JPS6341009B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an ignition timing control for an internal combustion engine that has a function of detecting knocking by vibrations generated inside and outside the cylinder due to the internal cylinder pressure of the internal combustion engine, and adjusting the ignition timing to a predetermined knocking level. This invention relates to a knocking detection device used in devices and the like.

By the way, it is generally known that there is a strong correlation between ignition timing and cylinder pressure;
When the air-fuel mixture is exploded, the cylinder internal pressure is a harmonic when no knocking occurs (component in a frequency band usually determined by the bore diameter of the engine cylinder and the sound speed during combustion, which is caused by intermittent rapid combustion) However, when knocking occurs, this harmonic wave rises near the maximum value of the internal pressure,
As a result, vibrations or noise are generated outside the cylinder. If we look closely at the internal pressure signal generated within the cylinder or the vibration or sound generated outside the cylinder, we can see that knocking (trace knock) begins at the engine crank angle where the internal pressure reaches its maximum value, and gradually increases. When knocking occurs (light knock, heavy knock), the harmonics become large in front of the maximum internal pressure (that is, on the ignition side). By the way, as mentioned above, the frequency of harmonics caused by this knocking is thought to be uniquely determined by the bore diameter of the cylinder and the sound speed during combustion, and the frequency is limited to a specific frequency band (usually 7 to 10 KHz). is said to occur.
Therefore, in conventional engines, knocking can be detected by simply detecting vibrations occurring outside the engine or by focusing on a specific frequency, and the ignition timing is controlled by detecting knocking. However, it has been found that with the above method, the detection accuracy deteriorates depending on the operating conditions of the engine, and a region occurs where it becomes difficult to detect weak trace knocking. That is, 7KHz ~
When detecting knocking in the 10KHz band, when the engine speed becomes high, vibration noise generated in the engine body (for example, valve seating vibration) increases, and the S/N ratio deteriorates.
This effect is particularly large at high speeds and high loads, and trace knocking becomes almost impossible to detect. Furthermore, even if the S/N ratio is poor, if the ignition timing is forcibly controlled, excessive knocking is likely to occur, and damage to the engine body, including melting of the spark plug, may occur. To prevent this damage, it is generally necessary to control the ignition timing and stop the engine at high speeds and high loads. Furthermore, in a method that simply detects vibration without focusing on a specific frequency band, the influence of vibration noise is too large, trace knocking can hardly be detected, and smooth control cannot be expected. Therefore, we investigated various knocking detection methods that eliminate the drawbacks of conventional methods, and found that knocking exists not only in a single frequency band, but in multiple frequency bands. It was found that knocking could be detected accurately even at high rotation speeds, since the vibration noise of the engine was difficult to detect.

Figure 1 shows a piezoelectric element type vibration detector attached to the engine block, and frequency analysis of the vibration output depending on the presence or absence of knocking.

In the figure, A and B are the vibration output (back noise) without knocking at high load (WOT) at engine speeds of 1500 and 3000 rpm, and C is the engine speed.
This is the vibration output when knocking occurs at WOT at 3000 rpm.

As is clear from this result, Notsking is 5
~10KHz band (hereinafter referred to as low frequency band) and 11~13KHz band (hereinafter referred to as high frequency band), and 11~13KHz band (hereinafter referred to as high frequency band)
The 13KHz band has high rotation speed and is less affected by vibration noise.
Good N ratio. Conversely, it can be seen that the sensitivity in the low frequency band is good at low rotations. Further, vibrations in a high frequency band occur largely even near the peak of acupressure, and vibrations in a low frequency band tend to occur after the peak of acupressure. This result corresponds well to the acupressure waveform, and as previously thought, the knocking frequency is not uniquely determined, but a special combustion region exists. Furthermore, these high and low frequencies are affected by the shape and conditions of the combustion chamber, so they may not be absolutely determined depending on the engine type, but knocking will definitely occur in multiple frequency bands.

