JP2018003631A - Control device for internal combustion engine and knock judgement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve accuracy in knock judgement at an internal combustion engine.SOLUTION: This invention has a feature comprising: a knock frequency filter processing part 202 for extracting a knock frequency band that is a specific frequency band to a knock; a disturbance noise filter processing part 204 for extracting a disturbance noise frequency band that is a frequency band specific to the disturbance noise; a knock frequency correcting part 206 for calculating a strength ratio difference that is an influence degree of the disturbance noise frequency at a disturbance noise frequency band extracted by the disturbance noise filter processing part 204 in respect to the knock frequency at the knock frequency band extracted by the knock frequency filter processing part 202, determining a correction counted number of the knock frequency band strength on the basis of the strength ratio difference, and correcting the knock frequency band strength in reference to the correction counted number; and a judgement processing part 208 for judging whether or not a knock is produced on the basis of the corrected knock frequency band strength.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a technology for a control device and a knock determination method for an internal combustion engine that detects occurrence of a knock in the internal combustion engine.

  In recent years, regulations on fuel consumption and exhaust have been reinforced in vehicles such as automobiles. Such regulations are expected to become even stronger in the future. In particular, regulations relating to fuel consumption are extremely interesting due to recent problems such as high volatility in fuel prices, impact on global warming, and depletion of energy resources.

  Under such circumstances, for example, in the automobile industry, various technical developments for the purpose of improving the fuel efficiency and exhaust performance of a vehicle are being promoted. As one of the development technologies aimed at improving the fuel efficiency, for example, there is a high compression ratio technology for increasing the compression ratio of an internal combustion engine. In addition, as one of the development technologies aimed at improving exhaust performance, for example, fuel is injected in multiple times during the intake stroke, and the PN (Particulate Number) is reduced by reducing the fuel injection amount per time There are multistage injection technologies.

  By the way, in the above-described high compression ratio technology, the compression ratio of the internal combustion engine increases, so that the thermal efficiency is improved and the fuel efficiency is improved. However, it is known that, in the high compression ratio technology, the temperature in the combustion chamber rises and knocking easily occurs.

  For this reason, in a conventional internal combustion engine, the fact that a specific frequency signal level rises when knocking occurs is used. That is, a vibration type knock sensor is attached to the cylinder block. The occurrence of knocking is detected by performing FFT (Fast Fourier Transform) analysis on the signal of the predetermined crank angle section output from the knock sensor.

  However, since the knock sensor transmits vibrations of the internal combustion engine, if disturbance noise such as injector noise occurs in the knock determination angle section, the disturbance noise may be erroneously detected as knocking. For this reason, the fuel injection timing cannot be set in the knock determination angle section, and for example, there may arise a problem that the potential of the multi-stage injection technology for reducing PN cannot be fully exhibited. The knock determination angle section is a section of a crank angle at which knocking is likely to occur.

  To deal with such a problem, Patent Document 1 discloses that “the output signal of the knock sensor is processed by a plurality of bandpass filters to extract the vibration waveform components of the plurality of frequency bands f1 to f4, and the vibration waveform of each frequency band is extracted. The weighting factors G1 to G4 to be multiplied by the components are set to smaller values as the noise intensity in each frequency band is larger, so that the vibration waveform components in a plurality of frequency bands can be set according to the influence level of the noise intensity in each frequency band. Therefore, even if noise is superimposed on the vibration waveform component of any frequency band, it is possible to reduce the influence of the noise and synthesize the vibration waveform component of each frequency band. The knock determination device for the internal combustion engine is disclosed (refer to the summary).

JP 2009-42027 A

  The determination of knocking is performed based on the knock sensor signal in the knock determination angle section. However, whether or not disturbance noise is included in the knock determination angle section depends on the control state of the internal combustion engine. Therefore, even if the frequency band of vibration caused by knocking and the frequency band of vibration caused by disturbance noise are close to each other, if noise noise is not included in the knock determination angle section, disturbance noise The knock frequency band intensity can be obtained without being affected.

  The technique described in Patent Document 1 has a problem that even if no disturbance noise is generated, the knock frequency is lowered, so that the correct knock frequency band intensity cannot be obtained.

  Furthermore, in Patent Document 1, the weighting coefficient to be multiplied to the vibration waveform component in each frequency band is set to a smaller value as the noise intensity in each frequency band is larger. However, the frequency band intensity of knock and the frequency band intensity of disturbance noise do not always appear at a constant magnitude, and it has been confirmed by the inventors' experiments that the intensity varies with each cycle. Therefore, when disturbance noise is included in the knock determination angle section, the degree of influence of the disturbance noise on the knock frequency band intensity varies for each cycle of the internal combustion engine. The degree of influence of disturbance noise also varies depending on the overlap between the frequency band of vibration caused by knock and the frequency band of vibration caused by disturbance noise. Therefore, as in Patent Document 1, it is not always necessary to set a smaller weighting factor to multiply the vibration waveform component of each frequency band as the frequency band intensity of disturbance noise is higher.

  As described above, the technique described in Patent Document 1 has a problem that it is difficult to correct the knock frequency band intensity according to the influence of disturbance noise that varies from cycle to cycle.

  The present invention has been made in view of such a background, and an object of the present invention is to improve the accuracy of knock determination.

In order to solve the above-described problem, the present invention provides a knock filter processing unit that extracts a knock frequency band that is a frequency band specific to knocks from a knock signal measured by the knock measurement unit, and a frequency band specific to disturbance noise. A disturbance noise filter processing unit that extracts a certain disturbance noise frequency band, and a knock frequency in the knock frequency band extracted by the knock filter processing unit, in the disturbance noise frequency band extracted by the disturbance noise filter processing unit It has an influence degree calculation part which calculates the influence degree of a disturbance noise frequency, and the determination part which determines whether knocking has generate | occur | produced based on the said influence degree.
Other solutions will be described later.

According to the present invention, the accuracy of knock determination can be improved.
Problems, configurations, and effects other than those described above will become apparent from the following description of embodiments.

It is a figure showing the whole internal combustion engine composition concerning a 1st embodiment. It is a figure which shows the structure of ECU which concerns on 1st Embodiment. It is a figure which shows the structure of the control program which concerns on 1st Embodiment. It is a figure which shows a band pass filter characteristic. It is a figure which shows an example of the frequency band which knock frequency band intensity | strength and disturbance noise frequency band intensity generate | occur | produce. It is a figure which shows the knock frequency band intensity | strength of knock frequency band Fs2 in case only the knock has generate | occur | produced in the knock determination angle area. It is a figure which shows the disturbance noise frequency band intensity | strength in case knock does not generate | occur | produce and disturbance noise is contained in the knock determination angle area. It is a figure which shows a knock frequency band intensity | strength in case knocking generate | occur | produces and also disturbance noise is contained in the knock determination angle area. It is a figure which shows the knock frequency band intensity | strength and disturbance noise frequency band intensity | strength in the case of no disturbance noise mixing. It is a figure which shows the knock frequency band intensity | strength after the signal in the case of no disturbance noise mixing passing the filter processing part for knocking. It is a figure which shows the disturbance noise frequency band intensity after the signal in the case of no disturbance noise mixing after passing the filter process part for disturbance noise. It is a figure which shows a knock frequency band intensity and a disturbance noise frequency band intensity in case a knock frequency band intensity is larger than a disturbance noise frequency band intensity. It is a figure which shows the knock frequency band intensity after the signal whose knock frequency band intensity is larger than a disturbance noise frequency band intensity passes the filter processing part for knocks. It is a figure which shows the disturbance noise frequency band intensity after the signal whose knock frequency band intensity is larger than the disturbance noise frequency band intensity passes through the filter processing unit for disturbance noise. It is a figure which shows a knock frequency band intensity and a disturbance noise frequency band intensity in case a knock frequency band intensity and disturbance noise frequency band intensity are comparable. It is a figure which shows the knock frequency band intensity after a signal with the same knock frequency band intensity and disturbance noise frequency band intensity passes through the filter processing unit for knocking. The signal having the same level of the knock frequency band intensity and the disturbance noise frequency band intensity indicates the disturbance noise frequency band intensity after passing through the disturbance noise filter processing unit. It is a figure which shows a knock frequency band intensity and disturbance noise frequency band intensity in case a disturbance noise frequency band intensity is larger than a knock frequency band intensity. It is a figure which shows the knock frequency band intensity after the signal whose disturbance noise frequency band intensity is larger than the knock frequency band intensity passes through the filter processing unit for knocking. It is a figure which shows the disturbance noise frequency band intensity after the signal whose disturbance noise frequency intensity is larger than a knock frequency band intensity passes the filter processing part for disturbance noise. It is a flowchart which shows the process sequence in the control apparatus of the internal combustion engine which concerns on 1st Embodiment. It is a figure which shows the example of the correction necessity flag table which concerns on 1st Embodiment. It is a figure which shows an example of the knock frequency band intensity | strength correction table which concerns on 1st Embodiment. It is a detailed functional block diagram of the knock frequency band intensity correction unit according to the first embodiment. It is a detailed functional block diagram of the background level calculation part which concerns on 1st Embodiment. It is a detailed functional block diagram of the knock determination processing unit according to the first embodiment. It is a figure which shows the structure of the control program which concerns on 2nd Embodiment. It is a flowchart which shows the process sequence in the control apparatus of the internal combustion engine which concerns on 2nd Embodiment.

