JPH06331501A - Knock detector for internal combustion engine - Google Patents

Abstract

PURPOSE:To allow the decision of knocking without picking up the impact noise during explosion stroke by deciding the knocking based on a signal passed through means for regulating the pass rate of signal from a knock sensor. CONSTITUTION:A knocking sensor 12 is fixed to a cylinder block 10 and comprises a piezoelectric element, for example. A distributor 14 is provided with crank angle sensors 16, 18. The sensor 16 discriminates the cylinder and generates a pulse for each revolution of a distributor shaft, whereas the sensor 18 generates 24 pulses for each revolution of the distributor shaft. Electric signals are delivered from the sensors 12, 18 to a control circuit 20 comprising a microcomputor. The control circuit 20 delivers an ignition signal to an igniter 26 which distributes a spark current to the ignition plug 28 of each cylinder through the distributor 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a knock detection device for an internal combustion engine, and more particularly to controlling the passage rate of a signal from a knock sensor to a knock detection circuit according to the operating condition of the engine to eliminate the influence of noise. The present invention relates to a knock detection device for an internal combustion engine that detects the presence or absence of knocking.

[0002]

2. Description of the Related Art Mechanical vibration generated by abnormal combustion of an internal combustion engine, that is, knocking is converted into an electric signal by a vibration detecting element called a knock sensor, and the magnitude of the abnormal vibration is converted into the magnitude of the amplitude of the electric signal. A method for detecting knocking is known. In this knocking detection method, it is determined whether or not vibration due to abnormal combustion has occurred in the engine by comparing the amplitude of the electric signal output from the knock sensor with a comparison reference value.

The abnormal vibration sound of the engine detected as knocking has various frequency components, and generally, the center frequency has the largest component per 8 kHz.
As shown in, the output signal from the knock sensor 71 is passed through a bandpass filter 72 having a center frequency of 8 kHz, and an ECU (engine control unit) 74 knocks by a signal obtained by A / D converting the output signal from the bandpass filter 72. The presence or absence of the knock was judged, and when knocking was recognized, a knock judgment signal was output.

However, actual knocking also includes frequency components whose center frequency is higher than 8 kHz.
For example, the next most knocking frequency component has a center frequency of about 12 kHz or 15 kHz. Therefore, it is necessary to look up to this area to accurately determine the occurrence of knocking. Therefore, in order to improve the accuracy of knocking detection, a method has been proposed in which the output signal from the knock sensor is divided into three by frequency components and the occurrence of knocking is determined in each frequency component.
A digital filter has recently been used as a method for separating the frequency component from the output signal from the knock sensor.

[0005]

However, since the digital filter has feedback data, it is easily affected by past data, and is affected by the impact of the intake and exhaust valves immediately before the knocking determination section of the cylinder in the explosion stroke. There was a risk of misjudging the vibration as knocking. In particular, in a multi-cylinder internal combustion engine, the noises of the intake and exhaust valves of cylinders other than the cylinder in the explosive stroke are at a high level as noise, and there is a high risk of being erroneously determined as knocking.

Therefore, according to the present invention, a knocking detection buffer section is provided before and after the knocking determination section of the cylinder in the explosive stroke, and the sound of the intake and exhaust valves of the cylinders other than the cylinder in the explosive stroke is picked up as noise. An object of the present invention is to provide a knock detection device for an internal combustion engine, which is capable of performing knocking determination without the need.

[0007]

In a knock detecting device for an internal combustion engine according to a first aspect of the present invention, which achieves the above object, at least one knock sensor for converting mechanical vibration into amplitude fluctuation of an electric signal is provided in the internal combustion engine. In a knock detection device for an internal combustion engine, which is provided in the main body and detects the presence or absence of knocking in response to an electric signal from this sensor, a means for regulating the passage rate of the signal from the knock sensor and this regulation means are passed. Means for determining knock based on a signal from the knock sensor is provided.

