JP2007040207A - Controller for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controller for an internal combustion engine capable of controlling a cylinder even if a cylinder information detection means in the cylinder becomes an abnormal condition. <P>SOLUTION: This controller for the internal combustion engine having the cylinder information detection means for detecting information in the cylinder in each cylinder to control predetermined amount of control based on values detected by the cylinder information detection means per cylinder is provided with a means (S101) for detecting abnormality of the cylinder information detection means to control amount of control of the cylinder in which abnormality of the cylinder information detection means is detected by using values detected by the cylinder information detection means of the cylinder other than the cylinder in which the abnormality is detected (S105) when the abnormality of the cylinder information detection means in any cylinder is detected by the detection means (S102:YES). As a result, control of the cylinder becomes possible by this substitution even if the cylinder information detection means in any cylinder becomes an abnormal condition. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine that controls a control amount such as an ignition timing by using in-cylinder information detected by an in-cylinder information detecting means.

  In recent years, a control device for an internal combustion engine that controls a control amount such as an ignition timing by using in-cylinder information detected by an in-cylinder information detection unit has been developed. Typically, such in-cylinder information is in-cylinder pressure, and the in-cylinder information detection means is an in-cylinder pressure sensor. The measured value of the in-cylinder pressure by the in-cylinder pressure sensor is obtained by adding a value obtained by multiplying the true value of the in-cylinder pressure by a predetermined sensitivity and the bias value. However, the sensitivity of the in-cylinder pressure sensor changes with time. In addition, there are individual differences in the sensitivity. As a technique for eliminating the influence of the sensitivity of the in-cylinder pressure sensor and the variation (bias) of the bias value, the in-cylinder pressure of the internal combustion engine is synchronized with the crank angle at any two points during the compression stroke by the in-cylinder pressure sensor. There is known a technique for measuring the difference and normalizing the measured in-cylinder pressure difference with an in-cylinder pressure difference obtained in an arbitrary reference state of the internal combustion engine (see, for example, Patent Document 1).

Japanese Patent No. 2564933

  By the way, in such a control device for an internal combustion engine, if an in-cylinder pressure sensor of a certain cylinder becomes abnormal due to failure, deterioration or the like, accurate information on the cylinder cannot be obtained, and control cannot be executed in the cylinder. There is a problem.

  Therefore, an object of the present invention is to provide a control device for an internal combustion engine that can execute control of a cylinder even if an in-cylinder information detection unit of the cylinder falls into an abnormal state.

  The control device for an internal combustion engine according to the present invention has in-cylinder information detecting means for detecting predetermined in-cylinder information in each cylinder, and a predetermined control amount is determined for each cylinder based on the detection value of the in-cylinder information detecting means. In the control device for the internal combustion engine to be controlled, a detecting means for detecting an abnormality of the in-cylinder information detecting means is provided, and when the detecting means detects an abnormality of the in-cylinder information detecting means of any cylinder, this abnormality is detected. The control amount of the cylinder in which the abnormality is detected is controlled using the detection value of the in-cylinder information detecting means of the cylinder other than the cylinder in which the abnormality is detected.

  Preferably, cylinders other than the cylinder in which the abnormality is detected are cylinders whose ignition order is one before that of the cylinder in which the abnormality is detected.

  Further preferably, a means for learning a deviation between a detected value of the in-cylinder information detecting means for each cylinder and a predetermined value before an abnormality of the in-cylinder information detecting means is detected, is provided by the detecting means. When an abnormality is detected in the in-cylinder information detection unit of any cylinder, using a value obtained by correcting the detection value of the in-cylinder information detection unit of a cylinder other than the cylinder in which the abnormality is detected by the deviation, The control amount of the cylinder in which the abnormality is detected is controlled.

  Further preferably, the in-cylinder information detecting means is an in-cylinder pressure sensor that detects an in-cylinder pressure as the in-cylinder information, and the detecting means detects the in-cylinder pressure sensor at a predetermined point during an intake stroke. Value, the pressure of the intake air at a time corresponding to a predetermined point during the intake stroke, and the detected value and the cylinder volume of the cylinder pressure sensor at at least two predetermined points during the compression stroke or the expansion stroke Based on the result of comparing the estimated value of the sensitivity of the in-cylinder pressure sensor calculated by the calculating means with a predetermined threshold value Determining means for determining the abnormality.

  In this case, it is preferable that the predetermined one point during the intake stroke is a time when the intake valve is closed during the intake stroke. In addition, there is further provided means for setting a time point corresponding to a predetermined point in the intake stroke in accordance with a phase delay amount until the pressure of the intake air in the intake system substantially matches the in-cylinder pressure. Is preferred.

  The control amount may be at least one of an ignition timing, a fuel injection amount, and a fuel injection timing.

  According to the present invention, it is possible to realize a control device for an internal combustion engine that can execute control of a cylinder even if an in-cylinder information detection unit of the cylinder falls into an abnormal state.

  The present inventor has intensively studied to enable highly accurate control of the internal combustion engine while reducing the calculation load, and as a result, based on the in-cylinder information detected by the in-cylinder information detection means. It came to develop the device which controls various controlled variables. That is, in the conventional method, a map for controlling the engine by preliminarily obtaining a map of the control amount that seems to be optimal for each operating state of the engine by experimentally or the like, and applying each map value during actual engine operation. Control was common. In contrast, the method developed by the present inventor directly detects the combustion state in the cylinder during engine operation, and performs various controls so as to adjust the detected combustion state to a predetermined optimum combustion state. The amount is to be controlled. According to this new method, it is possible to greatly simplify the process of creating various maps, that is, the adaptation, which has conventionally required a lot of time and labor, and to greatly shorten the development period. There is.

