JP2003004573A - Device for detecting background level - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for detecting background level which employs a DC power source low in cost and can prevent deterioration of the accuracy of detecting a background level in detecting the background level becoming a noise when the signal detection is carried out. SOLUTION: An internal combustion engine controller 1 includes a CPU 3, a peak hold circuit 5 and a device for detecting background level 11, and carries out the detection of knocking. The device for detecting background level 11 employs operational amplifiers (IC1-IC5) applied with a supply voltage in the range of 0 V to 5 V, carries out a process of full-wave rectification or the like using an offset potential BL as reference applied to an offset potential line VMM, and thereby detects the background level. Therefore, the device for detecting background level 11 can prevent deterioration in the accuracy of detecting the background level even in the case the DC power source is made up as a structure of single power source at a low cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention, when detecting a specific frequency component from the output of a piezoelectric sensor provided in an internal combustion engine, has the same frequency band as the specific frequency component among the noise components superimposed on the output. The present invention relates to a background level detection device that detects a background level corresponding to a signal level.

[0002]

2. Description of the Related Art In an internal combustion engine, the temperature in the combustion chamber may become overheated, for example, when the operation at high rotation and high load continues for a long time. If a part of the mixture becomes overheated, unburned gas (end gas) in the air-fuel mixture may self-ignite due to this overheated portion in the combustion process, resulting in knocking. When such knocking occurs, problems such as a reduction in output of the engine and a reduction in fuel consumption are caused, and when the knocking is severe, the engine burns and is damaged. Therefore, in order to avoid such a problem caused by knocking, it is important to detect the occurrence of knocking with high accuracy, and conventionally, an internal combustion engine equipped with a knocking detection device for detecting the occurrence of knocking is known.

Such a knocking detection device is generally
A knock sensor for detecting the mechanical vibration of the internal combustion engine, or a piezoelectric sensor such as a pressure sensor for detecting the cylinder pressure in the combustion chamber is attached to the internal combustion engine, and the output from this sensor is converted into a voltage signal. It is configured to determine whether or not knocking occurs by determining whether or not the voltage signal includes a frequency component unique to knocking. That is, in such a knocking detection device, the frequency component is extracted by passing the output from the piezoelectric sensor through a frequency circuit specific to knocking through a filter circuit (filter processing unit).

However, in such a knocking detection device, when the frequency component peculiar to knocking is extracted from the output of the knock sensor or the pressure sensor, the vibration of the engine itself due to the operation and the seating noise due to the opening / closing of the intake / exhaust valve. A noise component generated due to factors other than knocking, such as a noise component in the same frequency band as knocking (hereinafter referred to as background component), is also extracted. As described above, when the frequency component unique to knocking is extracted, if the background component is extracted (superposed), it may be determined that knocking has occurred even if knocking has not occurred. The detection accuracy of detection will be reduced. Therefore, in order to suppress a decrease in knocking detection accuracy, it is necessary to remove the signal level of the background component from the extracted frequency component, identify the frequency component generated by knocking, and then perform knocking determination.

Therefore, a knocking detection device is equipped with
Background Art A device for detecting a signal level of a background component (hereinafter referred to as a background level) is a background level detecting device. This background level detection device first converts the output of a piezoelectric sensor such as a knock sensor or a pressure sensor into a voltage signal, passes this voltage signal through a filter processing unit, and performs filter processing to obtain the same frequency band as knocking. Extract background components. Then, the extracted background component is rectified by the full-wave rectification processing unit to detect the background level which is the signal level of the background component.
The background level detection device can detect the background level only during a period in which knocking does not occur (specifically, a predetermined period from the closing of the intake valve to the ignition timing).

[0006]

The filter processing unit and the full-wave rectification processing unit of the background level detection device are generally configured by including an operational amplifier, and the filter processing unit includes a resistance element, a capacitor, and the like. The full-wave rectification processing unit is configured to include a diode and the like. In addition, the filter processing unit and the full-wave rectification processing unit configured by the operational amplifier and the resistance element in this way are
By operating with the reference potential as a reference, signal processing (such as full-wave rectification processing) is performed on the input output. Generally, the reference potential is the negative potential of the DC power supply (for example,
The ground potential (0 [V]) is set.

