JP2011190739A - Ion current detecting and processing device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ion current detecting and processing device for an internal combustion engine, capable of eliminating an error of processing due to an influence of noise. <P>SOLUTION: A control device ECU starts a signal processing routine R1 when an ignition signal SG trails. In the signal processing routine R1, an ion current detecting signal V0 is detected at every AD timing, and the detected information is stored in a memory circuit (S01). Thereafter, BPF processing about a noise detection section W1 is carried (S02), and output values of the BPF processing about the noise detection section W1 are cumulatively computed (S03). Thereafter, an analysis object section W3 required for analysis of a specified signal is selected, and BPF processing about the analysis object section W3 is carried out (S04). Thereafter, output values of the BPF processing about the analysis object section W3 is cumulatively computed (S05). When the processing S05 is completed, processing for offsetting a component of the regular noise from the cumulation value Vsum for analysis is performed (S06). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an ion current detection processing apparatus for an internal combustion engine, and is particularly suitable for use in eliminating processing errors due to the influence of noise.

  In recent years, research on combustion control in which an ion current generated in a cylinder of an internal combustion engine is detected and the behavior of the internal combustion engine is analyzed based on information on the ion current has been advanced. Research on the combustion control has been attempted in various ways, such as combustion / misfire determination processing and knock determination processing.

  For example, Japanese Patent Laid-Open No. 2001-073914 (Patent Document 1) introduces a knock control device for an internal combustion engine. The knock control device detects a ionic current and performs a first process for holding a detected value of the ionic current in a memory circuit built in an ECU (Engine Contrl Unit) or the like, and a BPF ( Band-Pass-Filter), a second process for acquiring a detection value corresponding to the knock signal, a third process for accumulating the detection value of the knock signal, and the cumulative value obtained by the third process in advance. A fourth process for comparing the set threshold value and performing a knock determination is executed.

  In the knock control device in which such processing is programmed, when an ion current is detected, a window corresponding to the knocking analysis interval is opened, and BPF processing of the ion current waveform is performed in the analysis interval. When the knock signal is superimposed on the ion current, the knock control device causes the detection value corresponding to the knock signal to be cumulatively calculated, and if this cumulative value exceeds a preset threshold value, it is determined that knocking has occurred, and this cumulative value Is lower than the threshold value, it is determined that the operation is normal (no knocking). Thereafter, the knock control device appropriately performs the retard / advance control of the combustion timing based on the knock determination.

  In recent combustion control, not only the knock determination process but also other combustion control processes, a technique for accumulating the detected value of the ionic current and using this accumulated value to analyze the behavior of the internal combustion engine is used. It has been.

JP 2001-073914 A

  Here, a constant noise that appears chronically regardless of the combustion cycle is superimposed on the detection signal of the ion current. The frequency band of the constant noise is unspecified and distributed over a wide area because the cause of the generation of the constant noise is complex. For this reason, when trying to analyze a signal distributed at a specific frequency by BPF processing, the signal value acquired by BPF processing may include a constant noise component distributed in the passband of BPF processing.

  For example, when the ionic current of the first cylinder is detected, if the combustion is performed in the cylinders other than the first cylinder, the detection signal of the ionic current in the first cylinder is continuous according to the combustion operation in the other cylinders. Therefore, constant noise based on the combustion operation of other cylinders is superimposed.

  In addition, since a plurality of in-vehicle devices that are electrically driven are installed in recent automobiles, the ground potential becomes unstable depending on the driving state of the in-vehicle devices. Depending on the fluctuation, the above-mentioned constant noise may be superimposed. Furthermore, although such a vehicle-mounted device is provided with a filter circuit that suppresses noise, a residual component that cannot be completely removed by this filter circuit may cause constant noise.

  According to the technique of Patent Document 1, since the constant noise distributed in the frequency band of the knock signal is included in the detection signal indicating the knock signal, when the signal value detected as the knock signal is cumulatively calculated, There is a problem that a large error is given to the accumulated value due to the constant noise component. The error generated in the accumulated value of the detection signal induces an erroneous determination in the knock determination process, causing a problem that the correct combustion control of the internal combustion engine is hindered.

  Furthermore, not only in the knock determination process but also in other combustion control processes, when the accumulated value of the detection signal (Oin current) is used, the process determination for analyzing the behavior of the internal combustion engine becomes inaccurate.

