JP2011106335A - Sensitivity correction device of vibration sensor, and combustion condition monitoring device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sensitivity correction device of a vibration sensor simply and easily carrying out a sensitivity correction of the vibration sensor mounted to an internal combustion engine, in a frequency range suitable for monitoring the normal combustion condition of the engine. <P>SOLUTION: In a predetermined operating condition where the engine is not ignited, the amplitude C1 of the fundamental frequency component C1 corresponding to the engine speed, contained in the signal detected by the vibration sensor (pressure sensor), is calculated. Simultaneously, reference amplitude C1M corresponding to the fundamental frequency in the predetermined operating condition is calculated. A sensor output correction coefficient KS, which is the ratio between the fundamental frequency amplitude C1 and the reference amplitude C1M, is calculated. The pressure sensor output is corrected with use of the sensor output correction coefficient KS. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a sensitivity correction device for a vibration sensor mounted on an internal combustion engine, and a combustion state monitoring device that calculates a combustion state parameter indicating a combustion state of the internal combustion engine based on a detection signal of the vibration sensor.

  Patent Document 1 discloses a sensitivity correction method for a piezoelectric pressure sensor which is a typical vibration sensor mounted on an internal combustion engine. According to this method, the signal component of the frequency band to be measured is extracted from the detection signal of the piezoelectric pressure sensor, and the extracted signal is corrected so that the detection sensitivity is substantially constant by the correction reference value. The correction reference value is calculated using a specific frequency component in the same frequency band as the extracted signal component.

Japanese Patent Laid-Open No. 2003-83153

  The technique disclosed in Patent Document 1 is a technique specifically applied to sensitivity correction of a piezoelectric pressure sensor used for detecting knocking, and an average of signal levels obtained by bandpass filter processing of 6 to 10 kHz. A value (for example, a value obtained by averaging signal levels detected in a period from 12 degrees before top dead center to top dead center in a period of about 10 cycles).

  On the other hand, when the detected value of the pressure sensor is applied to the calculation of the indicated mean effective pressure, which is a parameter indicating the normal combustion state of the engine, the main frequency components (primary component, secondary component) of the required pressure sensor output ) Is a component having a frequency lower than 300 Hz even in a state where the engine speed is considerably high (for example, 8000 rpm), and the pressure sensor sensitivity correction cannot be performed by applying the method disclosed in Patent Document 1.

  In addition, when the detected value of the pressure sensor is applied to the calculation of the indicated mean effective pressure that is a parameter indicating the combustion state of the engine, the intensity of the component synchronized with the engine rotation obtained from the sensor detected value can be obtained with higher accuracy. It is desirable to correct.

  The present invention has been made paying attention to the above points, and the sensitivity of the vibration sensor that can easily perform sensitivity correction of the vibration sensor mounted on the engine in a frequency band suitable for monitoring the normal combustion state of the engine. It is a first object to provide a correction device, and further provides a combustion state monitoring device for an internal combustion engine capable of calculating a combustion state parameter indicating an engine combustion state with high accuracy based on a detection value of a vibration sensor. That is the second purpose.

  In order to achieve the above object, according to a first aspect of the present invention, in a sensitivity correction device for a vibration sensor (11) mounted on an internal combustion engine, a rotation speed detection means for detecting a rotation speed (NE) of the engine; In a predetermined operating state where the engine is not ignited, a fundamental frequency intensity parameter (C1) indicating the intensity of the fundamental frequency component corresponding to the engine speed (NE) included in the detection signal of the vibration sensor (11) is set. Basic intensity parameter calculating means for calculating, reference intensity parameter calculating means for calculating a reference intensity parameter (C1M) corresponding to the basic frequency in the predetermined operation state, the basic frequency intensity parameter (C1) and the reference intensity parameter Correction coefficient calculating means for calculating a correction coefficient (KS) according to the ratio to (C1M), and the vibration coefficient using the correction coefficient (KS). Characterized in that it comprises a sensor output correcting means for correcting the sensor output (Eo).