The frequency component extracted from the voltage signal by the filtering process may have a lower potential than the reference potential because it fluctuates around the reference potential, and at least at a portion corresponding to the signal after passing through the filtering unit. The potential may be lower than the reference potential. Therefore, the operational amplifier provided in the filter processing unit and the full-wave rectification processing unit needs to output an output signal having a potential lower than the reference potential, and this operational amplifier has a potential higher than the reference potential. In addition to the power supply voltage, it is necessary to apply a power supply voltage having a lower potential than the reference potential. That is, the reference potential of the filter processing unit and the full-wave rectification processing unit is the ground potential (0
[V]), the power source voltage of both positive and negative potentials (for example, ±
5 [V]) must be applied to operate the operational amplifier.

On the other hand, a device driven by a voltage supply such as a knocking detection device provided in an automobile or the like is generally operated by a voltage supply from a single battery (DC power supply device) and has a reference potential of 0 [. Many are set to V]. Therefore, in order to apply a power supply voltage of both positive and negative potentials to the arithmetic processing unit that constitutes the filter processing unit and the full-wave rectification processing unit of the background level detection device, a DC-DC converter or the like is separately provided, 0 [V]
It is necessary to generate the following negative potential power supply voltage. As described above, when the DC power supply device for supplying a voltage to each part of the internal combustion engine is configured to be capable of supplying a power supply voltage of both positive and negative potentials (hereinafter referred to as a dual power supply configuration), a power supply voltage of a negative potential is generated. There is a problem in that the cost increases as much as a device (DC-DC converter or the like) is required.

Even when a direct-current power supply device having a structure capable of supplying only positive-potential power supply voltage (hereinafter referred to as a single power supply structure) is used instead of a direct-current power supply device having a dual power supply structure, the operational amplifier has at least the reference potential. Since a higher potential output signal can be output, it is possible to detect the background level by performing half-wave rectification after filtering the output from the piezoelectric sensor. However, when the background level is detected by half-wave rectification, it is difficult to perform accurate detection because the background level is detected without the signal waveform in the period when the signal is lower than the reference potential. is there. Therefore, in order to accurately detect the background level, it is desirable to detect based on the entire waveform of the signal, and it is desirable to detect the background level by full-wave rectification instead of half-wave rectification.

In addition, when the output variation due to the individual difference of the piezoelectric type sensor is corrected, and / or the output change due to the change over time of the piezoelectric type sensor is corrected, the knocking or the misfire is also determined. It is considered to use the background level at the time of correction, and it is effective to accurately detect the background level.

The present invention has been made in view of these problems, and in detecting the background level,
An object of the present invention is to provide a background level detection device that can configure a DC power supply device at low cost and prevent a decrease in background level detection accuracy.

[0012]

The invention according to claim 1 made in order to achieve the above object, when a specific frequency component is detected from the output of the piezoelectric type sensor provided in the internal combustion engine, is output to this output. A background level detection device for detecting a background level, which is a signal level in the same frequency band as the specific frequency component among the superimposed noise components, wherein the voltage conversion processing unit converts the output of the piezoelectric sensor into a voltage signal. And a full-wave rectification processing unit for full-wave rectifying the specific frequency component from the voltage signal, and a full-wave rectification processing unit for full-wave rectifying the specific frequency component. The operational amplifier includes an amplifier, which is the first of the pair of terminals that receives the power supply voltage from the DC power supply device.
The positive potential of the DC power supply is applied to the terminal and the negative potential of the DC power supply is applied to the second terminal to supply the power supply voltage, and the reference potential in the filter processing unit and the full-wave rectification processing unit. Is set to an offset potential that is an intermediate potential between the positive electrode potential and the negative electrode potential of the DC power supply device, and the signals input to the operational amplifiers of the filter processing unit and the full-wave rectification processing unit are centered around the offset potential. The output is within a range from the potential applied to the first terminal to the potential applied to the second terminal of the operational amplifier.

That is, when the reference potential in the filter processing unit and the full-wave rectification processing unit is set to an offset potential higher than the negative potential of the DC power supply device, the inside of the filter processing unit and the full-wave rectification processing unit is set. The signal processing (filtering processing, full-wave rectification processing) related to the voltage signal from the input piezoelectric sensor is executed with the offset potential higher than the negative potential of the DC power supply device as a reference.