  In view of the above problems, an object of the present invention is to provide an ion current detection processing apparatus for an internal combustion engine that can eliminate processing errors due to the influence of noise.

In order to solve the above problems, the present invention has the following configuration of an ion current detection processing apparatus for an internal combustion engine. That is, an ignition coil having a primary coil and a secondary coil, a switching element that controls energization of the primary coil, a control device that supplies an ignition signal to the switching element to perform an ON / OFF operation, and a secondary coil An ignition plug that receives an induced voltage to perform a discharge operation and an ion current detection circuit that detects an ion current detection signal proportional to the ion current generated in the internal combustion engine,
The control device includes a signal holding unit that holds the ion current detection signal, a waveform conversion unit that executes a BPF process using a predetermined frequency set as a pass band among the waveform components superimposed on the ion current detection signal, Noise accumulation calculating means for accumulating the output value of the noise detection section provided for detecting constant noise among the output values of the BPF processing, and for analyzing the ionic current among the output values of the BPF processing. Analysis cumulative calculation means for cumulatively calculating the output value of the analysis target section, and noise cancellation means for canceling the constant noise component from the cumulative value calculated by the analysis cumulative calculation means; To do.

  Preferably, the noise accumulation calculation means is executed corresponding to each processing operation of the analysis accumulation calculation means. Here, the noise detection section is preferably set at a timing different from that of the analysis target section, and more preferably, set at a timing before the primary coil is energized.

  More preferably, the noise cumulative value calculated by the noise cumulative calculation means and the analysis cumulative value calculated by the analysis cumulative calculation means are calculated before the processing start time of the noise cancellation means. And

  More preferably, the noise canceling unit subtracts an estimated noise cumulative value calculated based on the noise cumulative value from the analysis cumulative value.

  According to the ionic current detection processing apparatus for an internal combustion engine according to the present invention, the accumulated value calculated based on the ionic current cancels the constant noise component, so that most of the error included in the accumulated value is eliminated. Is done.

  Further, when analyzing the behavior of the internal combustion engine using the above-described accumulated value, the accumulated value is corrected to an accurate value. Therefore, knock determination processing, misfire / combustion determination processing, and various other combustion control processing are performed. Exactly done.

The figure which shows the circuit structure of the ion current detection processing apparatus which concerns on embodiment. The timing chart explaining operation | movement of the ion current detection processing apparatus which concerns on embodiment. The flowchart explaining operation | movement of the ion current detection processing apparatus which concerns on embodiment. The figure which shows the waveform of a constant noise, and the cumulative value of a constant noise. The figure which shows the cumulative value of the waveform of an ion current, the output waveform after BPF processing, and the ion current after BPF processing (embodiment). The flowchart explaining operation | movement of the ion current detection processing apparatus which concerns on the example of a change of embodiment. 5 is a flowchart of knock determination processing according to the first embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a circuit configuration of an ion current detection processing apparatus for an internal combustion engine. As shown in the figure, the ion current detection processing device 100 includes an ignition plug PG, an ignition coil CL, a switching element Tr, a control device ECU, and an ion current detection circuit INS.

  The ignition plugs PG are respectively provided in the plug holes of the internal combustion engine, and discharge between the plug gaps according to the applied voltage (inductive voltage of the secondary coil) to burn the air-fuel mixture in the cylinder.

  The ignition coil CL includes a primary coil L1, a secondary coil L2, and an iron core. When the current flowing through the primary coil L1 fluctuates, the ignition coil CL generates an induced voltage from the secondary coil L2 according to the fluctuation of the current value. The ignition coil CL is packaged with an insulating resin and attached to the terminal portion of the ignition plug PG. Thereby, the secondary coil L2 is electrically connected to the ignition plug PG, and when the passing current of the primary coil L1 fluctuates, the induced voltage is output to the ignition plug PG. In addition, VB shown on the primary coil side indicates a battery voltage supplied from the in-vehicle battery.

  As the switching element Tr, a power transistor such as an IGBT (Insulated Gate Bipolar Transistor), a MOSFET, or the like that operates ON / OFF according to an ignition signal is used. The switching element Tr is interposed between the output terminal of the primary coil L1 and the ground, and controls the energization state of the primary coil L1 according to the ignition signal.

