JP5737196B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine having a cylinder pressure sensor failure determination function.

  As a prior art, for example, as disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 7-310585), a control device for an internal combustion engine having a function of determining a failure of an in-cylinder pressure sensor is known. In the prior art, the in-cylinder pressure detected by the in-cylinder pressure sensor is integrated in a predetermined integration interval to calculate an in-cylinder pressure integrated value. Also, calculate the standard in-cylinder pressure integral value (basic integral value) corresponding to the normal combustion state based on the basic fuel injection amount, and compare the actually obtained in-cylinder pressure integral value with the basic integral value. Thus, the failure of the in-cylinder pressure sensor is determined.

JP-A-7-310585 JP 7-332152 A JP 7-318458 A JP 2010-133329 A JP 2005-248703 A

  By the way, in the above-described conventional technology, it is necessary to execute failure determination in a certain operation region in which basic integral value data (data map or the like) is prepared in advance, and there is a problem that the operation region in which failure determination is possible is limited. is there. In addition, if it is attempted to execute failure determination in all operation regions, a large number of basic integration value data in all operation regions is required, and there is a problem in that the number of man-hours for data increase.

As a method for avoiding these problems, for example, by comparing the first parameter affected by the output sensitivity (sensitivity error) of the in-cylinder sensor with the second parameter not affected by the output sensitivity, A method for determining a sensor failure (sensitivity abnormality) is conceivable. Here, as the first parameter, for example, a calorific value PV ^κ calculated based on the in-cylinder pressure P, the in-cylinder volume V, and the specific heat ratio κ, or a multiplication value of the in-cylinder pressure and the in-cylinder volume in one cycle. A parameter ΔPVmax obtained by subtracting the multiplication value PV0 during non-combustion from the maximum value PVmax can be mentioned. Further, the second parameter includes a ratio of two indexes including the in-cylinder pressure P (for example, the indicated torque ratio before and after the TDC, and the ratio of ΔPVmax and PV0). However, in the state in which the air-fuel ratio control that controls the exhaust air-fuel ratio in the vicinity of the stoichiometric air-fuel ratio is executed, the ratio between the two indexes is almost constant. There is a problem that it is difficult to judge.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to accurately determine whether or not the in-cylinder pressure sensor has failed in a wide operating range, and to make a high determination even during execution of air-fuel ratio control. An object of the present invention is to provide a control device for an internal combustion engine capable of realizing accuracy.

The first invention provides an in-cylinder pressure sensor that outputs a signal corresponding to the in-cylinder pressure;
Pmax calculating means for calculating the maximum in-cylinder pressure that is the maximum value of the in-cylinder pressure in one cycle based on the output of the in-cylinder pressure sensor;
A combustion timing index that is a parameter that changes according to the combustion timing of the in-cylinder gas and that is correlated with the maximum in-cylinder pressure and that is not affected by the output sensitivity of the in-cylinder pressure sensor is represented by the in-cylinder pressure sensor. Index calculation means for calculating based on the output;
An abnormality detection means for detecting an abnormality in output sensitivity of the in-cylinder pressure sensor based on the maximum in-cylinder pressure and the combustion timing index;
It is characterized by providing.

A second invention is the in-cylinder pressure, based on the cylinder volume and the specific heat ratio to calculate the calorific value PV ^kappa, calorific value PV ^kappa and based on the heating value PV ^kappa and burnout crank angle at the combustion start crank angle And MFB calculating means for calculating the combustion mass ratio at an arbitrary crank angle,
The combustion timing index is a crank angle when the combustion mass ratio reaches a predetermined reference value.

  According to a third aspect of the invention, the combustion timing index is a crank angle at the time when the in-cylinder pressure detected by the in-cylinder pressure sensor reaches the maximum in-cylinder pressure.