On the other hand, in this operational amplifier provided in each of the filter processing section and the full-wave rectification processing section, the positive potential of the DC power supply device is applied to the first terminal (plus side power supply input terminal) and the second terminal (minus side). Since the negative electrode potential of the DC power supply device is applied to the side power supply input terminal), the signal input to each operational amplifier can be output within the range from the positive electrode potential to the negative electrode potential of the DC power supply device.

From these facts, in the filter processing section and the full-wave rectification processing section of the background level detecting apparatus, the signals input to the respective operational amplifiers are centered on the offset potential and the first terminal of the operational amplifier is provided. Output is possible within the range from the potential applied to the second terminal to the potential applied to the second terminal. As a result, if the signal (voltage signal or signal of specific frequency component) input to the operational amplifier provided in these processing units is higher in potential than the negative potential of the DC power supply device, the signal is higher than the reference potential (offset potential). It is possible to detect the signal waveform even at a low potential. In other words, since it is possible to detect the signal waveform during the period when the potential is lower than the reference potential, the signal waveform based on a wider range of signal waveforms is compared with the case where half-wave rectification is performed using the negative potential of the DC power supply device as the reference potential. It becomes possible to carry out the processing.

At this time, the offset potential does not have to be limited to the average value of the positive electrode potential and the negative electrode potential of the DC power supply device. That is, it is possible to extract the entire waveform of the signal generated as a result of performing the filtering process and the full-wave rectification process on the voltage signal obtained from the piezoelectric sensor through the voltage conversion process unit by the filtering process unit and the full-wave rectification process unit. In consideration of the range of the power supply voltage output from the DC power supply device (range from the positive electrode potential to the negative electrode potential), the offset potential serving as the reference potential of the filter processing unit and the full-wave rectification processing unit may be set. As a result, the DC power supply device that supplies voltage to the operational amplifier can output only the power supply voltage of positive potential (hereinafter referred to as a single power supply structure).
However, since the entire waveform of the signal can be extracted, full-wave rectification processing can be performed. That is, in order to perform the full-wave rectification process, it is not necessary to configure the DC power supply device that supplies a voltage to the operational amplifier with a configuration capable of supplying both positive and negative power supply voltages (hereinafter, referred to as a dual power supply configuration).

Therefore, the full-wave rectification process can be performed even when the DC power supply device in the background level detecting device is not the expensive DC power supply device having the dual power supply structure but the inexpensive DC power supply device having the single power supply structure. This makes it possible to detect the background level with high accuracy even when the DC power supply device is constructed at low cost.

Therefore, according to the background level detecting device of the present invention (claim 1), the DC power supply device is constituted by a single power source, so that the cost is low, and the detection accuracy in detecting the background level is high. Can be prevented from decreasing. By the way, regarding the configuration of the voltage conversion processing unit that converts the output of the piezoelectric sensor into a voltage signal,
There is no particular limitation as long as it can be converted into a voltage signal that can be output to the filter processing unit. However, when the voltage conversion processing unit includes at least an operational amplifier like the filter processing unit and the full-wave rectification processing unit, as described in claim 2,
The voltage conversion processing unit includes a second operational amplifier and a feedback capacitor that connects the inverting input terminal and the output terminal of the second operational amplifier, and the second operational amplifier is driven by the supply of the power supply voltage in the DC power supply device. It is preferable that the reference potential set to the non-inverting input terminal of the second operational amplifier is set to the offset potential, while the inverting input terminal is connected to the piezoelectric sensor.

As a result, the DC power supply device for supplying the voltage to the second operational amplifier can output only the power supply voltage of positive potential similar to the above-mentioned filter processing section and full-wave rectification processing section (single power supply configuration). ), The output from the piezoelectric sensor input to the second operational amplifier can be converted into a voltage signal in both positive and negative directions centering on the offset voltage in the voltage conversion processing unit. As a result, the voltage signal output from the voltage conversion processing unit including the second operational amplifier is extracted from the entire waveform of the signal even when passing through the filter processing unit, and thus the full-wave rectification processing unit performs full-wave extraction. Rectification processing becomes possible.

Therefore, when the voltage conversion processing unit is configured to include an operational amplifier (second operational amplifier), by configuring the voltage conversion processing unit as described above (claim 2), the operational amplifier is The DC power supply for operation can have a low-cost single power supply configuration, and further, while using the DC power supply with the single power supply configuration, it is combined with the configuration of the filter processing unit and the full-wave rectification processing unit described above. Even if
Full-wave rectification can be performed on the signal in the piezoelectric sensor, and the background level can be detected with high accuracy.