  In the present embodiment, the control device ECU is an Engine Control Unit, and the Engine Control Unit is one of in-vehicle devices mounted on the automobile. The Engine Control Unit includes a CPU, a memory circuit, an AD conversion circuit, and the like, centrally manages vehicle operation information, and calculates various signals such as an ignition signal based on the information. The arithmetically processed signal is appropriately output by the control device ECU. That is, as one of such functions, the control device ECU supplies the ignition signal SG to the switching element Tr and controls the ON / OFF operation of the switching element Tr.

  In the control device ECU, various control programs are stored in the memory circuit, and the control programs are appropriately activated in accordance with a predetermined activation operation. In the present embodiment, the memory circuit has a constant noise value based on a processing program for holding an ion current detection signal, a processing program for extracting a specific frequency of the ion current detection signal, and an output value of the BPF processing. A processing program for accumulating, a processing program for accumulating the value of the ionic current based on the output value of the BPF processing, a processing program for offsetting the constant noise component from the accumulated value calculated by the accumulative computing means for analysis, In addition, various processing programs are stored. Then, by executing these processing programs, the control unit ECU causes the various means described in the claims (signal holding means, waveform conversion means, noise accumulation calculation means, analysis accumulation calculation means, noise cancellation means) Etc.). Various means defined by the processing program will be described in detail later.

  As shown in the figure, the ion current detection circuit INS includes a Zener diode ZD, diodes D1 and D2, a capacitor C1, resistors R1 to R3, and an operational amplifier AMP. The ion current detection circuit INS is built in a circuit unit such as an igniter that directly controls ignition of the ignition coil CL or a control unit ECU. Note that a circuit configuration unnecessary for the description of the present embodiment is omitted for convenience.

  The zener diode ZD and the capacitor C1 form a parallel circuit, one end is connected to the secondary coil, and the other end is connected to the ground side via the diode D1. Among them, the Zener diode ZD has the anode side arranged in the ground direction, and the diode D1 has the cathode side arranged in the ground direction.

  The contact point between the parallel circuit and the diode D1 is connected to the inverting input terminal (−) of the operational amplifier AMP via the resistor R1. The inverting input terminal (−) of the operational amplifier AMP is further connected to a diode D2 and a resistor R2. Among these, the diode D2 is arranged so that the forward direction is on the operational amplifier side, and the other end of the resistor R2 is connected to the output terminal of the operational amplifier AMP. The operational amplifier AMP is provided with a resistor R3 at the output terminal, the non-inverting input terminal (+) is grounded to the ground, and an inverting amplifier circuit is formed as a whole. Further, the output terminal is connected to an AD input terminal of the control unit ECU via a signal line, and outputs a detection signal V0 (hereinafter referred to as an ion current detection signal) amplified by the operational amplifier AMP to the AD input terminal. The ion current detection signal V0 defines an amplification value (proportional value) with respect to the ion current I2 by these resistors R1 to R3.

  Here, when the switching element Tr is switched from the ON state to the OFF state by the control operation of the control device ECU (see FIG. 2a), the energization current Ic1 of the primary coil L1 is interrupted (see FIG. 2b), and the secondary coil L2 An induced voltage is generated. When the spark plug PG discharges in response, a discharge current I1 flows in the circuit through a path indicated by the spark plug PG → secondary coil L2 → capacitor C1 → diode D1. At this time, the voltage across the capacitor C1 is regulated to a predetermined value by the Zener diode ZD, and charges corresponding to the voltage across the capacitor C1 are accumulated. Thereafter, when a chemical reaction by combustion proceeds, a large number of ionic substances are formed in the cylinder, and an ionic current I2 using the voltage value of the capacitor C1 as a power source flows. More specifically, an ionic current I2 flows in the circuit through a path indicated by a resistor R2, a resistor R1, a capacitor C1, a secondary coil L2, and a spark plug PG.

  In the ion current detection signal V0, the signal value detected by the ion current detection circuit INS is transmitted as a voltage value, and the voltage value is input to the AD input terminal of the control device ECU. As shown in FIG. 2C, the ion current detection signal V0 is formed with a pulse current Ip generated when the ignition signal SG rises, and an ion current Iion generated according to the discharge operation of the spark plug PG. Further, the above-described constant noise (not shown) is superimposed on the ion current detection signal V0, and since this constant noise is a noise that appears chronically, a region where the ion current detection signal V0 is stable, It is also superimposed on the waveform of the ion current Iion.

