JP4190109B2 - Internal combustion engine knock detection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a knocking detection device that detects knocking generated in an internal combustion engine.
[0002]
[Prior art]
Conventionally, a knock detection device for an internal combustion engine detects a vibration of the internal combustion engine, a pressure in a cylinder, and the like, and passes the detection signal through a filter circuit that allows a knock frequency component to pass to a detection signal that can be knocked. Conversion is performed, and the detection signal after the conversion is compared with a threshold value for knock determination, and when the detection signal is larger than the threshold value, it is determined that knocking has occurred in the internal combustion engine.
[0003]
Further, knocking occurs in the internal combustion engine within a predetermined crank angle range from the compression stroke to the combustion (explosion) stroke. Therefore, in the conventional knocking detection device, the crank angle of the internal combustion engine is usually set. Based on the detection signal from the crank angle sensor that detects the knock, a knock determination period is set, and knock detection is performed only during the knock determination period, so that the detection accuracy of knocking is improved (for example, JP-A-5-248332). Issue gazette).
[0004]
[Problems to be solved by the invention]
However, conventionally, for example, based on the crank angle signal for each predetermined crank angle output from the crank angle sensor and the reference crank angle signal corresponding to the specific crank angle, the number of crank angles from the reference crank angle signal is determined. The knock determination period is set in such a manner that the number of crank angle signals is from the signal.
[0005]
For this reason, the circuit for setting the knock determination period must be composed of a timing circuit composed of a counter and various gate circuits, and the configuration of the knocking detection device becomes complicated, which in turn increases the cost. was there.
In addition, for example, an internal combustion engine mounted on some racing vehicles such as motorcycles may not be equipped with a crank angle sensor, and such an internal combustion engine is equipped with a conventional knocking detection device to detect knocking. Even if trying to do so, there is also a problem that the knock determination period cannot be set and good knocking detection cannot be performed.
[0006]
The present invention has been made in view of these problems, and it is possible to set a knock determination period without using a crank angle sensor, and knocking of an internal combustion engine that can detect knocking with high accuracy using the set knock determination period. An object is to provide a detection device.
[0007]
[Means for Solving the Problems and Effects of the Invention]
  In order to achieve this object, the invention according to claim 1 is a pressure sensor for detecting a pressure in a cylinder of an internal combustion engine, a signal processing means for performing signal processing on an output of the pressure sensor, and a signal processing means. A knock detection device for an internal combustion engine, comprising: knock determination means for determining that knocking has occurred in the internal combustion engine based on an output; and knock determination permission means for permitting determination of knocking in the knock determination means. And the knock determination permission means compares the divided peak value output means for dividing and outputting the peak value of the output of the pressure sensor, the output of the pressure sensor and the output of the divided peak value output means, and Comparing and determining means for allowing determination of knocking when the output of the sensor is higher than the output of the divided peak value output means,The divided peak value output means completely discharges the charge held in the capacitor with a peak hold circuit that charges the capacitor with a voltage corresponding to the output of the pressure sensor during one cycle of the internal combustion engine. A discharge circuit that discharges with a time constant set so as not to occur, and a voltage dividing circuit that takes in the voltage value of the capacitor through a buffer and outputs the divided voltageIt is characterized by that.
[0008]
As described above, in the present invention, the knock determination permission means for permitting the knock determination means to determine the knock based on the output of the signal processing means divides and outputs the peak value of the output of the pressure sensor by the divided peak value output means. Then, it is determined whether or not the output of the pressure sensor is higher than the output of the divided peak value output means in the comparison determination means, and the output of the pressure sensor is higher than the output of the divided peak value output means in this comparison determination means. Is determined, the knock determination means is allowed to determine knocking.
[0009]
This is because knocking occurs in the internal combustion engine during a specific period from the compression stroke to the combustion (explosion) stroke, during which the cylinder pressure also increases.
That is, in the present invention, the detection signal from the crank angle sensor (crank angle signal) is not used as in the prior art, but the detection signal from the pressure sensor for detecting knocking is used to detect the pressure sensor. The knock determination period is set from the pressure change in the cylinder.
[0010]
Therefore, according to the present invention, the knock determination means can be realized by using only the pressure sensor for knock detection without using the crank angle sensor and without using a special sensor for setting the knock determination period as in the prior art. A knock determination period for determining knocking can be set.