  The invention according to claim 2 comprises an internal combustion state parameter calculating means for calculating a combustion state parameter (IMEP) indicating the combustion state of the engine based on the output of a vibration sensor (11) mounted on the internal combustion engine. In the engine combustion state monitoring device, the rotational speed detection means for detecting the rotational speed (NE) of the engine, and a detection signal of the vibration sensor (11) in a predetermined operating state where the ignition of the engine is not performed. A first basic intensity parameter calculating means for calculating a first frequency intensity parameter (C1) indicating the intensity of the fundamental frequency component corresponding to the engine speed (NE), and corresponding to the fundamental frequency in the predetermined operating state. First reference intensity parameter calculating means for calculating a first reference intensity parameter (C1M), the first frequency intensity parameter (C1), and the first base A first correction coefficient calculating means for calculating a first correction coefficient (K1) according to a ratio to the intensity parameter (C1M); and the first frequency intensity included in a detection signal of the vibration sensor in a normal operation state of the engine. A normal intensity parameter calculating means for calculating a parameter (C1) and a second frequency intensity parameter (C2) indicating the intensity of a component having a frequency twice the fundamental frequency included in the detection signal of the vibration sensor; First frequency component intensity correction means for correcting the first frequency component intensity parameter (C1) calculated by the normal intensity parameter calculation means using the first correction coefficient (K1), the combustion state parameter calculation means, By the first frequency component intensity parameter (C1C) corrected by the first frequency component intensity correcting means and the normal intensity parameter calculating means. Using a second frequency component strength parameter calculated (C2), and calculates the combustion state parameter (IMEP).

  According to a third aspect of the present invention, in the combustion state monitoring apparatus for an internal combustion engine according to the second aspect, in the predetermined operation state, a second basic strength parameter calculating means for calculating the second frequency strength parameter (C2); , Second reference intensity parameter calculating means for calculating a second reference intensity parameter (C2M) corresponding to the double frequency in the predetermined operation state, the second frequency intensity parameter (C2) and the second reference intensity parameter. A second correction coefficient calculating means for calculating a second correction coefficient (K2) according to the ratio to (C2M), and a second frequency component intensity parameter (C2) calculated by the normal intensity parameter calculating means for the second And a second frequency component intensity correction unit that corrects using a correction coefficient (K2), wherein the combustion state parameter calculation unit includes the first and first frequency components. First and second frequency component intensity parameter (C1C, C2C) corrected by the frequency component intensity correcting means, characterized in that said calculating a combustion state parameter (IMEP) with.

  According to a fourth aspect of the present invention, in the combustion state monitoring apparatus for an internal combustion engine according to the second aspect, the first correction coefficient is compared with a deterioration determination threshold value, and the first correction coefficient exceeds the deterioration determination threshold value. In some cases, the apparatus further comprises a deterioration determining means for determining that the vibration sensor has deteriorated.

  According to a fifth aspect of the present invention, in the combustion state monitoring apparatus for an internal combustion engine according to the third aspect, the first and second correction coefficients are compared with a deterioration determination threshold value, and the first correction coefficient and the second correction coefficient are compared. When at least one of the above exceeds a deterioration determination threshold value, it further includes a deterioration determination means for determining that the vibration sensor has deteriorated.

  As the vibration sensor, a piezoelectric pressure sensor using a piezoelectric element is generally used, but an acceleration sensor, a force sensor, or a clearance sensor mounted at an appropriate position of the internal combustion engine can also be used. The “predetermined operating state” is an operating state in which ignition is not performed in a cylinder to which a sensor for correcting sensitivity is attached, and is typically being cranked (including when restarting after an idle stop). And the operating state before starting ignition. In addition, for example, a cylinder that is deactivated in an engine that performs cylinder deactivation operation also corresponds to the “predetermined operation state”.

  When an acceleration sensor, a force sensor, or a clearance sensor is used as the vibration sensor, the correction coefficients (K1, K2) are indirect information due to the in-cylinder pressure, and therefore, indirect information such as vibration and force, By applying a constant for correlating internal pressure data, it is possible to improve the correlation between the indicated mean effective pressure obtained from the indirect information and the indicated mean effective pressure obtained from the pressure sensor output.