  In-cylinder information representative of such in-cylinder combustion state is typically in-cylinder pressure. Therefore, as means for detecting in-cylinder information, in-cylinder pressure detecting means, specifically, in-cylinder pressure sensor is typical. is there. In addition, since the combustion in the cylinder is a chemical reaction and ions are generated during combustion, this ion generation amount is used as in-cylinder information, and an ion current detection device that outputs a current corresponding to this ion generation amount is provided in the cylinder. It can be used as inside information detection means. In any case, the in-cylinder information and the means for detecting this are not limited to these. For example, the in-cylinder information may be indirectly detected as well as the in-cylinder pressure sensor and the ion current detection device in which the detection unit is exposed in the cylinder.

  The control amount to be controlled is typically a combustion start timing (ignition timing for a gasoline engine, ignition timing for a diesel engine), a fuel injection amount, a fuel injection timing, etc., but is not limited to these, for example, a valve overlap amount Or the amount of air sucked into the cylinder may be used. As an example, the case of the combustion start time will be mainly described below.

The inventor has determined that the in-cylinder pressure detected by the in-cylinder pressure sensor and the in-cylinder volume at the time of detection of the in-cylinder pressure to enable highly accurate control of the combustion start timing in the cylinder of the internal combustion engine. It came to pay attention to the control parameter calculated based on it. More specifically, the inventors set P (θ) as the in-cylinder pressure detected by the in-cylinder pressure detecting means when the crank angle is θ, and the in-cylinder volume when the crank angle is θ as V (Θ), where the specific heat ratio is κ, the in-cylinder pressure P (θ) and the value V ^κ (θ) obtained by raising the in-cylinder volume V (θ) to the specific heat ratio (predetermined index) κ The control parameter P (θ) · V ^κ (θ) obtained as a product (hereinafter referred to as “PV ^κ ” as appropriate) was focused on. Then, the present inventor first has a correlation as shown in FIG. 1 between the change pattern of the heat generation amount Q in the cylinder of the internal combustion engine with respect to the crank angle and the change pattern of the control parameter PV ^κ with respect to the crank angle. I found out. In FIG. 1, −360 °, 0 °, and 360 ° correspond to the top dead center, and −180 ° and 180 ° correspond to the bottom dead center.

In FIG. 1, the solid line shows the in-cylinder pressure detected at a predetermined minute crank angle in a predetermined model cylinder and the value obtained by raising the in-cylinder volume at the time of detection of the in-cylinder pressure by a predetermined specific heat ratio κ. This is a plot of the control parameter PV ^κ which is the product. In FIG. 1, the broken line is calculated and plotted with the heat generation amount Q in the model cylinder as Q = ＱdQ based on the following equation (1). In either case, for simplicity, κ = 1.32.
dQ / dθ = {dP / dθ · V + κ · P · dV / dθ} / {κ-1} (1)

As can be seen from the results shown in FIG. 1, the change pattern of the heat generation amount Q with respect to the crank angle and the change pattern of the control parameter PV ^κ with respect to the crank angle are almost the same (similar), and in particular, before and after the start of combustion mixture (ignition time or the ignition) (e.g., ranging from about -180 ° to about 135 ° in Figure 1), the change pattern of the heat generation amount Q, the control parameter PV ^kappa change pattern It can be seen that it agrees very well.

In one aspect of the present invention, the cylinder pressure detected by the cylinder pressure detecting means is utilized using the correlation between the newly generated in-cylinder heat generation amount Q and the control parameter PV ^κ, and the cylinder Based on the control parameter PV ^κ calculated from the in-cylinder volume at the time of detecting the internal pressure, the ratio of the heat generation amount up to a predetermined timing between the two points with respect to the total heat generation amount between the two points A combustion rate (MFB) is determined. Here, if the combustion ratio in the cylinder is calculated based on the control parameter PV ^κ , the combustion ratio in the cylinder can be accurately obtained without requiring high-load calculation processing. That is, as shown in FIG. 2, the combustion rate obtained based on the control parameter PV ^κ (see the solid line in the figure) is substantially the same as the combustion rate obtained based on the heat generation rate (see the broken line in the figure). To do.

In FIG. 2, the solid line represents the combustion ratio at the timing when the crank angle = θ in the model cylinder described above, calculated according to the following equation (2), and plotted based on the detected in-cylinder pressure P (θ). Is. However, for simplicity, κ = 1.32.
MFB = {P (θ) · V ^κ (θ) −P (−120 °) · V ^κ (−120 °)} / {P (120 °) · V ^κ (120 °) −P (−120 °)・^Vκ (−120 °)} × 100 (%)
... (2)

  In FIG. 2, the broken line indicates the combustion ratio at the timing when the crank angle = θ in the above model cylinder, according to the above equation (1) and the following equation (3), and the detected in-cylinder pressure P (θ). Calculated based on the above and plotted. Also in this case, for simplicity, κ = 1.32.

And in one form of this invention, the combustion ratio calculated ^| required based on the control parameter PV ( ^kappa) calculated from the cylinder pressure detected by the cylinder pressure detection means and the cylinder volume at the time of the said cylinder pressure detection The combustion start timing (spark ignition timing or compression ignition timing) in the cylinder is controlled so that the value matches the target value. That is, when the combustion state in the cylinder is optimal, in other words, when the combustion is started from the optimal combustion start timing (MBT), the combustion ratio at a certain crank angle can be obtained experimentally or empirically. Therefore, by controlling the combustion start timing in the cylinder so that the actual combustion ratio at the constant crank angle matches the target value, and by controlling other control amounts, combustion in the cylinder Can be optimized.