[0011]
In addition, the knock determination permission means only needs to divide the peak value of the output from the pressure sensor and compare it with the output from the pressure sensor, and shapes the output from the crank angle sensor as in the conventional case. Thus, it is not necessary to use a counter or a timing circuit including various gate circuits in order to count the number or generate a gate signal based on the count value.
[0012]
Therefore, the knocking detection device of the present invention can simplify the device configuration and reduce the manufacturing cost as compared with the conventional device.
As described above, according to the present invention, since it is not necessary to configure the knock determination permission means with a timing circuit composed of a counter or the like, even if pulsed noise enters from the outside, knocking is affected by the influence. The determination period does not fluctuate, and noise resistance can be improved as compared with the conventional apparatus.
[0013]
  Furthermore, according to the present invention, since it is not necessary to use a crank angle sensor as in the prior art, it can be easily applied to an internal combustion engine that does not include a crank angle sensor, and the versatility of the apparatus can be improved. it can.
  For this reason, for example, it is mounted on a racing vehicle such as a motorcycle not equipped with a crank angle sensor, and the number and frequency of knocking occurring in the internal combustion engine when the vehicle is running are measured. It can also be used for tuning internal combustion engines, such as adjusting the ignition timing.
In the present invention, the divided peak value output means includes a peak hold circuit that charges the capacitor with a voltage corresponding to the output of the pressure sensor, and the charge charged in the capacitor is completely transferred during one cycle of the internal combustion engine. It consists of a discharge circuit that discharges with a time constant set so as not to discharge, and a voltage dividing circuit that takes in the voltage value of the capacitor through a buffer and divides and outputs it. This is because the output from the engine constantly fluctuates according to the pressure change in the cylinder of the internal combustion engine.
That is, if the divided peak value output means is configured as in the present invention, the voltage of the capacitor charged and discharged by the peak hold circuit and the discharge circuit will change according to the peak of the output from the pressure sensor, In the voltage dividing circuit, a divided peak value corresponding to the peak value of the output from the pressure sensor can be obtained.
[0014]
Here, as a specific configuration for allowing the knock determination permission means to permit the knock determination by the knock determination means, for example, as described in claim 2, the comparison determination means provides a gate signal for permitting the knock determination. The output and the knock determination means may be configured to operate in response to the gate signal. If the knock determination permission means (more specifically, comparison determination means) and the knock determination means are configured in this way, execution / non-execution of the knock determination by the knock determination means can be easily switched by the gate signal.
[0015]
As a specific configuration for determining knocking by the knock determination means, for example, as described in claim 3, a knock determination threshold value is generated in the knock determination means based on the output of the signal processing means. When threshold value generating means is provided, and the output of the signal processing means is compared with the threshold value generated by the threshold value generating means, and knocking occurs when the output of the signal processing means is greater than the threshold value. It is good to comprise so that it may determine. That is, if the knock determination means is configured in this way, the threshold value for knock determination changes according to the output from the signal processing means, so that it is affected by fluctuations in the output level of the signal from the signal processing means. Without being able to make a knock determination, the accuracy of the knock determination can be improved.
[0017]
  The output from the pressure sensor includes other vibration components of the internal combustion engine and noise components input from the outside in addition to the signal component accompanying knocking generated in the internal combustion engine. as,Claim 4As described above, it is preferable that a frequency component peculiar to knocking generated in the internal combustion engine among the outputs of the pressure sensor is passed and output. That is, if the signal processing unit is configured in this way, only the signal component corresponding to the knocking generated in the internal combustion engine can be input to the knocking determination unit, and the knocking determination accuracy by the knocking determination unit can be improved.
[0018]
  Furthermore, in the present invention, in order to set the knock determination period from the pressure in the cylinder of the internal combustion engine, a pressure sensor that detects the pressure in the cylinder is used as a detection element for detecting knocking.Claim 5As described above, a washer-type piezoelectric element that is attached to the attachment portion of the spark plug to the internal combustion engine, and a charge amplifier that converts an output from the piezoelectric element into a voltage signal may be used. That is, such a washer-type pressure sensor can simultaneously detect vibration due to knocking of the internal combustion engine and the pressure in the cylinder, and does not need to be directly provided in the cylinder of the internal combustion engine. Since it is only necessary to sandwich the spark plug between the ignition plug and the internal combustion engine at the time of mounting, the mounting operation is extremely simple, so that the knocking detection device of the present invention can be easily realized.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a circuit diagram showing the overall configuration of a knocking detection apparatus according to an embodiment to which the present invention is applied.