Therefore, in view of the above points, the present invention is configured to detect knocking vibrations in different frequency bands of an internal combustion engine and to switch the output of each of these vibrations as necessary, thereby reducing the vibration noise of the engine relatively. When the engine is running at low speeds and under light load, the vibration output on the low frequency side is used. When the vibration noise becomes large, the vibration output in the high frequency band is switched and used, making it possible to detect weak knocking stably and accurately even when engine operating conditions change.
Problems with the conventional method were that vibration noise at high rotation speeds made it impossible to detect knocking and control, or that the S/N ratio worsened and only caused relatively strong noise (heavy knocking). If you try to control the ignition timing in a situation where it is not possible to control the ignition timing, it may cause melting of the spark plug and sometimes damage to the engine itself, or it may cause serious problems such as not being able to smoothly control knocking under high load and high rotation speeds, which is the area where fuel efficiency is most expected to be improved. It is an object of the present invention to provide a knocking detection device for an internal combustion engine that can eliminate the drawbacks and significantly improve the durability and efficiency of the engine.

The present invention will be described below with reference to embodiments shown in the drawings. FIG. 2 is a diagram of a knocking feedback ignition system using the device of the present invention.

In the figure, reference numeral 1 denotes a four-cylinder in-line internal combustion engine, and a vibration detector 2 is firmly attached to a cylinder block portion of the engine 1 (on the fourth cylinder side in the figure) using screws or the like.
This vibration detector 2 has two resonance points in different frequency bands, and outputs vibration output in each frequency band from two signal lines a and b, respectively. 3 is a knocking detection circuit that detects engine knocking from the output signal of the vibration detector 2; 4 is an ignition timing control device that advances or retards the ignition timing in accordance with the output of the detection circuit 3 to control it to an optimum position. The output signal of the control device 4 is passed through the ignition device 5 to ignite the air-fuel mixture by a spark plug attached to the engine 1.

Next, a specific configuration of the vibration detector 2 will be explained. FIG. 3 shows a first embodiment of a vibration detector using a piezoelectric element. Reference numerals 21A and 21B are two piezoelectric vibration detecting elements called bimorph, in which a center electrode 21c is sandwiched and bonded between two piezoelectric elements 21a and 21b, respectively. Each vibration detection element 2
1A and 21B are sandwiched between two insulators 22a and 22b made of ceramic, baked or the like with recesses together with an outer electrode 21d that connects the upper and lower piezoelectric elements 21a and 21b, and are firmly attached to a metal stay 29 with screws 23. Fasten with screws. Each vibration detection element 21A, 2
The signal of 1B is transmitted from the end of each center electrode 21c and each outer electrode 21d to each lead wire 24a, 24b, 2.
5a and 25b by soldering, caulking, etc., and output to the outside through each electrode of a sealing terminal 26 (usually called a hermetic seal) constructed by insulating four electrodes with glass. The terminal 26 is soldered to a metal cover 27 through its metal housing 26a, and the cover 27 is attached to the stay 29 together with a sealing member 28 such as rubber.
Attach by caulking the end of 7. The stay 29 has a mounting threaded portion 29a at its lower portion, and is firmly fixed to the cylinder block of the engine by this threaded portion. The sensing direction of this detector 2 is the up and down direction of the arrow in the figure. In addition, each vibration detection element 21 attached to the detector
Since they are both made of the same material and have the same configuration, the resonance frequency of A and 21B is determined by their length. In the figure, the shorter vibration detection element 21B is designed to have a high resonance point, and the vibration detection element 21A has a resonance peak at 8KHz, and the vibration detection element 21B has a resonance peak at 12KHz. Furthermore, each vibration detection element 21A,
Care must be taken to insulate between 21B and 21B.

Each of these vibration detection elements 21A and 21B has resonance characteristics at a specific frequency. Therefore, the sensitivity is good for vibration frequencies around that frequency, and the S/N ratio is very good for noise in other bands.

When the detector 2 is attached to a cylinder block and the engine is operated, each vibration detection element 21A, 21B receives a force in the direction of the arrow, and outputs an output corresponding to this force. Each of these vibration detection elements 21
Since A and 21B are configured to be electrically independent from each other, the vibration detection element 21A responds with high sensitivity to knocking in the low frequency band, and the vibration detection element 21A responds to knocking in the low frequency band.
B has good response in high frequency band. Both of these vibration detection elements 21A and 21B have different vibration frequency bands in which knocking occurs depending on the engine conditions, and also have different S/N ratios. Since the output on the better side can be used, knocking can always be detected properly.

Therefore, the S/N ratio does not deteriorate at high speeds or at high speeds and high loads, which has been a problem in conventional detection methods, and it is possible to successfully detect weak knocking.

FIG. 4 is a detailed block diagram of the knocking detection circuit 2 and the ignition timing control device 4.

