JP6429938B1 - Control device for internal combustion engine - Google Patents

Abstract

A control device for an internal combustion engine capable of avoiding a situation in which a lower limit clip value of a knock determination threshold value is detrimental in calculating an ignition timing learning value when the operation state of the internal combustion engine is in a steady state.
A lower limit clip value calculation unit that calculates a lower limit clip value of a knock determination threshold value based on an ignition timing learned value, and when the operation state detection unit determines that the state is a transient state, the lower limit clip value is determined. Apply clip values.
[Selection] Figure 3

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a knock detection device for an internal combustion engine that detects a knock generated in the internal combustion engine.

  2. Description of the Related Art Conventionally, a method for detecting a knock phenomenon occurring in an internal combustion engine (hereinafter also referred to as an engine) with a vibration sensor is known. This is to extract the vibration component of the natural frequency in the predetermined knock detection window by using the vibration of the natural frequency corresponding to the vibration mode of the engine and the knock when the knock occurs during the operation of the engine. In this case, knock detection is performed. For the extraction of the vibration level of the natural frequency, a digital signal such as a method using an analog band-pass filter circuit, STFT (short-time Fourier transform), DFT (discrete Fourier transform), etc. The implementation of the process is generally known.

  Then, as disclosed in, for example, Japanese Utility Model Publication No. 6-41151 (Patent Document 1), a value obtained by extracting the vibration level (hereinafter referred to as a knock signal) is filtered for each ignition. There is a method of determining the occurrence of knock by obtaining a filter value of a knock signal and comparing the knock determination threshold calculated based on the filter value with the knock signal. In this method, the filter coefficient used in the filter processing is corrected so as to be reduced in the transient state, thereby increasing the ratio of the knock signal reflected in the filter value of the knock signal in the transient state, thereby filtering the knock signal. The follow-up of the value is accelerated so that the accuracy of knock determination in a transient state is improved.

  However, even with the same engine speed or load change rate determined as a transient state, the followability of the filter signal of the knock signal required at low speed and high speed is different. For example, the engine speed is changed from low to high. Although it changes, even if the engine speed and the load are not so transient, it may be necessary to quickly follow the filter value of the knock signal in the region where the engine speed is low. In such a case, a quick followability of the filter value of the knock signal is necessary, but since it is not so transient, the correction amount of the filter coefficient is small and the correction of the filter coefficient is not sufficient. In the technique disclosed in Patent Document 1, there is a problem that the knock is erroneously determined due to the delay in tracking the filter value of the knock signal.

  On the other hand, Japanese Patent Laid-Open No. 10-259778 (Patent Document 2) proposes a method of setting a lower limit clip value as a knock determination threshold value. According to the method of Patent Document 2, when the knock determination threshold is less than the lower limit clip value (the lower limit guard A in Patent Document 2), the lower limit clip value is set as the knock determination threshold and the filter coefficient is decreased. Yes. As a result, when accelerating from a state where the knock determination threshold is lower than the lower limit clip value, the followability of the filter value of the knock signal can be improved even if it is not so transient, and the knock is erroneously determined. Can be prevented.

Japanese Utility Model Publication No. 6-41151 Japanese Patent Laid-Open No. 10-259778

In describing the problem to be solved by the present invention, first, the relationship between the ignition timing and the knock signal in a predetermined steady state will be described.
FIG. 10 is an image diagram showing the relationship between the ignition timing and the knock signal in a predetermined steady state where the engine speed and the charging efficiency are substantially constant, where the horizontal axis indicates the ignition timing and the vertical axis indicates the knock signal. 10 indicates the average value of the knock signal (≈the filter value of the knock signal), and the two-dot chain line indicated by the symbol b in FIG. 10 indicates the upper side of the knock signal (excluding the knock signal when the knock occurs). The difference between the two-dot chain line indicated by the symbol b and the average value indicated by the symbol a indicates the upper distribution width of the knock signal. 10 indicates the lower distribution of the knock signal, and the difference between the average value indicated by the reference a and the one-dot chain line indicated by the reference c indicates the lower distribution width of the knock signal. .

  Further, in FIG. 10, IG2 indicates an ignition timing at which knocking begins to occur under standard conditions (octane number, intake air temperature, engine oil temperature, water temperature, etc.) when the engine control constant is adapted. IG1 is an ignition timing when the ignition timing at which knocking begins to occur on the retard side of IG2 under conditions such as a lower octane number, a higher intake air temperature, a higher engine oil temperature, and a water temperature than the standard conditions. It is. In addition, IG3 is an ignition timing when the ignition timing at which knocking begins to occur on the more advanced side than IG2 under conditions such as a higher octane number, lower intake air temperature, lower engine oil temperature, and water temperature than the standard conditions. It is.