  Next, modes for carrying out the present invention (referred to as “embodiments”) will be described in detail with reference to the drawings as appropriate.

[Overview of this embodiment]
In the present embodiment, a knock sensor signal in a knock determination angle section, which is a section of a crank angle where knock occurs, is acquired based on the crank angle sensor and information obtained from the knock sensor.
Then, the influence level of the disturbance noise frequency band intensity with respect to the knock frequency band intensity in the knock angle determination section is calculated, and the knock frequency band intensity or the slice level (threshold) for knock determination is corrected based on this influence degree. .
Therefore, in the present embodiment, first, a description will be given from the first embodiment in which the knock frequency band intensity is corrected. In the first embodiment, first, the overall configuration of the internal combustion engine will be described. Thereafter, an ECU (Electric Control Unit) which is a control device will be described, and a program configuration for performing control in the present embodiment will be described.
Thereafter, the concept of the degree of influence described above (in this embodiment, the intensity ratio difference) will be described, and a flowchart will be described.
Subsequently, the second embodiment for correcting the slice level will be described.

[First Embodiment]
(Internal combustion engine)
FIG. 1 is a diagram showing an overall configuration of the internal combustion engine according to the first embodiment.
An internal combustion engine Z shown in FIG. 1 is, for example, an automobile four-cylinder gasoline engine that performs spark ignition combustion.
The internal combustion engine (engine) Z includes an air flow sensor 20, an electronic control throttle 2, an intake air temperature sensor 15, and an intake pressure sensor 21.
The air flow sensor 20 measures the amount of intake air in the intake pipe 6.
The electronic control throttle 2 adjusts the pressure of the intake pipe 6.
The intake air temperature sensor 15 measures the intake air temperature.
The intake pressure sensor 21 measures the pressure in the intake pipe 6.

The internal combustion engine Z includes a cylinder C (C1 to C4), an injector 3, and an ignition system 4 in the cylinder head 7.
The injector 3 is a fuel injection device that injects fuel into the combustion chamber 12 of each cylinder C for each cylinder C (C1 to C4) communicating with each intake pipe 6, and is also referred to as an in-cylinder direct injection injector. The
The ignition system 4 is a system for igniting an air-fuel mixture, and includes a signal generator, an ignition coil, a distributor, a spark plug, and the like.

Further, the internal combustion engine Z includes a coolant temperature sensor 14 and a variable valve 5.
The coolant temperature sensor 14 is provided in the cylinder head 7 and measures the coolant temperature of the internal combustion engine Z.
The variable valve 5 includes an intake valve variable device 5a that adjusts the intake gas flowing into the cylinder C, and an exhaust valve variable device 5b that adjusts the exhaust gas discharged from the cylinder C. Here, the variable valve 5 has a phase angle sensor (not shown) for detecting the phase angle of the intake valve variable device 5a and the exhaust valve variable device 5b. The ECU 1 adjusts the phase angle of the variable valve 5 (particularly, the intake valve variable device 5a and the exhaust valve variable device 5b) to thereby adjust the intake amount of each cylinder C from the cylinder C1 to the cylinder C4 and EGR (Exhaust Gas Recirculation). Adjust the amount.

A high pressure fuel pump 17 for supplying high pressure fuel to the injector 3 is connected to the injector 3 of the internal combustion engine Z via a fuel pipe. The fuel pipe is provided with a fuel pressure sensor 18 for measuring the fuel pressure.
Further, the crankshaft (not shown) of the internal combustion engine Z is provided with a crank angle sensor 13 for calculating the rotation angle. The cylinder block (not shown) of the internal combustion engine Z is provided with a knock sensor (knock measurement unit) 22 that detects vibration of the internal combustion engine Z.

The internal combustion engine Z includes a three-way catalyst 10, an air-fuel ratio sensor 9, and an exhaust temperature sensor 11.
The three-way catalyst 10 is installed in the exhaust pipe 8 and purifies the exhaust.
The air-fuel ratio sensor 9 detects the air-fuel ratio of the exhaust on the upstream side of the three-way catalyst 10.
The exhaust temperature sensor 11 measures the exhaust temperature on the upstream side of the three-way catalyst 10.
Reference numeral 23 denotes a camshaft.

The internal combustion engine Z includes an ECU (Engine Control Unit) 1 that controls the combustion state of the internal combustion engine Z. The ECU 1 acquires signals from the air flow sensor 20, the air-fuel ratio sensor 9, the cooling water temperature sensor 14, the intake air temperature sensor 15, and the like. Further, the ECU 1 acquires signals from the exhaust temperature sensor 11, the crank angle sensor 13, the fuel pressure sensor 18, the intake pressure sensor 21, the ignition system 4, the variable valve 5, the knock sensor 22, and the like. The ECU 1 also acquires a signal from an accelerator opening sensor 16 that detects the depression amount of the accelerator pedal, that is, the accelerator opening.
Among these, signals important in the present embodiment are signals acquired from the crank angle sensor 13 and the knock sensor 22.

The ECU 1 calculates a required torque for the internal combustion engine Z based on a signal obtained from the accelerator opening sensor 16. Details of the ECU 1 will be described later.
Further, the ECU 1 calculates the rotation speed of the internal combustion engine Z based on a signal obtained from the crank angle sensor 13. Further, the ECU 1 calculates the operating state of the internal combustion engine Z based on signals obtained from the outputs of the various sensors described above. Then, the ECU 1 calculates main operation amounts related to the internal combustion engine Z such as an air flow rate, a fuel injection amount, an ignition timing, a throttle opening, an operation amount of the variable valve 5, a fuel pressure, and the like.

  The fuel injection amount calculated by the ECU 1 is converted into a valve opening pulse signal and transmitted to the injector 3. Further, an ignition signal generated so as to be ignited at the ignition timing calculated by the ECU 1 is transmitted from the ECU 1 to the ignition system 4. Further, the throttle opening calculated by the ECU 1 is transmitted to the electronic control throttle 2 as a throttle drive signal. Then, the operation amount of the variable valve 5 calculated by the ECU 1 is transmitted to the variable valve 5 as a variable valve drive signal. Further, the fuel pressure calculated by the ECU 1 is transmitted to the high pressure fuel pump 17 as a high pressure fuel pump drive signal.

  Based on the valve opening pulse signal transmitted from the ECU 1 to the injector 3, a predetermined amount of fuel is injected from the injector 3 to the air flowing into the combustion chamber 12 from the intake pipe 6 via the intake valve (not shown). . Thereby, an air-fuel mixture is formed.

  Further, the air-fuel mixture formed in the combustion chamber 12 explodes due to a spark generated from an ignition plug (not shown) of the ignition system 4 at a predetermined ignition timing based on the ignition signal. A piston (not shown) is pushed down by the combustion pressure resulting from the explosion, and a driving force for the internal combustion engine Z is generated. The exhaust gas after the explosion is sent to the three-way catalyst 10 through the exhaust pipe 8, and the exhaust components of the exhaust gas are purified in the three-way catalyst 10 and discharged to the outside.

(ECU)
FIG. 2 is a diagram illustrating a configuration of the ECU according to the first embodiment.
The ECU 1 mainly includes a CPU (Central Processing Unit) 101, a RAM (Random Access Memory) 102, a ROM (Read Only Memory) 103, an input circuit 104, and an input / output port 105 including an input port and an output port. have.
The CPU 101 performs arithmetic processing according to a control program stored in the ROM 103.
The RAM 102 stores a value indicating the operation amount of each actuator calculated according to the control program.
The ROM 103 stores a control program that describes the contents of calculation processing.
In FIG. 2, a thick arrow between the CPU 101, the RAM 102, the ROM 103, and the input / output port 105 indicates a bus.

The ECU 1 also has an electronic control throttle drive circuit 106 that drives the electronic control throttle 2 and an injector drive circuit 107 that drives the injector 3 in accordance with a calculation process by the control program. Furthermore, the ECU 1 includes an ignition control circuit 108 that controls the ignition system 4 and a variable valve drive circuit 109 that controls the intake valve variable device 5a and the exhaust valve variable device 5b. The ECU 1 has a high-pressure fuel pump drive circuit 110 that drives the high-pressure fuel pump 17.
In addition, the drive circuit in ECU1 is not limited to these.

  Further, as shown in FIG. 2, output signals from the air flow sensor 20, the ignition system 4, the air-fuel ratio sensor 9, the exhaust temperature sensor 11, the crank angle sensor 13, and the like are input to the input circuit 104 of the ECU 1. Further, output signals from the coolant temperature sensor 14, the intake air temperature sensor 15, the accelerator opening sensor 16, the fuel pressure sensor 18, the intake pressure sensor 21, the knock sensor 22, and the like are input to the input circuit 104. Note that the input signal input to the input circuit 104 is not limited thereto. The signal of each sensor input to the input circuit 104 is transmitted to the input port in the input / output port 105, stored in the RAM 102, and then processed by the control program.

  A value indicating the operation amount of each actuator calculated by the control program (hereinafter referred to as operation amount as appropriate) is stored in the RAM 102 and then transmitted to the output port in the input / output port 105. Thereafter, the operation amount is controlled by electronic control throttle 2, injector 3, ignition system 4, via electronic control throttle drive circuit 106, injector drive circuit 107, ignition control circuit 108, variable valve drive circuit 109, high pressure fuel pump drive circuit 110, etc. It is transmitted to the intake valve variable device 5a, the exhaust valve variable device 5b, the high pressure fuel pump 17, and the like.