Reference numeral 6 denotes an engine state detector that detects the operating state of the engine 1, and detects engine speed, load state, temperature, etc. 41 is an input processing circuit that converts various detected engine state signals into signals suitable for calculating ignition timing; 42;
is the engine speed under the engine conditions (for example, the engine speed is detected by installing multiple protrusions on the rotating parts of the distributor shaft, crankshaft, etc. and using a power generation method using a magnet and coil, and converting this into a digital signal) signal with proportional frequency),
This is a base advance angle calculation circuit that determines a predetermined advance angle value (for example, a minimum advance angle value, an advance angle control range for failsafe, etc.) that changes depending only on the engine speed. Reference numeral 43 denotes an ignition timing calculation circuit that determines the optimal ignition timing for engine operation using the outputs of the base advance angle calculation circuit 42 and the input processing circuit 41 and the corrected advance angle calculation circuit 44 that determines the amount of advance value according to the notching state. It is a circuit. 45 divides a predetermined period L in which knocking does not occur immediately after ignition and a period in which knocking occurs by using an igniter drive signal (for example, a digital signal instructing the ignition coil energization time and ignition timing) from the ignition timing calculation circuit 43, which will be described later. This is a divided signal circuit for determining knocking and bass vibration noise using a knocking discrimination circuit 32. Reference numeral 5 denotes the above-mentioned known ignition device which drives an ignition coil (not shown) by the output of the ignition timing calculation circuit 43, and uses the high voltage generated in the secondary coil to cause the ignition plug to ignite and burn the spark.

2 is the aforementioned vibration detector, 3 is a knocking detection circuit, 31 is a switching circuit that switches two types of signals generated in the vibration detector 2 according to the output of the input processing circuit 41, and 32 is a division signal generation circuit. 45
This knocking determination circuit compares the vibration noise and the knocking output at a predetermined timing according to the output of the knocking, and determines the presence or absence of knocking.

FIG. 5 is a detailed block diagram of the switching circuit 31. Reference numeral 2 indicates the aforementioned vibration detector, and reference numerals a and b indicate two types of output lines for the high frequency band and low frequency band of this detector 2. Reference numerals 311 and 312 are analog switches that become conductive when a "1" level signal is applied to their control terminals, and only one of them becomes conductive depending on the output of the comparator 317 and the output of the NOT gate 313.

Reference numeral 314 denotes an amplifier that amplifies the output of the vibration detector 2 that passes through each analog switch 311, 312. A digital signal proportional to the engine speed N out of the output of the input processing circuit 41 described above is inputted to the terminal C, and an analog voltage proportional to the engine speed N is outputted via a differentiating circuit 315 and an integrator 316. 3
A comparator 17 compares the output of the voltage setter 318 and the output of the integrator 316.

Next, the operation of the above configuration will be explained.
In addition to the normal ignition means, this ignition system has a base advance function (this is an ignition advance function) that is determined by the engine speed to maintain the minimum operation without damaging the engine in the event of any abnormality in the engine. (Used in cases where abnormal knocking occurs due to equipment malfunction for some reason), an advance angle function that is determined by normal engine speed, load, water temperature, etc., and an advance angle function that advances or retards depending on the presence or absence of knocking. The ignition timing is calculated and determined as a combination of these functions. When the ignition timing is determined during normal operation and the engine ignites, the vibration detector 2 outputs signals corresponding to two types of vibrations having resonance points in different frequency bands. The switching circuit 31 compares the outputs of the differentiating circuit 315 and the integrator 316 with the predetermined voltage Vc of the voltage setter 318 and the output V of the integrator 316, since the outputs of the differentiator circuit 315 and the integrator 316 increase in proportion to the rotation. In the example
It detects whether the speed is above or below (set at 3000 rpm). If the rotation speed voltage V is larger than the predetermined value Vc (V>
Vc), the output of the comparator 317 becomes "0" level, the analog switch 311 becomes conductive, and the high frequency band output signal from the vibration detector 2 is transmitted to the amplifier 314.
Therefore, a signal in a high frequency band (resonance point is 12 KHz) with low vibration noise from the engine body and a good S/N ratio is input to the knocking discrimination circuit 32, so that knocking can be detected with high accuracy. On the contrary (V<Vc)
Then, the output of the comparator 317 becomes "1" level, the analog switch 312 becomes conductive, and the output of the low frequency band (resonance point of 8KHz), where vibration noise is relatively small and knocking vibration is detected with high sensitivity, is used to determine knocking. It is input to circuit 32. Therefore,
The knocking discrimination circuit 32 always uses a signal in the high frequency band, which has good signal sensitivity when the engine speed increases and the vibration noise of the engine increases;
When vibration noise is only weak (10KHz), it is possible to use a low frequency band signal that is sensitive to knocking, making it possible to always determine knocking with a good S/N ratio.