[0020]
As shown in FIG. 1, the knocking detection apparatus of the present embodiment includes a detection element 2 made of a piezoelectric element that detects an in-cylinder pressure of an internal combustion engine (not shown). As shown in FIG. 2, the detection element 2 comprises a washer-type piezoelectric element that can be attached as a washer to the attachment portion of the ignition plug 3 to the internal combustion engine. When the ignition plug 3 is attached to the internal combustion engine, its attachment portion Thus, the electric charge corresponding to the vibration of the internal combustion engine and the pressure in the cylinder is generated between the spark plug 3 and the internal combustion engine.
[0021]
The output (charge) from the detection element 2 is converted by the charge amplifier 4 into a first detection signal S1 (see FIGS. 3 and 5) consisting of a voltage signal. The first detection signal S1 is input to the filter circuit 6 including a band pass filter or a high pass filter, and is also input to the gate signal generation circuit 10 serving as a knock determination permission unit.
[0022]
  The filter circuit 6 is provided in the present invention.Claim 4In the first detection signal S1 input through the charge amplifier 4, a frequency component peculiar to knocking generated in the internal combustion engine is passed. The second detection signal S2 (see FIG. 3) that has passed through the filter circuit 6 is input to the knock determination circuit 8 and also to the determination level setting circuit 20. The knock determination circuit 8 and the determination level setting circuit 20 function as knock determination means of the present invention (Claim 1), and the determination level setting circuit functions as threshold value generation means of the present invention (Claim 3). To do.
[0023]
Although not shown, knock determination circuit 8 compares second detection signal S2 input from filter circuit 6 with knock determination level Vth (in other words, a threshold value) input from determination level setting circuit 20. And a gate circuit that receives the gate signal Sg representing the knock determination period output from the gate signal generation circuit 10 and outputs the output from the comparator as the knock detection signal Sn representing the presence or absence of knocking. .
[0024]
For this reason, from the knock determination circuit 8 of the present embodiment, the second detection signal S2 exceeds the knock determination level Vth during the knock determination period in which the output from the gate signal generation circuit (gate signal Sg) is at the low level. At this time, a knock detection signal Sn indicating that knocking has occurred in the internal combustion engine is output.
[0025]
On the other hand, in the determination level setting circuit 20, the second detection signal S2 from the filter circuit 6 is input to the multiplexer 22 serving as a switching circuit. The multiplexer 22 inputs the second detection signal S2 input from the filter circuit 6 to the peak hold circuit 24 at the subsequent stage, or is input via a resistor R0 and a buffer circuit (comprising an operational amplifier OP1). This is for switching whether to input a voltage value Vc (refer to FIG. 3) of a peak hold capacitor (hereinafter simply referred to as a capacitor) C1, and operates by receiving a gate signal Sg from the gate signal generation circuit 10.
[0026]
That is, the multiplexer 22 inputs the voltage value Vc of the capacitor C1 to the subsequent peak hold circuit 24 during the knock determination period (see FIG. 3) in which the gate signal Sg from the gate signal generation circuit 10 is at a low level. When it is outside the knock determination period, the second detection signal S2 is input to the peak hold circuit 24 at the subsequent stage.
[0027]
The peak hold circuit 24 charges the capacitor C1 with the input signal from the multiplexer 22 (the second detection signal S2 or the voltage value Vc of the capacitor C1), thereby causing the capacitor C1 to have a background noise peak of the second detection signal S2. A signal having a positive potential with respect to the ground potential is obtained by charging a charge corresponding to the value, and by rectifying the input signal by a resistor R1 for signal input, an operational amplifier OP1 constituting a buffer circuit for signal input. It comprises a diode D1 that extracts only the component, and an operational amplifier OP1 and a charging resistor R2 that charges the capacitor C1 with an input signal that has passed through the diode D1.
[0028]
It should be noted that the resistance value of the charging resistor R2 does not form an integration circuit having a large time constant with the capacitor C1 (in other words, the capacitor C1 is charged with a charge corresponding to the peak value of the input signal). To be able to)) is set to a small value.
[0029]
The capacitor C1 is connected in parallel with a discharging resistor R3 that discharges the charge charged by the operation of the peak hold circuit 24 with a constant time constant determined by the capacitance of the capacitor C1 and its own resistance value. The voltage value Vc of the capacitor C1 is output to the multiplexer 22 via the resistor R0 and the operational amplifier OP0 (buffer circuit), and also to the integrating circuit 26 via the buffer circuit including the operational amplifier OP2 and the rectifying diode D2. Is input.