  According to the first aspect of the present invention, in a predetermined operation state where the engine is not ignited, the fundamental frequency intensity parameter indicating the intensity of the fundamental frequency component corresponding to the engine rotational speed is included in the detection signal of the vibration sensor. In addition, the reference intensity parameter corresponding to the fundamental frequency in a predetermined operating state is calculated, and the vibration sensor output is corrected using a correction coefficient calculated according to the ratio between the fundamental frequency intensity parameter and the reference intensity parameter. The In an operating state in which the engine is not ignited, the intensity of the fundamental frequency component corresponding to the engine speed included in the vibration sensor detection signal is the largest, so that the detected fundamental frequency intensity parameter is set in advance. The correction coefficient is calculated according to the ratio to the reference intensity parameter, and the vibration sensor output is corrected using this correction coefficient, so that the sensitivity correction of the vibration sensor is performed in a frequency band suitable for monitoring the normal combustion state of the engine. This can be done relatively easily.

  According to the second aspect of the present invention, in a predetermined operating state where the engine is not ignited, the first frequency intensity parameter indicating the intensity of the fundamental frequency component corresponding to the engine speed included in the detection signal of the vibration sensor. Is calculated, a first reference intensity parameter corresponding to the fundamental frequency in a predetermined operating state is calculated, and a first correction coefficient is calculated according to the ratio of the first frequency intensity parameter and the first reference intensity parameter. . Then, a first frequency intensity parameter included in the detection signal of the vibration sensor in a normal operation state of the engine and a second frequency intensity parameter indicating the intensity of the frequency component twice the fundamental frequency are calculated, and the first correction coefficient The combustion state parameter is calculated using the first frequency component intensity parameter corrected by the above and the second frequency intensity parameter not corrected. By using the intensity (amplitude) of the fundamental frequency component and the second harmonic component included in the vibration sensor output, the indicated mean effective pressure, which is a representative combustion state parameter, can be calculated with relatively high accuracy. By correcting the detected first frequency intensity parameter using the first correction coefficient, the first frequency intensity parameter indicating the main frequency component of the vibration sensor output is appropriately corrected according to the sensitivity of the vibration sensor, and combustion is performed. The state parameter can be calculated with high accuracy.

  According to the third aspect of the present invention, the second frequency intensity parameter is calculated in the predetermined operating state where the engine is not ignited, and the second reference intensity parameter corresponding to the double frequency in the predetermined operating state. Is calculated, and the second correction coefficient is calculated according to the ratio between the second frequency intensity parameter and the second reference intensity parameter. The first and second frequency intensity parameters included in the detection signal of the vibration sensor in the normal operation state of the engine are corrected using the first and second correction coefficients, and the corrected first and second frequency component intensities are corrected. A combustion state parameter is calculated using the parameter. By correcting the second frequency component intensity parameter using the second correction coefficient, sensitivity correction of the vibration sensor is performed more appropriately, and the calculation accuracy of the combustion state parameter can be further increased.

  According to the fourth aspect of the present invention, since the first correction coefficient is compared with the deterioration determination threshold value, and it is determined that the vibration sensor has deteriorated when the first correction coefficient exceeds the deterioration determination threshold value, the vibration sensor It is possible to easily detect the sensitivity deterioration.

  According to the fifth aspect of the present invention, when the first and second correction coefficients are compared with the deterioration determination threshold value, and at least one of the first correction coefficient and the second correction coefficient exceeds the deterioration determination threshold value, the vibration sensor Therefore, it is possible to easily detect the sensitivity deterioration of the vibration sensor.

It is a figure which shows the structure of the internal combustion engine and its control apparatus concerning one Embodiment of this invention. It is a circuit diagram which shows the structure of the equivalent circuit of a piezoelectric type pressure sensor, and an integral amplifier. It is a figure which shows the ratio of the frequency component contained in a piezoelectric type pressure sensor output. It is a flowchart of a process which calculates an indicated mean effective pressure (IMEP). It is a flowchart of the process which calculates the correction coefficient (KS) which corrects a piezoelectric type pressure sensor output. It is a flowchart of the modification of the process shown in FIG.