The knocking discrimination circuit 32 uses the output of the divided signal circuit 45 to detect the vibration noise sampling signal shown in FIG. 7C for the time immediately after ignition when knocking does not occur, and the notch shown by the solid line or broken line in FIG. 7D for the subsequent time when knocking occurs. The output of the vibration detector 2 is sampled by dividing it into a king sampling signal. (Here, in FIG. 7, A is the output signal of the ignition timing calculation circuit 43, and B is the output waveform of the power transistor that intermittents the primary current of the ignition coil of the ignition device 5.) Alternatively, find the rectified integral value and compare the ratio of both signals and the magnitude of the potential (however, since the noise level is smaller than the level of the knocking signal, it is judged as KX (noise) = knocking), and if knocking is larger than a predetermined value, knocking is detected. Assuming that there is, the correction advance angle calculation circuit 44 calculates the advance/retard amount according to the level of knocking.

The ignition timing calculation circuit 43 adds the correction amount due to this knocking to the advance amount calculated based on the engine conditions, and based on this result, drives the ignition device 5 to ignite. At this time, if knocking does not occur, the correction advance angle calculation circuit 44 issues a signal to advance the angle by a predetermined amount. In other words, in this device, if there is knocking according to the output of the detector 2, the engine is retarded by a predetermined amount, if not, it is advanced by a predetermined amount, and if an abnormality occurs in the engine, the base advance is advanced by the base advance angle calculation circuit 42. The ignition timing is controlled by the amount of angle.

Note that in the above embodiment, knocking was determined by calculating the ratio of base noise to knocking for each ignition, but this was determined statistically (for example, what percentage out of 100 firings).
It can also be treated to reduce the risk of knocking. However, in this case, the response will be delayed.

In addition, in the embodiment, the output of the detector 2 was switched depending on the engine speed because as the engine speed increases, the vibration noise in the low frequency band increases, but the output of the detector 2 is switched by detecting the level of vibration noise. Figure 6 will be explained. In FIG. 6, the same numbers as in FIG. 4 indicate the same configurations. 315a is a rectifier circuit to which the output of the low frequency band detection signal from the vibration detector 2 is input and rectified while the vibration noise sampling signal from the divided signal circuit 45 is at the "1" level, and 316a is the output of the rectifier circuit 315a. This integrator 316a integrates and holds the signal, and this integrator 316a receives a reset signal R that is issued immediately before the next vibration noise sampling signal is input (this signal is generated in synchronization with time or angle). , this reset signal R
The integral data from immediately after the input of the reset signal R to immediately before the next input of the reset signal R is held. Comparator 31
7 is the output V of the integrator 316a and the voltage setting device 318
A is compared with a predetermined noise level voltage VN from a to generate an output. Therefore, when detecting vibration noise during a period in which knocking does not occur, the output of the detector 2 is switched to high frequency if V>VN, and to low frequency if V<VN. The operation after this switching circuit 31 is the same as described above.

It is also known that the vibration noise generated in the engine increases as the load increases. In this case, if the intake pipe pressure is detected and a voltage proportional to the pressure is taken out and inputted to the comparator 317, the signal can be switched depending on the intake pipe pressure. It is also possible to select switching conditions by using both rotation and load parameters, particularly by creating a rotation and load matrix.
In this case, there is an advantage that switching can be made more precisely.

Furthermore, in the above-mentioned embodiment, a piezoelectric element type vibration detector 2 was explained as an example of the vibration detector 2 having resonance points in different frequency bands, but since the detector only needs to have resonance points in different frequency bands, Its detection principle,
Any type can be used regardless of its form. Therefore, it is clear that detection is possible even if the detector 2 is not included in one container, but two or more vibration detectors having independent resonance points are attached to the cylinder block. However, since the degree of vibration changes depending on the mounting position, both
Care must be taken when installing.