In one embodiment of the present invention, the in-cylinder combustion state is optimal when the combustion ratio reaches 50% when the crank angle θ is 8 ° after compression top dead center. However, this value can take various values depending on the engine. Therefore, from the equation (2) and the control parameter PV ^κ at the time when the crank angle θ is −120 °, 8 ° and 120 °, the actual combustion ratio at the time when the crank angle θ is 8 ° after compression top dead center is measured. The measured value is calculated and compared with the target value of 50%. If the measured value is larger than the target value, the combustion start timing is retarded because the combustion start timing is too early, and the measured value is smaller than the target value. If the combustion start timing is too late, the combustion start timing is advanced. Thus, only the crank angle and the in-cylinder pressure at three points (-120 °, 8 ° and 120 °) are detected, and the calculation is only a simple four arithmetic operation according to the equation (2). Therefore, the control amount of the engine can be controlled by extremely simple detection and calculation, and the calculation load and control load can be remarkably reduced.

  Next, an embodiment of a control device for an internal combustion engine that executes such control will be specifically described.

  FIG. 3 is a schematic configuration diagram showing an internal combustion engine according to the present invention. The internal combustion engine 1 shown in FIG. 1 generates power by burning a fuel / air mixture in a combustion chamber 3 formed in a cylinder block 2 and reciprocating a piston 4 in the combustion chamber 3. Is. Although only one cylinder is shown in FIG. 3, the internal combustion engine 1 is configured as a multi-cylinder engine, and the internal combustion engine 1 of the present embodiment is configured as a four-cylinder engine, for example. The internal combustion engine 1 of the present embodiment is a spark ignition internal combustion engine, more specifically a gasoline engine.

  The intake port of each combustion chamber 3 is connected to the intake pipe 5 via an intake manifold, and the exhaust port of each combustion chamber 3 is connected to the exhaust pipe 6 via an exhaust manifold. In addition, an intake valve Vi that opens and closes an intake port and an exhaust valve Ve that opens and closes an exhaust port are provided for each combustion chamber 3 in the cylinder head of the internal combustion engine 1. Each intake valve Vi and each exhaust valve Ve are opened and closed by a valve mechanism VM having a variable valve timing function. Further, the internal combustion engine 1 has a number of spark plugs 7 corresponding to the number of cylinders, and the spark plugs 7 are disposed in the cylinder heads so as to face the corresponding combustion chambers 3.

  The intake pipe 5 is connected to a surge tank 8 as shown in FIG. An air supply pipe L1 is connected to the surge tank 8, and the air supply pipe L1 is connected to an air intake port (not shown) via an air cleaner 9. A throttle valve (electronically controlled throttle valve in this embodiment) 10 is incorporated in the middle of the supply pipe L1 (between the surge tank 8 and the air cleaner 9). On the other hand, as shown in FIG. 3, a front-stage catalyst device 11 a including a three-way catalyst and a rear-stage catalyst device 11 b including a NOx storage reduction catalyst are connected to the exhaust pipe 6.

  Furthermore, as shown in FIG. 3, the internal combustion engine 1 has an injector 12 for each cylinder, and the injector 12 is disposed in the cylinder head so as to face the corresponding combustion chamber 3. Each piston 4 of the internal combustion engine 1 is configured as a so-called deep dish top surface type, and a recess 4a is formed on the upper surface thereof. In the internal combustion engine 1, fuel such as gasoline is directly injected from each injector 12 toward the recess 4 a of the piston 4 in each combustion chamber 3 in a state where air is sucked into each combustion chamber 3. As a result, in the internal combustion engine 1, the fuel / air mixture layer is formed (stratified) in the vicinity of the spark plug 7 so as to be separated from the surrounding air layer. And stable stratified combustion can be performed. The internal combustion engine 1 of the present embodiment is described as a so-called direct injection engine, but is not limited to this, and the present invention can be applied to an intake pipe (intake port) injection type internal combustion engine. Not too long.

  Each of the spark plugs 7, the throttle valve 10, the injectors 12, the valve operating mechanism VM and the like described above are electrically connected to an electronic control unit (hereinafter referred to as ECU) 20 that functions as a control device for the internal combustion engine 1. The ECU 20 includes a CPU, a ROM, a RAM, an input / output port, a storage device, and the like, all not shown. As shown in FIG. 3, various sensors including the crank angle sensor 14 of the internal combustion engine 1 are electrically connected to the ECU 20 via an A / D converter or the like (not shown). The ECU 20 uses the various maps stored in the storage device and the spark plug 7, the throttle valve 10, the injector 12, and the valve mechanism VM so that a desired output can be obtained based on detection values of various sensors. Control etc.

  The internal combustion engine 1 has an in-cylinder pressure sensor 15 including a semiconductor element, a piezoelectric element, an optical fiber detection element, or the like in each cylinder. Each in-cylinder pressure sensor 15 is disposed on the cylinder head so that the pressure receiving surface faces the corresponding combustion chamber 3, and is electrically connected to the ECU 20 via an A / D converter (not shown). Each in-cylinder pressure sensor 15 detects the in-cylinder pressure (relative pressure) in the corresponding combustion chamber 3 and gives a signal indicating the detected value to the ECU 20. Furthermore, the internal combustion engine 1 has an intake pressure sensor 16 that detects the pressure (intake pressure) of intake air in the surge tank 8 as an absolute pressure. The intake pressure sensor 16 is electrically connected to the ECU 20 via an A / D converter (not shown) or the like, and gives a signal indicating the detected absolute pressure of the intake air in the surge tank 8 to the ECU 20. The detection values of the crank angle sensor 14, each in-cylinder pressure sensor 15 and the intake pressure sensor 16 are sequentially given to the ECU 20 every minute time, and stored in a predetermined storage area (buffer) of the ECU 20 by a predetermined amount.

  Incidentally, as described above, the internal combustion engine 1 uses the in-cylinder pressure value detected by the in-cylinder pressure sensor 15 to control the control amount such as the combustion start timing (ignition timing in this embodiment) for each cylinder. . If an in-cylinder pressure sensor 15 of a cylinder becomes abnormal due to failure, deterioration, or the like, accurate information on the cylinder cannot be obtained, and control cannot be executed in the cylinder.