  Here, as described above, the output signal (knock sensor signal) of the knock sensor 22 is input to the input circuit 104 of the ECU 1. The ECU 1 detects the knock of the internal combustion engine Z based on the input knock sensor signal. When the ECU 1 detects the occurrence of knocking in the internal combustion engine Z, the control program transmits a control signal to the ignition system 4 via the ignition control circuit 108 to control the ignition timing.

Next, the knock detection method of the internal combustion engine Z by the ECU 1 will be outlined with reference to FIGS.
(Control program)
FIG. 3 is a diagram illustrating a configuration of a control program according to the first embodiment.
Details of the processing of each unit 201 to 209 in FIG. 3 will be described later.
The control program includes a signal selection unit 200, a high-speed ADC (Analog Digital Converter) 201, a knock filter processing unit 202, and a knock frequency band intensity calculation unit 203. Furthermore, the control program includes a disturbance noise filter processing unit 204 and a disturbance noise frequency band intensity calculation unit 205. Further, the control program includes a knock frequency band intensity correction unit (influence calculation unit, correction unit) 206, a background level calculation unit (background noise calculation unit) 207, a knock determination processing unit 208, and a knock avoidance control unit 209. doing.
Hereinafter, an outline of the operation of each unit will be described in order. Details of the processing of each part will be described later.

The knock sensor 22 (see FIG. 1) converts the vibration of the internal combustion engine Z into a voltage signal and transmits it to the ECU 1. Then, the signal selection unit 200 determines the signal from the crank angle sensor 13, and only when the signal of the crank angle sensor 13 indicates the knock determination angle section, the signal of the knock sensor 22 (knock sensor signal) is converted to the high speed ADC 201. Output to.
The high speed ADC 201 performs high speed AD conversion on the input knock sensor signal. When knocking occurs, a high frequency component of several tens of kHz is superimposed on the knock sensor signal in the internal combustion engine Z. Therefore, it is desirable for the high-speed ADC 201 to perform AD conversion at a frequency that is at least twice the frequency to be detected by the sampling theorem. For example, when detecting vibrations up to 20 kHz, the high-speed ADC 201 performs high-speed AD conversion at a sampling frequency of 40 kHz (= 25 μs) or more.

  The signal AD-converted by the high-speed ADC 201 is output to the knock filter processing unit 202 and the disturbance noise filter processing unit 204, respectively.

  The knock filter processing unit 202 extracts frequency components of each knock frequency band in a frequency band (knock frequency band) in which a characteristic frequency intensity is generated when a knock occurs. The knock frequency band is known in advance by experiments or the like. The knock filter processing unit 202 sets a band pass filter (knock band pass filter) for each knock frequency band in order to extract the frequency component of the knock frequency band. When there are n knock frequency bands, n knock bands FLs1 to FLsn are set. The knock bandpass filters FLs1 to FLsn are filters that pass the frequency components of a predetermined frequency band from the center frequency, with the center frequencies of the respective filters being Fs1, Fs2,. As a result, the knock filter processing unit 202 can extract the frequency components of each knock frequency band.

  Knock frequency band intensity calculation section 203 calculates the knock frequency band intensity, which is the frequency intensity of each knock frequency band, using the frequency components of each knock frequency band extracted by knock filter processing section 202. The calculation result by knock frequency band intensity calculation unit 203 is output to knock frequency band intensity correction unit 206.

The disturbance noise filter processing unit 204 extracts a frequency component of the disturbance noise frequency band in a frequency band (disturbance noise frequency band) in which a characteristic frequency intensity is generated when the disturbance noise is generated. The disturbance noise frequency band is known in advance through experiments and the like. The disturbance noise filter processing unit 204 sets a disturbance noise band-pass filter in order to extract a frequency component of the disturbance noise frequency band. Here, the disturbance noise band-pass filter is set for a frequency band adjacent to the knock frequency band. When there are m disturbance noise frequency bands adjacent to the knock frequency band, m band pass filters FLn1 to FLnm are also set. Even if a bandpass filter for disturbance noise is set in a frequency band that is not adjacent to the knock frequency band, the disturbance noise in this frequency band does not affect the knock frequency band intensity and is not used for correction. Therefore, it is desirable not to set an unnecessary disturbance noise bandpass filter in terms of reducing processing load and resources.
Note that the frequency intensity is a portion having the highest intensity in the frequency characteristics in the bandpass filter. In many cases, it matches the intensity at the center frequency.

  As a result, the disturbance noise filter processing unit 204 can extract only the frequency component of the disturbance noise frequency band that affects the knock frequency band intensity.

  The disturbance noise frequency band intensity calculation unit 205 uses the frequency components of each disturbance noise frequency band extracted by the disturbance noise filter processing unit 204 to calculate the disturbance noise frequency band intensity, which is the frequency intensity of each disturbance noise frequency band, respectively. calculate. The calculation result by the disturbance noise frequency band intensity calculation unit 205 is output to the knock frequency band intensity correction unit 206.

  Knock frequency band intensity correction section 206 corrects the disturbance noise influence for the frequency band considered to be affected by disturbance noise in the frequency intensity of each knock frequency band. The knock frequency band intensity correction unit 206 does not perform disturbance noise correction for the knock frequency band intensity of the frequency band not affected by the disturbance noise.

If knock control is performed without correcting the influence of the disturbance noise in the knock frequency band intensity considered to be affected by the disturbance noise, there is a possibility that the occurrence of knocking may be erroneously detected even when no knock occurs. As a result, the output of the internal combustion engine Z (see FIG. 1) may be reduced or the fuel consumption may be deteriorated. For this reason, when the knock frequency band intensity is affected by disturbance noise, the knock control is correctly performed by correcting the disturbance noise influence.
The calculation result by the knock frequency band intensity correction unit 206 is output to the background level calculation unit 207 and the knock determination processing unit 208.

The background level calculation unit 207 calculates the background level BGL when no knock occurs in each knock frequency band. The background level BGL is the magnitude of background noise (mechanical noise) generated with the operation of each component of the internal combustion engine Z. The main cause of background noise is often due to cylinder rotation. The calculation method of the background level BGL of each knock frequency band may be performed by weighted average processing or the like as will be described later. The background level calculation unit 207 will be described later.
The calculation result by the background level calculation unit 207 is output to the knock determination processing unit 208.

  Knock determination processing unit 208 generates knock in internal combustion engine Z using the calculation result by knock frequency band intensity correction unit 206, the calculation result by background level calculation unit 207, and a preset slice level (threshold). It is determined whether or not. As a determination method, the difference or ratio between the calculation result by the knock frequency band intensity correction unit 206 and the calculation result by the background level calculation unit 207 is compared with a slice level set in advance for each operation condition. If the result of comparison indicates that the slice level is greater than the slice level, knock determination processing section 208 determines that knock has occurred.

  When knock determination processing unit 208 determines that knock has occurred, knock avoidance control unit 209 performs control for knock avoidance. Methods for avoiding knocking include moving the ignition timing to the retarded side and increasing the fuel injection amount. However, there is little impact on fuel consumption and exhaust, and retarding the ignition timing with quick response is common. It is a workaround.

(Band pass filter characteristics)
FIG. 4 is a diagram showing bandpass filter characteristics.
In FIG. 4, the horizontal axis indicates the frequency, and the vertical axis indicates the gain (dB).
When configuring a band-pass filter, the signal pass band is narrower than the center frequency, and the gain outside the center frequency band is set to be low. As a result, the signal that has passed through the band-pass filter does not substantially contain noise components outside the center frequency band, so the SN ratio, which is the ratio of the signal (knock frequency band intensity) and noise, is high. The “noise” here is not limited to disturbance noise but is noise in a general sense. Therefore, it is desirable for the knock filter processing unit 202 (see FIG. 3) and the disturbance noise filter processing unit 204 (see FIG. 3) to obtain the frequency intensity of each frequency band using such a bandpass filter.

(Knock frequency band intensity and disturbance noise frequency band intensity)
FIG. 5 is a diagram illustrating an example of a frequency band in which the knock frequency band intensity and the disturbance noise frequency band intensity are generated.
In both the upper and lower stages of FIG. 5, the horizontal axis indicates the frequency, and the vertical axis indicates the frequency intensity. Note that the frequency axes in the upper and lower stages of FIG. 5 are the same.
Hereinafter, the knock frequency band whose center frequency is Fsn is referred to as a knock frequency band Fsn. Similarly, a disturbance noise frequency band whose center frequency is Fnm is referred to as a disturbance noise frequency band Fnm.
The upper part of FIG. 5 shows the characteristics of the knock frequency band intensity. The upper part of FIG. 5 shows an example in which a frequency intensity peak peculiar to knock appears in the frequency band of Fs1 to Fs5.

Further, the lower part of FIG. 5 shows the frequency intensity characteristics of disturbance noise. The lower part of FIG. 5 shows an example in which a frequency intensity peak peculiar to disturbance noise appears in the frequency band of Fn1 to Fn3.
Originally, background noise is included in all frequency bands in the upper and lower stages of FIG. 5, but since background noise is generated regardless of knocking, in the upper and lower stages of FIG. The illustration is omitted.