Next, a second embodiment of the vibration detector 2 that detects magnetically will be described. FIG. 8 is a structural diagram of the detector, in which 21' is a magnetic lead piece made of iron or iron-nickel alloy that has a resonance point that resonates at a specific knocking frequency, 22' is a magnet with magnetic force, and 23' is a magnetic lead piece made of iron or iron-nickel alloy. Connect the magnetic path between lead piece 21' and magnet 2.
The core is made of iron, iron-nickel alloy, ferrite, etc., and is shaped from 2'. In this magnetic path, an air gap G is provided between the lead piece 21' and the core 23', and the tips of the lead piece 21' and the core 23' facing the gap G are made at acute angles. Therefore, when the reed piece 21' vibrates in the direction of the arrow, the gap G changes and the magnetic resistance of the magnetic path changes. 24' is a coil that detects changes in this magnetic flux. Coil bobbin 24a' is core 23'
A hole is drilled through the center of the bobbin 24a', and a coil conductor is wound around the outer periphery of this bobbin 24a'. or,
In order to prevent changes in the number of interlinked magnetic fluxes due to changes in the relative positions of the coil 24' and core 23', the bobbin 24a' is fixed to the core 23' by means of adhesive or the like. Reference numeral 25' is a stay made of iron or brass, which has a threaded portion 25a' on the lower part for attaching the detector to the cylinder block of the engine, and support parts 25b' and 25c' on the upper part for attaching the core 23'. Reference numeral 26' denotes a holding rod for each component forming the aforementioned magnetic path, and includes insulating plates 27', 29', a lug plate 28' for attaching the coil output terminal 24b', a washer 210', and a screw 21.
1', it is firmly fixed to the support portion 25b' of the stay 25'. The coil output terminal 24b' is connected to the lug plate 28'
After it is fixed by soldering, caulking, etc., lead wire 2
12' to the outside. 213' is a cover that is attached to the stay 25' by sandwiching a sealing material 214' such as rubber and caulking the lead wire 21.
A hole 213a' is provided to take out the hole 213'. 21
5' is a rubber bushing for fixing the lead wire 212'. Then, this lead piece 21', the coil 2
4' etc., the vibration detection section consists of lead piece 2.
By making the lengths of 1' different, there are two sets having resonance points at different frequencies, and these are supported independently and in parallel with the support parts 25b' and 25.
It is attached to c′. Then, the detector is firmly attached to the cylinder block by tightening the threaded portion 25a' so that the entire detector vibrates together with the cylinder block.

According to the structure shown in FIG. 8, the knocking vibration generated in the cylinder block is transmitted to the reed piece 21' via the stay 25'. This reed piece 21' vibrates in addition to the natural vibration of the reed piece itself depending on the frequency and intensity of this vibration, but at this time, the core 23', coil 24', and magnet 22' are integrated with the stay 25'. Since it is made strongly to vibrate, only the lead piece 21' is in the magnetic path.
It vibrates relatively in response to the knocking vibration, and the distance of the air gap G changes in accordance with the knocking. Here, the core 23' and the lead piece 21' are designed in advance so that a predetermined magnetic flux is passed through the magnet 22', and a change in the air gap G results in a change in the number of magnetic fluxes in the closed magnetic path. The coil 24' detects this change in magnetic flux, that is, the vibration caused by knocking, as a voltage. The detected voltage signal is output to the knocking detection circuit 3 via the lead wire 212'. By the way, each lead piece 21' of the two sets of magnetic detection parts is designed to have a resonance point at a knocking frequency (7 to 10 KHz) usually around 8 KHz and 12 KHz by having different lengths. The knock detection sensitivity is particularly high in this frequency band,
S/N due to poor sensitivity of signals in other frequency bands
ratio is improved.

FIG. 9 is a principle diagram showing a third embodiment of a vibration detector in which a magnetic path is provided in a position opposite to that shown in FIG. 8 in which magnetic paths are provided in parallel. Reference numeral 201 corresponds to the reed piece having the resonance point described above, and has air gaps G ₁ and G ₂ at opposing positions. This lead piece may be a single plate, or it may be divided into two pieces without any problem as long as they are firmly fixed. 202 is a magnet, and 203 is a U-shaped core made of magnetic material. One side of the magnetic flux is the N pole of the magnet 202,
One side 201a of the lead piece 201, gap G ₁ ,
It flows in the path of one side 203a of the core 203, the other side is the N pole of the magnet 202, the other side 201b of the lead piece 201, the gap _G2 , and the other side 20 of the core 203.
It flows through route 3b. Coils 204 and 205 are wound around the cores 203 of the two magnetic paths. In this case as well, the resonance point changes by changing the left and right lengths of the lead piece 201.