  As shown in FIG. 10, the average value and the upper distribution width of the knock signal are smaller in the case of IG1 than in the case of IG2, and the average value and the upper distribution width of the knock signal are smaller than those in the case of IG2. In the case of IG3, the average value of the knock signal and the upper distribution width are larger. For the ignition timing at which knocking starts to occur, a generally known ignition timing learning value may be used. For example, the ignition delay amount during a predetermined cycle in a steady state (in this specification, a negative value is used). ), The ignition timing learning value is updated in the positive value direction (ignition advance side) if the average value of the ignition delay amount during a predetermined cycle is zero, and the ignition delay amount during the predetermined cycle is updated. If the average value is smaller than a predetermined value, there is a method of updating in the negative value direction (ignition retarding side).

  Here, assuming that the knock determination threshold is calculated based on the average value of the knock signal and the upper distribution width of the knock signal, and the lower limit clip value of the knock determination threshold is applied to the upper distribution width of the knock signal, In consideration of not inhibiting the detection of the knock signal when the knock occurs, the lower limit clip value of the knock determination threshold is set to a value slightly larger than the upper distribution width of the knock signal in FIG. 10, and the ignition timing learning value It is considered desirable to be variable depending on the situation.

  However, in Patent Document 2, the lower limit clip value of the knock determination threshold is a constant, and the contents that can be changed according to some parameter are not considered. Therefore, for example, when the lower limit clip value of the knock determination threshold is set based on the case of IG2 in FIG.

  FIG. 11 is a time chart schematically showing a steady state → transient state → steady state when the ignition timing learning value is on the retard side in the prior art such as Patent Document 2 described above. The time chart describes three parts, an upper stage, a middle stage, and a lower stage. In the upper stage, the horizontal axis is time, and the vertical axis is a time chart of operating state values such as engine speed and charging efficiency. In the middle stage, the horizontal axis is time, and the vertical axis is a knock signal time chart, and shows a state where a total of six knocks are generated between the time charts. In addition, a thick line indicated by a symbol d in the middle stage indicates a filter value of the knock signal, and a long broken line indicated by a symbol e indicates a knock determination threshold. In the lower part, the horizontal axis is time, and the vertical axis is a knock intensity time chart. The knock intensity is calculated, for example, by multiplying a value corresponding to the knock signal exceeding the knock determination threshold by a predetermined gain.

  If the ignition timing learned value is on the retard side, for example, the lower limit clip value of the knock determination threshold corresponding to IG1 in FIG. 10 should be set, and knock determination corresponding to IG2 larger than that is set. The lower limit clip value of the threshold is set. Therefore, as shown in the middle and lower stages of FIG. 11, there is a problem that the lower limit clip value of the knock determination threshold is too large to detect the knock.

  FIG. 12 is a time chart schematically showing a steady state → transient state → steady state when the ignition timing learning value is on the advance side in the prior art such as Patent Document 2 described above. The time chart shows the upper, middle, and lower stages in the same manner as FIG. 11. The horizontal axis and vertical axis of each time chart are the same as those in FIG. 11, but in FIG. Indicates a non-occurring state.

  When the ignition timing learning value is on the advance side, if the lower limit clip value of the knock determination threshold value corresponding to IG3 in FIG. 10 should be set, for example, the knock determination threshold value corresponding to IG2 smaller than that is set. The lower limit clip value is set. Therefore, as shown in the middle and lower stages of FIG. 12, there is a problem that the lower limit clip value of the knock determination threshold is too small to erroneously detect knock. Furthermore, for the purpose of not unnecessarily increasing the filter value of the knock signal due to the knock signal when the knock occurs, the filter coefficient when determining that the knock has occurred is more than the filter coefficient when determining that the knock has not occurred. In the case of increasing the value, there is a problem that the tracking of the filter value of the knock signal is further delayed due to erroneous detection of the knock.

In response to the above-described problem, by calculating the lower limit clip value of the knock determination threshold value from the ignition timing learned value, even when the ignition timing learned value is on the advance side, or even when the ignition timing learned value is on the retard side A lower limit clip value of an appropriate knock determination threshold can be applied.

However, the following problem arises even if a means for calculating the lower limit clip value of the knock determination threshold value from the ignition timing learned value is provided.
When the ignition timing at which knocking begins to occur is on the IG1 side in FIG. 10, the ignition retard amount is calculated by detecting knock in a steady state, and the ignition learning value is zero (= the ignition timing is Since the lower limit clip value of the knock determination threshold value at IG2 is applied to the IG1 side from IG2) to the IG1 side, the ignition retard amount is not calculated without detecting knock on the retard side from IG2. The ignition learning value does not reach the value on the IG1 side. That is, there is a problem that the ignition learning value cannot be learned from the zero value to the ignition delay side by applying the lower limit clip value only by providing means for calculating the lower limit clip value from the ignition timing learned value.