In the example of FIG. 5, the knock frequency band Fs2 and the disturbance noise frequency band Fn1 exist in adjacent frequency bands. That is, knock frequency band Fs2 and disturbance noise frequency band Fn1 influence each other.
On the other hand, since the disturbance noise frequency bands Fn2 and Fn3 are present at positions away from any knock frequency band, these disturbance noises do not affect the knock frequency band intensity.
Therefore, the knock frequency band intensity of the knock frequency band Fs2 that is affected by disturbance noise corrects the influence of disturbance noise. On the other hand, disturbance noise correction need not be performed for knock frequency bands Fs1, Fs3 to Fs5 that are not affected by disturbance noise.

(Knock frequency band intensity and disturbance noise frequency band intensity)
Next, the relationship between the knock frequency band Fs2 and the disturbance noise frequency band Fn1 will be described with reference to FIGS. Reference is made to FIG. 3 as appropriate.
6 to 20, the horizontal axis indicates the frequency, and the vertical axis indicates the frequency intensity. 6 to 20, the frequency axes are the same.

<About intensity ratio difference>
First, an example in which disturbance noise affects the knock frequency band intensity will be described with reference to FIGS.
FIG. 6 is a diagram illustrating the knock frequency band strength of the knock frequency band when only knock occurs in the knock determination angle section and no disturbance noise is included.
The knock frequency band intensity of the knock frequency band Fs2 is composed of a band pass filter FLs2 centered on the knock frequency Fs2. The frequency components shown in FIG. 6 correspond to the frequency components after passing through the knocking filter processing unit 202.

  Since one of the frequency intensity peaks appearing at the occurrence of knock appears at the knock frequency Fs2, the frequency intensity at the knock frequency Fs2 is high, and the frequency intensity decreases as the distance from the knock frequency Fs2 increases. And, the frequency intensity outside the pass band of the band pass filter is hardly obtained.

FIG. 7 is a diagram illustrating the disturbance noise frequency band intensity of the disturbance noise frequency band when no knock has occurred and disturbance noise is included in the knock determination angle section. For reference, the band pass filter FLs2 is also shown.
The disturbance noise frequency band intensity of the disturbance noise frequency band Fn1 is composed of a bandpass filter FLn1 centered on the disturbance noise frequency Fn1. The frequency component shown in FIG. 7 corresponds to the frequency component after passing through the disturbance noise filter processing unit 204.
Since one of the frequency intensity peaks that appear when disturbance noise occurs appears in the disturbance noise frequency Fn1, the frequency intensity at the disturbance noise frequency Fn1 is high, and the frequency intensity decreases as the distance from the disturbance noise frequency Fn1 increases. Then, the frequency intensity outside the pass band of the band pass filter FLn1 is hardly obtained.

FIG. 8 is a diagram illustrating the knock frequency band intensity when knocking occurs and disturbance noise is included in the knock determination angle section.
FIG. 8 shows a state where both the knock frequency band intensity of knock frequency band Fs2 shown in FIG. 6 and the disturbance noise frequency band intensity shown in FIG. 7 are generated.
The knock frequency band Fs2 and the disturbance noise frequency band Fn1 are adjacent to each other, and some of the frequency bands are overlapped. Therefore, in the overlapped portion, the disturbance noise frequency band intensity is superimposed on the knock frequency band intensity. Therefore, the frequency intensity actually generated by knocking is the magnitude shown in FIG. 6, but when affected by disturbance noise, a part of the frequency intensity becomes larger than the actual magnitude as shown in FIG.

  FIG. 8 shows an example in which knocking occurs in the knock determination angle section, but in that case, excessive knocking due to the influence of disturbance noise even though the knocking is actually small. There is a risk of false detection. For this reason, when the knock avoidance control amount (for example, the retard amount of the ignition timing) is changed depending on the magnitude of the generated knock frequency band intensity, the ignition timing may be retarded more than necessary, leading to deterioration of fuel consumption.

  In addition, when no knock has occurred in the knock determination angle section, the knock avoidance control which may be erroneously detected as having occurred due to the influence of disturbance noise (see FIG. 7) and may not be executed originally. May be executed. If such control is executed, there is a possibility that fuel consumption is deteriorated.

  Therefore, in order to detect the knock correctly, the disturbance noise frequency band that affects the knock frequency band is corrected regardless of whether or not the knock occurs.

Here, the intensity ratio difference ΔRKD used in determining the knock frequency band intensity correction coefficient in the present embodiment will be described.
In the following description, in FIG. 5, attention is paid to the knock frequency band Fs2 that is affected by disturbance noise, and this frequency intensity (knock frequency band intensity) is SKD2. In FIG. 5, the frequency intensity (disturbance noise frequency band intensity) of the disturbance noise frequency band Fn1 that affects the knock frequency band Fs2 is NKD1.

  Here, between the knock frequency band intensity SKD2 and the disturbance noise frequency band intensity NKD1, the higher frequency intensity is defined as 100%, and the ratio of the other frequency intensity to the frequency intensity is obtained. This ratio is called a frequency intensity ratio. In the example of the present embodiment, the frequency intensity ratio includes a knock frequency intensity ratio RSKD2 related to the knock frequency band intensity SKD2 and a disturbance frequency band intensity ratio RNKD1 related to the disturbance noise frequency band intensity NKD1.

That is, when the knock frequency band strength SKD2 is larger than the disturbance noise frequency band strength NKD1, the knock frequency band strength SKD2 is set to 100%, and the ratio of the disturbance noise frequency band strength NKD1 to the knock frequency band strength SKD2 is x (0 ≦ x <100)%.
For example, it is assumed that knock frequency band intensity SKD2 is larger than disturbance noise frequency band intensity NKD1, and disturbance noise frequency band intensity NKD1 is half the magnitude of knock frequency band intensity SKD2. In such a case, knock frequency band intensity ratio RSKD2 and disturbance noise frequency band intensity ratio RNKD1 are as follows.
RSKD2 = 100%
RNKD1 = 50%

When the disturbance noise frequency band intensity NKD1 is larger than the knock frequency band intensity SKD2, the disturbance noise frequency band intensity NKD1 is set to 100%, and the ratio of the knock noise band intensity SKD2 to the disturbance noise frequency band intensity NKD1 is x (0 ≦ x <100)%.
For example, it is assumed that the disturbance noise frequency band intensity NKD1 is larger than the knock frequency band intensity SKD2, and the knock frequency band intensity SKD2 is half the magnitude of the disturbance noise frequency band intensity NKD1. In such a case, knock frequency band intensity ratio RSKD2 and disturbance noise frequency band intensity ratio RNKD1 are as follows.
RSKD2 = 50%
RNKD1 = 100%

  Then, as shown in the following formula (1), a difference obtained by subtracting the disturbance noise frequency band intensity ratio RNKD1 from the knock frequency band intensity ratio RSKD2 is defined as an intensity ratio difference ΔRKD.

  ΔRKD = RSKD2-RNKD1 (1)

Here, −100% ≦ ΔRKD ≦ + 100%.
The intensity ratio difference ΔRKD is an evaluation value indicating how much the disturbance noise frequency affects the knock frequency. That is, the influence degree of the disturbance frequency with respect to the knock frequency.
If the intensity ratio difference ΔRKD is on the + side, it indicates that the knock frequency band intensity SKD2 is larger than the disturbance noise frequency band intensity NKD1. The greater the intensity ratio difference ΔRKD is on the positive side, the greater the knock frequency band intensity SKD2 is than the disturbance noise frequency band intensity NKD1. That is, the influence of the disturbance noise frequency is small.

  Further, if the intensity ratio difference ΔRKD is on the negative side, it indicates that the disturbance noise frequency band intensity NKD1 is larger than the knock frequency band intensity SKD2. The smaller the intensity ratio difference ΔRKD is to the minus side, the greater the disturbance noise frequency band intensity NKD1 is than the knock frequency band intensity SKD2. That is, the influence of the disturbance noise frequency is large.

<Disturbance noise frequency band intensity ≒ 0>
Next, an example in which the disturbance noise frequency band intensity is substantially zero will be described with reference to FIGS.
FIG. 9 is a diagram illustrating frequency intensities when knocking occurs and disturbance noise is not mixed in the knock determination angle section.
Regarding the knock frequency band intensity, the center frequency of the generated knock frequency band intensity is Fs2. Further, since disturbance noise is almost non-mixed, the disturbance noise frequency band intensity hardly appears.
The knock frequency band intensity after passing through the knock filter processing unit 202 is as shown in FIG. Similarly, the disturbance noise frequency band intensity after passing through the disturbance noise filter processing unit 204 is as shown in FIG.

FIG. 10 is a diagram illustrating the knock frequency band intensity after the signal of the condition in FIG. 9 passes through the knock filter processing unit.
Here, knock frequency band Fs2 and disturbance noise frequency band Fn1 are adjacent to each other, and some frequency bands overlap. However, since the disturbance noise is not mixed, it is hardly affected by the disturbance noise as shown in FIG.

FIG. 11 is a diagram illustrating the disturbance noise frequency band intensity after the signal of the condition in FIG. 9 has passed through the disturbance noise filter processing unit.
Incidentally, the knock frequency band intensity SKD2 and the disturbance noise frequency band intensity NKD1 indicate peak values in the respective bandpass filters in the frequency characteristics in which the knock frequency and the disturbance noise frequency are superimposed on each other.