The detector used for this knocking detection may be a photoelectric type or one based on any other detection principle as long as it has a resonance point other than the above and can detect engine vibration. Furthermore, it is clear that methods other than those described in the embodiments can also be used for the knocking determination means (for example, a method that does not detect the base noise of vibrations or a method that determines based on the average value of the base noise and the peak value of the vibrations). Further, although an analog switch is used as a signal switching circuit, any switching means such as a contact type switch can be used. however,
Pay attention to responsiveness and insulation resistance.

In addition, although the detectors shown in each of the above-mentioned embodiments each have one resonance point corresponding to a low frequency band and one high frequency band, it is possible to have two or more resonance points in the same frequency band. You can also switch bands.

As described above, in the present invention, knocking vibrations in different frequency bands of the internal combustion engine are detected, and knocking is detected by switching the respective vibration outputs. Sensitivity is low when the engine is running with little noise, which is a serious problem in that vibration noise increases and knocking cannot be detected accurately, resulting in poor fuel consumption and efficiency, or vibration plug melting as a result of control. It uses a relatively good low frequency band output, and conversely, at noisy high rotations and high loads, it can use a high frequency band output with a good S/N ratio, so it can always be used accurately over the entire operating range of the engine. It has the excellent effect of significantly improving fuel efficiency and engine efficiency by detecting weak trace knocking.

[Brief explanation of the drawing]

Fig. 1 is a frequency analysis diagram of vibrations caused by knocking in a specific internal combustion engine, Fig. 2 is a block diagram of a knocking detection feedback ignition system to which the device of the present invention is applied, and Fig. 3 is a diagram of the vibration detector in the device of the present invention. 3A is a longitudinal sectional view thereof, FIG. 3B is a cross-sectional view thereof, FIG. 3C is a longitudinal sectional view of the main part thereof, and FIG. 3D is an enlarged longitudinal sectional view of the main part thereof. 4 is a detailed block diagram of the main part of the system illustrated in FIG. 2, FIGS. 5 and 6 are detailed block diagrams showing two examples of the switching circuit 31 in FIG. 4, and FIG. 8 is a vertical sectional view showing a second embodiment of the vibration detector, and FIG. 9 is a diagram showing a third embodiment of the vibration detector. FIG. 1... Internal combustion engine, 2... Vibration detector, 21A,
21B...Vibration detection element as a vibration detection section, 2
1', 22', 23', 24'...Reed piece, magnet, core, coil, 2, which constitute the vibration detection section
7, 29...Cover and stay constituting the container, 2
5', 213'... Stay and cover constituting the container, 31... Switching circuit, 201, 202, 2
03, 204, 205...Reed pieces, magnets, cores, and coils that constitute the vibration detection section.

Claims (1)

[Scope of Claims] 1. Vibration detecting means that includes a plurality of vibration detecting sections having mutually different resonance characteristics and each detecting knocking vibrations in different frequency bands of an internal combustion engine, and an engine speed and a vibration detected by the vibration detecting means. An engine state determining means for determining whether either noise or engine load is above or below a predetermined value; and one of engine speed, vibration noise, and engine load depending on the engine state determined by the engine state determining means. a selection means for selecting a low frequency band side among the vibration outputs of the vibration detection means when is below a predetermined value, and selecting a high frequency band side when the vibration output is above a predetermined value; and a vibration output selected by the selection means. A knocking detection device for an internal combustion engine, comprising: a determining means for determining the presence or absence of knocking by comparing the vibration output with a vibration noise level created according to the vibration output. 2. Among the knocking vibrations detected by the vibration detection means, the high frequency band side is set between 11 KHz and 13 KHz, and the low frequency band side is set between 7 KHz and 10 KHz. The knocking detection device for an internal combustion engine as described above. 3. Knocking for an internal combustion engine according to claim 2, wherein among the knocking vibrations detected by the vibration detection means, the high frequency band side is set to approximately 12 KHz, and the low frequency band side is set to approximately 8 KHz. Detection device. 4. The knocking detection device for an internal combustion engine according to claim 4, wherein each of the vibration detection sections is housed in the same container. 5. The internal combustion noise level according to any one of claims 1 to 4, wherein the vibration noise level is created by sampling the vibration output during a period in which knocking does not occur among the vibration outputs selected by the selection means. Engine knocking detection device.