Embodiments of the present invention will be described below with reference to the drawings.
[First Embodiment]
FIG. 1 is an overall configuration diagram of an internal combustion engine (hereinafter referred to as an “engine”) and a control device thereof according to an embodiment of the present invention. It is arranged. A throttle valve opening sensor 4 for detecting the throttle valve opening TH is connected to the throttle valve 3, and a detection signal of the sensor 4 is supplied to an electronic control unit (hereinafter referred to as “ECU”) 5.

  The fuel injection valve 6 is provided for each cylinder between the engine 1 and the throttle valve 3 and slightly upstream of the intake valve (not shown) of the intake pipe 2, and each injection valve is connected to a fuel pump (not shown). At the same time, it is electrically connected to the ECU 5 and the valve opening time of the fuel injection valve 6 is controlled by a signal from the ECU 5. Each cylinder of the engine 1 is provided with a spark plug 7, and the spark plug 7 is connected to the ECU 5. The ECU 5 supplies an ignition signal to the spark plug 7.

  An intake pressure sensor 8 for detecting the intake pressure PBA and an intake air temperature sensor 9 for detecting the intake air temperature TA are provided on the downstream side of the throttle valve 3. A cooling water temperature sensor 10 for detecting the engine cooling water temperature TW is attached to the main body of the engine 1. Further, a piezoelectric pressure sensor 11 for detecting the in-cylinder pressure is mounted in the vicinity of the ignition plug 7 of each cylinder of the engine 1. Detection signals from the sensors 8 to 11 are supplied to the ECU 5.

  A crank angle position sensor 12 that detects a rotation angle of a crankshaft (not shown) of the engine 1 is connected to the ECU 5, and a signal corresponding to the rotation angle of the crankshaft is supplied to the ECU 5. The crank angle position sensor 12 is a cylinder discrimination sensor that outputs a pulse (hereinafter referred to as “CYL pulse”) at a predetermined crank angle position of a specific cylinder of the engine 1, and relates to a top dead center (TDC) at the start of the intake stroke of each cylinder. A TDC sensor that outputs a TDC pulse at a crank angle position before a predetermined crank angle (every 180 degrees of crank angle in a four-cylinder engine) and one pulse (hereinafter referred to as “CRK”) with a constant crank angle cycle shorter than the TDC pulse (for example, a cycle of 6 °). The CYL pulse, the TDC pulse, and the CRK pulse are supplied to the ECU 5. These pulses are used for various timing controls such as fuel injection timing and ignition timing, and detection of engine speed (engine speed) NE.

  The ECU 5 shapes input signal waveforms from various sensors, corrects the voltage level to a predetermined level, converts an analog signal value into a digital signal value, etc., and a central processing unit (hereinafter referred to as “CPU”). A storage circuit (memory) for storing various calculation programs executed by the CPU, calculation results, and the like, an output circuit for supplying a drive signal to the fuel injection valve 6 and the spark plug 7, and the like.

  The ECU 5 calculates the indicated mean effective pressure IMEP, which is a combustion state parameter, using the in-cylinder pressure PCYL detected by the pressure sensor 11, and performs ignition timing control according to the indicated mean effective pressure IMEP. Details of this ignition timing control are disclosed in Japanese Patent No. 3993951.

  FIG. 2 is a diagram illustrating a configuration of an equivalent circuit of the pressure sensor 11 and the connection cable, and an integration amplifier that amplifies the output signal of the pressure sensor 11. The equivalent circuit of the pressure sensor 11 and the connection cable can be expressed as a parallel circuit of a voltage source that outputs the voltage Ei, a combined resistance Roc of the sensor and the cable, and a combined capacitance Coc. The integrating amplifier 21 includes an operational amplifier AMP, a feedback resistor Rf, and a feedback capacitor Cf. In the present embodiment, the integrating amplifier 21 is provided in the input circuit of the ECU 5.

When a force is applied to the pressure sensor 11, a charge Q corresponding to the sensor sensitivity Ss is generated, and the charge Q is proportional to the applied force F (Q = Ss × F). The output voltage Eo of the integrating amplifier 21 is given by the following equation (1) and is proportional to the force F applied by the pressure sensor 11.
Eo = Q / Cf = Ss × F / Cf (1)
Therefore, when the sensor sensitivity Ss varies, the output voltage Eo corresponding to the force F changes. Therefore, sensitivity correction of the pressure sensor 11 described later is performed.