4th invention is provided with the normal determination value calculation means which calculates Pmax estimated value which is the maximum in-cylinder pressure when the output sensitivity of the in-cylinder pressure sensor is normal based on the combustion timing index,
The abnormality detecting means is configured to determine that the output sensitivity is abnormal when a ratio between the maximum in-cylinder pressure actually detected by the in-cylinder pressure sensor and the estimated Pmax is out of a predetermined normal range. It is said.

  According to a fifth aspect of the invention, there is provided a normal determination value correcting means for correcting the Pmax estimated value based on a load state of the internal combustion engine.

  According to a sixth aspect of the invention, the abnormality detection means is configured to execute the output sensitivity abnormality determination process only when the operating region of the internal combustion engine is a fully open region.

  According to the first aspect, it is possible to detect an abnormality in the output sensitivity of the in-cylinder pressure sensor based on the maximum in-cylinder pressure obtained from the output of the in-cylinder pressure sensor and the combustion timing index. As a result, it is possible to detect an abnormality in sensitivity based only on the output of the in-cylinder pressure sensor without using another sensor output or the like supplementarily, and the system can be simplified. In addition, it is possible to accurately detect an abnormality without being affected by output errors of other sensors. Furthermore, even without preparing a large number of determination data and the like, abnormality detection can be performed under a wide range of operating conditions (operation regions), and the amount of determination data and the data man-hours can be suppressed. Moreover, the combustion timing index is a parameter that changes according to the combustion timing of the in-cylinder gas even when the theoretical air-fuel ratio is maintained by the air-fuel ratio control. For this reason, it is possible to avoid a phenomenon in which the combustion timing index and the parameter derived therefrom are held at a constant value by the air-fuel ratio control, and high detection accuracy can be realized even when the air-fuel ratio control is executed.

  According to the second invention, the crank angle at the time when the combustion mass ratio reaches the predetermined reference value can be used as the combustion timing index. Thereby, it is possible to accurately detect abnormality in output sensitivity of the in-cylinder pressure sensor even when air-fuel ratio control is executed.

  According to the third aspect, the crank angle at the time when the in-cylinder pressure detected by the in-cylinder pressure sensor reaches the maximum in-cylinder pressure can be used as the combustion timing index. Thereby, even when the air-fuel ratio control is executed, an abnormality in the output sensitivity of the in-cylinder pressure sensor can be accurately detected, and the calculation load of the control device can be reduced.

  According to the fourth invention, when the ratio between the estimated Pmax value calculated based on the combustion timing index and the maximum in-cylinder pressure actually detected by the in-cylinder pressure sensor is out of a predetermined normal range, the output sensitivity Can be determined as abnormal. Thereby, it is possible to easily detect an abnormality in sensitivity based on the ratio of the two parameters obtained from the output of the in-cylinder pressure sensor.

  According to the fifth aspect of the invention, the normal judgment value correcting means cancels the change even if the relationship between the maximum in-cylinder pressure and the combustion timing index changes according to the load state (charging efficiency) of the internal combustion engine. In addition, the estimated Pmax value can be corrected appropriately. Thereby, even if it does not hold | maintain filling efficiency uniformly, abnormality detection of a cylinder pressure sensor can be performed. Therefore, it is possible to expand the operation range in which the abnormality can be detected, increase the chance of detecting the abnormality, and improve the reliability.

  According to the sixth aspect of the invention, the abnormality detecting means can execute abnormality detection of the in-cylinder pressure sensor only when the operating region of the internal combustion engine is the fully open region. As a result, high detection accuracy can be realized under certain operating conditions.

It is a block diagram for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a characteristic diagram which shows the relationship between the timing of a combustion start, and the largest in-cylinder pressure Pmax. It is explanatory drawing for demonstrating the combustion gravity center CA50 as an example of a combustion timing parameter | index. FIG. 6 is a characteristic diagram showing the relationship between the maximum in-cylinder pressure Pmax and the combustion center of gravity CA50 for each of cases where the output sensitivity of the in-cylinder pressure sensor is normal and abnormal. In Embodiment 1 of this invention, it is a flowchart of the control performed by ECU. In Embodiment 2 of this invention, it is a flowchart of the control performed by ECU.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
The first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a configuration diagram for explaining a system configuration according to the first embodiment of the present invention. The system according to the present embodiment includes an engine 10 as a multi-cylinder internal combustion engine. In FIG. 1, only one cylinder of the engine 10 is illustrated. Further, the present invention is applied to an engine having an arbitrary number of cylinders including a single cylinder. Each cylinder of the engine 10 has a combustion chamber 14 defined by a piston 12, and the piston 12 is connected to a crankshaft 16 of the engine.