In the knock detecting device for the internal combustion engine according to the first embodiment, the signal path from the knock sensor is branched into a plurality of parallel circuits, and each branched circuit is provided with a bandpass filter having a different center frequency. The regulating means according to the band of the signal passing through each band pass filter may be provided at the subsequent stage of each band pass filter. Further, a knock detection device for an internal combustion engine according to a second aspect of the present invention which achieves the above object, is provided with at least one knock sensor for converting mechanical vibration into amplitude fluctuation of an electric signal in an internal combustion engine body,
In a knock detection device for an internal combustion engine that detects the presence or absence of knocking in response to an electrical signal from this sensor, means for determining the level of the signal from the knock sensor,
The present invention is characterized in that a means for replacing a signal, which is judged to be equal to or more than a predetermined prescribed value by the level judging means, with a representative value, and a means for judging knock by the representative value are provided.

In the knock detecting device for an internal combustion engine according to the second aspect, the signal path from the knock sensor is branched into a plurality of parallel circuits, and each branched circuit is provided with a bandpass filter having a different center frequency. The level determining means and the replacing means may be provided at the subsequent stage of each bandpass filter.

[0010]

According to the knock detecting device for the internal combustion engine of the present invention,
By providing a buffer section before or after the knock determination section of the signal from the knock sensor, noise such as suction noise of other cylinders, striking sound of the exhaust valve, etc. is removed, and a knock signal with a certain noise level or higher is generated. If so, knock determination is performed by this signal. As a result, the possibility that a noise component is included in the knock determination section is reduced, and accurate knock determination is performed.

[0011]

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 schematically shows the overall configuration of an internal combustion engine including an embodiment of the knock detection device according to the present invention. In FIG. 1, 10 is a cylinder block of an internal combustion engine, and 12 is a knock sensor attached to the cylinder block 10. The knock sensor 12 is composed of, for example, a piezoelectric element or an electromagnetic element, and is a well-known one that converts mechanical vibration into electrical amplitude fluctuation. Reference numeral 14 denotes a distributor, and this distributor 14
Is provided with crank angle sensors 16 and 18.
The crank angle sensor 16 is for cylinder discrimination, and assuming that the engine has 6 cylinders, each time the distributor shaft makes one revolution, that is, every two revolutions of the crank shaft (720 ° CA).
One pulse is generated every time. The generation position is set, for example, like the top dead center of the first cylinder. The crank angle sensor 18 is 24 each time the distributor shaft rotates once.
Pulse is generated, that is, a pulse is generated every 30 ° of crank angle.

Knock sensor 12 and crank angle sensor 1
The electric signals from 6, 18 are sent to a control circuit (ECU) 20 equipped with a microcomputer. The control circuit 20 is also fed with a signal representing the amount of intake air from an air flow meter 24 provided in the intake passage 22 of the engine.
On the other hand, the control circuit 20 outputs an ignition signal to the igniter 26, and the spark current generated by the igniter 26 is distributed to the spark plug 28 of each cylinder via the distributor 14.

The engine is usually provided with various other sensors for detecting operating condition parameters, and the control circuit 20 also controls the fuel injection valve 30 and the like, which are directly related to the present invention. Therefore, all of them are omitted in the following description. As shown in FIG. 2, the electric signal from the air flow meter 24 is sent to the analog multiplexer (MPX) 32 via the buffer 30, selected according to the instruction from the microcomputer, and applied to the A / D converter 34. It The electric signal is converted into a binary signal in the A / D converter 34, and then the input / output port 36 is used.
It is taken into the microcomputer through.

Crank angle 7 from crank angle sensor 16
The pulse every 20 ° CA is applied to the interrupt request signal generation circuit 40 via the buffer 38. On the other hand, the pulse from the crank angle sensor 18 for each crank angle of 30 ° CA is applied to the interrupt request signal generation circuit 40 and the speed signal generation circuit 44 via the buffer 42. The interrupt request signal generation circuit 40 generates various interrupt request signals from each pulse at each crank angle of 720 ° CA and every 30 ° CA. These interrupt request signals are applied to the microcomputer via the input / output port 46. The speed signal generation circuit 44 produces a binary signal representing the engine rotation speed Ne from the cycle of the pulse for each crank angle of 30 ° CA. This rotation speed signal is sent to the microcomputer via the input / output port 46.

The output signal of the knock sensor 12 is input to the buffer 49 for impedance conversion, converted to a digital value by the A / D converter 50, and then input to the input / output port 46. On the other hand, when an ignition signal is output from the microcomputer to the drive circuit 60 via the input / output port 46, this is converted into a drive signal and the igniter 26 is energized, depending on the duration and duration of the ignition signal. Ignition control is performed.