  Accordingly, the present invention has been made to solve the above-described problem, and an internal combustion engine that can avoid a situation in which the lower limit clip value of the knock determination threshold value is detrimental in the ignition timing learning value calculation when the operation state of the internal combustion engine is in a steady state. An object of the present invention is to provide an engine control device.

The control device for an internal combustion engine according to the present invention includes an operation state determination unit that calculates an operation state value indicating an operation state of the internal combustion engine and determines a steady state and a transient state, and a vibration or pressure wave generated in a cylinder of the engine. A vibration data detection unit that detects the vibration data as a vibration data, a vibration data processing unit that extracts a knocking characteristic vibration component from the vibration data to obtain a knock signal, and an average value obtained by filtering the knock signal for each ignition. An average value calculating unit that calculates a standard deviation by filtering a difference between the knock signal and the average value for each ignition, and a knock determination threshold value using the average value and the standard deviation a knock determination threshold value calculation unit for calculating, said by comparing the knock signal and the knock determination threshold value to determine the occurrence or non-occurrence of knocking, knock onset of outputting a signal corresponding to the knock intensity A determining unit, according to a result of comparison between the knock signal and the previous value of the knock determination threshold value, a filter coefficient calculator for calculating a filter coefficient used for the filtering process, output from the knock determining unit An ignition retard amount calculation unit for each ignition that calculates a retard amount or an advance amount of the ignition timing according to the knock intensity for each ignition by a signal corresponding to the knock intensity, and a steady state in the operating state determination unit and when it is determined to update the retard amount or the advance amount of said each ignition spark retard amount calculated retardation amount of the ignition timing calculated by the unit or the advance amount of the learning ignition timing learning value An ignition timing learning value update unit, and a lower limit clip value calculation unit that calculates a lower limit clip value of the knock determination threshold from the ignition timing learning value,
When calculating the knock determination threshold value, when it is determined that the transient state by the driving state judging unit, characterized in that the knock determination threshold value to the lower limit clip value.

According to the control apparatus for an internal combustion engine according to the present invention, by calculating the lower limit clip value of the knock determination threshold value according to the ignition timing learned value, the knock signal that changes depending on the ignition timing learned value and the appropriate distribution corresponding to the upper distribution width can be obtained. The lower limit clip value can be calculated. And when it determines with the driving | running state value which shows the driving | running state of an internal combustion engine being a transient state, by making a knock determination threshold value into a lower limit clip value , in calculation of the ignition timing learning value in a steady state, the lower limit of the knock determination threshold value An effect of avoiding a situation in which the clip value is harmful can be obtained.

1 is a configuration diagram schematically showing an engine according to Embodiment 1 of the present invention. FIG. It is a block diagram which shows roughly the engine control part which concerns on Embodiment 1 of this invention. It is a block diagram which shows roughly the knock control part which concerns on Embodiment 1 of this invention. It is a flowchart from the driving | running state value acquisition which concerns on Embodiment 1 of this invention to a lower limit clip value calculation. It is an image figure which shows the relationship between the engine speed which concerns on Embodiment 1 of this invention, and a minimum clip value. It is a lower limit clip value map concerning Embodiment 1 of this invention. It is a flowchart which calculates the filter coefficient which concerns on Embodiment 1 of this invention. It is a time chart which shows roughly the steady state-> transient state-> steady state in case the ignition timing learning value which concerns on Embodiment 1 of this invention is a retard side. It is a time chart which shows roughly the steady state-> transient state-> steady state in case the ignition timing learning value which concerns on Embodiment 1 of this invention is an advance side. It is an image figure which shows the relationship between the ignition timing in a predetermined steady state, and a knock signal. 6 is a time chart schematically showing steady state → transient state → steady state when the ignition timing learning value according to the prior art is on the retard side. It is a time chart which shows roughly the steady state-> transient state-> steady state when the ignition timing learning value by a prior art is an advance side.

  Preferred embodiments of a control device for an internal combustion engine according to the present invention will be described below in detail with reference to the drawings.

Embodiment 1 FIG.
1 is a block diagram schematically showing an engine according to Embodiment 1 of the present invention, and FIG. 2 is a block diagram schematically showing an engine control unit according to Embodiment 1. As shown in FIG.
In FIG. 1, an electronically controlled throttle valve (hereinafter referred to as a throttle valve) 2 that is electronically controlled to adjust the intake air flow rate is provided upstream of the intake system of the engine 1. A throttle opening sensor 3 is provided to detect the opening of the throttle valve 2. Instead of the throttle valve 2, a mechanical throttle valve connected directly to an accelerator pedal (not shown) with a wire may be used.