In the example shown in FIGS. 9 to 11, since the knock frequency band intensity ratio RSKD2 = 100% and the disturbance noise frequency band intensity ratio RNKD1 = 0%, the intensity ratio difference ΔRKD is + 100%.
As described above, the intensity ratio difference ΔRKD is a difference obtained by subtracting the disturbance noise frequency band intensity ratio RNKD1 from the knock frequency band intensity ratio RSKD2.
The intensity ratio difference ΔRKD = + 100% indicates that the influence of disturbance noise is almost zero. In such a case, the correction of the knock frequency band intensity is not executed.

If the disturbance noise frequency band intensity ratio RNKD1 is not 0%, the knock frequency band intensity ratio RSKD2 = 100% and the disturbance noise frequency band intensity ratio RNKD1 = 10%, the intensity ratio difference ΔRKD is + 90%. Become.
The intensity ratio difference ΔRKD = + 90% indicates that the influence of disturbance noise is very small. In such a case, the correction of the knock frequency band intensity may be small.
When the influence of disturbance noise is small, such as when the intensity ratio difference ΔRKD is + 90% or more, it is desirable not to execute the correction of the knock frequency band intensity. It should be noted that the intensity ratio difference ΔRKD at which the knock frequency band intensity is not corrected is not limited to + 90% or more.

(Knock frequency band intensity> disturbance noise frequency band intensity)
Next, referring to FIG. 12 to FIG. 14, disturbance noise is mixed, and the influence of the disturbance noise on the knock frequency band intensity is larger than the example shown in FIG. 9 to FIG. An example larger than the example shown in FIG.
FIG. 12 is a diagram showing the knock frequency band intensity and the disturbance noise frequency band intensity when the knock frequency band intensity is larger than the disturbance noise frequency band intensity.
FIG. 12 shows a state where the knock frequency band intensity and the disturbance noise frequency band intensity are not superimposed.
As shown in FIG. 12, the center frequency of the generated knock frequency band intensity is Fs2. Since disturbance noise is mixed, the disturbance noise frequency band intensity is generated with the disturbance noise frequency band Fn1 as the center frequency, though not as high as the knock frequency band intensity.
In such a case, the knock frequency band intensity after passing through the knock filter processing unit 202 is as shown in FIG. Further, the disturbance noise frequency band intensity after passing through the disturbance noise filter processing unit 204 is as shown in FIG.

  FIG. 13 is a diagram illustrating the knock frequency band intensity after the signal of the condition in FIG. 12 has passed through the knock filter processing unit. Since knock frequency band Fs2 and disturbance noise frequency band Fn1 are adjacent to each other and some frequency bands overlap, the knock frequency band intensity is affected by disturbance noise (disturbance noise is superimposed) and is partially The frequency intensity is larger than the original knock frequency band intensity.

FIG. 14 is a diagram illustrating the disturbance noise frequency band intensity after the signal of the condition in FIG. 12 passes through the disturbance noise filter processing unit.
As described above, disturbance noise is mixed in the knock determination angle section, and the knock frequency band Fs2 and the disturbance noise frequency band Fn1 are adjacent to each other. Therefore, disturbance noise is affected by knocking (with frequency intensity superimposed), and in part, the frequency intensity is larger than the original large disturbance noise frequency band intensity.

  The examples shown in FIGS. 12 to 14 are cases where the knock frequency band intensity is larger than the disturbance noise frequency band intensity. For example, if the knock frequency band intensity ratio RSKD2 = 100% and the disturbance noise frequency band intensity ratio RNKD1 = 50%, the intensity ratio difference ΔRKD is + 50%. The intensity ratio difference ΔRKD = + 50% indicates that the knock frequency band intensity SKD2 is larger than the disturbance noise frequency band intensity NKD1. However, since it is affected by disturbance noise as compared with the examples shown in FIGS. 9 to 11, the correction amount of the knock frequency band intensity is made larger than the examples shown in FIGS.

<Knock frequency band intensity ≒ disturbance noise frequency band intensity>
Next, referring to FIGS. 15 to 17, an example in which the influence of the disturbance noise frequency band intensity on the knock frequency band intensity is larger than that in FIGS. 12 to 14 and the correction amount is larger than that in FIGS. 12 to 14. explain.
FIG. 15 is a diagram illustrating the knock frequency band intensity and the disturbance noise frequency band intensity when the knock frequency band intensity and the disturbance noise frequency band intensity are approximately the same.
FIG. 15 shows a state where the knock frequency band intensity and the disturbance noise frequency band intensity are not superimposed.
As shown in FIG. 15, the center frequency of the generated knock frequency band intensity is Fs2. A part of the knock frequency is affected by disturbance noise of the center frequency Fn1. The center frequency of the generated disturbance noise frequency band intensity is Fn1. Part of the disturbance noise frequency band intensity is affected by knocking. In this case, the knock frequency band intensity after passing through the knock filter processing unit 202 is as shown in FIG. Further, the disturbance noise frequency band intensity after passing through the disturbance noise filter processing unit 204 is as shown in FIG.

FIG. 16 is a diagram showing the knock frequency band intensity after the signal of the condition in FIG. 15 has passed through the knock filter processing unit.
As described above, the knock frequency band Fs2 and the disturbance noise frequency band Fn1 are adjacent to each other. Therefore, the knock frequency band Fs2 and the disturbance noise frequency band Fn1 are partially overlapped. Therefore, the knock frequency band intensity of knock frequency band Fs2 is affected by disturbance noise, and a part of the knock frequency band intensity is higher than the original knock frequency band intensity.

FIG. 17 shows the disturbance noise frequency band intensity after the signal of the condition in FIG. 15 has passed through the disturbance noise filter processing unit.
As described above, the knock frequency band Fs2 and the disturbance noise frequency band Fn1 are adjacent to each other. For this reason, the disturbance noise frequency band intensity is influenced by knocking, and a part of the disturbance noise frequency band intensity is larger than the original disturbance noise frequency band intensity.

  The example shown in FIGS. 15 to 17 shows a case where the knock frequency band intensity and the disturbance noise frequency band intensity are approximately the same. In such a case, for example, if the knock frequency band intensity ratio RSKD2 = 100% and the disturbance noise frequency band intensity ratio RNKD1 = 80%, the intensity ratio difference ΔRKD is + 20%. The intensity ratio difference ΔRKD = + 20% indicates that the knock frequency band intensity SKD2 is larger than the disturbance noise frequency band intensity NKD1, but is more strongly affected by disturbance noise than in the case of FIGS. ing. For this reason, the amount of correction of the knock frequency band intensity is made larger than in the case of FIGS.

<Knock frequency band intensity <Disturbance noise frequency band intensity>
Next, an example in which the influence of disturbance noise on the knock frequency band intensity is larger than that in FIGS. 15 to 17 and the correction amount is larger than that in FIGS. 15 to 17 will be described with reference to FIGS. That is, FIGS. 18-20 demonstrates the case where disturbance noise frequency band intensity | strength is larger than knock frequency band intensity | strength.
FIG. 18 is a diagram illustrating the knock frequency band intensity and the disturbance noise frequency band intensity when the disturbance noise frequency band intensity is greater than the knock frequency band intensity.
FIG. 18 shows a state where the knock frequency band intensity and the disturbance noise frequency band intensity are not superimposed.
As shown in FIG. 18, the center frequency of the knock frequency band intensity is Fs2. The knock frequency band intensity of knock frequency band Fs2 is affected by disturbance noise.
On the other hand, the center frequency of disturbance noise is Fn1. A part of the disturbance noise frequency band intensity of the disturbance noise frequency band Fn1 is affected by knocking.
In such a case, the knock frequency band intensity after passing through the knock filter processing unit 202 is as shown in FIG. Further, the disturbance noise frequency band intensity after passing through the disturbance noise filter processing unit 204 is as shown in FIG.

FIG. 19 is a diagram illustrating the knock frequency band intensity after the signal of the condition in FIG. 18 passes through the knock filter processing unit.
As described above, the knock frequency band Fs2 and the disturbance noise frequency band Fn1 are adjacent to each other. Therefore, the knock frequency band Fs2 and the disturbance noise frequency band Fn1 partially overlap each other. Therefore, knock frequency band strength SKD2 is affected by disturbance noise, and a part thereof has a frequency strength larger than the original knock frequency band strength.

FIG. 20 is a diagram illustrating the disturbance noise frequency band intensity after the signal condition in FIG. 18 passes through the disturbance noise filter processing unit.
As described above, the knock frequency band Fs2 and the disturbance noise frequency band Fn1 are adjacent to each other. Therefore, the disturbance noise frequency band intensity NKD1 is affected by knocking, and a part of the disturbance noise frequency band intensity NKD1 is larger than the original frequency intensity.

  In the example shown in FIGS. 18 to 20, the disturbance noise frequency band intensity is larger than the knock frequency band intensity. For example, if the knock frequency band intensity ratio RSKD2 = 50% and the disturbance noise frequency intensity ratio RNKD1 = 100%, the intensity ratio difference ΔRKD is −50%. The intensity ratio difference ΔRKD = −50% indicates that the knock frequency band intensity SKD2 is smaller than the disturbance noise frequency intensity NKD1, and is more strongly affected by the disturbance noise than in the case of FIGS. Yes. Therefore, the correction amount of the knock frequency band intensity is made larger than in the case of FIGS.

  From the above description, regarding the relationship between the intensity ratio difference ΔRKD and the knock frequency band intensity correction amount, the correction amount decreases as the intensity ratio difference ΔRKD increases toward the plus side, and increases as it decreases toward the minus side.