As the piezoelectric type sensor in the background level detecting apparatus according to the second aspect of the present invention, in which the voltage conversion processing section using the second operational amplifier is used, the piezoelectric element may be a piezoelectric element. A plug washer that is configured to be built-in and that is provided at a mounting seat of an ignition plug that is installed in an internal combustion engine and that detects a cylinder pressure of the internal combustion engine by detecting a change in a tightening load of the ignition plug. As a pressure sensor, it has a high effect.

The reason is that the plug washer pressure sensor having a built-in piezoelectric element has a structure for outputting electric charge according to a change in the load applied to the piezoelectric element. This is because, by using the voltage conversion processing unit including, it is possible to favorably output (change to the filter processing unit) a change in the amount of charge detected by the piezoelectric element as a voltage change.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 1 shows a block diagram of an internal combustion engine control device 1 including a background level detection device 11 of the present embodiment. The internal combustion engine control device 1 is provided in an internal combustion engine provided with a DC power supply device having a configuration capable of supplying only a positive potential power supply voltage (hereinafter referred to as a single power supply configuration), and the background level detection device 11 Is supplied with only a positive potential power supply voltage.

As shown in FIG. 1, the internal combustion engine controller 1 comprises a central processing unit 3 (hereinafter also referred to as a CPU), a peak hold circuit 5, and a background level detector 11. . The background level detection device 11 includes a voltage conversion processing unit 13 and
The filter processing unit 7 and the full-wave rectification processing unit 19 are included.

First, the CPU 3 is composed of a semiconductor integrated circuit and executes a control process for comprehensively controlling the ignition timing, the idle rotation speed and the like of the internal combustion engine. Then, the CPU 3 performs knocking detection processing for detecting knocking caused by self-ignition of the air-fuel mixture due to temperature rise in the combustion chamber of the internal combustion engine, based on signals from the peak hold circuit 5 and the background level detection device 11. Is running.

When this knocking detection process is executed, the peak hold circuit 5 performs a fixed period (peak value detection period) after the piston of the cylinder, which is the period in which knocking occurs, reaches the top dead center (TDC). After detecting and holding the peak value of the signal output from the filter processing unit 7 described later, and performing A / D conversion on the held peak value (A / D converter is not shown), the peak value signal Sp Is output to the CPU 3. The peak hold circuit 5 deletes the held peak value immediately before the start time of the peak value detection period based on a command signal (not shown in FIG. 1) from the CPU 3, and then the peak CPU for peak value detection during value detection period
It is started based on the command signal from 3.

Further, the background level detecting device 11
Is the average value of the signal level (amplitude) output from the full-wave rectification processing unit 19 within a certain period (BGL detection period) before the piston of the cylinder, which is the period in which knocking does not occur, reaches the top dead center (TDC). Is calculated and held by an average value processing unit (not shown), and after the held average value is A / D converted (A / D converter is not shown), it is output to the CPU 3 as a background level signal Sb. Perform processing. The background level detection device 1
No. 1 is always operating, and the CPU 3 performs a process of reading the background level signal Sb at an arbitrary timing within the BGL detection period. Then, in the knocking detection processing, a value obtained by removing the background level signal Sb from the peak value signal Sp is calculated as a knocking detection value, and knocking occurs when the calculated knocking detection value becomes larger than the determination value for knocking determination. The process of determining that it has been performed is performed.

In addition to the knocking detection process, the CPU 3 performs, for example, an ignition timing control process for setting an ignition timing according to an operating state, or a spark discharge to an ignition plug at an ignition timing set in the ignition timing control process. Ignition control processing for generating the engine, operating state detection processing for detecting the operating state of the engine based on detection signals of sensors provided in various parts of the engine, and fuel control processing for setting the fuel supply amount based on the detected operating state And so on. Also, CPU3
Inputs and outputs signals not only with the background level detection device 11 and the peak hold circuit 5 shown in FIG. 1 but also with other sensors, actuators, and the like.