  Further, an airflow sensor 4 for detecting the intake air flow rate is provided upstream of the throttle valve 2, and an intake manifold pressure sensor 6 for detecting the pressure in the surge tank 5 is provided on the engine 1 downstream of the throttle valve 2. Is provided. Note that both the airflow sensor 4 and the intake manifold pressure sensor 6 may be provided, or only one of them may be provided.

  A variable intake valve mechanism 7 capable of variably controlling the opening / closing timing and lift amount of the intake valve is attached to the intake valve provided in the intake port downstream of the surge tank 5, and fuel is injected into the intake port. An injector 8 is provided. The injector 8 may be provided so that it can be directly injected into the cylinder of the engine 1. Further, the engine 1 detects an ignition coil 9 and a spark plug 10 for igniting the air-fuel mixture in the cylinder of the engine 1, and an edge of a plate provided on the crankshaft for detecting the engine speed and the crank angle. The crank angle sensor 11 that performs the vibration data detection unit that detects vibration generated in the cylinder of the engine 1 as vibration data, that is, the knock sensor 12 and the state of the gas contained in the exhaust gas (hereinafter referred to as A / F). An A / F sensor 13 is provided for detecting. Instead of the knock sensor 12, for example, an in-cylinder pressure sensor that measures a pressure wave in the cylinder as vibration data may be provided.

  FIG. 2 is a block diagram schematically showing the engine control unit. In FIG. 2, the intake air flow rate detected by the airflow sensor 4, the intake manifold pressure detected by the intake manifold pressure sensor 6, the opening degree of the throttle valve 2 detected by the throttle opening sensor 3, and the output from the crank angle sensor 11. Each state quantity indicating the pulse synchronized with the edge of the plate provided on the crankshaft, the vibration data detected by the knock sensor 12, and the A / F detected by the A / F sensor 13 is an electronic control unit ( Hereinafter, it is referred to as an ECU).

  Also, detection values are input to the ECU 14 from various sensors other than those described above, and signals from other controllers (for example, control systems such as automatic transmission control, brake control, traction control, etc.) are also input. The ECU 14 controls the throttle valve 2 by calculating the target throttle opening based on the accelerator opening and the operating state of the engine 1. Further, the variable intake valve mechanism 7 that variably controls the opening / closing timing of the intake valve is controlled according to the operating state at that time, and the injector 8 is driven so as to achieve the target air-fuel ratio, so as to achieve the target ignition timing. Energization of the ignition coil 9 is performed. When knock is detected by a method described later, control for suppressing the occurrence of knock is also performed by setting the target ignition timing to the retard side. Further, command values for various actuators other than those described above are also calculated.

Next, an outline of knock control performed by the ECU 14 will be described with reference to FIG.
FIG. 3 is a block diagram showing a configuration of the entire knock control. In FIG. 3, reference numerals 12 and 14 denote the knock sensor and ECU described in FIGS. 1 and 2, respectively.
Here, the structure of the knock control part in ECU14 is demonstrated. The ECU 14 includes a microcomputer 14A and various I / F circuits 14B. The microcomputer 14A executes an A / D converter that converts analog signals into digital signals, a ROM area that stores control programs and control constants, and programs. It is composed of a RAM area or the like for storing variables at the time. The knock control I / F circuit 15 in the various I / F circuits 14B includes a low-pass filter (hereinafter referred to as LPF) for removing high-frequency components of vibration data.

  The A / D conversion of the microcomputer 14A is executed by the A / D converter 16 at regular time intervals (for example, 10 μs, 20 μs, etc.). The I / F circuit 15, that is, the LPF 15 has a function of biasing to 2.5 V (for example, setting the center of the vibration data to 2.5 V) in order to capture all vibration data by the A / D converter 16. Gain conversion that amplifies around 2.5V when the vibration data is small and decreases around 2.5V when the vibration data is small, so that the vibration data is within the range of 0-5V around 2.5V Features are also included. The A / D conversion in the A / D conversion unit 16 is always performed, and a knock detection window (ATDC (After Top Dead Center) in this embodiment) −10 ° CA is used. Only the vibration data of ATDC 80 ° CA) may be sent to the vibration data processing unit 17 and later, or only the knock detection window may be A / D converted and sent to the vibration data processing unit 17 and later.

  The vibration data processing unit 17 performs time-frequency analysis by digital signal processing. As this digital signal processing, for example, a spectrum sequence of a plurality of natural frequencies is calculated by STFT or DFT, a peak value is calculated for each spectrum sequence of the natural frequency, and is output as a knock signal for each natural frequency. As digital signal processing, the vibration level of the natural frequency may be extracted by using an IIR (Infinite impulse response) filter or an FIR (Finite impulse response) filter. The calculation of the vibration data processing unit 17 may be performed while performing A / D conversion, or may be performed collectively by an interrupt process synchronized with the rotation of the engine 1.