(Processing procedure)
Next, a processing procedure in the ECU according to the present embodiment will be described with reference to FIGS.
FIG. 21 is a flowchart showing a processing procedure in the control apparatus for an internal combustion engine according to the first embodiment.
The processing in FIG. 21 is started when the internal combustion engine Z is turned “ON”.
First, the signal selection unit 200 selects a signal input from the knock sensor 22 based on the signal from the crank angle sensor 13 and outputs the selected signal to the high-speed ADC 201. That is, the signal selection unit 200 outputs the signal of the knock sensor 22 to the high-speed ADC 201 only when the signal of the crank angle sensor 13 is in the knock determination angle section.
Then, the high speed ADC 201 reads the knock sensor signal from the knock sensor 22 in the knock determination angle section in which the knock determination is performed (S101).
The knock determination angle section is a crank angle section that is set in advance (for example, from the top dead center until the crank angle is advanced by 90 deg). Whether or not it is a knock determination angle section may be determined based on a signal acquired from the crank angle sensor 13.
Alternatively, the start position of the knock determination angle section and the crank angle determination section may be variable depending on the engine speed and the load.

  The high-speed ADC 201 performs high-speed AD conversion on the read knock sensor signal (S102). The knock sensor signal subjected to the high-speed AD conversion is sent to the knock filter processing unit 202 and the disturbance noise filter processing unit 204 in order to calculate the knock frequency band intensity and the disturbance noise frequency band intensity.

Next, the knocking filter processing unit 202 performs knocking filter processing on the knock sensor signal (S103).
The knock filter processing unit 202 is provided with n knock band-pass filters FLs1 to FLsn in order to obtain a characteristic frequency intensity peak when a knock occurs. The knock band-pass filters FLs1 to FLsn are set in advance based on a knock frequency band known in advance through experiments.
For example, the knocking bandpass filter FLs1 is a filter that extracts only a signal having a frequency intensity within a predetermined frequency band having a center frequency of Fs1 (kHz). The other knock bandpass filters FLs2 to FLsn have similar characteristics. Knock filter processing section 202 extracts knock frequency band intensities SKD1 to SKDn of the respective frequency bands from the knock sensor signal using knock bandpass filters FLs1 to FLsn.

  Then, the knock frequency band intensity calculation unit 203 performs knock frequency band intensity calculation for calculating the frequency intensity of the knock sensor signal that has passed through the knock band pass (S104).

Further, the disturbance noise filter processing unit 204 performs disturbance noise filter processing on the knock sensor signal (S105).
In the disturbance noise filter processing unit 204, a disturbance noise band-pass filter having a peak of a disturbance noise frequency band intensity characteristic when disturbance noise occurs is set. When there are m frequency bands having peaks in the disturbance noise frequency band intensity, m disturbance noise band-pass filters FLn1 to FLnm are set. Note that the disturbance noise band-pass filters FLn1 to FLnm are set in advance based on a disturbance noise frequency band known in advance by experiments.
For example, the disturbance noise band-pass filter FLn1 is a band-pass filter that extracts a signal having only a frequency component within a predetermined frequency band having a center frequency of Fn1 (kHz). The other disturbance noise band-pass filters FLn2 to FLnm have similar characteristics. The disturbance noise filter processing unit 204 extracts disturbance noise frequency band intensities NKD1 to NKDm of each frequency band from the knock sensor signal using each disturbance noise bandpass filter.

Then, the disturbance noise frequency band intensity calculation unit 205 performs disturbance noise frequency band intensity calculation for calculating the frequency intensity of the knock sensor signal that has passed through the disturbance noise band pass (S106).
Note that steps S103 to S104 and steps S105 to S106 are performed in parallel.

Next, the knock frequency band intensity correction unit 206 corrects the necessity / unnecessity flag table (see FIG. 2) stored in the ROM 103 (see FIG. 2) for the knock frequency band intensity SKD1 to SKDn of each knock frequency band calculated in step S104. 22)), the correction necessity flag fHOS is read (S111).
The correction necessity flag fHOS is a flag for identifying whether correction due to the influence of disturbance noise is to be performed.
A knock frequency band in which a peak of a knock frequency band intensity that is characteristic when knock occurs and a disturbance noise frequency band in which a characteristic peak of a disturbance noise frequency band that appears when disturbance noise occurs are different for each type of internal combustion engine Z. Therefore, the manufacturer specifies in advance a frequency band that is easily affected by disturbance noise through experiments or the like. A correction necessity flag fHOS is assigned in advance to each of the knock frequency band strengths SKD1 to SKDn of each knock frequency band. FIG. 22 shows how the correction necessity flag fHOS is assigned.

FIG. 22 is a diagram illustrating an example of a correction necessity flag table according to the first embodiment.
The correction necessity flag table is stored in the ROM 103 (see FIG. 2).
FIG. 22 shows which knock frequency band intensity is corrected and which knock frequency band intensity is not corrected.
Correction necessity flags fHOS1 to fHOSn are assigned to knock frequency band intensities SKD1 to SKDn, respectively. When the correction necessity flag is “1”, the disturbance noise frequency band intensity affecting the corresponding knock frequency band intensity is shown.

In the example of FIG. 22, only the SKD2 of the knock frequency band intensities SKD1 to SKDn has the correction necessity flag fHOS2 = “1”. The other knock frequency band intensities have a correction necessity flag = “0”. This indicates that the knock frequency band intensity affected by disturbance noise is only SKD2. In other words, it can be seen from the correction necessity flag fHOS shown in FIG. 22 that only the knock frequency band intensity SKD2 needs to be corrected for the influence of disturbance noise. Then, in the correction necessity flag fHOS shown in FIG. 22, it is shown that the disturbance noise frequency band intensity that is affected in this case is NKD1. That is, since the frequency band of the disturbance noise frequency band intensity NKD1 is adjacent to the frequency band of the knock frequency band intensity SKD2, the frequency band of the knock frequency band intensity SKD2 is affected by the frequency band in the disturbance noise frequency band intensity NKD1. receive. Therefore, the correction necessity flag fHOS in FIG. 22 indicates that the knock frequency band strength SKD2 is corrected.
As described above, the correction necessity flag fHOS is created in advance based on experiments and the like.

Returning to the description of FIG.
After step S111, knock frequency band intensity correction unit 206 reads knock frequency band intensity SKD for which correction necessity flag fHOS = 1 and disturbance noise frequency band intensity NKD corresponding thereto. Here, knock frequency band strength SKD is a generalization of knock frequency band strengths SKD1 to SKDn. Similarly, the disturbance noise frequency band intensity NKD is a generalization of the disturbance noise frequency band intensity NKD1 to NKDm.

  Then, knock frequency band intensity correction unit 206 calculates knock frequency band intensity ratio RSKD (S112), and calculates disturbance noise frequency band intensity ratio RNKD (S113).

Then, the knock frequency band intensity correcting unit 206 calculates the intensity ratio difference ΔRKD according to the above-described equation (1) (S114).
Next, using the intensity ratio difference ΔRKD as a key, the knock frequency band intensity correction unit 206 searches the correction coefficient COHOS with reference to the knock frequency band intensity correction table described later in FIG. 23 (S115).

Here, the correction coefficient COHOS is a correction coefficient for correcting the influence of disturbance noise included in the knock frequency band intensity SKD.
In the correction coefficient COHOS, COHOS = “1” when no correction is applied. In the case of correction, the correction coefficient COHOS is a numerical value smaller than “1” (0 <COHOS <1). The reason is that the correction coefficient COHOS is a correction coefficient for excluding the influence of disturbance noise from the knock frequency band intensity SKD, so that the correction is made to reduce the knock frequency band intensity SKD.

(Knock frequency band intensity correction table)
FIG. 23 is a diagram illustrating an example of a knock frequency band intensity correction table according to the first embodiment.
The knock frequency band intensity correction table is stored in the ROM 103 (see FIG. 2).
It is set so that the value of the correction coefficient COHOS approaches 0 and the correction amount increases (the knock frequency band intensity SKD decreases) as the value of the intensity ratio difference ΔRKD increases toward the minus side. Conversely, as the value of the intensity ratio difference ΔRKD increases toward the plus side, the value of the correction coefficient COHOS approaches 1, and the correction amount is set to decrease (the knock frequency band intensity SKD increases). .
As described with reference to FIGS. 9 to 20, the greater the value of the intensity ratio difference ΔRKD is in the positive direction, the greater the knock frequency band intensity is than the disturbance noise frequency band intensity. That is, the influence of disturbance noise is small.
In addition, the larger the value of the intensity ratio difference ΔRKD is in the negative direction, the greater the disturbance noise frequency band intensity is than the knock frequency band intensity. That is, the influence of disturbance noise is large.
Therefore, the correction amount is set to increase as the value of the intensity ratio difference ΔRKD increases toward the minus side. Further, the correction amount is set to be smaller as the value of the intensity ratio difference ΔRKD is larger on the plus side.

Returning to the description of FIG.
Knock frequency band intensity correction unit 206 multiplies correction coefficient COHOS searched in step S115 by knock frequency band intensity SKD (knock determination reference amount), so that the corrected knock frequency is the corrected knock frequency band intensity. The band intensity HSKD is calculated (S116).

