of the sample rate counter 42 is input to the enable terminal of the sample counter 44. It is also input to the set terminal of the sample rate counter 42 itself, and is further output as a sampling signal. Zero output of sampling counter 44 is AND gate
Entered in 43.

Delay time t _d from CPU20 to port 27, number of sampling
When n _s and the division ratio t _s are output, the delay counter is t _d , the sample rate counter is t _s , and the sample counter is n _s.
Are set as the initial values of the down counters 4, respectively. Each counter has a zero terminal set to 1 when a signal is input to the set terminal, and counts down each time a signal is input to the enable terminal. When the count reaches zero, the zero terminal output becomes zero.

When the TDC signal is input to the set terminal of the delay counter 41, the zero output becomes 1, and the counter sequentially counts down each time the signal of the clock 33 is input to the enable terminal. The TDC signal is a signal that is output when the angle of the crankshaft reaches the angle corresponding to the top dead center (top-to-bottom center). From the Ref signal and Pos signal output by the crank angle sensor, the TDC signal is stored in the hardware or CPU 20. Made by software. When the down count value of the delay counter becomes zero, the zero output of the delay counter becomes zero and 1 is input to the AND gate 43. In this state, since the sample counter 44 has already received the TDC signal and the zero output is 1, the output signal of the clock 33 is directly input to the enable terminal of the sample rate counter 42.

The sample rate counter 42 counts down each time a clock signal is generated, and outputs a sampling signal each time the count value becomes zero. Also, input a signal to its own set terminal and set t _s as the count value again. The zero output is input to the enable terminal of the sampling counter 44. When the counter value of the sample counter 44 is down-counted to zero and the zero output becomes zero, the clock signal cannot pass through the AND gate and the sampling signal is not output.

The operation of the arithmetic processing for determining whether or not the CPU 29 is knocking will be described with reference to the flow chart of FIG. The operation of this flow chart is executed every time in successive explosion cycles, and is started at a predetermined number n _s of A times initiated by the TDC signal.
It is started immediately after the end of / D conversion. That is, when a predetermined number of digital values of the processing of the vibration sensor 15 are held in the memory of the RAM 32, that is, when the zero terminal output of the sample counter 44 falls from 1 to 0, an interrupt signal is output to the CPU 29. And is started.

First, in step 300, the frequency data of the vibration sensor measurement data is analyzed by FFT. The data to be analyzed are sampling values held in a predetermined memory of the RAM 32. In order to analyze the resonance frequency component contained in the output of the vibration sensor, the FFT method (Fast Fourier Transf
orm). The WFT method (Walsh to Fourier T
ransform) can also be used for frequency analysis.

In step 301, the resonance frequency used when calculating the knocking determination index I by the equation (1) is selected. This selection method is based on the power spectrum P for five resonance frequencies.
Only n pieces (n ≦ 5) are selected from the largest one of ( ₀₁ ), P ( ₀₂ ), P ( ₀₁ ), P ( ₃₀ ), and P ( ₁₁ ). Next, in step 302, the knocking determination index I is calculated.

The notking determination index I is calculated based on the equation (1) with some of these selected Ps. For example,
If P ( ₁₀ ) and P ( ₀₁ ) are selected, the state of calculation of the index I is as shown in FIG.

Here, the average value of the power spectrum, that is, the value standardized by the background level can be used instead of P in the equation (1). For example P ₍₁₀ may use P ₍₁₀₎ / ₍₁₀₎ in place of. Is calculated pursuant to the following equation (2) from the value of P calculated in each explosion.

= A * + (1-a) * P ... (2) However, a is a contribution rate of the conventional value of. This update is executed only when it is not determined that there is knocking, and this becomes the background level. The initial value of is preset in the ROM 31 and can be obtained by reading it.

At step 303, the engine speed N and the intake air amount Q are read from the RAM 32. In step 304, the threshold value I ₀₁ or I ₀₂ is selected from the intake air amount Q of the engine speed N based on the table stored in the ROM 31.

If the knocking determination index I is larger than I ₀₁ or I ₀₂ , it is determined in step 305 that knocking has occurred, and the knock flag is set to 1
If the knocking determination index I is small, it is determined that no knocking has occurred, the knock flag is set to 0, and DPRAM25
The write flow ends.