  Further, the engine 10 includes an intake passage 18 that sucks intake air into the combustion chamber 14 (cylinder) of each cylinder, and an exhaust passage 20 that exhausts exhaust gas from each cylinder. The intake passage 18 is provided with an electronically controlled throttle valve 22 that adjusts the intake air amount based on the accelerator opening and the like. The exhaust passage 20 is provided with a catalyst 24 such as a three-way catalyst for purifying exhaust gas. Each cylinder has a fuel injection valve 26 for injecting fuel into the intake port, an ignition plug 28 for igniting an air-fuel mixture in the cylinder, an intake valve 30 for opening and closing the intake port with respect to the cylinder, and an exhaust port. And an exhaust valve 32 that opens and closes the cylinder with respect to the inside of the cylinder.

  The system of the present embodiment also includes a sensor system including sensors 40 to 44 and an ECU (Electronic Control Unit) 50 that controls the operating state of the engine 10. The crank angle sensor 40 outputs a signal synchronized with the rotation of the crankshaft 16, and the air flow sensor 42 detects the intake air amount. The in-cylinder pressure sensor 44 is constituted by a known pressure sensor having a piezoelectric element, for example, and outputs a signal corresponding to the in-cylinder pressure P, and is provided for each cylinder. In addition to this, the sensor system includes various sensors necessary for engine control (a throttle sensor that detects the opening of the throttle valve 22, a water temperature sensor that detects the temperature of engine cooling water, and an air-fuel ratio that detects the exhaust air-fuel ratio. Sensor, etc.).

  ECU50 is comprised by the arithmetic processing apparatus provided with the memory circuit containing ROM, RAM, a non-volatile memory etc., for example. Each sensor of the sensor system is connected to the input side of the ECU 50, and various actuators including the throttle valve 22, the fuel injection valve 26, the spark plug 28, and the like are connected to the output side of the ECU 50. In addition, the ECU 50 has a function of storing various data that changes in accordance with the crank angle as time series data together with the crank angle. The time series data includes an output value of the in-cylinder pressure sensor 44 and various parameters calculated based on the output value.

  Then, the ECU 50 controls the operating state by driving each actuator while detecting engine operation information by the sensor system. Specifically, the engine speed (engine speed) and the crank angle are detected based on the output of the crank angle sensor 40, and the intake air amount is calculated based on the output of the air flow sensor 42. Further, the engine load factor (charging efficiency) KL is calculated based on the intake air amount, the engine speed, and the like. Then, the fuel injection timing and ignition timing are determined based on the crank angle, and when these timings arrive, the fuel injection valve 26 and the spark plug 28 are driven. Thereby, the air-fuel mixture is combusted in the cylinder, and the engine is operated. Further, the ECU 50 executes known air-fuel ratio control for controlling the exhaust air-fuel ratio to be close to the stoichiometric air-fuel ratio based on the output of the air-fuel ratio sensor. Further, based on the output of the in-cylinder pressure sensor 44, known combustion control is executed, and knocking, pre-ignition, and the like are detected.

[Features of Embodiment 1]
Since the output sensitivity of the in-cylinder pressure sensor 44 may be out of the allowable range due to initial failure, deterioration with time, failure, etc. of the sensor, it is preferable to detect abnormality of the output sensitivity. However, in the method of the prior art, it is necessary to prepare a large amount of reference data in order to limit the operation region where abnormality detection is performed or to expand this region. As a method of solving this problem, for example, the first parameter affected by the output sensitivity of the in-cylinder sensor is compared with the second parameter not affected by the output sensitivity, thereby detecting an abnormality in the output sensitivity. A way to do this is conceivable.