[0030]
The integration circuit 26 is a well-known circuit composed of a resistor R4 and a capacitor C2, and its time constant is set to a value larger than the discharge time constant when the resistor R3 discharges the electric charge accumulated in the capacitor C1. . Then, the integration value (voltage value of the capacitor C2) by the integration circuit 26 is input to an amplification circuit 28 as a correction circuit, amplified by the amplification circuit 28, and then knocked as a knock determination level Vth (see FIG. 3). It is output to the determination circuit 8.
[0031]
In addition, a resistor R5 having a large resistance value is connected in parallel to the charge storage capacitor C2 constituting the integrating circuit 26 in order to stabilize the input to the amplifier circuit 28. In addition, the amplification circuit 28 is provided with a gain adjustment circuit 30 for switching the amplification factor (gain) stepwise in a range of 1.2 to 1.5, for example, so that the gain can be adjusted. ing.
[0032]
Next, FIG. 4 is a circuit diagram illustrating a configuration of the gate signal generation circuit 10 that generates the gate signal Sg representing the knock determination period based on the first detection signal S1 input from the detection element 2 via the charge amplifier 4. is there.
As shown in FIG. 4, in the charge amplifier 4 of this embodiment, a capacitor C3 and a resistor R6 are connected in parallel between the inverting input terminal (−) and the output terminal, and the non-inverting input terminal (+) is connected to the ground line. By connecting the other end of the detection element (piezoelectric element) 2 with one end connected to the inverting input terminal (−) of the operational amplifier OP3, the operational amplifier OP3 is installed. Accordingly, the electric charge generated by the detection element 2 is converted into a voltage signal (first detection signal) S1. The charge amplifier 4 functions as a pressure sensor that detects the pressure in the cylinder of the internal combustion engine together with the detection element 2 formed of a washer-type piezoelectric element.
[0033]
In the gate signal generation circuit 10, the first detection signal S1 from the charge amplifier 4 is input to the peak hold circuit 12 and the comparator CMP, which is a comparison circuit.
The peak hold circuit 12 charges the capacitor C10 with a charge corresponding to the peak value of the first detection signal S1 by charging the capacitor C10 with the first detection signal S1, and serves as a buffer circuit for signal input. A functioning operational amplifier OP10, a diode D10 that extracts only a signal component having a positive potential from the ground potential of the first detection signal S1 by rectifying the first detection signal S1, and a capacitor by a signal that has passed through the operational amplifier OP10 and the diode D10. It is comprised from the resistance R10 for charge which charges C10. The capacitor C10 is connected in parallel with a discharging resistor R11 for discharging the charge charged by the operation of the peak hold circuit 12 with a constant time constant determined by the capacitance of the capacitor C10 and its own resistance value.
[0034]
The resistance value of the charging resistor R10 does not form an integrating circuit having a large time constant with the capacitor C10, like the resistor R2 in the peak hold circuit 24 in the determination level setting circuit 20 (in other words, In this case, the capacitor C10 is set to a small value (in order to charge the capacitor C10 with a charge corresponding to the peak value of the first detection signal S1).
[0035]
As a result, the voltage value Vd, which is the voltage across the capacitor C10, increases as the signal level of the first detection signal S1 increases as the in-cylinder pressure of the internal combustion engine increases, as shown in FIG. Thereafter, when the signal level of the first detection signal decreases, the first detection signal is attenuated with a constant slope by a time constant determined by the capacitance of the capacitor C10 and the discharge resistor R11. The time constant at the time of discharging does not discharge the capacitor C10 from the peak of the first detection signal S1 to the next peak (in other words, during one cycle of the internal combustion engine). It is set to a sufficiently large value.
[0036]
Thus, the voltage value Vd of the capacitor C10 that changes in accordance with the maximum value (peak) of the first detection signal S1 is input to the voltage dividing circuit including the resistors R12 and R13 through the buffer circuit including the operational amplifier OP11. The voltage is divided by a divided voltage value (R13 / (R12 + R13)) determined by the resistance values of these resistors R12 and R13, and is lower than the original voltage value Vd by a certain ratio (divided voltage value) as shown in FIG. It is converted into a voltage value Vg (= Vd × R13 / (R12 + R13)). The divided voltage value Vg is input to the non-inverting input terminal of the comparator CMP as a reference value for setting the knock determination period, and the first detection signal S1 input to the inverting input terminal by the comparator CMP. Compared with large and small.