  Hereinafter, the processing operation of the ion current detection signal performed by the control unit ECU will be described with reference to FIG. In the control device ECU, when the ignition signal SG falls, the signal processing routine R1 according to the present embodiment is started. The signal processing routine R1 first detects the ion current detection signal V0 at every AD timing, and holds the information detected here in the memory circuit (S01 / signal holding means). Such a memory circuit may be a volatile memory circuit or a non-volatile memory circuit as long as the information of the ion current detection signal is processed during the operation of the control unit ECU. In the present embodiment, as shown in FIG. 2C, information on the ion current detection signal V0 is held for the noise detection section W1 and the ion current holding section W2. The noise detection section W1 is provided at a timing when the ion current detection signal V0 converges to the reference value, and the ion current holding section W2 is provided at a timing when the ion current Iion is predicted to be generated.

  Note that the ion current holding section W2 or the analysis target section W3 described later is set to a region where the ion current Iion appears. On the other hand, the noise detection section W1 is preferably set at a different timing from the ion current holding section W2 or the analysis target section W3. Then, the noise detection section W1 is set at a timing at which the ion current detection signal V0 converges, and only the constant noise Wa can be detected in the section. In particular, the noise detection section W1 may be set to a timing Tx after the ion current has converged in the previous combustion cycle and until the primary coil is energized in the combustion cycle being detected. When the noise detection section W1 is set in such a range, only the constant noise Wa is detected in the noise detection section W1 without being affected by the pulse current Ip caused by energization of the primary coil.

  When the process S01 is completed, the BPF process is executed for the noise detection section W1 (S02 / waveform converting means). The BPF process is a process for extracting only a waveform having a predetermined frequency from the waveform component superimposed on the ion current detection signal V0 using a predetermined frequency set in advance. This predetermined frequency matches the frequency of the BPF process performed in process S05 described later.

  When the process S02 is completed, the output value of the BPF process is cumulatively calculated for the noise detection section W1 (S03 / noise cumulative calculation means). In the process S03, as shown in FIG. 4A, since the noise detection section W1 is provided at a timing at which an extra waveform other than the constant noise Wa is not formed, only the component of the constant noise Wa that has passed through the BPF process is accumulated. It will be calculated. The accumulated noise value Vnc calculated in the process S03 may be calculated by accumulating the fluctuation amount (absolute value) of the detected value at every AD timing as shown in FIG. 4B. It may be calculated by accumulating only positive values of.

  When the process S03 is completed, the control unit ECU selects the analysis target section W3 necessary for analyzing the specific signal from the ion current holding section W2, and executes the BPF process for the analysis target section W3 (S04 / waveform converting means). ). The BPF process is a process in which the frequency of a specific signal superimposed on the ion current Iion is used as a passband, and only the frequency waveform of the specific signal is extracted. More specifically, in step S03, as shown in FIG. 2D, the analysis target section W3 is selected from the range of the ion current holding section W2 in accordance with the operating state of the internal combustion engine, and the BPF is selected for this analysis target section W3. Execute the process. When such processing is performed, when a specific signal is superimposed on the ion current Iion, a waveform representing the specific signal is extracted from the filtered waveform (see FIG. 2e1). On the other hand, when the specific signal is not superimposed on the ion current Iion, the waveform indicating the specific signal does not appear in the filtered waveform.

  In the analysis target section W3, the width and timing of the section are appropriately defined depending on the operating state (the rotational speed, the load, etc.) of the internal combustion engine. Specifically, in the memory circuit of the control device ECU, appropriate values regarding the timing at which the specific signal appears and the generation interval are stored for each operation state, and the control device ECU reads information on the current operation state of the internal combustion engine. Then, the analysis target section W3 is specified from the range of the ion current holding section W2 (FIG. 5a), and a specific signal is extracted in this section by BPF processing (FIG. 5b). Note that the set frequency in the BPF process when detecting the constant noise and the set frequency in the BPF process when detecting the specific signal coincide with the frequency band of the constant noise included in the specific signal and the process This is because by matching the frequency band of the constant noise detected in S02, both the constant noise components are the same, and the accuracy related to noise cancellation in the subsequent stage is improved.