Here, as the first parameter, for example, a calorific value PV ^κ calculated based on the in-cylinder pressure P, the in-cylinder volume V, and the specific heat ratio κ, or a multiplication value of the in-cylinder pressure and the in-cylinder volume in one cycle. A parameter ΔPVmax obtained by subtracting the multiplication value PV0 during non-combustion from the maximum value PVmax can be mentioned. The parameter ΔPVmax is a known parameter described in, for example, Japanese Patent Application Laid-Open No. 2005-248703. On the other hand, examples of the second parameter include a ratio of two indexes including the in-cylinder pressure P (for example, the indicated torque ratio before and after TDC and the ratio of ΔPVmax and PV0). However, the indicated torque and parameter ΔPVmax after TDC have characteristics that correlate with the heat generation amount and torque (fuel injection amount), and the indicated torque before TDC and the multiplication value PV0 during non-combustion have characteristics that correlate with the intake air amount. There is. Therefore, in the state where the stoichiometric air-fuel ratio is maintained by the air-fuel ratio control, the above-described torque ratio and ratio (ΔPVmax / PV0) are constant. Therefore, by comparing these ratios with the first parameter, the output sensitivity can be improved. It is difficult to detect anomalies.

  Therefore, in the present embodiment, the maximum in-cylinder pressure Pmax and the combustion timing index T are adopted as examples of parameters that accurately reflect the state of output sensitivity of the in-cylinder pressure sensor 44 even when air-fuel ratio control is executed. Then, abnormality detection is executed based on these parameters. Here, the combustion timing index T is a parameter that changes according to the combustion timing of the in-cylinder gas, and is defined as a parameter that is correlated with the maximum in-cylinder pressure Pmax and that is not affected by the output sensitivity of the in-cylinder pressure sensor 44. Is done. In the present embodiment, the combustion center of gravity CA50 is adopted as an example of the combustion timing index T. Hereinafter, parameters used in the present embodiment and an abnormality detection method will be described.

(Maximum cylinder pressure Pmax)
FIG. 2 is a characteristic diagram showing the relationship between the combustion start timing and the maximum in-cylinder pressure Pmax. The maximum in-cylinder pressure Pmax is defined as the maximum value of the in-cylinder pressure P in one cycle, and is a parameter influenced by the output sensitivity of the in-cylinder pressure sensor 44. When the combustion start timing is early, the gas expands in a state where the volume of the combustion chamber 14 is small, so that the in-cylinder pressure increases greatly. Therefore, as shown in FIG. 2, the maximum in-cylinder pressure Pmax has a characteristic that it increases as the combustion start timing is earlier.

(Combustion center of gravity CA50)
FIG. 3 is an explanatory diagram for explaining the combustion center of gravity CA50 as an example of the combustion timing index T. The characteristic line shown in this figure is a known parameter called a mass fraction of burned fuel (MFB) and is calculated by the following equation (1). As shown in FIG. 3, the combustion mass ratio changes from 0 to 100% when the crank angle θ changes from the combustion start crank angle θs to the combustion end crank angle θe. The combustion center of gravity CA50 is defined as the crank angle when the combustion mass ratio reaches 50%. As can be seen from FIG. 3, the combustion center of gravity CA50 moves to the advance side when the combustion start timing is early, and moves to the retard side when the combustion start timing is late, so that it depends on the combustion timing of the in-cylinder gas. Change. In the following equation (1), PV ^κ (θ), PV ^κ (θs), and PV ^κ (θe) are the calorific values PV ^κ at the crank angle θ, the combustion start crank angle θs, and the combustion end crank angle θe, respectively. Show.