On the other hand, the indicated mean effective pressure IMEP indicating the combustion state of the engine 1 can be calculated with relatively high accuracy and simplicity by the following equation (2). The calculation method of the indicated mean effective pressure by this equation (2) is disclosed in Japanese Patent Publication No. 8-20339.

  C1 in Expression (2) is an amplitude of a component (hereinafter referred to as “fundamental frequency component”) of a frequency (fundamental frequency) f1 (= NE / 60) corresponding to the engine speed NE [rpm] included in the sensor output Eo. Yes, C2 is the amplitude of the secondary component corresponding to a frequency twice the fundamental frequency f1. Φ1 is the phase of the fundamental frequency component indicated by the crank angle, φ2 is the phase of the secondary component, h is set to “1/2” for a 4-cycle engine, and set to “1” for a 2-cycle engine Λ is a ratio (s / r) between the connecting rod length s and the crank radius r of the engine.

Next, a method for calculating the amplitudes C1 and C2 will be described.
A time-varying waveform P (ωt) of the output voltage Eo obtained by amplifying the output signal of the pressure sensor 11 by the integrating amplifier 21 is finite as shown by the following formula (3) by performing discrete Fourier transform. Can be shown (approximate) as a sum of sine wave functions. In Expression (3), ω is an angular velocity, and t is time. In this embodiment, ωt corresponds to a crank angle. If the number of data samples in one combustion cycle is n, m in equation (3) is n / 2. Further, when the amplitude Ck and the phase φk are defined by the equations (4) and (5), the equation (3) is transformed into the equation (6). That is, the amplitudes C1 and C2 and the phases φ1 and φ2 can be calculated by equations (4) and (5), respectively.

Further, ak and bk in the equations (4) and (5) are given by the following equations (7) and (8), and a0 in the equation (6) is given by the following equation (9).

  FIG. 3 shows the relative intensity of the frequency component included in the output voltage Eo (based on the amplitude C1 of the fundamental frequency component). The solid line, the broken line, and the alternate long and short dash line shown in this figure correspond to the indicated mean effective pressure IMEP of 231.3 kPa, 411.9 kPa, and 586 kPa, respectively. As is clear from this figure, even if the indicated mean effective pressure IMEP changes, the distribution of frequency component intensities is almost the same, and the relative intensity rapidly decreases as the order increases. Therefore, the comparatively accurate indicated mean effective pressure IMEP can be obtained by the equation (2) using the amplitudes C1 and C2.

FIG. 4 is a flowchart of a process for calculating the indicated mean effective pressure IMEP. This process is executed by the CPU of the ECU 5 in synchronization with the generation of the TDC pulse.
In step S11, data Pj (j = 1 to n) sampled at every predetermined crank angle is read. In step S12, the discrete Fourier transform operation described above is executed on the read data Pj, and the amplitude C1 of the fundamental frequency component and the amplitude C2 of the secondary component are calculated (hereinafter referred to as “first frequency amplitude” and “second frequency amplitude”, respectively). Called).

  In step S13, it is determined whether the engine 1 is being cranked and before ignition is started. If the answer is affirmative (YES), the C1M map and the engine pressure NE and the intake pressure PBA are The C2M map is searched, and the first reference frequency amplitude C1M corresponding to the fundamental frequency component and the second reference frequency amplitude C2M corresponding to the secondary component are calculated. The C1M map and the C2M map are set in advance based on data actually measured using a pressure sensor having an average characteristic.

In step S15, the first and second correction coefficients K1 and K2 are calculated by the following equations (10) and (11).
K1 = C1M / C1 (10)
K2 = C2M / C2 (11)

  During cranking and before starting ignition, the engine speed NE is substantially constant and the fundamental frequency f1 is substantially constant. Therefore, the correction coefficients K1 and K2, which are ratios between the first and second frequency amplitudes C1 and C2 and the first and second reference frequency amplitudes C1M and C2M, are obtained from the sensitivity of the pressure sensor in use and the average sensor. It can be used as a parameter indicating sensitivity deviation.