Then, the driving state determination is performed using a plurality of driving state values detected from signals of a plurality of sensors (for example, throttle opening sensor 3, airflow sensor 4, intake manifold pressure sensor 6, and crank angle sensor 11 shown in FIG. 2). The unit 18 calculates a transient correction coefficient K_th, which will be described later, and determines the operating state, and sends the results to the filter coefficient calculation unit 19, the lower limit clip value calculation unit 20, and the ignition timing learned value update unit 21. The flow from the calculation of the transient correction coefficient K_th in the driving state determination unit 18 to the lower limit clip value MINCLIP in the lower limit clip value calculation unit 20 will be described later.

  The average value calculation unit and the standard deviation calculation unit 22 calculate the filter value VBGL and the standard deviation VSGM of the knock signal used in the calculation of the knock determination threshold value VTH. The knock signal filter value VBGL and the standard deviation VSGM are calculated using the following equations (1) to (3) at each of a plurality of natural frequencies. First, a filter process is performed on the knock signal calculated for each cycle (in the case of a control device for an internal combustion engine that does not calculate a knock determination threshold for each cylinder, and averaged).

  The knock determination threshold value calculation unit 23 calculates the knock determination threshold value VTH by the following equation (4).

The first filter coefficient K1 and the second filter coefficient K2 are calculated by the filter coefficient calculation unit 19 before the execution of the expression (1), and the filter coefficient calculation unit 19 will be described later. Further, in the present embodiment, as shown in Equation (4), the use of the lower clip values at locations corresponding to the upper distribution width of the knock signal and configured to use the lower clip value VTH itself Also good.

The knock occurrence presence / absence determination unit 24 compares the knock signal VP with the knock determination threshold value VTH, determines the presence / absence of knock occurrence according to the following equation (5), and outputs a signal corresponding to the knock intensity.

The ignition retard amount calculation unit 25 for each ignition calculates an ignition delay amount corresponding to the knock intensity for each ignition from the signal corresponding to the knock intensity output from the knock occurrence determination unit 24 by the following equation (6). To do.

  When ΔθR (n)> 0, the ignition timing is retarded according to ΔθR (n), and when ΔθR (n) = 0, the ignition is returned to the advance side by a predetermined amount.

The ignition timing learning value updating unit 21 determines that the steady state continues for a predetermined period, and the ignition retard amount ΔθR for each ignition for a predetermined period calculated by the ignition delay amount calculation unit 25 for each ignition during the predetermined period. When the average value (negative value) of the ignition timing is smaller than the predetermined value, the ignition timing learning value is updated by a predetermined amount to the retard side, and 1 of the predetermined period calculated by the ignition retard amount calculating unit 25 for each ignition during the predetermined period. When the average value of the ignition retardation amount ΔθR for each ignition is zero, the ignition timing learning value is updated by a predetermined amount to the advance side.

In the above, the A / D conversion unit 16, the vibration data processing unit 17, the operation state determination unit 18, the filter coefficient calculation unit 19, the lower limit clip value calculation unit 20, the ignition timing learned value update unit 21, the average value calculation unit, and the standard deviation The calculation unit 22, the knock determination threshold value calculation unit 23, the knock occurrence presence / absence determination unit 24, and the ignition retard amount calculation unit 25 for each ignition detect knock using the frequency analysis result by digital signal processing, and retard the ignition timing. A processing method for realizing knock control, such as avoidance of knock due to this and ignition timing learning using the ignition timing retard amount, has been described.
Next, the driving state determination unit 18, the lower limit clip value calculation unit 20, and the filter coefficient calculation unit 19 will be described in detail.

  First, the driving state determination unit 18 and the lower limit clip value calculation unit 20 will be described with reference to FIGS. 4 to 6. FIG. 4 is a flowchart from the calculation of the transient correction coefficient K_th in the driving state determination unit 18 to the calculation of the lower limit clip value MINCLIP in the lower limit clip value calculation unit 20, and acquisition of the driving state value and the ignition timing learning value (step 101). It consists of calculation of a transient correction coefficient (step 102), operation state determination (step 103), and calculation of a lower limit clip value (steps 104 and 105). Note that step 104 and step 105 in FIG. 4 are performed for each of a plurality of frequencies used for knock detection. Hereinafter, description will be made in order from step 101.

In step 101, the engine speed of the present cycle from the output values of various sensors 3,4,6,11 NE (n), the charging efficiency EC (n), calculates a throttle opening TP (n). Further, the ignition timing learning value θLrn (n−1) of the previous cycle calculated by the ignition timing learning value update unit 21 is acquired, and the process proceeds to step 102.