The combustion center of gravity CA50 has a characteristic that is not influenced by the output sensitivity of the in-cylinder pressure sensor 44. More specifically, first, the calorific value Q (= PV ^κ ) can be expressed by the following equation (2) using the in-cylinder pressure P, and the value is proportional to the gain of the in-cylinder pressure P. On the other hand, in the equation (1) for calculating the combustion center of gravity CA50, the calorific value Q (in-cylinder pressure P) is included in both terms of denominator and numerator. For this reason, even if the gain (output sensitivity) of the in-cylinder pressure P fluctuates, the influence is canceled between the denominator and the numerator of the equation (1) and is not reflected in the calculated value of the combustion center of gravity CA50.

  Next, FIG. 4 is a characteristic diagram showing the relationship between the maximum in-cylinder pressure Pmax and the combustion center of gravity CA50 when the output sensitivity of the in-cylinder pressure sensor is normal and abnormal. A characteristic line L shown by a solid line in FIG. 4 represents the relationship between the maximum in-cylinder pressure Pmax and the combustion center of gravity CA50 when the output sensitivity of the sensor is normal, and its data characteristics (for example, the gradient α and The intercept β) is stored in the ECU 50 in advance. As indicated by this characteristic line L, when the output sensitivity of the in-cylinder pressure sensor is normal, a certain relationship is established between the maximum in-cylinder pressure Pmax and the combustion center of gravity CA50. This relationship is held substantially constant even when the engine speed and torque fluctuate, as shown by the data points (marks ◯, □, Δ) in FIG.

  On the other hand, when the output sensitivity of the sensor changes from the normal state (reference state), as described above, the change in output sensitivity is reflected only in the maximum in-cylinder pressure Pmax and not in the combustion center of gravity CA50. As a result, for example, when the output sensitivity is reduced from the reference sensitivity, the relationship between the maximum in-cylinder pressure Pmax and the combustion center of gravity CA50 changes from a normal state as shown by a dotted line in FIG. Therefore, in the present embodiment, an estimated Pmax value that is the maximum in-cylinder pressure when the output sensitivity is normal is calculated based on the combustion center of gravity CA50 and the data characteristics (constants α, β) at an arbitrary time. When the ratio A between the detected Pmax value that is the maximum in-cylinder pressure actually obtained by the in-cylinder pressure sensor 44 and the estimated Pmax value is out of the predetermined normal range (Amax to Amin), the output sensitivity of the sensor Is determined to be abnormal.

[Specific Processing for Realizing Embodiment 1]
Next, specific processing for realizing the above-described control will be described with reference to FIG. FIG. 5 is a flowchart of the control executed by the ECU in the first embodiment of the present invention. The routine shown in this figure is repeatedly executed while the engine is operating. In the routine shown in FIG. 5, first, in step 100, it is determined whether or not there is an abnormality in the engine function and parts. If this determination is established, the routine proceeds to step 102. If the determination is not established, an abnormality in sensitivity of the in-cylinder pressure sensor 44 cannot be accurately detected, and this routine is terminated.

  Next, in step 102, it is determined whether or not an operating condition suitable for detecting a sensitivity abnormality is satisfied. As a specific example, in step 102, it is determined whether or not the engine speed NE is 2000 rpm or more and the load state is a fully open region (WOT region). When this determination is established, the routine proceeds to step 104, and when this determination is not established, since this is not an operation state suitable for abnormality detection, this routine is terminated. The fully open region is defined as an operation region where the charging efficiency KL increases to a practical maximum value determined according to the engine speed. In the operation region other than the fully open region, it is difficult to stably detect abnormality while the charging efficiency KL is kept constant. Therefore, it is preferable to exclude the operation region other than the fully open region in the determination process of step 102. Thereby, it is possible to accurately determine an abnormality in sensitivity of the in-cylinder pressure sensor under a certain operating condition. This point will also be described later in the second embodiment.