In the peak value detection period set by the CPU 3 as described above, the in-cylinder pressure signal Si output from the plug washer pressure sensor GPS is converted to the voltage used in common with the background level detecting device 11. The voltage signal that has passed through the processing unit 13 is converted, and the voltage signal thus converted into voltage is used in common with the background level detecting device 11 (the filter processing unit 7).
Is composed of a combination of a high-pass filter processing unit 15 and a low-pass filter processing unit 17, as will be described later, and a band-pass filter (for example, 6 [kHz] to 10 [kHz]
z) degree)) and a vibration frequency component (hereinafter referred to as a knocking signal) peculiar to knocking is extracted. Next, the peak value of the extracted knocking signal is held by the peak hold circuit 5, and as a result, the maximum value (peak value) of the knocking signal is detected. Then, the peak value of the detected knocking signal is output to the CPU 3 as a peak value signal Sp.

The plug washer pressure sensor GPS is
The piezoelectric element is built in, one end is grounded, and the other end is connected to the voltage conversion processing unit 13. Although not shown, the plug washer pressure sensor GPS is sandwiched between a spark plug (more specifically, a mounting seat of a metal shell forming the spark plug) and a cylinder head of an internal combustion engine. , (Fixed) to the cylinder head in the state where the initial load due to the tightening load of the spark plug is given. Then, when combustion / explosion of the air-fuel mixture occurs in the combustion chamber, the ignition plug itself is pushed up from the combustion chamber side by the pressure (cylinder pressure) generated by the combustion, so the load applied to the piezoelectric element changes from the initial load. As the load changes, the electric signal (electric charge) output from the piezoelectric element changes, so that the plug washer pressure sensor GPS detects the electric signal (in-cylinder pressure signal Si in accordance with the in-cylinder pressure in the cylinder). ) Is output.

The background level detecting device 1
In the noise component superimposed on the in-cylinder pressure signal Si output from the plug washer pressure sensor GPS, a signal in the same frequency band as the knocking signal (hereinafter referred to as a background signal) passed through the voltage conversion processing unit 13. The signal level of the background signal extracted by the subsequent filter processing unit 7 is detected via the full-wave rectification processing unit 19. Then, the detected signal level is set to the background level signal S
It is output to the CPU 3 as b.

Here, the background level detecting device 1
The circuit diagram of No. 1 is shown in FIG. As shown in FIG. 2, the background level detection device 11 includes a voltage conversion processing unit 13,
The high-pass filter processing unit 15, the low-pass filter processing unit 17, and the full-wave rectification processing unit 19 are provided. Also,
Voltage conversion processing unit 1 of background level detection device 11
3, operational amplifiers IC1, IC2, IC3, IC4, IC5 provided in each of the high-pass filter processing unit 15, the low-pass filter processing unit 17, and the full-wave rectification processing unit 19.
Of the pair of terminals that receive the power supply voltage from the DC power supply device, the positive electrode potential (5 [V]) of the DC power supply device is applied to the first terminal, and the negative electrode potential of the DC power supply device (5 [V]) is applied to the second terminal. The ground potential (0 [V]) is applied. The filter processing unit 7 is configured by combining the high-pass filter processing unit 15 and the low-pass filter processing unit 17.

The voltage conversion processing unit 13 is mainly composed of the first operational amplifier IC1, and the non-inverting input terminal (+) of the first operational amplifier IC1 has a positive potential and a negative potential of the DC power supply device. Offset potential BL which is the intermediate potential of
Is connected to the offset potential line VMM to which is applied, and the inverting input terminal (−) of the first operational amplifier IC1 is connected to the input terminal T1 of the background level detection device 11 via the series circuit of the capacitor C2 and the resistor R1. Connected,
The output terminal of the first operational amplifier IC1 is a capacitor C3.
It is connected to the inverting input terminal (−) of the first operational amplifier IC1 via a parallel circuit of (feedback capacitor) and the resistor R2, and is also connected to the offset potential line VMM via the capacitor C4 and the resistor R3.

The offset potential BL is a potential between the positive potential (5 [V]) of the DC power supply and the negative potential (ground potential (0 [V]) of the DC power supply as described above. Is set. The voltage conversion processing unit 13 configured as described above serves as an inverting amplifier circuit that voltage-converts and amplifies the signal (specifically, the cylinder pressure signal Si) input from the input terminal T1 with the offset potential BL as a reference. Operate.