The routine of FIG. 7 is executed before the routine of FIG. 4 (a) is started. That is, the routine shown in FIG. 4 (a) is a program that determines the ignition timing before the explosion process of a cylinder, and is normally executed in the compression process or the intake process, but the routine in FIG. 7 is executed immediately after the explosion. It is something.

〔The invention's effect〕

According to the present invention, it is possible to determine whether or not knocking has occurred even at high load and high speed in which back ground vibration becomes large.

[Brief description of the drawings]

FIG. 1 is a system diagram, FIG. 2 is a diagram showing a control unit, FIG. 3 is a diagram showing characteristics of a vibration sensor, FIG. 4 is a flow chart diagram showing calculation of ignition timing, and FIG. 5 is basic ignition timing. Map, FIG. 6 is a timing circuit and its operation diagram, FIG. 7 is a flow chart diagram showing the operation of the notking determination, FIG. 8 is a diagram showing the output signal of the vibration sensor and the frequency analysis result, and FIG. 9 is the notking determination. Figure showing indicators, 10th
The figure shows the relationship between the frequency of occurrence of knocking and the strength of knocking. 9 ... Control unit, 12 ... Crank angle sensor, 15 ... Vibration sensor, 28 ... Timing circuit, 30 ...
A / D converter, 33 …… Clock.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-60-4824 (JP, A) JP-A-62-214326 (JP, A) JP-A-1-92624 (JP, A) JP-A-1- 148924 (JP, A)

Claims (11)

(57) [Claims] 1. A knocking detection device for detecting engine vibration or cylinder internal pressure vibration to determine whether knocking has occurred or not. A vibration sensor for detecting engine vibration or cylinder internal pressure vibration, and a plurality of outputs from the vibration sensor. The presence or absence of knocking is determined by obtaining a resonance frequency component, creating a knocking index based on at least two resonance frequency components of the plurality of resonance frequency components, and comparing the knocking index with a predetermined value for determining knocking. And a knocking detection device. 2. The knocking detection device according to claim 1, wherein the knocking index is a sum of the at least two resonance frequency components. 3. The knocking detection device according to claim 1, wherein the vibration sensor is a sensor whose detection sensitivity is substantially constant from at least 5 kHz to 18 kHz. 4. The A / D converter for converting the output of the vibration sensor into a digital signal according to claim 1, and the signal converted by the A / D converter for vibration based on knocking. A knocking detection device having a component for separating a component and a component based on other vibrations. 5. A knocking detection device for detecting the vibration of an engine or the internal pressure of a cylinder to determine the presence or absence of knocking, wherein a vibration sensor for detecting the vibration of the engine or the internal pressure of a cylinder, and an output of said vibration sensor are A / D. Convert and perform digital frequency analysis to obtain multiple frequency components, select the frequency component to make a knocking determination index from the obtained multiple frequency components, and determine the knocking index based on the selected frequency components. And a means for determining the presence or absence of knocking by comparing the knocking index with a predetermined value for determining knocking. 6. A knocking detection device for detecting vibration of an engine or internal pressure of a cylinder to determine whether knocking is present, a vibration sensor for detecting vibration of an engine or internal pressure of a cylinder, and an output of the vibration sensor is A / D. Convert and perform digital frequency analysis to obtain multiple frequency components, select the frequency component to make a knocking determination index from the obtained multiple frequency components, and add the selected frequency components to knocking index And a means for determining the presence or absence of knocking based on the knocking index, the knocking detection device. 7. The knocking detection device according to claim 5, wherein the frequency component is a resonance frequency component. 8. The knocking detection device according to claim 5, wherein the frequency component is selected from those having a large power spectrum. 9. The knocking index according to claim 5, wherein the knocking index is created based on a power spectrum of frequency components standardized based on a background level (average value of power spectra of frequency components). A knocking detection device characterized by the above. 10. The knocking detection device according to claim 5, wherein the number of sampling points in the digital frequency analysis is 32. 11. The sum of the frequency components according to claim 2 or 6, when the sum of the frequency components is calculated by multiplying each frequency component by a weight (ω) determined for each frequency component according to the engine speed. A knocking detection device characterized by the above.