If the answer to step S13 is negative (NO), the process proceeds to step S16, and the following equations (12) and (13) are used to calculate the first and second frequency amplitudes C1 and C2, and the first and second correction coefficients K1, Applying K2, first and second correction frequency amplitudes C1C and C2C are calculated.
C1C = K1 × C1 (12)
C2C = K2 × C2 (13)

In step S17, the indicated mean effective pressure IMEP is calculated by applying the first and second correction frequency amplitudes C1C and C2C to the above equation (2).
The indicated mean effective pressure IMEP is a parameter calculated for each cylinder, and the above-described parameters C1, C2, K1, K2, C1C, and C2C are calculated for each cylinder.

  In step S18, it is determined whether or not the first correction coefficient K1 is greater than the deterioration determination threshold KDTH. If the answer is negative (NO), whether or not the second correction coefficient K2 is greater than the deterioration determination threshold KDTH. Is discriminated (step S19). If the answer to steps S18 and S19 is negative (NO), the process is immediately terminated.

  If the answer to step S18 or S19 is affirmative (YES), it is determined that the sensitivity of the pressure sensor 11 has deteriorated, and the sensitivity deterioration flag FSD is set to “1” (step S20). When the sensitivity deterioration flag FSD is set to “1”, for example, a warning display indicating that is performed.

  As described above, in the present embodiment, the amplitude of the fundamental frequency component corresponding to the engine speed NE included in the detection signal of the pressure sensor 11 during cranking where the engine speed NE is substantially constant and before the start of ignition. The first frequency amplitude C1 and the second frequency amplitude C2, which is the amplitude of the secondary component, are calculated and correspond to the first and second frequency amplitudes C1 and C2 and are averaged during cranking before the start of ignition. First and second reference frequency amplitudes C1M and C2M, which are large amplitudes, are calculated. Then, the first and second correction coefficients K1 and K2 are calculated as the ratio between the first and second frequency amplitudes C1 and C2 and the first and second reference frequency amplitudes C1M and C2M, and the normal operation state of the engine 1 is calculated. Then, the indicated mean effective pressure IMEP is calculated using the first and second correction frequency amplitudes C1C and C2C obtained by correcting the first and second frequency amplitudes C1 and C2 with the first and second correction coefficients K1 and K2. Therefore, the sensitivity of the pressure sensor 11 is appropriately corrected, and the indicated mean effective pressure IMEP can be calculated with high accuracy.

  Further, the first and second correction coefficients K1 and K2 are compared with the deterioration determination threshold value KDTH, and when the first correction coefficient K1 or the second correction coefficient K2 exceeds the deterioration determination threshold value KDTH, it is determined that the pressure sensor 11 has deteriorated. Therefore, the sensitivity deterioration of the pressure sensor 11 can be easily detected.

  In the present embodiment, the pressure sensor 11 and the crank angle position sensor 12 correspond to a vibration sensor and a rotational speed detection unit, respectively, and the ECU 5 includes first and second basic strength parameter calculation units, first and second reference strength parameters. The calculating means, the first and second correction coefficient calculating means, the normal intensity parameter calculating means, the first and second frequency component intensity correcting means, the combustion state parameter calculating means, and the deterioration determining means are configured. Specifically, steps S11 and S12 in FIG. 4 correspond to first and second basic intensity parameter calculation means and normal intensity parameter calculation means, and step S14 corresponds to first and second reference intensity parameter calculation means, Step S15 corresponds to the first and second correction coefficient calculation means, step S16 corresponds to the first and second frequency component intensity correction means, step S17 corresponds to the combustion state parameter calculation means, and steps S18 to S20 correspond to. It corresponds to a deterioration determination means.

[Second Embodiment]
In the present embodiment, the sensor output correction coefficient KS is calculated as a ratio between the first frequency amplitude C1 and the first reference frequency amplitude C1M, and the sensor output Eo is corrected by the sensor output correction coefficient KS. Except for the points described below, the second embodiment is the same as the first embodiment.