The microcomputer includes the above-mentioned input / output ports 36 and 46 and the microprocessor (MPU) 6.
2, a random access memory (RAM) 64, a read only memory (ROM) 66, a clock generation circuit (not shown), a memory control circuit, a bus 68 connecting these, and the like, and is stored in the ROM 66. Various processes are executed according to the control program.

Further, in the ROM 66, a map of the basic ignition timing represented by the engine speed and the engine load, and a map of the retard amount slightly advanced from the knock limit value according to the engine speed and the engine load. Is stored in advance, and when the occurrence of knocking is detected, control is executed to correct the ignition timing and suppress it, but the description thereof will be omitted here and only the detection of knocking will be described. .

Next, the knocking detection operation of the control circuit 20 shown in FIGS. 1 and 2 will be described with reference to the flow chart shown in FIG. The routine of FIG. 3 is executed every predetermined time. In step 300, first, the A / D shown in FIG.
The output value of the converter 50 is stored in the RAM 64 as the output signal D. In the following step 301, it is determined whether or not it is the knock determination section. This knock determination section is when the piston position T is in the range of 70 ° after the top dead center TDC (ATDC 70 °) from the top dead center TDC, and when the piston is not in this section, the routine proceeds to step 303, where the knock sensor output The coefficient (gain) G by which the value is multiplied is set to 0, and this routine ends.

On the other hand, when the piston position T is in the knock determination section, the routine proceeds to step 303, where the gain G for multiplying the knock sensor output value D is set to 1 and then step 304.
At, it is determined whether the piston position T is the top dead center TDC. Then, when the piston position T is at the top dead center TDC, the routine proceeds to step 305, where the maximum output value D of the knock sensor D
The max, the gain G by which the output value D of the knock sensor is multiplied, and the output correction value D1 of the knock sensor are set to 0, and the routine proceeds to step 310.

When it is determined in step 304 that the piston position T is not at the top dead center TDC, the routine proceeds to step 306, where the piston position T is 5 degrees after the top dead center TDC from the top dead center TDC.
It is determined whether the arm is between (ATDC5 °). And
When TDC <T ≦ ATDC5 °, the routine proceeds to step 307, where the gain G by which the knock sensor detection value D is multiplied by 1 /
Then, the process proceeds to step 310. Further, step 306
When it is determined that TDC <T ≤ ATDC 5 °, the process proceeds to step 308, and the piston position T is 5 ° after top dead center (A
It is determined whether the arm is between TDC 5 ° and 10 ° after top dead center (ATDC 10 °). And TDC 5 ° <T <A
When TDC is 10 °, the routine proceeds to step 309, where the gain G for multiplying the detection value D of the knock sensor is halved, and then the routine proceeds to step 310, where TDC 5 ° <T <ATDC10.
When it is determined that the angle is not °, the process directly proceeds to step 310.

Then, in step 310, the output correction value D1 of the knock sensor is calculated by the following equation: D1 = 0.5 × G × D + 0.5 × D1. This is a kind of digital filter. In the following step 311, it is determined whether or not the piston position T is smaller than 10 ° after the top dead center (ATDC 10 °). If not smaller, this routine is ended and T <ATD
In the case of C10 °, the routine proceeds to step 312, where it is judged whether or not the maximum output value Dmax of the knock sensor is smaller than the output correction value D1 of the knock sensor. When Dmax ≧ D1, the process directly proceeds to step 314, and when Dmax <D1, in step 313, the maximum output value D of the knock sensor D
The knock sensor output correction value D1 is stored as max, and the routine proceeds to step 314.

In step 314, it is determined whether or not the maximum output value Dmax of the knock sensor is larger than the knock determination value K. If Dmax> the determination value K, the process proceeds to step 315, it is determined that knock determination is present, and Dmax is determined. If ≤K, the routine proceeds to step 316, where it is determined that there is no knock determination, and this routine ends. 4 (a) to 4 (c) show changes in the gain G by which the output value D of the knock sensor is multiplied by the control procedure of FIG. 3, the output D of the knock sensor, the maximum output value Dmax of the knock sensor, and the conventional knock sensor. Maximum output value Dma
Change in x from top dead center TDC to 70 ° after top dead center (ATDC
70 °).