  In step 102, a transient correction coefficient K_th is calculated from the engine speed NE, charging efficiency EC, and throttle opening TP acquired in step 101. In this embodiment, the deviation from the previous cycle value | ΔNE (n) | (= the absolute value of NE (n) −NE (n−1)), | ΔEC (n) | (= EC (n) −EC (Absolute value of (n-1)), | ΔTP (n) | (= Absolute value of TP (n) −TP (n−1)) and each deviation reference value are calculated by the following formula (7).

  In step 102, the transient correction coefficient K_th (n) is calculated, and after the transient correction coefficient K_th (n) is transmitted to the filter coefficient calculation unit 19, the process proceeds to step 103.

In step 103, the transient correction coefficient K_th (n) is compared with a predetermined value TR, and if K_th (n) ≧ TR, it is determined as a transient state, otherwise it is determined as a steady state. Then, after transmitting the determination result to the lower limit clip value calculation unit 20 and the ignition timing learned value update unit 21, the lower limit clip value calculation unit 20 calculates the lower limit clip value MINCLIP in the next step.

  If it is determined that the steady state is determined in step 103, MINCLIP (n) = 0 is set in step 105, and the lower limit clip value MINCLP is transmitted to the filter coefficient calculation unit 19 and the knock determination threshold calculation unit 23. This flow ends. If it is determined in step 103 that the state is a transient state, the process proceeds to step 104.

  In step 104, the lower limit clip value MINCLIP is calculated from the engine speed NE (n) calculated and acquired in step 101, the ignition timing learned value θLrn (n−1) of the previous cycle, and the lower limit clip value map, and the lower limit clip value is calculated. The MINCLP is transmitted to the filter coefficient calculation unit 19 and the knock determination threshold value calculation unit 23, and this flow ends.

Next, the relationship between the engine speed and the lower limit clip value will be described with reference to FIG. 5, and the lower limit clip value map will be described with reference to FIG.
FIG. 5 is an image diagram showing the relationship between the engine speed and the lower limit clip value, where the horizontal axis represents the engine speed and the vertical axis represents the lower limit clip value. In FIG. 5, the thick line α is the lower limit clip value when the ignition timing learned value = 0, the long broken line β is the lower limit clip value when the ignition timing learned value is the maximum value (ignition advance side), and the broken line γ is the ignition timing learned value. Indicates the lower limit clip value when is the minimum value (ignition retarded side).

  Since the magnitude of the knock signal when no knock occurs and the magnitude of the upper distribution width increase as the engine speed increases, the lower limit when the ignition timing learning value = 0 as shown by the thick line α in FIG. The clip value is set larger as the engine speed increases. Further, as described with reference to FIG. 10, the knock signal and the upper distribution width are larger when the ignition timing learning value = 0 than when the ignition timing learning value = 0, so the lower limit clip value when the ignition timing learning value is the maximum value. Is set above the thick line α as indicated by the long broken line β in FIG.

  Further, since the knock signal and the upper distribution width are smaller when the ignition timing learning value = 0 than the ignition timing learning value = 0, it is set below the thick line α as shown by the broken line γ in FIG. The lower limit clip value when the ignition timing learning value = 0 is set based on actual machine test data under standard conditions when the engine control constant is adapted. The lower limit clip value when the ignition timing learning value is the maximum value is Set based on actual machine test data of higher octane number, lower intake air temperature, lower engine oil temperature, and water temperature than standard conditions. The lower limit clip value when the ignition timing learning value is the minimum value is lower than the standard condition. Set based on actual machine test data under conditions of high intake air temperature, high engine oil temperature, and water temperature.

The lower limit clip value map in FIG. 6 is written in the ROM area of the ECU 14, and the engine speed and the ignition timing learning value are used as parameters, and the lower limit clip value is set in the map. In FIG. 6, the engine speed is set in increments of 1000 [r / min], but the increment may be changed according to the model that performs this control. In addition, the ignition timing learning value is also in increments of the maximum value, 0, and minimum value. However, depending on the model, this may be in increments of several points between the maximum value and 0 and between 0 and the minimum value. Good. The lower limit clip value described in FIG. 5 is set in this lower limit clip value map, and in step 104 of FIG. 4, the engine speed NE (n) of the current cycle and the ignition timing learned value θLrn (n of the previous cycle) are set. -1) and the lower limit clip value MINCLIP from the lower limit clip value map. Although the lower limit clip value in the load direction is not mentioned in this embodiment, the lower limit clip value map of FIG. 12 may be provided for each load in order to set the lower limit clip value with higher accuracy.

  Next, processing in the filter coefficient calculation unit 19 will be described. FIG. 7 is a flowchart for calculating the first filter coefficient K1 (n) used in the expression (1). Calculation of the knock determination threshold VTH ′ (step 201), knock determination (step 202), and steady state Filter coefficient calculation (steps 201 to 204), operation state determination (step 205), and calculation of the first filter coefficient K1 (steps 206 and 207). Note that the flowchart of FIG. 7 is performed for each of a plurality of frequencies used for knock detection. Hereinafter, description will be made in order from step 201.