The high-pass filter processing section 15 is mainly composed of the second operational amplifier IC2, and the non-inverting input terminal (+) of the second operational amplifier IC2 is applied with the offset potential BL via the resistor R5. Is connected to the offset potential line VMM via the capacitor C6, the capacitor C5 and the resistor R4, and the inverting input terminal (−) of the second operational amplifier IC2 is connected via the resistor R6. It is connected to the offset potential line VMM and is also connected to the second via the resistor R8.
It is connected to the output terminal of the operational amplifier IC2, the output terminal of the second operational amplifier IC2 is connected to the non-inverting input terminal (+) of the second operational amplifier IC2 via the resistor R7 and the capacitor C6, and the resistor R9 is connected to the non-inverting input terminal (+). It is connected to the offset potential line VMM via. The connection point between the capacitor C5 and the resistor R4 in the high pass filter processing unit 15 is connected to the connection point between the resistor R3 and the capacitor C4 in the voltage conversion processing unit 13.

The high-pass filter processing unit 15 thus configured operates to extract the high frequency band component from the signal output from the voltage conversion processing unit 13. Next, the low-pass filter processing unit 17 is mainly configured by the third operational amplifier IC3, and the non-inverting input terminal (+) of the third operational amplifier IC3 is applied with the offset potential BL via the capacitor C7. It is connected to the offset potential line VMM and is also connected to the output terminal of the second operational amplifier IC2 via the resistors R11 and R10, and the inverting input terminal (−) of the third operational amplifier IC3 is offset via the resistor R13. It is connected to the potential line VMM and is also connected to the output terminal of the third operational amplifier IC3 via the resistor R14, and the output terminal of the third operational amplifier IC3 is connected to the third operational amplifier IC via the capacitor C8 and the resistor R11.
3 is connected to the non-inverting input terminal (+) and is also connected to the offset potential line VMM via the resistor R15.

The low-pass filter processing unit 17 thus configured operates so as to extract the low frequency band component from the signal output from the high-pass filter processing unit 15.
The high-pass filter processing unit 15 and the low-pass filter processing unit 17 extract the vibration frequency component specific to knocking from the signal output from the voltage conversion processing unit 13. Then, the signals extracted by the high-pass filter processing unit 15 and the low-pass filter processing unit 17 have a waveform that fluctuates around the offset potential BL,
For example, the waveform is as shown in FIG. Note that FIG.
In the above, the offset potential BL is described as an offset potential, and the ground potential (0 [V]) is described as GND.

Further, the full-wave rectification processing unit 19 is mainly composed of the fourth operational amplifier IC4 and the fifth operational amplifier IC5, and the non-inverting input terminal (+) of the fourth operational amplifier IC4 has a resistor R17. Is connected to the output terminal of the third operational amplifier IC3 via the resistor R16 and the inverting input terminal (−) of the fourth operational amplifier IC4 is connected to the offset potential BL.
Is connected to the offset potential line VMM to which is applied, and the output terminal of the fourth operational amplifier IC4 is connected to the diode D.
3 and a diode D4 in parallel, and a resistor R1
9 and a parallel circuit including a resistor R20 and a non-inverting input terminal (+) of the fourth operational amplifier IC4, and an offset potential line VMM via a resistor R22.
It is connected to the. The cathode of the diode D3 is connected to the output terminal of the fourth operational amplifier IC4,
The anode of the diode D4 is connected to the output terminal of the fourth operational amplifier IC4.

Further, in the full-wave rectification processing section 19, the non-inverting input terminal (+) of the fifth operational amplifier IC5 is connected to the offset potential line VMM via the resistor R24, and the inverting input terminal of the fifth operational amplifier IC5. (-) Is the diode D
3 and the resistor R23 to be connected to the output terminal of the fourth operational amplifier IC4, and also to the output terminal of the third operational amplifier IC3 via the resistor R21 to provide the fifth operational amplifier I4.
The output terminal of C5 is connected to the inverting input terminal (-) of the fifth operational amplifier IC5 via the resistor R25, is connected to the offset potential line VMM via the resistor R26, and is further connected to the background level detecting device 11 Of the output terminal T2.

Further, in the full-wave rectification processing section 19, the resistance R
Of the end portions of 17, the end portion on the output terminal side of the third operational amplifier IC3 is connected to the + 5V power supply line via the diode D1 and is connected to the ground line (0 [V]) via the diode D2. It is connected (grounded). The diode D1 has an anode connected to the resistor R17 and a cathode connected to a + 5V power supply line.
The diode D2 has an anode connected to the ground line and a cathode connected to the resistor R17. By thus providing the diode D1 and the diode D2, the signal input to the full-wave rectification processing unit 19 is 0
It will be limited within the range of [V] to 5 [V].