The gain G by which the output D of the knock sensor shown in FIG. 4 (b) is multiplied is, as shown in FIG. 4 (a), the top dead center TD.
It is 0 up to C, and 5 ° after top dead center TDC (A
It becomes 0.25 (= 1/4) up to TDC 5 °, and 5 ° after top dead center (ATDC 5 °) to 10 ° after top dead center (ATD).
It becomes 0.5 (= 1/2) up to C10 °, from 10 ° after top dead center (ATDC10 °) to 70 ° after top dead center (ATD).
It becomes 1 up to C70 °.

As a result, as shown in FIG. 4 (c), the maximum value Dmax of the knock sensor output correction value D1 is 5 ° after the top dead center.
Is limited to 1/4 during the period up to 5 ° to 10 after top dead center.
Since it is limited to 1/2 during °, even if there is valve noise due to the intake and exhaust valves during this period as shown in Fig. 2 (b), the passage rate of that value is regulated and it will not be judged as a knock. . On the other hand, as shown in Fig. 4 (d), if the passage rate of the signal from the knock sensor is not restricted within 10 ° after the top dead center (gain = 1), 10 ° after the top dead center. The valve noise appearing during the period is detected as a knock signal, and the engine is controlled in the wrong direction.

In the above embodiment, the gain switching is executed after the A / D conversion by the A / D converter 50 shown in FIG. 2, but the gain switching may be executed in the buffer 49. Further, another embodiment of the knocking detection operation of the control circuit 20 shown in FIGS. 1 and 2 will be described with reference to the flowchart shown in FIG. The routine of FIG. 5 is also executed every predetermined time.

In step 500, the output value of the A / D converter 50 shown in FIG. 2 is stored in the RAM 64 as the output signal D, and in the following step 501, the piston position T is the top dead center T.
It is determined whether or not the knock determination section is within the range of 70 ° after the top dead center (ATDC 70 °) from DC. Then, when the piston is not in this section, this routine is ended. on the other hand,
When the piston position T is in the knock determination section, the routine proceeds to step 502, where it is determined whether the piston position T is the top dead center TDC. Then, when the piston position T is at the top dead center TDC, the routine proceeds to step 503, where the maximum output value Dmax of the knock sensor, the output value D of the knock sensor, and the output correction value D1 of the knock sensor are set to 0, and the routine proceeds to step 510.

When it is determined in step 502 that the piston position T is not at the top dead center TDC, the routine proceeds to step 504, where the piston position T is 5 degrees after the top dead center TDC from the top dead center TDC.
It is determined whether or not it is within (ATDC 5 °). Then, when TDC <T ≦ ATDC5 °, the routine proceeds to step 505, where it is determined whether or not the detection value D of the knock sensor is larger than the first reference value K1, and when D ≦ K1, the routine directly proceeds to step 510. , D> K1, the first reference value K1 is set as the detection value D of the knock sensor in step 506, and the process proceeds to step 510.

On the other hand, if it is determined in step 504 that the piston position T is not within 5 ° after the top dead center TDC (ATDC 5 °), the process proceeds to step 507, where the piston position T is 5 after the top dead center. 10 ° after TDC from AT (ATDC 5 °)
It is determined whether or not it is between 0 (ATDC 10 °). Then, when TDC5 ° <T <ATDC10 °, the routine proceeds to step 508, where it is determined whether or not the detection value D of the knock sensor is larger than the second reference value K2. When D ≦ K2, the routine directly proceeds to step 510. Go to step 5 if D> K2
09, the second reference value K2 is set to the detection value D of the knock sensor.
And proceed to step 510. If it is determined in step 507 that TDC 5 ° <T <ATDC 10 °, the process directly proceeds to step 510.

Then, in step 510, the knock sensor output correction value D1 is calculated by the equation: D1 = 0.5 × D + 0.5 × D1. In the following step 511, it is determined whether or not the piston position T is smaller than 10 ° after the top dead center (ATDC 10 °). If it is not smaller, this routine is ended, and if T <ATDC 10 °, the routine proceeds to step 512. It is determined whether or not the maximum output value Dmax of the knock sensor is smaller than the output correction value D1 of the knock sensor. And
When Dmax ≧ D1, the process directly proceeds to step 514 and Dm
When ax <D1, in step 513, the knock sensor maximum output value Dmax is set as the knock sensor output correction value D.
Store 1 and proceed to step 514.