  In step 201, a knock determination threshold value VTH 'is calculated by the following equation (8).

Although the expression is similar to the knock determination threshold value VTH shown in Expression (4), the difference is that the filter value VBGL and the standard deviation VSGM of the knock signal use the values of the previous cycle. This is because the first filter coefficient K1 is calculated before calculating the knock determination threshold value VTH by the equation (4). Note that the lower limit clip value MINCLIP uses the value of the current cycle instead of the previous cycle, but this is the lower limit clip without delay in cases where it is determined that the current cycle is a steady state and the current cycle is a transient state. This is because the value MINCLIP is used . After calculating knock determination threshold value VTH ′ (n), the routine proceeds to step 202.

  In step 202, knock determination threshold value VTH ′ (n) is compared with knock signal VP (n). If VP (n)> VTH ′ (n), it is determined that knock signal VP (n) is large due to the occurrence of knock. The process proceeds to step 203. Otherwise, the process proceeds to step 204. When the process proceeds to step 203, K1_k is input to the filter coefficient K1_s (n) in the steady state, and when the process proceeds to step 204, K1_n is input to the filter coefficient K1_s (n), and the process proceeds to step 205. By setting K1_k to a value larger than K1_n, the knock signal filter value VBGL and the standard deviation VSGM are not increased unnecessarily due to an increase in the knock signal VP (n) due to the occurrence of knock.

  In step 205, the transient correction coefficient K_th (n) is compared with a predetermined value TR. If K_th (n) ≧ TR, it is determined as a transient state, and the process proceeds to step 206. Otherwise, it is determined as a steady state. Proceed to Since step 205 is the same processing as step 103 in FIG. 4, the transient state and the steady state may be determined based on the result of step 103.

  When the process proceeds to step 206, the first filter coefficient K1 (n) is calculated by interpolating the filter coefficient K1_tr in the transient state and the filter coefficient K1_s (n) in the steady state with the transient correction coefficient K_tr (n). This flow is finished. Specifically, the first filter coefficient K1 (n) is calculated by the following equation (9).

  The filter coefficient K1_tr in the transient state is set to a value smaller than K1_n in step 204, thereby increasing the ratio of the knock signal to be reflected in the filter value VBGL of the knock signal and the standard deviation VSGM. Improves trackability.

  When the routine proceeds to step 207, the filter coefficient K1_s (n) in the steady state is set to the first filter coefficient K1 (n), and this flow is finished. The second filter coefficient K2 (n) used in the equation (2) can also be calculated by the same method.

The control device for the internal combustion engine according to the first embodiment has been described above. Next, the effect will be described with reference to FIGS. 8 and 9.
FIG. 8 is a time chart schematically showing a steady state → transient state → steady state when the ignition timing learning value according to the first embodiment is on the retard side, and the graph axes and the like are obtained when the conventional technique is implemented. This is the same as FIG. In FIG. 11, there is a problem that the knock cannot be detected because the lower limit clip value is too large. However, in FIG. 8, an appropriate lower limit clip value is used to obtain the effect of detecting the knock.

FIG. 9 is a time chart schematically showing a steady state → transient state → steady state when the ignition timing learning value according to the first embodiment is on the advance side, and the graph axis and the like are related to the prior art. This is the same as FIG. In FIG. 12, there is a problem that the knock is erroneously detected during the transition because the lower limit clip value is too small. However, in FIG. 9, an appropriate lower limit clip value is used , and the effect of not erroneously detecting the knock during the transition is obtained.

As described above, the control apparatus for an internal combustion engine according to the first embodiment includes the lower limit clip value calculation unit 20 that calculates the lower limit clip value of the knock determination threshold value from the ignition timing learned value, and calculates the knock determination threshold value. When the operation state determination unit 18 determines that the state is a transient state, the lower limit clip value of the knock determination threshold is used . By doing so, it is possible to calculate the appropriate lower limit clip value of the knock determination threshold corresponding to the knock signal and the upper distribution width that varies depending on the ignition timing learned value, and in the calculation of the ignition timing learned value in the steady state, the knock determination threshold Thus, an effect of avoiding a situation in which the lower limit clip value is harmful can be obtained.

In addition, when the vibration data processing unit 17 performs frequency analysis on vibration data at a plurality of frequencies at the same time to extract a knock signal for each frequency and perform knock control, the lower limit clip value calculation unit 20 performs the frequency analysis for each frequency. The lower limit clip value of the knock determination threshold is calculated . By doing in this way, the effect which can use the lower limit clip value of a more suitable knock determination threshold value with respect to the magnitude | size of a knock signal changing for every frequency is acquired.