  When the process S04 is completed, the output value of the BPF process is cumulatively calculated for the analysis target section W3 (S05 / analysis cumulative calculation means). In the process S05, as shown in FIG. 5C, an analysis accumulated value Vsum which is a result of accumulating output values by the BPF process is obtained. As described above, the constant noise Wa component is included in the output value of the BPF process that expresses the specific signal. The accumulated value Vsum for analysis is a large value obtained by accumulating the constant noise Wa in the analysis target section W3. An error will be included. However, the error included in the analysis cumulative value Vsum is estimated using the noise cumulative value Vnc calculated in the process S03, and this error is canceled in the subsequent process. In addition, even in the calculation method of the cumulative calculation performed in the process S05, the method is not questioned as in the process S03.

  In the signal processing routine R1 according to the present embodiment, the process S03 (noise accumulation calculation means) is executed corresponding to each processing operation of the process 05 (analysis accumulation calculation means). In such a case, since the noise accumulated value Vnc is updated every combustion cycle, the noise component estimation performed in the noise cancellation processing S06 is made more accurate. However, when the operating state (rotation speed, load, etc.) of the internal combustion engine is stable, the process 02 may be omitted, and the burden associated with the process of updating the noise accumulated value Vnc may be reduced.

  It is preferable that the analysis cumulative value Vsum and the noise cumulative value Vnc described above are calculated before the processing start time of the subsequent processing S06 (noise canceling means). As described above, when the calculation result of both the accumulated values (Vsum, Vnc) has been obtained, the subsequent process S06 (noise canceling means) performs noise cancellation using this accumulated value. The operation can be shifted to the noise canceling operation without waiting.

  When the process S05 is completed, the process of canceling out the constant noise component from the analysis cumulative value Vsum is performed (S06 / noise canceling means). In the present embodiment, a process of subtracting an estimated noise accumulated value described later from the analysis accumulated value Vsum is performed, thereby calculating the true analysis accumulated value Vrsum that does not include a noise component. Here, the inspection time of the noise detection section W1 is t1, and the inspection time of the analysis target section W3 is t2. In such a case, the estimated noise accumulated value Vcn ′ is obtained by multiplying the noise accumulated value Vcn by the conversion coefficient Cv (Cv = t2 / t1). That is, the estimated noise cumulative value Vcn ′ is obtained as an estimated value of the constant noise component in the analytical cumulative section W3 (see FIG. 5c). Then, the true analysis cumulative value Vrsum not including the noise component is obtained by subtracting the estimated noise cumulative value Vcn ′ from the analysis cumulative value Vsum. As described above, in the process S06, the detection accuracy of the true analysis cumulative value Vrsum is improved by performing the above-described noise cancellation.

  If the inspection time t1 of the noise detection section W1 and the inspection time t2 of the analysis target section W3 match, the noise cancellation process described above may be performed with the conversion coefficient Cv = 1. The calculated noise accumulated value Vcn may be used as it is as the estimated noise accumulated value Vcn ′.

  According to the ion current detection processing apparatus 100 according to the present embodiment, the true analysis cumulative value Vrsum calculated based on the ion current I2 cancels out the constant noise component, so that the error included in the cumulative value Most will be eliminated.

  Further, when the behavior of the internal combustion engine is analyzed using the true analysis cumulative value Vrsum, the cumulative value is corrected to an accurate value not including a noise component, so that the knock determination process, the combustion / misfire determination process, and the like. Various combustion control processes are accurately performed.

  FIG. 6 shows a modification of the signal processing routine described above. In the signal processing routine R1 according to this modification, a constant noise accumulated value correctness determination process S03a and a constant noise accumulated value setting process S03b are added after the process S03 for calculating the constant noise accumulated value.

As described above, the process S03 detects the ion current detection signal V0 in the current combustion cycle, and uses this to calculate the noise accumulated value Vsum in the current cycle. That is, the noise accumulated value Vsum calculated here is a value corresponding to the latest combustion cycle.

  Here, when some noise waveform appears accidentally in the noise detection section W1 to be detected, the noise accumulated value Vsum calculated in the process 03 is added with the noise component picked up accidentally. It cannot be a value that accurately represents the cumulative value of constant noise. If an error occurs in the accumulated noise value Vsum as described above, noise canceling more than a necessary value is performed in the process S06, and as a result, an error is caused in the accumulated value used in the combustion control determination process.