At step 514, it is determined whether or not the maximum output value Dmax of the knock sensor is larger than the knock determination value K. If Dmax> the determination value K, the routine proceeds to step 515, where it is determined that knock determination is present, and D1max When ≦ K, the routine proceeds to step 516, where it is determined that there is no knock determination, and this routine ends. In this embodiment, the maximum value Dmax of the knock sensor output correction value D1 is limited to 5 ° after the top dead center by being replaced with K1 when it exceeds the first reference value K1, and the top dead center. Second between 5 ° and 10 °
If the reference value K2 of is exceeded, it is replaced with K2, so even if there is valve noise due to the intake and exhaust valves during this period,
The value is regulated and it will not be judged as a knock.

The knock determination in the two embodiments described above may be carried out for each frequency in which a knocking signal exists. FIG. 6 shows a third embodiment in which the knock determination for each frequency is performed in the procedure described in FIG. In this embodiment, the same steps as those explained in FIG. 3 are given the same step numbers. The processing in steps 300 to 304 is the same as that of the embodiment described in FIG.

When it is determined in step 304 that the piston position T is at the top dead center TDC, step 305 '.
Then, the knock sensor maximum output values D1max, D2max, D3max at each frequency, the gains G1, G2, G3 for multiplying the knock sensor output value D, and the knock sensor output correction values D1, D2, D3 are set to 0. Step 31
Go to 0 '.

When it is determined in step 304 that the piston position T is not at the top dead center TDC, the routine proceeds to step 306, where the piston position T is 5 degrees after the top dead center TDC from the top dead center TDC.
It is determined whether the arm is between (ATDC5 °). And
When TDC <T ≦ ATDC5 °, the routine proceeds to step 307 ′, where the gain G for multiplying the detection value D of the knock sensor by 1 is set.
/ 4 is set to G1, G3, 1/3 is set to G2, and then the process proceeds to step 310 '. Further, when it is determined in step 306 that TDC <T ≦ ATDC5 ° is not established, the routine proceeds to step 308, where the piston position T is 5 ° after top dead center (AT
It is determined whether the arm is between DC5 ° and 10 ° after top dead center (ATDC10 °). And TDC 5 ° <T <AT
When DC is 10 °, the routine proceeds to step 309 ', where the gain G by which the detection value D of the knock sensor is multiplied is halved.
1, G2, 2/3, G3, then step 3
When it is determined that TDC 5 ° <T <ATDC 10 °, the process proceeds to step 310 ′.

Then, in step 310 ', the output correction values D1, D2, D3 of the knock sensor for each frequency are expressed by the following equation: D1 = 0.5 × G1 × D + 0.5 × D1 D2 = 0.6 × G2 × D + 0 .4 × D2 D3 = 0.7 × G3 × D + 0.3 × D3. This is a kind of digital filter.

In the following step 311, it is judged whether or not the piston position T is smaller than 10 ° after the top dead center (ATDC 10 °). If not smaller, this routine is ended and T <T
If ATDC is 10 °, the routine proceeds to step 312A, where it is determined whether or not the maximum output value D1max of the knock sensor is smaller than the output correction value D1 of the knock sensor. And D1
When max ≧ D1, the process directly proceeds to step 314A and D
When 1max <D1, in step 313A, the knock sensor output correction value D1 is stored as the maximum output value D1max of the knock sensor, and the flow proceeds to step 314A. In step 314A, it is determined whether or not the maximum output value D1max of the knock sensor is greater than the knock determination value K1, and when D1max> the determination value K1, the process proceeds to step 315, it is determined that knock determination is present, and if D1max ≦ K1. When step 312
Go to B.

At step 312B, it is determined whether or not the maximum output value D2max of the knock sensor is smaller than the output correction value D2 of the knock sensor. When D2max ≧ D2, the process directly proceeds to step 314B, and when D2max <D2, the knock sensor output correction value D2 is stored as the maximum output value D2max of the knock sensor at step 313B, and the process proceeds to step 314B. In step 314B, it is determined whether or not the maximum output value D2max of the knock sensor is greater than the knock determination value K2. If D2max> determination value K2, the process proceeds to step 315, it is determined that knock determination is present, and if D2max≤K2. If so, the process proceeds to step 312C.