[0037]
As a result, the gate signal Sg output from the comparator CMP becomes a high level when the voltage value Vg, which is a reference value for setting the knock determination period, is larger than the first detection signal S1, as shown in FIG. When Vg becomes equal to or lower than the first detection signal S1, it becomes a low level (knock determination period).
[0038]
  In this embodiment, the peak hold circuit 12 provided on the path from the charge amplifier 4 to the non-inverting input terminal of the comparator CMP among the above-described units constituting the gate signal generation circuit 10 as the knock determination permission means, The resistors R11 to R13 and the operational amplifier 11 function as divided peak value output means of the present invention (Claim 1), and the comparator CMP functions as comparison determination means of the present invention (Claim 1). In addition, the peak hold circuit 12, the resistors R11 to R13, and the operational amplifier 11 which function as the divided peak value output unit in this way, the resistor R11 is the present invention (Claim 1), And the operational amplifier 11 and the resistors R12 and R13Claim 1) Function as a voltage divider circuit.
[0039]
As described above, in the knock detection device according to the present embodiment, the knock determination period is expressed based on the output signal (first detection signal S1) from the charge amplifier 4 functioning as the output circuit of the pressure sensor for knock detection. A gate signal Vg is generated.
[0040]
For this reason, according to the present embodiment, the pressure sensor (detecting element 2+) for detecting knocking can be used without using a crank angle sensor and without using a special sensor for setting the knock determination period as in the conventional device. Only the charge amplifier 4) can set the knock determination period and perform the knock determination.
[0041]
Further, the gate signal generation circuit 10 for setting the knock determination period can be constituted by a simple analog circuit using an operational amplifier or the like, and the output from the crank angle sensor is waveform-shaped as before, and the number is counted. In addition, since it is not necessary to use a timing circuit composed of a counter and various gate circuits in order to generate a gate signal based on the count value, the circuit configuration can be simplified.
[0042]
In addition, since there is no need to use a timing circuit consisting of a counter or the like as in the conventional apparatus, even if pulsed noise enters the circuit, the knock determination period does not fluctuate due to the influence. Compared to conventional devices, noise resistance can be improved.
[0043]
Therefore, the knocking detection apparatus of the present embodiment can simplify the apparatus configuration and reduce the manufacturing cost as compared with the conventional apparatus.
In addition, since the knocking detection device of the present embodiment does not require the use of a crank angle sensor for setting the knock determination period, it can be easily applied to an internal combustion engine that does not include a crank angle sensor. Versatility can be improved.
[0044]
For this reason, for example, it is mounted on a racing vehicle such as a motorcycle not equipped with a crank angle sensor, and the number and frequency of knocking occurring in the internal combustion engine when the vehicle is running are measured. It can also be used for tuning internal combustion engines, such as adjusting the ignition timing.
[0045]
Specifically, for example, if the knock detection device of the present embodiment is provided with a counter having a display function of a count value, the number of outputs of the knock detection signal Sn from the knock determination circuit 8 can be counted and displayed. Since the number of occurrences of knocking during traveling of the vehicle can be known, it can be an extremely convenient device when tuning the ignition timing of a racing vehicle on the racetrack.
[0046]
Further, according to the knocking detection device of the present embodiment, if the rising (or falling) edge of the gate signal Sg output from the gate signal generation circuit 10 is counted, the number of rotations of the internal combustion engine after the count is started can be known. Therefore, if the number of rotations and the number of occurrences of knocking are respectively counted by a counter, the frequency of occurrence of knocking can be obtained from each count value, and the tuning operation of the internal combustion engine can be performed. It can be performed more efficiently.
[0047]
Further, according to the knocking detection device of the present embodiment, if the rising (or falling) edge of the gate signal Sg is counted per unit time, the rotational speed of the internal combustion engine can be obtained from the count value. Further, the cylinder pressure can be known from the output from the charge amplifier 4 (first detection signal S1). Therefore, if the knocking detection device of the present embodiment is used, it is possible to sample the in-cylinder pressure for each rotation speed of the internal combustion engine, or sample the number of occurrences and frequency of knocking for each rotation speed.