  Therefore, in order to reduce such an error to some extent, in the present modification example, the constant noise accumulated value correctness determination process S03a and the constant noise accumulated value setting process are performed after the process S03 for calculating the constant noise accumulated value. S03b is performed.

  In step S03a, the noise accumulated value Vsum 'calculated in the previous combustion cycle is read from the memory circuit, and the past noise accumulated value Vsum' is compared with the noise accumulated value Vsum calculated in the current combustion cycle. Then, both noise accumulated values are subtracted to perform threshold determination. That is, when the fluctuation amount of the noise cumulative value is within the allowable range, the currently calculated noise cumulative value Vsum is determined to be an appropriate value. On the other hand, when the fluctuation amount of the noise cumulative value exceeds the allowable range, The accumulated noise value Vsum is determined to be an inappropriate value including unnecessary noise.

  When the process S03a is completed, the noise accumulated value on the side determined to be an appropriate value in the process S03a is stored in the memory area for noise cancellation (S03b). That is, in step S03b, when it is determined that the current noise accumulated value Vsum is an appropriate value, the current noise accumulated value Vsum is stored in the noise canceling memory area, while the current noise accumulated value Vsum is not valid. If it is determined to be appropriate, it is stored in the noise canceling memory circuit so that the past accumulated noise value Vsum can be referred again. In this way, in the noise cancellation process S06, an inappropriate value of the accumulated noise value is not used, and an appropriate amount of noise cancellation is performed.

  As described above, according to the ion current detection processing device according to the present modification, when an accidental noise appears in the noise detection section W1, avoid using a cumulative noise value that does not accurately indicate the constant noise. By reading the correct accumulated noise value from the past data, it is possible to optimize the constant noise cancellation amount performed in the process 06.

  Hereinafter, specific examples of the signal determination process described above will be described. In FIG. 7, the signal determination process in the embodiment is incorporated in the knock determination process. The knock determination device that performs such processing has substantially the same configuration as the above-described ion current detection processing device, and a predetermined program is replaced with a processing program that performs knock determination. In the present example, the specific signal described in the embodiment refers to a knock signal distributed in a frequency band of about 5 kHz to 10 kHz. In the figure, portions that perform the same processing as the processing operations described above are denoted by the same reference numerals, and description thereof is omitted.

  In the control device ECU according to the present embodiment, as described above, when the ignition signal SG falls, the signal processing routine R2 is started. The signal processing routine R2 first stores the ion current detection signal V0 for each AD timing (S01 / signal holding means), executes the BPF process for the noise detection section W1 (S02 / waveform conversion means), and the noise detection section. The output value of the BPF process is cumulatively calculated for W1 (S03 / noise cumulative calculation means).

  When the process S03 is completed, the knock detection section W3 necessary for the analysis of the knock signal is selected from the ion current holding section W2, and the BPF process is executed on the knock detection section W3 (S14 / waveform conversion means). The BPF process is a process in which the frequency of the knock signal is used as a passband and only the waveform of the frequency of the knock signal is extracted.

  In the knock detection section W3, the section in which the knock signal appears and the timing at which the knock signal is generated are appropriately defined depending on the operating state (rotation speed, load, etc.) of the internal combustion engine. The knock detection section W3 is adjusted by the control unit ECU so as to coincide with the generation timing of the knock signal. Since this knock signal appears after the second peak value of the ionic current, it is preferable that the noise detection section W3 also coincides with this.

  When the process S14 is completed, the output value of the BPF process is cumulatively calculated for the knock detection interval W3 (S15 / analysis cumulative calculation means). The analysis cumulative value Vsum calculated in the process S15 includes a large error due to the constant noise Wa.

  However, in the process 16, the estimated noise cumulative value Vcn 'is subtracted from the analysis cumulative value Vsum, thereby canceling out the constant noise component from the analysis cumulative value Vsum (S16 / noise canceling means). In this process S16, as described above, the true analysis accumulated value Vrsum is calculated through the calculation process of the conversion coefficient Cv and the estimated noise accumulated value Vcn '. The true analysis cumulative value Vrsum indicates a value from which the constant noise component is eliminated.