  In order to prevent this, in the present embodiment, detection means for detecting an abnormality of the in-cylinder pressure sensor 15 is provided, and when this detects an abnormality of the in-cylinder pressure sensor 15 of any cylinder, this abnormality is detected. The control amount of the abnormal cylinder is controlled using the detected value of the cylinder pressure sensor 15 of a cylinder (referred to as a normal cylinder) other than the cylinder (referred to as an abnormal cylinder). This point will be described in detail below.

  FIG. 4 shows a routine regarding detection of abnormality of the in-cylinder pressure sensor 15 and processing when abnormality is detected. This routine is executed by the ECU 20 of the internal combustion engine 1 every predetermined time. When the execution timing of this routine is reached, the ECU 20 detects whether the in-cylinder pressure sensor 15 is normal or abnormal by a method described later (S101), and determines that the in-cylinder pressure sensor 15 is abnormal in any cylinder (S102). : YES), the warning light is turned on (S103: YES), and the user is alerted. Then, it is determined whether or not the number of in-cylinder pressure sensors 15 having an abnormality is equal to or less than a predetermined value (S105). If the number of in-cylinder pressure sensors 15 having an abnormality is equal to or less than a predetermined value, the in-cylinder pressure sensor 15 having the abnormality is determined. The ignition timing control of the abnormal cylinder is executed using the detected value of the cylinder pressure sensor 15 of the cylinder (normal cylinder) other than the cylinder (abnormal cylinder) provided (S105). On the other hand, when the ECU 20 determines in S104 that the number of in-cylinder pressure sensors 15 having an abnormality is larger than a predetermined value, the ECU 20 performs retreat to enable temporary retreat operation (retreat travel in the case of a vehicle engine). The internal combustion engine 1 is controlled in the operation mode (S106). If the ECU 20 determines in S102 that there is no abnormality in the in-cylinder pressure sensors 15 of all the cylinders (S102: NO), the present routine is immediately terminated.

  In the present embodiment, the predetermined value in S104 is 1. That is, when there is only one in-cylinder pressure sensor with abnormality, the sensor value of the other normal cylinder is substituted to control the abnormal cylinder, and when there are two or more in-cylinder pressure sensors with abnormality, it is no longer normal Since it is impossible to continue the control or operation, the evacuation operation is performed. In this way, the predetermined value is set from the viewpoint of whether normal control or operation can be secured by substituting the sensor values of other normal cylinders. Note that this predetermined value can be changed, and can be set to 2 or the like in a multi-cylinder engine such as 8 or 12 cylinders.

  In the course of development, the inventor has found that the variation between cylinders is not so great if the engine is manufactured with a certain degree of accuracy, and even if the cylinder pressure sensor of a certain cylinder is abnormal, the cylinder pressure sensors of other cylinders By substituting the output value of, it was confirmed that abnormal cylinders can be operated within the range that does not affect drivability. Therefore, according to this control apparatus, even if an in-cylinder pressure sensor of a certain cylinder is abnormal, it is possible to control the abnormal cylinder using information on other cylinders. This improves the robustness.

  However, if the number of abnormal sensors is less than a predetermined value such as one, such substitution / replacement is possible. However, when the number of abnormal sensors increases, engine operation is no longer a problem due to such substitution / replacement. In this case, control is performed in the evacuation operation mode. In this evacuation operation mode, ignition timing control is performed by map control similar to the conventional one. Maps, programs, and the like used in the retreat operation mode are stored in advance in the ECU 20. Of course, this mode is only for emergency use. In the case of a vehicle, it is only necessary to carry out retreating to a maintenance shop or the like. The ignition timing used in the mode may be a constant value.

  Here, as another normal cylinder (also referred to as a substitute cylinder) in which the sensor value is substituted, it is preferable that the ignition order is as close as possible to the abnormal cylinder, and in particular, the cylinder immediately before (immediately before). Is preferred. This is because the operating state of the engine changes from moment to moment, and the cylinder as close as possible becomes an in-cylinder state closer to the abnormal cylinder and is suitable for substitution. From this point of view, the priority order is the immediately preceding cylinder, the immediately following cylinder, and the immediately preceding cylinder.

  Further, in the present embodiment, before the abnormality of the in-cylinder pressure sensor is detected, that is, while the in-cylinder pressure sensors of all the cylinders are normal (sound), the detection value of the in-cylinder pressure sensor of each cylinder and the predetermined value When the deviation of the in-cylinder pressure sensor is detected in any of the cylinders, the detection value of the in-cylinder pressure sensor of the substitute cylinder is corrected with the deviation, and the value after this correction is used to correct the abnormal cylinder. Control is performed.

  This point will be described below. FIG. 5 shows the detected values or output values of the normal cylinder pressure sensors of each cylinder in the order of ignition during steady operation of the engine (for example, during idling or constant speed operation). The ignition sequence is # 1. , # 3, # 4, and # 2. Here, if the cylinder immediately before the abnormal cylinder is used as a substitute cylinder, for example, when the cylinder pressure sensor of the # 4 cylinder becomes abnormal, the output value of the cylinder pressure sensor of the # 3 cylinder is substituted for the control of the # 4 cylinder. The As can be seen, the output value of the in-cylinder pressure sensor of each cylinder is considered to be the same during the steady operation of the engine, that is, although it is considered that the same operation or combustion state is realized in each cylinder. There are variations due to individual differences. Causes of this variation include variations in sensitivity (gain) and bias value (offset amount) of each sensor. The ECU 20 stores, that is, learns, the deviation of the output value of the in-cylinder pressure sensor between each cylinder and the cylinder immediately before it while the in-cylinder pressure sensors of all the cylinders are normal. When the output value of the in-cylinder pressure sensor of a certain cylinder i is Vi and the output value of the in-cylinder pressure sensor of the immediately preceding cylinder j is Vj, the ECU 20 expresses a deviation ΔVi used when a certain cylinder i becomes abnormal: Calculated from ΔVi = Vi−Vj and stored in a predetermined storage area. When an abnormality in a certain cylinder i is detected, the ECU 20 uses a value obtained by adding the deviation ΔVi to the output value Vj of the in-cylinder pressure sensor of the substitute cylinder for controlling the abnormal cylinder.