Further, at the lower limit clipping value calculating section 20 calculates the lower limit clipping value of the knock determination threshold value for each engine speed. By doing in this way, there exists an effect which can use the lower limit clip value of a more suitable knock determination threshold value with respect to the tendency for a knock signal to become large when an engine speed becomes high.

Further, the lower limit clip value of the knock determination threshold is made smaller as the ignition timing learned value becomes closer to the ignition timing retard side than the zero value with respect to the lower limit clip value when the ignition timing learned value is zero. By doing so, as shown in FIG. 10, the knock signal and the upper distribution width at the same engine speed and the same load tend to become smaller as the ignition timing learning value becomes closer to the ignition delay side. Thus, an effect that a lower limit clip value of a more appropriate knock determination threshold can be used is obtained.

Further, the lower limit clip value of the knock determination threshold is increased as the ignition timing learning value becomes closer to the ignition timing advance side than the zero value. By doing so, as shown in FIG. 10, the knock signal and the upper distribution width at the same engine speed and the same load tend to increase as the ignition timing learning value becomes the ignition advance side. Te, Ru more appropriate knock determination threshold effect the lower clipping values can be used in to obtain.

  The internal combustion engine control apparatus according to the first embodiment of the present invention has been described above. However, the present invention can be modified or omitted as appropriate within the scope of the present invention.

1 engine, 2 electronically controlled throttle valve, 3 throttle opening sensor, 4 air flow sensor, 5 surge tank, 6 intake manifold pressure sensor, 7 variable intake valve mechanism, 8 injector, 9 ignition coil, 10 ignition plug, 11 crank angle sensor , 12 knock sensor, 13 A / F sensor, 14 electronic control unit (ECU), 14A microcomputer, 14B various I / F circuits, 15 I / F circuit (LPF), 16 A / D converter, 17 vibration data processing Unit, 18 driving state determination unit, 19 filter coefficient calculation unit, 20 lower limit clip value calculation unit, 21 ignition timing learning value update unit , 22 average value calculation unit and standard deviation calculation unit, 23 knock determination threshold value calculation unit, 24 knock generation Presence / absence determination unit , 25 ignition retard amount calculation unit for each ignition

Claims (5)

An operation state determination unit that calculates an operation state value indicating an operation state of the internal combustion engine and determines a steady state and a transient state;
A vibration data detector that detects vibration or pressure waves generated in the cylinder of the engine as vibration data;
A vibration data processing unit that extracts a knocking characteristic vibration component from the vibration data and generates a knock signal;
An average value calculating unit that filters the knock signal for each ignition and calculates an average value;
A standard deviation calculating unit that calculates a standard deviation by filtering a deviation of the knock signal and the average value for each ignition;
A knock determination threshold value calculation unit for calculating a knock determination threshold value using the average value and the standard deviation;
A knock determining unit that determines presence or absence of occurrence of knocking, and outputs a signal corresponding to the knock intensity by comparing the knock signal and the knock determination threshold value,
A filter coefficient calculation unit that calculates a filter coefficient used for the filter processing according to a comparison result between the previous value of the knock determination threshold and the knock signal;
An ignition retard amount calculation unit for each ignition that calculates a retard amount or an advance amount of the ignition timing corresponding to the knock intensity for each ignition based on a signal corresponding to the knock intensity output from the knock occurrence determination unit; ,
When it is determined that the operating state determination unit is in a steady state, the ignition timing retard amount or the advance amount calculated by the ignition delay amount calculation unit for each ignition is learned to retard the ignition timing learning value . An ignition timing learning value update unit for updating the angular amount or the advance amount ;
A lower limit clip value calculation unit that calculates a lower limit clip value of the knock determination threshold from the ignition timing learning value,
The knock when calculating the determination threshold, if it is determined that the transient state by the operating condition determining module, a control apparatus for an internal combustion engine of the knock determination threshold value, characterized in that said lower clip value. In the vibration data processing unit, the vibration data is simultaneously subjected to time-frequency analysis at a plurality of frequencies to extract a knock signal for each frequency,
In the lower clip value calculation unit, a control apparatus for an internal combustion engine according to claim 1, characterized in that calculating the lower limit clip value for each of the frequency. In the lower clip value calculation unit, a control apparatus for an internal combustion engine according to claim 1 or 2, characterized in that calculating the lower limit clip value for each engine speed.   2. The lower limit clip value is made smaller as the ignition timing learned value is closer to the ignition timing retard side than the zero value with respect to the lower limit clip value when the ignition timing learned value is zero. The control device for an internal combustion engine according to any one of claims 1 to 3.   2. The lower limit clip value is increased as the ignition timing learned value is closer to the ignition timing advance side than the zero value with respect to the lower limit clip value when the ignition timing learned value is zero. The control apparatus for an internal combustion engine according to any one of claims 1 to 4.

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