In step 312C, it is determined whether or not the maximum output value D3max of the knock sensor is smaller than the output correction value D3 of the knock sensor. When D3max ≧ D3, the process directly proceeds to step 314C, and when D3max <D3, the knock sensor output correction value D3 is stored as the maximum output value D3max of the knock sensor at step 313C, and the process proceeds to step 314C. In step 314C, it is determined whether or not the maximum output value D3max of the knock sensor is greater than the knock determination value K3. If D3max> the determination value K3, the process proceeds to step 315, it is determined that the knock determination is present, and if D3max≤K3. If so, the routine proceeds to step 316, where it is determined that there is no knock determination, and this routine ends.

As described above, the output signal of the knock sensor 12 is supplied to three filters (step 3) having different center frequencies.
The knock determination may be executed for each frequency through 10 '). Here, the center frequencies of the three filters are, for example, 8 kHz, 12 kHz, and 15 kHz.
As described above, in the present invention, the passage rate of the output value from the knock sensor in the portion of the piston position where valve noise is likely to occur is limited so that the knock component included in the output signal from the knock sensor is not erroneously detected by the valve noise. By doing so, or when the output exceeds the representative value corresponding to the piston position, the knock determination is performed by replacing the representative value with the representative value, so noise due to the impact sound of the intake and exhaust valves etc. from the determination section. The presence or absence of knock can be accurately detected.

[0039]

As described above, according to the present invention,
Since a knocking detection buffer section is provided before and after the knocking determination section of the cylinder in the explosion stroke, knocking determination is performed without picking up the impact sound of the cylinders other than the cylinder in the explosion stroke as the noise. Because you can
The possibility that a noise component is included in the knock determination section is reduced,
There is an effect that an accurate knock determination can be performed.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an internal combustion engine provided with a knock detection device for an internal combustion engine of the present invention.

FIG. 2 is a block circuit diagram showing a configuration of a control circuit of FIG.

FIG. 3 is a flowchart showing a knock determination procedure according to the first embodiment of this invention.

4 (a) to (c) are changes in gain by which the output value of the knock sensor is multiplied by the determination procedure of FIG. 3, the output of the knock sensor, the maximum output value of the knock sensor, and the maximum value of the conventional knock sensor. Change in output value from top dead center to 70 after top dead center
It is a time chart shown over °.

FIG. 5 is a flowchart showing a knock determination procedure according to the second embodiment of the present invention.

FIG. 6 is a flowchart showing a knock determination procedure according to the third embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a conventional knock detection device for an internal combustion engine.

[Explanation of symbols]

 10 ... Cylinder block of engine 12 ... Knock sensor 14 ... Distributor 16, 17 ... Crank angle sensor 20 ... Control circuit 22 ... Intake passage 24 ... Air flow meter 28 ... Spark plug 30 ... Fuel injection valve 49 ... Buffer 50 ... A / D conversion vessel

Claims (4)

[Claims] 1. A knock of an internal combustion engine, wherein at least one knock sensor for converting mechanical vibration into amplitude fluctuation of an electric signal is provided in an internal combustion engine main body, and the presence or absence of knocking is detected according to the electric signal from the sensor. A detection device, wherein the means for regulating the passage rate of the signal from the knock sensor, and the knock determination means for determining knock by the signal passed through the regulation means are provided. Knock detection device. 2. A signal path from the knock sensor is branched into a plurality of parallel circuits, each of the branched circuits is provided with a bandpass filter having a different center frequency, and each band is provided after the bandpass filter. The knock detection device for an internal combustion engine according to claim 1, wherein the regulating means is provided according to a band of a signal passing through the pass filter. 3. A knock of an internal combustion engine, wherein at least one knock sensor for converting mechanical vibration into amplitude fluctuation of an electric signal is provided in an internal combustion engine main body, and the presence or absence of knocking is detected according to the electric signal from the sensor. A detection device, means for determining the level of the signal from the knock sensor, and means for replacing the signal from the knock sensor determined to be equal to or higher than a predetermined prescribed value by the level determination means with a predetermined representative value, A knock detection device for an internal combustion engine, comprising: knock determination means for determining knock based on the representative value. 4. A signal path from the knock sensor is branched into a plurality of parallel circuits, each branched circuit is provided with a bandpass filter having a different center frequency, and the level is provided at a stage subsequent to each of the bandpass filters. The knock detection device for an internal combustion engine according to claim 3, further comprising a determination means and the replacement means.