  Various other methods are conceivable for obtaining a substitute value for the abnormal cylinder. For example, while the in-cylinder pressure sensors of all the cylinders are normal, the difference between the average value of the in-cylinder pressure sensors of all the cylinders and the detected value of the in-cylinder pressure sensor of each cylinder is obtained, and this can be used as a deviation. Good. Naturally, when the substitute cylinder is not the immediately preceding cylinder, the difference between the detected values of the in-cylinder pressure sensor of the substitute cylinder other than the immediately preceding cylinder and the target cylinder is a deviation.

  By correcting the substitute value based on such deviation, the substitute value can be brought close to the normal value that should be used, and the accuracy can be further improved.

  Next, the abnormality detection of the in-cylinder pressure sensor performed in S101 and S102 will be described. First, as a simple example, in the case of a disconnection or a short circuit, an abnormality of the in-cylinder pressure sensor can be detected by comparing the output value of the in-cylinder pressure sensor with a predetermined minimum value or maximum value. On the other hand, due to aging deterioration of the in-cylinder pressure sensor, deposit accumulation on the in-cylinder pressure sensor, etc., the abnormal state of the in-cylinder pressure sensor gradually proceeds, and the in-cylinder pressure sensor is not an extreme abnormal value but cannot be considered normal A value may be indicated, and determination in this case becomes a problem. In order to make this determination, a certain threshold value may be set and the detected value of the in-cylinder pressure sensor may be simply compared with the threshold value to make an abnormality determination. The abnormality determination is performed by adopting the following method focusing on sensitivity.

  The inventor conducted intensive research to easily and accurately estimate the sensitivity of the in-cylinder pressure sensor. In the process, the inventors first focused on the relationship between the actually measured value of the in-cylinder pressure sensor and the true value of the in-cylinder pressure. That is, the measured value of the in-cylinder pressure when the crank angle is θ (the value obtained by converting the output voltage value of the in-cylinder pressure sensor into pressure) is Pc (θ), and the true value of the in-cylinder pressure when the crank angle is θ. If the value is Pct (θ), the sensitivity (gain) of the in-cylinder pressure sensor is α, and the bias value (offset amount) of the in-cylinder pressure sensor is δ, the actual value of the in-cylinder pressure Pc (θ) The relationship represented by the following equation (4) is generally established between the value Pct (θ).

Further, for example, in the vicinity of the intake bottom dead center (when the intake valve is closed (starts to close) during the intake stroke), the in-cylinder pressure (true value) and the intake air pressure in the intake system substantially coincide with each other. If the pressure (absolute pressure) of the intake air when is θ is Pi (θ), and the crank angle becomes θ ₀ during the intake stroke, the in-cylinder pressure and the intake air pressure are approximately the same,

  This relationship holds.

Here, “λ” in the equation (5) is the amount of phase delay until the intake air pressure in the intake system substantially matches the in-cylinder pressure (the in-cylinder pressure and the intake air pressure substantially match). Timing phase difference). That is, due to the intake pulsation or the like, for example, the in-cylinder pressure near the intake bottom dead center (when the crank angle becomes θ ₀ ) is actually slightly delayed from the intake bottom dead center (the crank angle is It almost coincides with the pressure of the intake air at the time of θ ₀ + λ. In consideration of such a phenomenon, the phase delay amount λ is introduced into the equation (5).

On the other hand, since the compression stroke or expansion stroke of the internal combustion engine can be regarded as an adiabatic process, the in-cylinder volume when the crank angle is θ is V (θ), and the air-fuel mixture introduced into the cylinder is If the specific heat ratio is κ (for example, κ = 1.32), between the predetermined two points in the compression stroke or the expansion stroke (between the time points when the crank angles are θ ₁ and θ ₂ ), the following ( 6) The relationship shown in the equation is established.

The relational expression (6) is obtained by replacing the true values Pct (θ ₁ ) and Pct (θ ₂ ) with the actual measurement values Pc (θ ₁ ) and Pc (θ ₂ ) based on the expression (4).

  Can be rewritten.

  Then, after eliminating the bias value δ from the equation (5) and the equation (7) and solving for α, the estimated value αe of the sensitivity α of the in-cylinder pressure sensor is obtained as follows:

  Can be calculated as As a result, using this equation (8), the detected value of the in-cylinder pressure sensor at a predetermined point during the intake stroke and the pressure of the intake air (intake pressure at the point corresponding to the predetermined one point during the intake stroke). The estimated value αe of the in-cylinder pressure sensor α is easily and accurately calculated from the detected value of the sensor), the in-cylinder pressure sensor detection value and the in-cylinder volume at at least two predetermined points during the compression stroke or the expansion stroke. It becomes possible to do.

That is, when obtaining the estimated value αe of the sensitivity α of the in-cylinder pressure sensor using the above equation (8), first, a predetermined one point during the intake stroke (when the crank angle becomes θ ₀ ) and the compression stroke or expansion The in-cylinder pressure is detected at _two predetermined points during the stroke (when the crank angle becomes θ ₁ and θ ₂ ), and the time corresponding to the predetermined one point during the intake stroke (the crank angle is θ ₀ + λ The pressure of the intake air is detected at the point of time. Then, the in-cylinder pressure Pc (θ ₀ ) at the predetermined one point, the pressure Pi (θ ₀ + λ) of the intake air at the time corresponding to the predetermined one point, and the in-cylinder pressure Pc at the two predetermined points By substituting (θ ₁ ), Pc (θ ₂ ) and in-cylinder volume V (θ ₁ ), V (θ ₂ ) into the above equation (8), an accurate estimated value αe of the in-cylinder pressure sensor sensitivity α Can be easily obtained with a low load. Further, as described above, the estimated time αe of the sensitivity α can be obtained by setting the time point when the pressure of the intake air is detected (the time point corresponding to one predetermined point in the intake stroke) according to the phase delay amount λ. It is possible to further improve the calculation accuracy.