Next, at step 104, the detected Pmax value is calculated based on the output of the in-cylinder pressure sensor 44. In step 104, the calorific value ^PVκ is calculated based on the in-cylinder pressure P, the in-cylinder volume V, and the specific heat ratio κ at each crank angle in one cycle, and the combustion mass ratio is calculated by the above equation (1). Then, the combustion center of gravity CA50, which is the crank angle when the combustion mass ratio reaches 50%, is calculated as the combustion timing index T. The combustion center of gravity CA50 is an example of the combustion timing index T in the present embodiment, and other combustion timing indices T will be described later.

  Next, in step 106, based on the combustion timing index T (combustion center of gravity CA50), an estimated Pmax value at normal time is calculated by the following equation (3). Note that α and β in the following equation (3) are constants corresponding to the slope and intercept of the characteristic line L described above. Subsequently, in step 108, a ratio A between the detected Pmax value and the estimated Pmax value is calculated as shown in the following equation (4).

Pmax estimated value = α × T + β (3)
A = Detected Pmax value / Pmax estimated value (4)

  Next, in step 110, it is determined whether or not the ratio A is within a predetermined normal range (Amax to Amin), that is, whether or not Amax ≧ A ≧ Amax is satisfied. Here, the boundary values Amax and Amax of the normal range are set according to the tolerance of the variation of the detected Pmax value with respect to the estimated Pmax value at the normal time, and are stored in the ECU 50 in advance. If the determination in step 110 is established, it is determined that the output sensitivity of the in-cylinder pressure sensor 44 is normal, and this routine is terminated. On the other hand, if the determination in step 110 is not established, the sensor output sensitivity is out of the normal range, that is, the output sensitivity is abnormally lowered (Amin> A), or the output sensitivity is abnormal. (A> Amax). In this case, therefore, in step 112, the output sensitivity of the in-cylinder pressure sensor 44 is determined to be abnormal.

  As described above in detail, according to the present embodiment, the maximum in-cylinder pressure Pmax and the combustion timing index T are calculated based on the output of the in-cylinder pressure sensor 44, and the output sensitivity abnormality is determined based on the ratio A between the two. Can be detected. This makes it possible to detect an abnormality in sensitivity based only on the output of the in-cylinder pressure sensor 44 without supplementarily using other sensor outputs including an intake pressure sensor, an air flow sensor, an air-fuel ratio sensor, and the like. The system can be simplified. In addition, it is possible to accurately detect an abnormality without being affected by output errors of other sensors. Furthermore, even without preparing a large number of determination data and the like, abnormality detection can be performed under a wide range of operating conditions (operation regions), and the amount of determination data and the data man-hours can be suppressed.

  In addition, the combustion timing index T (combustion center of gravity CA50) is a parameter that changes according to the combustion timing of the in-cylinder gas even when the stoichiometric air-fuel ratio is maintained by the air-fuel ratio control. It is possible to avoid a phenomenon in which T (and determination ratio A) is held at a constant value. Therefore, high detection accuracy can be realized even when air-fuel ratio control is executed.

  In the first embodiment, step 104 in FIG. 5 shows a specific example of the Pmax calculation means and index calculation means in claim 1, and step 110 shows a specific example of the abnormality detection means. Further, the equation (1) shows a specific example of the MFB calculating means in claim 2, and step 106 in FIG. 5 shows a specific example of the normal judgment value calculating means in claim 4.

  In the first embodiment, the combustion center of gravity CA50, which is the crank angle when the combustion mass ratio reaches 50%, is used as the combustion timing index T. However, the present invention is not limited to this. For example, as shown in FIG. 3, the crank angle CAx when the combustion mass ratio reaches a predetermined reference value x% may be used as the combustion timing index T. At this time, the reference value x may be set to any value from 0 to 100%, and is not limited to 50%.

  Further, the combustion timing index T of the present invention is not limited to the crank angle CAx at the time when the combustion mass ratio reaches a predetermined value. That is, in the present invention, for example, the crank angle at which the in-cylinder pressure P detected by the in-cylinder pressure sensor 44 reaches the maximum in-cylinder pressure Pmax (hereinafter referred to as the maximum in-cylinder pressure crank angle CApmax) is used as the combustion timing index T. May be. More specifically, even if the in-cylinder pressure P fluctuates due to an error in output sensitivity, the relative magnitude relationship of the in-cylinder pressure P at each crank angle does not change greatly.