[0048]
On the other hand, in the knocking detection device of the present embodiment, when the determination level setting circuit 20 generates the knock determination level Vth, first, during the period excluding the knock determination period, the peak hold circuit 24 performs the second detection signal S2. In addition to charging the capacitor C1 with a charge corresponding to the peak value of the capacitor, and discharging the charged charge with a constant time constant, the voltage value Vc of the capacitor C1 is set to a value other than the knock determination period of the vibration component of the internal combustion engine. The voltage is controlled to a voltage value corresponding to the peak value of the background noise generated during the period (see FIG. 2). The voltage value Vc is further integrated by the integrating circuit 26, and the signal after the integration processing is further amplified by the amplifier circuit 28, thereby setting the knock determination level Vth (see FIG. 2).
[0049]
Therefore, according to the knocking detection device of the present embodiment, the knock determination level (threshold value) Vth can be made to correspond to the background noise (vibration caused by valve seating) superimposed on the second detection signal S2. As compared with the case where the knock determination level Vth is generated by simply integrating the second detection signal S2, the knock determination by the knock determination circuit 8 can be performed with high accuracy and the detection sensitivity can be lowered. It will be possible to perform well.
[0050]
That is, in the conventional apparatus, when setting the knock determination level Vth, usually, the detection signal (second detection signal S2) is integrated, and an offset value is added to the value after the integration processing, or the integration processing is performed. The knock determination level Vth is set by amplifying the subsequent signal. However, in this case, the knock determination level cannot be made to correspond to the background noise of the detection signal (second detection signal S2). The detection accuracy of knocking may be reduced due to noise.
[0051]
However, in this embodiment, since the knock determination level Vth can be made to correspond to the background noise of the second detection signal as described above, the knocking detection accuracy can be increased.
[Brief description of the drawings]
FIG. 1 is a circuit diagram illustrating a configuration of an entire knocking detection apparatus according to an embodiment.
FIG. 2 is an explanatory diagram illustrating a state in which a detection element is attached to a spark plug.
FIG. 3 is a time chart showing the operation of a knock determination level setting circuit.
FIG. 4 is a circuit diagram illustrating a configuration of a gate signal generation circuit.
FIG. 5 is a time chart showing the operation of the gate signal generation circuit.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 2 ... Detection element, 3 ... Spark plug, 4 ... Charge amplifier, 6 ... Filter circuit, 8 ... Knock determination circuit, 10 ... Gate signal generation circuit, 12 ... Peak hold circuit, 20 ... Determination level setting circuit, C10 ... Capacitor, CMP: Comparator, R11, R12, R13 ... Resistance.

Claims (5)

A pressure sensor for detecting the pressure in the cylinder of the internal combustion engine;
Signal processing means for signal processing the output of the pressure sensor;
Knock determination means for determining that knocking has occurred in the internal combustion engine based on the output of the signal processing means;
A knock detection device for an internal combustion engine comprising knock determination permission means for permitting determination of knocking in the knock determination means,
The knock determination permission means includes:
Divided peak value output means for dividing and outputting the peak value of the output of the pressure sensor;
Comparing and determining means for comparing the output of the pressure sensor and the output of the divided peak value output means, and allowing the determination of knocking when the output of the pressure sensor is higher than the output of the divided peak value output means. Yes, and
The divided peak value output means includes:
A peak hold circuit that charges the capacitor with a voltage according to the output of the pressure sensor;
A discharge circuit that discharges the electric charge charged in the capacitor with a time constant set so as not to be completely discharged during one cycle of the internal combustion engine;
A knocking detecting device for an internal combustion engine, comprising: a voltage dividing circuit that takes in the voltage value of the capacitor through a buffer and divides and outputs the voltage .   2. The knock detection device for an internal combustion engine according to claim 1, wherein the comparison determination unit outputs a gate signal that permits determination of knocking, and the knock determination unit operates in response to the gate signal. The knock determination means includes
Based on the output of the signal processing means, comprising threshold generation means for generating a threshold for knock determination,
The output of the signal processing means is compared with the threshold value, and it is determined that knocking has occurred when the output of the signal processing means is greater than the threshold value. The knocking detection device for an internal combustion engine according to claim.   2. The knock detection device for an internal combustion engine according to claim 1, wherein the signal processing means passes and outputs a frequency component peculiar to knocking generated in the internal combustion engine among the outputs of the pressure sensor.   2. The pressure sensor comprises a washer-type piezoelectric element attached to a mounting portion of an ignition plug to an internal combustion engine, and a charge amplifier that converts an output from the piezoelectric element into a voltage signal. The knocking detection device for an internal combustion engine according to claim.

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