By the way, the relationship shown in the above equation (5) is established in the vicinity of the timing at which the in-cylinder pressure (true value) and the intake air pressure in the intake system substantially coincide with each other, so that the crank angle becomes θ _X during the intake stroke. If the in-cylinder pressure and the intake air pressure substantially coincide with each other at θ _Y and θ _Y , the following relationships (9) and (10) are established.

  Then, if δ is eliminated from the above equations (9) and (10), the estimated value αe of the sensitivity α of the in-cylinder pressure sensor is

  Can be calculated as As a result, even if the equation (11) is used, the detected value of the in-cylinder pressure sensor at two predetermined points during the intake stroke and the pressure of the intake air at the time corresponding to each of the two predetermined points during the intake stroke. From the (detected value of the intake pressure sensor), the estimated value αe of the sensitivity α of the in-cylinder pressure sensor can be calculated easily and accurately.

That is, when obtaining the estimated value αe of the sensitivity α of the in-cylinder pressure sensor using the equation (11), first, the cylinder is determined at two predetermined points in the intake stroke (when the crank angle becomes θ _X and θ _Y ). The internal pressure is detected, and the pressure of the intake air is detected at the time corresponding to each of two predetermined points in the intake stroke (the time when the crank angle becomes θ _X + λ and the time when θ _Y + λ). The in-cylinder pressures Pc (θ _X ) and Pc (θ _Y ) at two predetermined points during the intake stroke, and the pressure Pi of intake air at the time corresponding to each of the two predetermined points during the intake stroke ( By substituting θ _X + λ) and Pi (θ _Y + λ) into the above equation (8), it is possible to easily obtain an accurate estimated value αe of the sensitivity α of the in-cylinder pressure sensor with a low load. Also, when the above equation (11) is used, the time point at which the pressure of the intake air is detected (the time point corresponding to each of the two predetermined points during the intake stroke) is set according to the phase delay amount λ. It is possible to further improve the calculation accuracy of the estimated value αe of α.

  Next, a procedure for calculating the estimated value αe of the sensitivity α of the in-cylinder pressure sensor 15 in the above-described internal combustion engine 1 and judgment of abnormality of the in-cylinder pressure sensor 15 will be described with reference to FIG. The routine shown in FIG. 6 is executed by the ECU 20 of the internal combustion engine 1 every predetermined time. When the execution timing of this routine is reached, the ECU 20 first rotates the internal combustion engine 1 based on the detected value of the crank angle sensor 14. The number is acquired (S10). When the engine speed is acquired, the ECU 20 sets the phase delay amount λ corresponding to the speed acquired in S10 using a predetermined map or function equation stored in the storage device (S12).

  Here, in the present embodiment, the phase delay amount λ is substantially equal to the time when the intake bottom dead center is reached (when the intake valve is closed during the intake stroke), and the cylinder pressure at the intake bottom dead center is the intake air pressure. Although it is an angle according to the difference from the substantially coincident time, according to the study of the present inventor, the phase delay amount λ increases as the engine speed increases and is approximately proportional to the engine speed. Has been found to increase. For this reason, in S12, a map or a function formula that defines the correlation between the engine speed and the phase delay amount λ as shown in FIG. 7 is used. Note that when creating the map or the function expression used in S12, it is preferable to consider the opening / closing timing and lift amount of the intake valve Vi and the exhaust valve Ve, and also the back pressure in the internal combustion engine 1.

When the phase delay amount λ is set in S12, the ECU 20 determines the in-cylinder pressure Pc (θ ₀ ) when the crank angle is θ ₀ (for example, −180 °) for each combustion chamber 3 from a predetermined storage area. a _first crank angle theta (e.g. -100 °) to become when the cylinder pressure Pc (theta _{1), 2} crank angle theta (e.g. -50 °) to become when the cylinder pressure Pc (theta ₂₎ And the intake air pressure Pi (θ ₀ + λ) when the crank angle is θ ₀ + λ (for example, −180 ° + λ) (near the intake bottom dead center) is read (S14). If the angles θ ₁ and θ ₂ are selected so as to be included in the compression stroke or the expansion stroke, the respective values can be arbitrary.

Then, for each combustion chamber 3, the ECU 20 converts the in-cylinder pressure Pc (θ ₀ ), Pc (θ ₁ ), Pc (θ ₂ ) read in S14 into the intake air pressure Pi (θ ₀ + λ) and the cylinder contents. By substituting into the above equation (5) together with the products V (θ ₁ ) and V (θ ₂ ), an estimated value αe of the sensitivity α is calculated for each in-cylinder pressure sensor 15 (S16). The values of the cylinder volumes V ^κ (θ ₁ ) and V ^κ (θ ₂ ) used in S16 (in this embodiment, values of V ^κ (−100 °) and V ^κ (−50 °)) are For example, κ = 1.32 is calculated in advance and stored in the storage device. The ECU 20 reads the values of V ^κ (θ ₁ ) and V ^κ (θ ₂ ) from the storage device, and performs the process of S20. Used for.

  When the estimated value αe of the sensitivity α is obtained, the ECU 20 determines, for each in-cylinder pressure sensor 15 (combustion chamber 3), whether the estimated value αe is below a predetermined threshold A (S18). Then, the ECU 20 updates the sensitivity α stored in the predetermined storage area with the estimated value αe calculated in S16 for the in-cylinder pressure sensor 15 determined that the estimated value αe is lower than the threshold A in S18. (S20) Thereby, the output of each in-cylinder pressure sensor 15 is corrected.