(Knock frequency band intensity correction unit)
Here, details of knock frequency band intensity correction unit 206 will be described.
FIG. 24 is a detailed functional block diagram of the knock frequency band intensity correction unit according to the first embodiment.
The knock frequency band intensity correction unit 206 includes a frequency intensity ratio calculation unit 401, an intensity ratio difference calculation unit (influence calculation unit) 402, a correction coefficient search unit 403, and a correction knock frequency band intensity calculation unit 404.
The frequency intensity ratio calculation unit 401 reads the knock frequency band intensity SKD and the disturbance noise frequency band intensity NKD, and also reads the correction necessity flag fHOS (S111 in FIG. 21). Then, in order to correct the influence of the disturbance noise, the frequency intensity ratio calculation unit 401 calculates the frequency intensity ratios RSKD and RNKD of the knock frequency band intensity and the disturbance noise frequency band intensity as described above (FIG. 21). S112 and S113).

Thereafter, the intensity ratio difference calculation unit 402 calculates the intensity ratio difference ΔRKD based on the difference between the calculated knock frequency band intensity ratio RSKD and the disturbance noise frequency band intensity ratio RNKD (the above-described equation (1)) (FIG. 21). S114).
Then, the correction coefficient search unit 403 searches the knock frequency band intensity correction table (see FIG. 23) using the calculated intensity ratio difference ΔRKD as a key (S115 in FIG. 21).
Subsequently, the corrected knock frequency band intensity calculation unit 404 calculates the corrected knock frequency band intensity by multiplying the knock frequency band intensity SKD to be processed by the correction coefficient COHOS (S116 in FIG. 21).

Returning to the description of FIG.
Next, the background level calculation unit 207 calculates the background level BGL of each frequency band using the knock frequency band intensity (S117).
As described above, the background level BGL is a mechanical noise generated with the operation of each component of the internal combustion engine Z, and is often derived from noise related to the engine speed. The calculation of the background level BGL will be described later.

FIG. 25 is a detailed functional block diagram of the background level calculation unit according to the first embodiment.
The background level calculation unit 207 includes a calculation unit 501, a previous intensity storage unit 502, and a background level storage unit 503.
The previous intensity storage unit 502 stores the knock frequency band intensity at the time of the previous process. When disturbance noise is corrected during the previous processing, the knock frequency band intensity stored in the previous intensity storage unit 502 becomes the corrected knock frequency band intensity. When disturbance noise is not corrected at the time of the previous processing, the knock frequency band intensity stored in the previous intensity storage unit 502 is the knock frequency band intensity that has not been corrected.
If no knock has been detected in the previous process, the previous strength storage unit 502 stores the knock frequency band strength at which the knock frequency band strength SKD = BGL. That is, the knock frequency intensity when no knock occurs is in a state where there is no peak in FIG.

  The background level storage unit 503 stores the background level BGL calculated in the background calculation process up to the previous time.

When the current value of (correction) knock frequency band intensity (H) SKD is input, calculation unit 501 reads previous knock occurrence flag fKNK stored in ROM 103 (see FIG. 2). The previous knock occurrence flag fKNK stores “1” when a knock is detected in the previous process, and stores “0” when no knock is detected in the previous process.
When the previous knock occurrence flag fKNK is “0”, the calculation unit 501 adds the background level BGL stored in the background level storage unit 503 to the previous process stored in the previous strength storage unit 502. The (corrected) knock frequency band intensity at the time is weighted averaged. The ratio of the weighted average is, for example, (correction) knock frequency band intensity at the time of the previous processing: background level BGL = 1: 3.
The calculation unit 501 outputs the result of the weighted average to the knock determination processing unit 208 as a new background level BGL and overwrites and saves the background level storage unit 503 with the newly calculated background level BGL.

  When the previous knock determination flag fKNK is “1”, the calculation unit 501 outputs the background level BGL stored in the background level storage unit 503 to the knock determination processing unit 208 as it is, and stores the background level. The part 503 is not updated.

When a series of processes for calculating the background level BGL is completed, the current value of the (correction) knock frequency band strength (H) SKD is overwritten and saved in the previous strength storage unit 502.
Note that the value of the background level BGL varies depending on the engine speed. Therefore, the background level BGL value may be updated each time the engine speed changes.
The background level BGL is calculated for each knock frequency band regardless of whether or not the disturbance noise frequency band is adjacent.

Returning to the description of FIG.
Then, the knock determination processing unit 208 reads the slice level SL in the knock determination (S118).
The slice level SL is set in advance for each engine speed.
Then, knock determination processing unit 208 determines whether or not knock has occurred in internal combustion engine Z (S121).
The knock determination is performed using the knock frequency band intensity of each knock frequency band corrected in step S116, the background level BGL of each knock frequency band calculated in step S117, and the slice level SL read in step S118. Done. Specifically, knock determination processing unit 208 calculates a difference obtained by subtracting background level BGL from the knock frequency band intensity for each knock frequency band. Then, knock determination processing section 208 adds the calculated difference (knock frequency band intensity excluding the influence of background noise). This addition result is compared with the slice level SL. When a value equal to or higher than the slice level SL is indicated, the knock determination processing unit 208 determines that knock has occurred (S121 → Yes), and the knock avoidance control unit 209 performs knock avoidance control (S122).
When each difference (the result of adding the knock frequency band intensity excluding the influence of background noise) indicates a value lower than the slice level SL, the knock determination processing unit 208 determines that no knock has occurred (S121 → No), ECU1 returns the process to step S101 (knock avoidance control is not executed).
The process shown in FIG. 21 continues to be executed until the internal combustion engine Z is turned “OFF”.

(Knock determination processing part)
FIG. 26 is a detailed functional block diagram of the knock determination processing unit according to the first embodiment.
The knock determination processing unit 208 includes a calculation unit 601, a slice level search unit 602, and a determination unit 603.
The calculation unit 601 reads the knock frequency band strength SKD or the corrected knock frequency band strength HSKD and the background level BGL corresponding to each knock frequency band.
Then, the calculation unit 601 subtracts the background level BGL of each knock frequency band from the knock frequency band intensity SKD of each knock frequency band or the corrected knock frequency band intensity HSKD. As a result, the calculation unit 601 determines that there are knock frequency band strengths KPn (n is a subscript indicating the knock frequency band, and n of KP1 to KPn) due to vibration at the time of knock occurrence that does not include mechanical noise (background noise). Are calculated for each knock frequency band.
Also, the slice level search unit 602 reads the current engine speed. Then, the slice level search unit 602 searches the slice level SL in the knock determination from a slice level table (not shown). The slice level SL in knock determination is the slice level SL corresponding to the current engine speed. The slice level table is a table in which the engine speed and the slice level SL are associated with each other.
The slice level SL for each engine speed is a value set in advance through experiments or the like.

Then, determination unit 603 adds a part or all of knock frequency band strength KPn calculated by calculation unit 601. Here, adding part or all of the knock frequency band strength KPn means adding i (1 ≦ i ≦ n) knock frequency band strengths KPn in descending order of the knock frequency band strength KPn. Meaning. If i <n, a part of knock frequency band strength KPn is added, and if i = n, all of knock frequency band strength KPn is added. Note that i is a value preset by the user.
Thereafter, the determination unit 603 compares the addition result of the knock frequency band strength KPn with the slice level SL. When the addition result of the knock frequency band strength KPn is equal to or higher than the slice level SL, the determination unit 603 determines that knock has occurred in the internal combustion engine Z (“Yes” in step S121 of FIG. 21). Conversely, when the addition result of the knock frequency KPn is smaller than the slice level SL, the determination unit 603 determines that no knock has occurred in the internal combustion engine Z (“No” in step S121 of FIG. 21).

(Knock avoidance control process)
As the avoidance control process in step S122 of FIG. 21, the knock avoidance control unit 209 changes the ignition timing to the retard side. The retard amount of the ignition timing may be always constant, or a step may be provided for the strength of the generated knock, and the retard amount may be determined according to the step.

  As described above, according to the present embodiment, the knock frequency band intensity is corrected according to the influence of the disturbance noise in the knock determination angle section by using the knock filter processing unit 202 and the disturbance noise filter processing unit 204. As a result, the occurrence of knocking in the internal combustion engine Z can be detected more precisely. Further, by performing the knock avoidance control by controlling the ignition timing based on the detection result of the occurrence of knock, the combustion state of the internal combustion engine Z can be controlled more precisely than before.

Also, the disturbance noise filter processing unit 204 sets a bandpass filter in a characteristic frequency band when disturbance noise occurs. However, in order to obtain a characteristic frequency band when disturbance noise occurs, a knock sensor signal in a section where disturbance noise is generated is used. Therefore, when adapting the setting of the disturbance noise band-pass filter, the knock sensor signal can be input to the disturbance noise filter processing unit 204 in synchronization with the timing at which the disturbance noise occurs.
In the present embodiment, the signal selection unit 200 outputs a knock sensor signal to the high speed ADC 201 based on the signal of the crank angle sensor 13.
In addition, for example, if it is known that disturbance noise is generated when the fuel injection valve is opened and closed, the signal selection unit 200 outputs a knock sensor signal of the injection start timing and the injection end timing to the high-speed ADC 201. Also good. In addition, when it is known that the disturbance noise is vibration when the intake / exhaust valve is seated, the signal selection unit 200 may output a knock sensor signal at the opening / closing timing of the intake / exhaust valve to the high-speed ADC 201. .