The full-wave rectification processing unit 19 thus configured
Performs a full-wave rectification process on the signals extracted by the high-pass filter processing unit 15 and the low-pass filter processing unit 17 with the offset potential BL as a reference. And
The signal that is full-wave rectified by the full-wave rectification processing unit 19 is shown in FIG.
It shows in (b). As shown in FIG. 3B, the waveform of a portion (a portion indicated by a dotted line in FIG. 3B) having a lower potential than the offset potential BL (described as an offset potential in FIG. 3B) is It can be seen that the offset potential BL is converted into a symmetrical waveform and full-wave rectified.

That is, the background level detecting device 1
1 performs a variety of signal processing (voltage conversion processing, filter processing, full-wave rectification processing) with the offset potential BL as a reference to extract a background signal from the in-cylinder pressure signal Si, and to extract the background signal. The background level, which is the signal level, is detected. Then, the background level detection device 11 outputs the detected background level as the background level signal Sb to the CPU 3.

As described above, the internal combustion engine control system 1 of this embodiment has the peak value signal Sp output from the peak hold circuit 5 and the background level detection system 1.
Background level signals S output from 1 respectively
Based on b, the central processing unit 3 (CPU) executes knocking detection processing to detect knocking.

Here, when half-wave rectification is performed using a DC power supply device having a single power supply configuration, full-wave rectification is performed using a DC power supply device having both power supply configurations, a DC power supply device having a single power supply configuration is used. FIG. 4 shows the measurement results of the measurement performed to compare the rectified waveforms of the three patterns in the case where the full-wave rectification was performed by the background level detection device of this example. Further, in FIG. 4, in addition to the rectified waveform, a moving average value that is an average value of the rectified waveform in a predetermined fixed period is shown.

First, FIG. 4A shows the measurement results when half-wave rectification was performed using a DC power supply device having a single power supply configuration.
In FIG. 4A, the rectified waveform has a ground potential (0
It is understood that there is a constant period of [V], which is represented by GND in FIG. 4), and the value of the moving average calculated based on the rectified waveform in this period is a small value. Therefore, it is difficult to accurately detect the signal level of the input signal when the half-wave rectification is performed using the DC power supply device having the single power supply configuration.

Next, FIG. 4B shows the measurement results when full-wave rectification was performed using a DC power supply device having a dual power supply configuration.
In FIG. 4B, there is no period in which the rectified waveform remains constant at the ground potential, and the value of the moving average does not drop sharply and the waveform does not change significantly. From this, it is understood that, when full-wave rectification is performed using the DC power supply device having the dual power supply configuration, the signal level of the input signal can be accurately detected according to the change of the signal.

Further, FIG. 4C shows the measurement result when full-wave rectification is performed by the background level detecting device of this embodiment using a DC power supply device having a single power supply structure. Figure 4
In (c), the rectified waveform does not have a period in which it remains constant at the ground potential, and the value of the moving average does not suddenly drop and the waveform does not fluctuate significantly. That is, the waveform shown in FIG. 4 (c) is almost the same as the waveform shown in FIG. 4 (b). Therefore, when full-wave rectification is performed by the background level detection device of the present embodiment using a DC power supply device with a single power supply configuration, the signal level of the input signal is accurately detected according to the change of the signal. I see that I can do it.

In FIG. 4 (c), the offset potential BL is simply described as "offset", and it can be seen that there is no period in which the rectified waveform is lower than the offset potential BL. From this measurement result, the background level detection device 11 of the present embodiment extracts the background signal from the in-cylinder pressure signal Si output by the plug washer pressure sensor GPS, and extracts the signal level of the extracted background signal (background level). ) Can be detected accurately. That is, by using the background level detection device 11 of the present embodiment, it is possible to prevent the background level detection accuracy from deteriorating even when the DC power supply device is configured as a single power supply device at low cost.

Further, the internal combustion engine control device provided with such a background level detecting device 11 subtracts the background level from the vibration frequency component extracted from the in-cylinder pressure signal Si output from the plug washer pressure sensor GPS. , Many noise components can be removed, and the knocking signal can be detected with high accuracy.