  In this embodiment, after the process of S20, the wall surface temperature of each combustion chamber 3 (the in-cylinder wall surface of the cylinder wall surface) is used by using the updated sensitivity α of each cylinder pressure sensor 15 (the estimated value αe calculated in S16). A process for estimating the temperature is executed (S22).

  Here, the sensitivity of the in-cylinder pressure sensor depends on the temperature of the sensor element such as a semiconductor element, a piezoelectric element, or an optical fiber detection element, and obtaining the sensitivity of the in-cylinder pressure sensor means grasping the temperature of the sensor element. It leads to doing. And since the temperature of a sensor element has a close correlation with the temperature (wall surface temperature) around the attachment location of an in-cylinder pressure sensor, the wall surface temperature in the predetermined location of a combustion chamber and the in-cylinder pressure provided in the said combustion chamber The amount of change from the initial value (or previous value) of the sensitivity of the sensor has a correlation as shown in FIG. 8, for example.

In view of such points, in the present embodiment, the cylinder wall temperature that defines the correlation between the wall surface temperature of the combustion chamber 3 and the amount of change from the initial value (or the previous value) α ₀ of the sensitivity α of the cylinder pressure sensor 15. An estimated map is created in advance and stored in a storage device. Then, ECU 20, at S22, for each cylinder pressure sensor 15, the sensitivity alpha with a deviation Δα between (estimated value .alpha.e) the initial value alpha _0, the wall temperature of the cylinder inner wall temperature estimation map, corresponding to the deviation Δα Is read for each combustion chamber 3. Further, in the present embodiment, in S22, an estimated value of the amount of fuel adhering to the wall surface is calculated for each combustion chamber 3 using the obtained wall surface temperature and a map prepared in advance, and the calculated fuel is calculated. The estimated value of the adhesion amount is used in fuel injection control. When the process of S22 is executed, the ECU 20 waits until the next execution timing of this routine.

  As described above, in the internal combustion engine 1, it is possible to obtain an accurate estimated value αe of the sensitivity α of the in-cylinder pressure sensor 15 provided in each combustion chamber 3. Then, if the accurate estimated value αe of the sensitivity α calculated as described above is used, the wall surface temperature in each combustion chamber 3 and the amount of fuel adhering to the wall surface can be easily and accurately grasped, and these can be obtained from the internal combustion engine 1. It is possible to use it effectively for the control of.

  On the other hand, when it is determined in S18 that the estimated value αe of the sensitivity α of any in-cylinder pressure sensor 15 is equal to or greater than the threshold value A, the sensitivity deterioration of the in-cylinder pressure sensor 15 has progressed to some extent. . For this reason, when a negative determination is made for any of the in-cylinder pressure sensors 15 in S18, the ECU 20 regards that the corresponding in-cylinder pressure sensor 15 is abnormal (S24), and shifts to a standby state.

  FIG. 9 is a flowchart for explaining another procedure for calculating the estimated value αe of the sensitivity α of the in-cylinder pressure sensor 15 in the internal combustion engine 1 described above and another abnormality determination for the in-cylinder pressure sensor 15.

The routine of FIG. 9 uses the above-described equation (11), and the ECU 20 acquires the rotational speed of the internal combustion engine 1 based on the detection value of the crank angle sensor 14 at the execution timing of this routine. (S30) Further, a phase delay amount λ corresponding to the rotational speed acquired in S30 is set (S32). When the phase delay amount λ is set in S32, the ECU 20 determines that the in-cylinder pressure Pc (θ _X ) when the crank angle is θ _X (eg, −300 °) and the crank angle θ _Y from a predetermined storage area. The in-cylinder pressure Pc (θ _Y ) when it becomes (for example, −200 °) is read for each combustion chamber 3 and the pressure Pi of the intake air when the crank angle becomes θ _X + λ (for example, −300 ° + λ). (Θ _X + λ) and the pressure Pi (θ _Y + λ) of the intake air when the crank angle is θ _Y + λ (for example, −200 ° + λ) are read (S34). Note that the angles θ _X and θ _Y can be set to arbitrary values as long as they are included in the intake stroke and the in-cylinder pressure and the intake air pressure substantially coincide with each other.

For each combustion chamber 3, the ECU 20 uses the in-cylinder pressure Pc (θ _X ) and Pc (θ _Y ) read in S 34 together with the intake air pressure Pi (θ _X + λ) and Pi (θ _Y + λ). By substituting into the above equation (8), the estimated value αe of the sensitivity α is calculated for each in-cylinder pressure sensor 15 (S36). When the estimated value αe of the sensitivity α is obtained, the ECU 20 determines, for each in-cylinder pressure sensor 15 (combustion chamber 3), whether the estimated value αe is below a predetermined threshold A (S38).

  Then, the ECU 20 updates the sensitivity α stored in the predetermined storage area with the estimated value αe calculated in S36 for the in-cylinder pressure sensor 15 determined in S38 that the estimated value αe is lower than the threshold A. (S40). Further, after the process of S40, the ECU 20 executes the same process as S22 described above using the updated sensitivity α of each in-cylinder pressure sensor 15 (the estimated value αe calculated in S36) (S42). If it is determined in S38 that the estimated value αe of the sensitivity α of any of the in-cylinder pressure sensors 15 is equal to or greater than the threshold value A, the ECU 20 regards that the corresponding in-cylinder pressure sensor 15 is abnormal. (S44), transition to the standby state.

  Thus, even if the routine of FIG. 9 using the above-described equation (11) is executed, it is possible to detect an abnormality in the in-cylinder pressure sensor 15 provided in each combustion chamber 3. Then, if an accurate estimated value αe of the sensitivity α calculated through the routine of FIG. 9 is used, the wall temperature in each combustion chamber 3 and the amount of fuel adhering to the wall surface can be easily and accurately grasped, and these can be obtained from the internal combustion engine. 1 can be effectively used for the control of 1.