  That is, the maximum in-cylinder pressure crank angle CApmax, which is the crank angle at which the peak value of the in-cylinder pressure P (maximum in-cylinder pressure Pmax) appears in one cycle, is a parameter that changes according to the combustion timing of the in-cylinder gas, This parameter has a correlation with the in-cylinder pressure Pmax and is not affected by the output sensitivity of the in-cylinder pressure sensor. Therefore, by using the maximum in-cylinder pressure crank angle CApmax as the combustion timing index T, it is possible to obtain substantially the same operation and effect as in the first embodiment, and to realize high detection accuracy even during execution of air-fuel ratio control. Can do. In addition, in this case, since it is not necessary to obtain the combustion mass ratio by the calculation of the equation (1), the calculation load of the ECU 50 can be reduced and the calculation speed can be improved. As specific processing when the maximum in-cylinder pressure crank angle CApmax is used, for example, in step 104 in FIG. 4, the maximum in-cylinder pressure crank angle CApmax is calculated as the combustion timing index T, and in step 106, this combustion timing is calculated. The estimated Pmax may be calculated based on the index T (maximum in-cylinder pressure crank angle CApmax).

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG. The present embodiment is characterized in that the estimated Pmax value is corrected based on the charging efficiency KL in the first embodiment. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

[Features of Embodiment 2]
In the first embodiment, the abnormality detection of the sensor is executed using the relationship between the maximum in-cylinder pressure Pmax and the combustion timing index T. More precisely, the relationship between the two is related to the engine load state (in-cylinder state). It changes in proportion to the amount of gas charged. For this reason, in the first embodiment, the operation region in which the abnormality detection is performed is limited to a fully open region where the in-cylinder charging gas amount is in a substantially constant state, and the influence of the in-cylinder charging gas amount on detection accuracy is affected. It was set as the structure excluded. On the other hand, the present embodiment is characterized in that the sensor abnormality detection is executed even in a region other than the fully open region by correcting the estimated Pmax value based on the load state (charging efficiency KL) of the internal combustion engine.

  More specifically, the estimated Pmax value is calculated as shown in the following equation (5) based on the combustion timing index T, the constants α and β, and the charging efficiency KL. According to this equation, even if the relationship between the maximum in-cylinder pressure Pmax (detected Pmax value) and the combustion timing index T changes proportionally according to the charging efficiency KL, the estimated Pmax value is canceled so that this change is canceled. It can be corrected appropriately.

Pmax estimated value = (α × T + β) × KL (5)

[Specific Processing for Realizing Embodiment 2]
Next, specific processing for realizing the above-described control will be described with reference to FIG. FIG. 6 is a flowchart of control executed by the ECU in the second embodiment of the present invention. The routine shown in this figure is repeatedly executed while the engine is operating. In the routine shown in FIG. 6, first, in step 200, it is determined whether or not there is an abnormality in the engine function and parts, and in step 202, whether or not an operation condition suitable for detecting an abnormality in sensitivity is satisfied. Determine whether.

  Then, when the determination is established in both steps 200 and 202, the routine proceeds to step 204, and when the determination is not established in any step, this routine is terminated. In the present embodiment, correction according to the filling efficiency KL is executed, so that it is not necessary to limit the sensitivity detection region to the fully open region. Therefore, in step 202, unlike step 102 in the first embodiment (FIG. 5), it is determined only whether or not the engine speed NE is 2000 rpm or more.