Therefore, according to the internal combustion engine control apparatus of the present embodiment, the knocking signal can be accurately detected even when the DC power supply apparatus having the single power supply configuration is used and the DC power supply apparatus is constructed at low cost. Therefore, the knocking detection accuracy can be improved. Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and can take various aspects.

For example, the sensor used for knocking detection is not limited to the plug washer type pressure sensor, but a piezoelectric type sensor capable of directly detecting the fluctuation of the in-cylinder pressure may be used.
Further, it may be a knock sensor which is a piezoelectric sensor that detects mechanical vibration generated by knocking. When the knock sensor is used, the voltage conversion processing unit that constitutes the background detection device does not need to be configured by the operational amplifier and the feedback capacitor, and may be configured by the resistance element.

Further, the power supply voltage output from the DC power supply device is not limited to 5 [V], and a DC power supply device outputting a power supply voltage other than 5 [V] can be used.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an internal combustion engine control device including a background level detection device according to an embodiment.

FIG. 2 is a circuit diagram of a background level detecting device according to an embodiment.

FIG. 3A is a signal waveform after filter processing in the background level detecting device according to the embodiment,
(B) is a signal waveform after the full-wave rectification process in the background level detection device of the embodiment.

FIG. 4 is a measurement result of a measurement performed for comparing rectified waveforms.

[Explanation of symbols]

1 ... Internal combustion engine control device, 3 ... Central processing unit (CP
U), 5 ... Peak hold circuit, 7 ... Filter processing unit, 11 ... Background level detection device, 13 ... Voltage conversion processing unit, 15 ... High-pass filter processing unit, 17 ... Low-pass filter processing unit, 19 ... Full wave Rectification processor, GPS
... Plug washer pressure sensor, IC1, IC2, IC3
IC4, IC5 ... Operational amplifier, VMM ... Offset potential line.

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) G01H 11/08 G01H 11/08 Z (72) Inventor Masayoshi Matsui 14-18 Takatsuji-cho, Mizuho-ku, Aichi Prefecture Special Ceramics Co., Ltd. F term (reference) 2F055 AA23 BB12 CC14 DD20 EE23 FF11 GG44 2G064 AB01 AC02 AC13 AC48 CC02 CC54 3G019 AC08 FA08 GA14 KA28 KD17 KD20 3G084 BA16 CA04 DA13 DA20 DA38 EA01 FA25

Claims (3)

[Claims] 1. When detecting a signal of a specific frequency component from an output of a piezoelectric sensor provided in an internal combustion engine, a noise component superimposed on the output has a signal level in the same frequency band as the specific frequency component. A background level detecting device for detecting a certain background level, comprising a voltage conversion processing unit for converting an output from the piezoelectric sensor into a voltage signal, and a filter processing for extracting a signal of the specific frequency component from the voltage signal. And a full-wave rectification processing unit for full-wave rectifying the signal of the specific frequency component, the filter processing unit and the full-wave rectification processing unit each include at least an operational amplifier, The amplifier is configured such that a positive potential of the DC power supply device is applied to a first terminal of a pair of terminals for receiving a power supply voltage from the DC power supply device, and a second end of the amplifier is used. The power supply voltage is supplied by applying the negative potential of the DC power supply to the reference potential in the filter processing unit and the full-wave rectification processing unit, the positive potential and the negative potential of the DC power supply. A signal which is set to an offset potential which is an intermediate potential between the first and second operational amplifiers of the filter processing section and the full-wave rectification processing section, with respect to the offset potential. A background level detection device, which outputs within a range from a potential applied to a terminal to a potential applied to the second terminal. 2. The voltage conversion processing unit includes a second operational amplifier, and a feedback capacitor connecting an inverting input terminal and an output terminal of the second operational amplifier, the second operational amplifier being the DC power supply. Driven by the supply of the power supply voltage in the device, the reference potential set in the non-inverting input terminal of the second operational amplifier is set in the offset potential, while the inverting input terminal is connected to the piezoelectric sensor. The background level detection device according to claim 1, wherein the background level detection device is connected. 3. The piezoelectric sensor is configured to have a piezoelectric element built therein and is provided at a mounting seat of an ignition plug mounted on an internal combustion engine to detect a change in tightening load of the ignition plug. The plug level washer pressure sensor for detecting the in-cylinder pressure of the internal combustion engine according to claim 2, wherein the background level detecting device according to claim 2.