  Thereafter, in knock determination processing S17, threshold determination is performed on the true analysis cumulative value Vrsum, and when the true analysis cumulative value Vrsum is larger than the threshold Vth, a flag indicating "knock occurrence" is stored in the memory circuit (S19). ) When the true analysis cumulative value Vrsum is smaller than the threshold value Vth, a flag indicating "normal (no knocking)" is stored in the memory circuit (S18). In such knock determination, since the constant noise component is not included in the true analysis cumulative value Vrsum, the determination result is very accurate.

  When such a series of processing is completed, the signal processing routine R2 is in a standby state until the next falling edge of the ignition signal SG is reached.

  As described above, the knock determination device according to the present embodiment cancels the noise component of the analysis cumulative value Vsum, so that the accuracy of the determination result in the knock determination process is improved.

  The ion current detection processing apparatus for an internal combustion engine according to the present invention is not limited to the above-described embodiment, and various modifications can be made. For example, the signal holding means in the present embodiment temporarily stores the information of the ion current detection signal V0 in the memory circuit in the noise detection section W1 and the ion current holding section W2. On the other hand, when the holding section is modified and the ionic current holding section W2 is extended until the constant noise can be detected, in the modified example, the constant noise Wa and the ionic current Iion can be detected from one holding section. Thus, the burden on the detection value holding operation is reduced.

  In this embodiment, the ion current detection processing device is applied to the knock determination device. However, the present invention is not limited to this, and the ion current detection processing device can also be applied to other determination devices. For example, in the combustion / misfire determination apparatus, there is a technique for calculating an area of an ion current waveform and performing a determination process of combustion / misfire based on the area value. In such a technique, when the area value for the combustion / misfire determination process is calculated, the detection value of the ion current detection signal is integrated (that is, cumulative calculation process), and the signal processing routine according to the present invention is applied. Thus, it is possible to improve the determination accuracy relating to the combustion / misfire determination.

  In addition, in the technique for calculating the pressure in the cylinder, the average value of the fluctuating pressure is calculated by an integral operation. If the signal processing routine according to the present invention is applied, the average pressure with less error can be calculated. It becomes.

DESCRIPTION OF SYMBOLS 100 Ion current detection processing apparatus for internal combustion engines CL Ignition coil Tr Switching element ECU Controller PG Ignition plug INS Ion current detection circuit S01 Signal holding means S02, S04 Waveform conversion means S03 Constant noise accumulation calculation means S05 Analysis accumulation calculation means S06 Noise canceling means

Claims (6)

An ignition coil having a primary coil and a secondary coil, a switching element that controls energization of the primary coil, a control device that supplies an ignition signal to the switching element to perform an ON / OFF operation, and an induced voltage of the secondary coil Receiving a spark plug that performs a discharging operation, and an ion current detection circuit that detects an ion current detection signal proportional to the ion current generated in the internal combustion engine,
The controller is
Signal holding means for holding the ion current detection signal;
Waveform converting means for executing BPF processing with a predetermined frequency set among the waveform components superimposed on the ion current detection signal as a passband;
Noise accumulation calculation means for accumulating the output value of the noise detection section provided for detecting constant noise among the output values of the BPF processing;
An analysis cumulative calculation means for cumulatively calculating an output value of an analysis target section provided for analyzing an ionic current among the output values of the BPF processing;
An ion current detection processing apparatus for an internal combustion engine, comprising: noise canceling means for canceling out the constant noise component from the cumulative value calculated by the analytical cumulative calculation means.   2. The ion current detection processing apparatus for an internal combustion engine according to claim 1, wherein the noise accumulation calculation means is executed corresponding to each processing operation of the analysis accumulation calculation means.   The ion current detection processing apparatus for an internal combustion engine according to claim 1 or 2, wherein the noise detection section is set at a timing different from that of the analysis target section.   4. The ion current detection processing apparatus for an internal combustion engine according to claim 1, wherein the noise detection section is set at a timing before the primary coil is energized.   The noise cumulative value calculated by the noise cumulative calculation means and the analysis cumulative value calculated by the analysis cumulative calculation means are calculated before the processing start time of the noise cancellation means. The ion current detection processing apparatus for an internal combustion engine according to claim 1. The noise canceling means is
6. The ion current detection processing apparatus for an internal combustion engine according to claim 1, wherein an estimated noise cumulative value calculated based on the noise cumulative value is subtracted from the analytical cumulative value.

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