FIG. 5 is a flowchart of a process for calculating the sensor output correction coefficient KS. This process is executed by the CPU of the ECU 5 during cranking of the engine 1 and before starting ignition.
In steps S21 and S22, the first frequency amplitude C1 is calculated as in steps S11 and S12 of FIG. In step S23, the first reference frequency amplitude C1M is calculated as in step S14 of FIG.

In step S24, the sensor output correction coefficient KS is calculated by the following equation (21).
KS = C1M / C1 (21)
The sensor output correction coefficient KS is also calculated for each cylinder (for each sensor of each cylinder).

  In the present embodiment, the corrected sensor output EoC is calculated by multiplying the sensor output Eo obtained in the normal operation state of the engine 1 by the sensor output correction coefficient KS, and the indicated mean effective pressure IMEP is calculated using the corrected sensor output EoC. And / or the maximum in-cylinder pressure PCYLMAX is calculated.

  As described above, in the present embodiment, the sensor output correction coefficient KS is calculated as the ratio between the first frequency amplitude C1 and the first reference frequency amplitude C1M, and the sensor output Eo is corrected by the sensor output correction coefficient KS. The sensitivity correction of the sensor 11 can be performed relatively easily in a frequency band suitable for monitoring the normal combustion state.

  In the present embodiment, the ECU 5 constitutes a basic intensity parameter calculation unit, a reference intensity parameter calculation unit, a correction coefficient calculation unit, and a sensor output correction unit. Specifically, steps S21 and S22 in FIG. 5 correspond to basic intensity parameter calculation means, step S23 corresponds to reference intensity parameter calculation means, and step S24 corresponds to correction coefficient calculation means.

  The present invention is not limited to the embodiment described above, and various modifications can be made. For example, in the first embodiment, the first and second correction coefficients K1 and K2 are calculated, and the first frequency amplitude C1 and the second frequency amplitude C1 and C2 are corrected by the first and second correction coefficients K1 and K2, respectively. However, only the first correction coefficient K1 may be calculated and only the first frequency amplitude C1 may be corrected as shown in FIG.

In the process of FIG. 6, steps S14 to S17 in FIG. 4 are replaced with steps S14a to S17a, respectively, and step S19 is deleted.
In step S14a, the first reference frequency amplitude C1M is calculated according to the engine speed NE and the intake pressure PBA. In step S15a, the first correction coefficient K1 is calculated. In step S16a, the first correction frequency amplitude C1C is calculated using the first correction coefficient K1, and in step S17a, the indicated mean effective pressure IMEP is calculated using the first correction frequency amplitude C1C and the second frequency amplitude C2. If the answer to step S18 is negative (NO), the process immediately ends.

  The indicated mean effective pressure IMEP is calculated by the above equation (2), but the second frequency amplitude C2 is about ½ of the first frequency amplitude C1, as shown in FIG. 1 / 2λ) is generally a value of about 0.125, so the contribution of the second frequency amplitude C2 in the calculation of the indicated mean effective pressure IMEP is considerably smaller than the first frequency amplitude C1. Therefore, the indicated mean effective pressure IMEP can be calculated with relatively high accuracy by correcting only the first frequency amplitude C1. It goes without saying that the calculation accuracy is further improved by correcting the second frequency amplitude C2 as in the first embodiment.

  In this modification, since the second correction coefficient K2 is not calculated, the pressure sensor sensitivity deterioration determination is performed using only the first correction coefficient K1 (steps S18 and S20).

  In the above-described embodiment, the most common piezoelectric pressure sensor is used as the vibration sensor. However, an acceleration sensor, a force sensor, or a clearance sensor may be used instead of the piezoelectric pressure sensor. Acceleration sensor, force sensor, or clearance as shown in known non-patent literature (Automotive Technology Society academic lecture preprint 2006/05 "Actual mean effective pressure monitoring method using acceleration, force, clearance sensor") The sensor can obtain detection data highly correlated with the piezoelectric pressure sensor.

  In the first embodiment described above, the sensor sensitivity deterioration determination is performed using the first and second correction coefficients K1 and K2 themselves. However, the correction coefficients K1 and K2 calculated during the previous operation are stored. In addition, the deterioration determination may be performed based on the amount of change or the rate of change from the previous value of the correction coefficients K1 and K2 calculated during the current operation.