In the present embodiment, a correction amount (correction coefficient) is determined based on the influence degree (intensity ratio difference) of the disturbance noise frequency band strength with respect to the knock frequency band strength, and the knock frequency band strength is corrected based on the correction amount. Then, knock determination is performed based on the corrected knock frequency band intensity. By setting it as such a structure, the knock determination which excluded the influence of disturbance noise can be performed, and the precision of a knock determination can be improved. In other words, when a disturbance noise is mixed, an appropriate knock determination can be made according to the influence level of the disturbance noise. In particular, by correcting the knock frequency band intensity and using it for knock determination, the knock frequency band intensity can be set to an appropriate value, and the accuracy of knock determination can be improved.
Moreover, the influence degree of the disturbance noise frequency band intensity with respect to a knock frequency band intensity can be quantified by making the intensity ratio difference by Formula (1) into the above-mentioned influence degree. Thereby, the correction amount (correction coefficient) can be determined quantitatively.

Further, as shown in FIGS. 5 and 22, only the knock frequency band adjacent to each other and the disturbance noise frequency band are used for calculation of the degree of influence (intensity ratio difference), so that there is no influence of disturbance noise. Bands can be excluded from processing. Thereby, the processing load can be reduced.
Further, by calculating the background level and subtracting this background level from the corrected knock frequency band intensity, the influence of the background noise can be excluded from the corrected knock frequency band intensity. Thereby, the accuracy of knock determination can be further increased.

[Second Embodiment]
Next, an internal combustion engine control apparatus according to a second embodiment of the present invention will be described with reference to FIGS.
(Control program configuration)
FIG. 27 is a diagram illustrating a configuration of a control program according to the second embodiment. In FIG. 27, a different part from FIG. 3 is demonstrated, about the structure similar to FIG. 3, the code | symbol same as FIG. 3 is attached | subjected and description is abbreviate | omitted.
In the control program shown in FIG. 27, a slice level correction amount calculation unit 701 is provided instead of the knock frequency band intensity correction unit 206 in FIG.
The slice level correction amount calculation unit 701 searches for a correction necessity flag, calculates a knock frequency band intensity ratio and a disturbance noise frequency band intensity ratio, calculates an intensity ratio difference, and calculates a knock frequency band intensity using the intensity ratio difference. Performs the same processing as the knock frequency band intensity correction unit 206 of FIG. However, after that, the slice level correction amount calculation unit 701 can calculate a slice level correction amount that is a correction amount of the slice level based on the knock frequency band intensity before correction and the knock frequency band intensity after correction. This is different from the knock frequency band intensity correction unit 206.

  In FIG. 27, the knock determination processing unit 208a corrects the slice level based on the slice level correction amount calculated by the slice level correction amount calculation unit 701.

(flowchart)
FIG. 28 is a flowchart showing a processing procedure in the control apparatus for an internal combustion engine according to the second embodiment. In FIG. 28, processing similar to that in FIG. 21 is denoted by the same step number and description thereof is omitted.
In FIG. 21, steps S111 to S116 are processes performed by the knock frequency band intensity correction unit 206, but in FIG. 28, the slice level correction amount calculation unit 701 performs the processes of steps S111 to S116.
After step S116, the slice level correction amount calculation unit 701 calculates the slice level correction amount ΔSL from the following equation (2) (S201).

  ΔSL = SKD−HSKD (2)

In Equation (2), SKD is the knock frequency band intensity before correction calculated in step S104, and HSKD is the knock frequency band intensity after correction calculated in step S116.
When there are a plurality of corrected knock frequency band intensities, the average value of ΔSL calculated by equation (2) may be ΔSL.

  After step S118, the knock determination processing unit 208a calculates the corrected slice level HSL by the following equation (3) (S211).

  HSL = SL + ΔSL (3)

In equation (3), SL is the slice level (knock determination reference amount) read in step S118, and ΔSL is the slice level correction amount calculated in step S201.
In step S121, a part or all of the knock frequency band intensity before correction is added, and the average value is compared with the corrected slice level HSL.

  According to the second embodiment, by correcting the slice level, the correction amount becomes uniform, and the processing concept becomes simple. By simplifying the processing concept in this way, bugs can be corrected efficiently.

  The present invention is not limited to the above-described embodiment, and includes various modifications. For example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to having all the configurations described. In addition, a part of the configuration of a certain embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of a certain embodiment. In addition, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

In the first and second embodiments, the background level calculation unit 207 is installed in the preceding stage of the knock determination processing unit 208 (see FIG. 3 and FIG. 27). It may be installed downstream of 208.
In such a case, the processing of the background level calculation unit 207 is as follows.
When a knock is detected by knock determination processing unit 208, background level calculation unit 207 weights and averages the current value of (corrected) knock frequency band intensity (H) SKD and the past background level BGL. Then, the background level calculation unit 207 overwrites and saves the result of the weighted average in the background level storage unit 503 as a new background level BGL.
If no knock is detected by the knock determination processing unit 208, the background level calculation unit 207 performs no processing.

In addition, each of the above-described configurations, functions, units 200 to 209, 401 to 404, 501 to 502, 601 to 603, 701, and 208a, the previous intensity storage unit 502, and the like may be partly or entirely, for example, integrated circuits. You may implement | achieve by hardware by designing etc. Further, as shown in FIG. 2, the above-described configurations, functions, and the like may be realized by software by a processor such as a CPU reading and executing a program that realizes each function. Information such as programs, tables, and files for realizing each function is stored in an HD (Hard Disk), a memory, a recording device such as an SSD (Solid State Drive), an IC (Integrated Circuit) card, It can be stored in a recording medium such as an SD (Secure Digital) card or a DVD (Digital Versatile Disc).
In each embodiment, control lines and information lines are those that are considered necessary for explanation, and not all control lines and information lines are necessarily shown on the product. In practice, it can be considered that almost all configurations are connected to each other.

1 ECU (control device)
13 Crank angle sensor 22 Knock sensor (knock measurement unit)
200 Signal Selection Unit 201 Knock Filter Processing Unit 203 Knock Frequency Band Strength Calculation Unit 204 Disturbance Noise Filter Processing Unit 205 Disturbance Noise Frequency Band Strength Calculation Unit 206 Knock Frequency Band Strength Correction Unit (Influence Calculation Unit, Correction Unit)
207 Background level calculator (background noise calculator)
208, 208a Knock determination processing unit (determination unit)
209 Knock avoidance control unit 401 Frequency intensity ratio calculation unit 402 Strength ratio difference calculation unit (influence calculation unit)
403 correction coefficient search unit 404 correction knock frequency band intensity calculation unit 501 calculation unit 502 previous intensity storage unit 601 calculation unit 602 slice level search unit 603 determination unit 701 slice level correction amount calculation unit (correction unit)
Z internal combustion engine

Claims (8)

A knock filter processing unit for extracting a knock frequency band, which is a frequency band specific to knock, from the knock signal measured by the knock measurement unit;
A disturbance noise filter processing unit that extracts a disturbance noise frequency band, which is a frequency band peculiar to disturbance noise,
An influence degree calculating unit for calculating an influence degree of the disturbance noise frequency in the disturbance noise frequency band extracted by the disturbance noise filter unit with respect to a knock frequency in the knock frequency band extracted by the knocking filter processing unit;
A determination unit that determines whether knocking has occurred based on the degree of influence;
A control apparatus for an internal combustion engine, comprising: Determining a correction amount of the knock determination reference amount based on the degree of influence, and having a correction unit that corrects the knock determination reference amount by the correction amount;
The determination unit
The control device for an internal combustion engine according to claim 1, wherein it is determined whether or not knocking has occurred based on the corrected knock determination reference amount. The control apparatus for an internal combustion engine according to claim 2, wherein the knock determination reference amount is a knock frequency band intensity that is a frequency intensity at the knock frequency. The control device for an internal combustion engine according to claim 2, wherein the knock determination reference amount is a slice level that is a threshold value for determining whether or not knock has occurred. There are a plurality of the knock frequency band and the disturbance noise frequency band,
Information indicating which knock frequency band and which disturbance noise frequency band are adjacent is preset,
The said correction | amendment part calculates the said influence with respect to the said knock frequency and disturbance noise frequency which are mutually adjacent | abutted among the extracted said knock frequency and the said disturbance noise frequency. The internal combustion engine control device described. The knock frequency band intensity is a frequency intensity in the knock frequency band,
The noise is different from the disturbance noise, and has a background noise calculation unit that calculates background noise over the entire observed frequency range,
The correction unit is
The control device for an internal combustion engine according to claim 2, wherein the knock frequency band intensity is corrected based on the background noise. The knock frequency band intensity is a frequency intensity in the knock frequency band,
Disturbance noise frequency band intensity is the frequency intensity in the disturbance noise frequency band,
Of the knock frequency band intensity and the disturbance noise frequency band intensity, the larger one is defined as 100%, and the ratio of the smaller frequency intensity to the larger frequency intensity of the knock frequency band intensity and the disturbance noise frequency band intensity. By calculating the knock frequency band intensity ratio and the disturbance noise frequency band intensity ratio, a value obtained by subtracting the disturbance noise frequency band intensity ratio from the knock frequency band intensity ratio is the disturbance noise frequency relative to the knock frequency. The control device for an internal combustion engine according to claim 1, wherein Extracting the knock frequency band, which is a frequency band specific to knock, from the knock signal measured by the knock measurement unit, and extracting the disturbance noise frequency band, which is a frequency band specific to disturbance noise,
Calculate the influence of the disturbance noise frequency in the disturbance noise frequency band on the extracted knock frequency in the knock frequency band,
A knock determination method comprising: determining whether knocking has occurred based on the degree of influence.

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