  Next, in step 204, as in the first embodiment, the detected Pmax value and the combustion timing index T are calculated. In this case, as the combustion timing index T, as described in the first embodiment, among the combustion center of gravity CA50, the crank angle CAx when the predetermined combustion mass ratio x% is reached, and the maximum in-cylinder pressure crank angle CApmax, Any parameter may be used. Next, in step 206, the estimated Pmax value corrected according to the charging efficiency KL is calculated by the equation (5). In steps 208 to 212, the same processing as in steps 108 to 112 of the first embodiment is executed to determine the output sensitivity of the in-cylinder pressure sensor 44.

  Also in the present embodiment configured as described above, the same operational effects as those of the first embodiment can be obtained. In addition, in this embodiment, the estimated Pmax value can be corrected based on the charging efficiency KL, so that the abnormality detection of the in-cylinder pressure sensor 44 can be detected even if the charging efficiency is not kept constant (other than the fully open region). Can be executed. As a result, it is possible to expand the operating range in which abnormality detection is possible, increase the chance of abnormality detection, and improve reliability.

  In the second embodiment, step 204 in FIG. 6 shows a specific example of the Pmax calculation means and index calculation means in claim 1, and step 210 shows a specific example of the abnormality detection means. The equation (1) shows a specific example of the MFB calculating means in claim 2, and step 206 in FIG. 6 is performed by the normal determination value calculating means in claim 4 and the normal determination value correcting means in claim 5. A specific example is shown.

10 Engine (Internal combustion engine)
12 Piston 14 Combustion chamber 16 Crankshaft 18 Intake passage 20 Exhaust passage 22 Throttle valve 24 Catalyst 26 Fuel injection valve 28 Spark plug 30 Intake valve 32 Exhaust valve 40 Crank angle sensor 42 Air flow sensor 44 In-cylinder pressure sensor 50 ECU
Pmax Maximum in-cylinder pressure T Combustion timing index

Claims (6)

An in-cylinder pressure sensor that outputs a signal corresponding to the in-cylinder pressure;
Pmax calculating means for calculating the maximum in-cylinder pressure that is the maximum value of the in-cylinder pressure in one cycle based on the output of the in-cylinder pressure sensor;
A combustion timing index that is a parameter that changes according to the combustion timing of the in-cylinder gas and that is correlated with the maximum in-cylinder pressure and that is not affected by the output sensitivity of the in-cylinder pressure sensor is represented by the in-cylinder pressure sensor. Index calculation means for calculating based on the output;
An abnormality detecting means for detecting an abnormality in output sensitivity of the in-cylinder pressure sensor by comparing a ratio between the maximum in-cylinder pressure and the combustion timing index and a normal range of the ratio ;
A control device for an internal combustion engine, comprising: The calorific value PVκ is calculated based on the in-cylinder pressure, the in-cylinder volume and the specific heat ratio, and the combustion mass ratio at an arbitrary crank angle based on the calorific value PVκ at the combustion start crank angle and the calorific value PVκ at the combustion end crank angle. MFB calculating means for calculating
The control apparatus for an internal combustion engine according to claim 1, wherein the combustion timing index is a crank angle when the combustion mass ratio reaches a predetermined reference value.   2. The control device for an internal combustion engine according to claim 1, wherein the combustion timing index is a crank angle when an in-cylinder pressure detected by the in-cylinder pressure sensor reaches the maximum in-cylinder pressure. A normal determination value calculating means for calculating a Pmax estimated value that is a maximum in-cylinder pressure when the output sensitivity of the in-cylinder pressure sensor is normal, based on the combustion timing index;
The abnormality detecting means is configured to determine that the output sensitivity is abnormal when a ratio between the maximum in-cylinder pressure actually detected by the in-cylinder pressure sensor and the estimated Pmax is out of a predetermined normal range. The control device for an internal combustion engine according to any one of claims 1 to 3.   5. The control apparatus for an internal combustion engine according to claim 4, further comprising normal determination value correction means for correcting the estimated Pmax value based on a load state of the internal combustion engine.   The control apparatus for an internal combustion engine according to claim 4, wherein the abnormality detection means is configured to execute the output sensitivity abnormality determination process only when the operation region of the internal combustion engine is a fully open region.

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