  The present invention can also be applied to a combustion state monitoring device such as a marine vessel propulsion engine such as an outboard motor having a vertical crankshaft.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 5 Electronic control unit (1st and 2nd basic intensity parameter calculation means, 1st and 2nd reference intensity parameter calculation means, 1st and 2nd correction coefficient calculation means, sensor output correction means, normal intensity parameter calculation means , First and second frequency component intensity correcting means, combustion state parameter calculating means, deterioration determining means)
11 Piezoelectric pressure sensor (vibration sensor)
12 Crank angle position sensor

Claims (5)

In a sensitivity correction device for a vibration sensor attached to an internal combustion engine,
A rotational speed detecting means for detecting the rotational speed of the engine;
Basic intensity parameter calculating means for calculating a basic frequency intensity parameter indicating the intensity of the fundamental frequency component corresponding to the engine speed, which is included in the detection signal of the vibration sensor, in a predetermined operating state in which the engine is not ignited; ,
A reference intensity parameter calculating means for calculating a reference intensity parameter corresponding to the fundamental frequency in the predetermined operation state;
Correction coefficient calculating means for calculating a correction coefficient according to a ratio between the fundamental frequency intensity parameter and the reference intensity parameter;
And a sensor output correcting means for correcting the vibration sensor output using the correction coefficient. In a combustion state monitoring apparatus for an internal combustion engine, comprising combustion state parameter calculation means for calculating a combustion state parameter indicating a combustion state of the engine based on an output of a vibration sensor attached to the internal combustion engine.
A rotational speed detecting means for detecting the rotational speed of the engine;
A first basic intensity parameter for calculating a first frequency intensity parameter indicating an intensity of a fundamental frequency component corresponding to the engine speed, which is included in a detection signal of the vibration sensor, in a predetermined operation state where the engine is not ignited. A calculation means;
First reference intensity parameter calculating means for calculating a first reference intensity parameter corresponding to the fundamental frequency in the predetermined operation state;
First correction coefficient calculating means for calculating a first correction coefficient in accordance with a ratio between the first frequency intensity parameter and the first reference intensity parameter;
The first frequency intensity parameter included in the detection signal of the vibration sensor in the normal operation state of the engine and the second intensity indicating the intensity of the frequency component twice the basic frequency included in the detection signal of the vibration sensor. A normal intensity parameter calculating means for calculating a frequency intensity parameter;
First frequency component intensity correction means for correcting the first frequency component intensity parameter calculated by the normal intensity parameter calculation means using the first correction coefficient;
The combustion state parameter calculation means uses the first frequency component intensity parameter corrected by the first frequency component intensity correction means and the second frequency component intensity parameter calculated by the normal intensity parameter calculation means. A combustion state monitoring device for an internal combustion engine, characterized by calculating a state parameter. A second basic intensity parameter calculating means for calculating the second frequency intensity parameter in the predetermined operation state;
Second reference intensity parameter calculating means for calculating a second reference intensity parameter corresponding to the double frequency in the predetermined operating state;
Second correction coefficient calculating means for calculating a second correction coefficient in accordance with a ratio between the second frequency intensity parameter and the second reference intensity parameter;
A second frequency component intensity correction unit that corrects the second frequency component intensity parameter calculated by the normal intensity parameter calculation unit using the second correction coefficient;
3. The combustion state parameter calculating means calculates the combustion state parameter using the first and second frequency component intensity parameters corrected by the first and second frequency component intensity correcting means. A combustion state monitoring device for an internal combustion engine according to claim 1.   The apparatus further comprises a deterioration determination unit that compares the first correction coefficient with a deterioration determination threshold and determines that the vibration sensor has deteriorated when the first correction coefficient exceeds the deterioration determination threshold. Item 3. The combustion state monitoring apparatus for an internal combustion engine according to Item 2.   Deterioration that compares the first and second correction coefficients with a deterioration determination threshold value and determines that the vibration sensor has deteriorated when at least one of the first correction coefficient and the second correction coefficient exceeds the deterioration determination threshold value. The combustion state monitoring apparatus for an internal combustion engine according to claim 3, further comprising a determination unit.

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