In the routines of FIGS. 6 and 9, when determining the abnormality of each in-cylinder pressure sensor 15 using the estimated value αe of the sensitivity α, the amount of change of the sensitivity α from the initial value α ₀ or the previous value, that is, A deviation between the estimated value αe and the initial value α ₀ (or the previous value) is obtained, and when the amount of change (deviation) exceeds a predetermined threshold, an abnormality has occurred in the in-cylinder pressure sensor 15. You may make it judge. Further, the processing in S22 and S42 may include a step of obtaining the amount of thermal energy transmitted to the combustion chamber wall (cylinder block 2) based on the wall surface temperature for each combustion chamber 3.

6 and FIG. 9, the sampling points θ ₀ , θ ₁ , θ ₂ or θ _X , θ _Y of the in-cylinder pressure and the intake air pressure are shifted little by little and based on a large number of sampling points. Thus, a plurality of estimated values αe of the sensitivity α of each in-cylinder pressure sensor 15 may be obtained, and the plurality of estimated values αe may be averaged. Thereby, the estimated value αe of the sensitivity α of each in-cylinder pressure sensor 15 can be calculated with higher accuracy.

  FIG. 10 shows another routine related to the abnormality detection of the in-cylinder pressure sensor 15 and the processing when the abnormality is detected. This routine is substantially the same as the above-described routine shown in FIG. 4, and steps corresponding to the respective steps S101, S102... Of the above-described routine are indicated as S201, S202. The only difference is that in step S205, the ignition timing control in step S105 is replaced with fuel injection control (ie, control of fuel injection amount and fuel injection timing). Thus, the present invention can be applied to control of other control amounts.

  Various other embodiments of the present invention are conceivable. For example, although the internal combustion engine 1 described above is a gasoline engine, the present invention is not limited to this, and the present invention can also be applied to a diesel engine.

It is a graph which shows the correlation between control parameter PV ( ^kappa) used in this invention, and the amount of heat generation in a combustion chamber. It is a graph which shows the correlation with the combustion rate calculated ^| required based on control parameter PV ( ^kappa) , and the combustion rate calculated ^| required based on a heat release rate. It is a schematic block diagram which shows the internal combustion engine containing the control apparatus by this invention. It is a flowchart which shows the routine regarding the abnormality detection of a cylinder pressure sensor, and the process when abnormality is detected. It is a graph which shows the output value of a cylinder pressure sensor for every cylinder. It is a flowchart for demonstrating the procedure which calculates the estimated value of the sensitivity of a cylinder pressure sensor, and abnormality determination of a cylinder pressure sensor. 4 is a graph illustrating the relationship between the rotational speed of an internal combustion engine and the amount of phase delay until the pressure of intake air in the intake system substantially matches the in-cylinder pressure. It is a graph which illustrates the relationship between the variation | change_quantity of the sensitivity of the cylinder pressure sensor provided in the combustion chamber, and the wall surface temperature of the said combustion chamber. It is a flowchart for demonstrating the other procedure which calculates the estimated value of the sensitivity of a cylinder pressure sensor, and the other abnormality determination of a cylinder pressure sensor. It is a flowchart which shows the other routine regarding the abnormality detection of a cylinder pressure sensor, and the process when abnormality is detected.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder block 3 Combustion chamber 4 Piston 5 Intake pipe 6 Exhaust pipe 7 Spark plug 8 Surge tank 10 Throttle valve 12 Injector 14 Crank angle sensor 15 In-cylinder pressure sensor 16 Intake pressure sensor L1 Intake pipe Ve Exhaust valve Vi Intake valve VM Valve mechanism ΔV Deviation

Claims (5)

In a control apparatus for an internal combustion engine that has in-cylinder information detection means for detecting predetermined in-cylinder information in each cylinder and controls a predetermined control amount based on a detection value of the in-cylinder information detection means for each cylinder.
A detecting means for detecting an abnormality of the in-cylinder information detecting means is provided,
When an abnormality is detected in the in-cylinder information detection unit of any cylinder by the detection unit, the abnormality is detected using the detection value of the in-cylinder information detection unit of a cylinder other than the cylinder in which the abnormality is detected. A control apparatus for an internal combustion engine, wherein the detected control amount of a cylinder is controlled.   2. The control apparatus for an internal combustion engine according to claim 1, wherein the cylinders other than the cylinder in which the abnormality is detected are cylinders whose ignition order is one before that of the cylinder in which the abnormality is detected. Means for learning a deviation between a detected value of the in-cylinder information detecting means of each cylinder and a predetermined value before an abnormality of the in-cylinder information detecting means is detected;
A value obtained by correcting the detected value of the in-cylinder information detection unit of a cylinder other than the cylinder in which the abnormality is detected by the deviation when an abnormality of the in-cylinder information detection unit of any cylinder is detected by the detection unit. The control apparatus for an internal combustion engine according to claim 1 or 2, wherein the control amount of the cylinder in which the abnormality is detected is controlled by using. The in-cylinder information detecting means is an in-cylinder pressure sensor that detects an in-cylinder pressure as the in-cylinder information.
The detection means is
The detected value of the in-cylinder pressure sensor at a predetermined point during the intake stroke, the pressure of the intake air at a time corresponding to the predetermined one point during the intake stroke, and at least a predetermined 2 during the compression stroke or the expansion stroke Calculating means for calculating an estimated value of the sensitivity of the in-cylinder pressure sensor based on the detected value and the in-cylinder volume of the in-cylinder pressure sensor at a point;
The determination means for determining abnormality of the in-cylinder pressure sensor based on a comparison result between the estimated value of the sensitivity of the in-cylinder pressure sensor calculated by the calculation means and a predetermined threshold value. 3. The control device for an internal combustion engine according to any one of 3). 5. The control device for an internal combustion engine according to claim 1, wherein the control amount is at least one of an ignition timing, a fuel injection amount, and a fuel injection timing.

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