JP4665788B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine.

  Conventionally, for example, Patent Document 1 discloses a misfire detection device for an internal combustion engine. This conventional misfire detection device has means for learning the difference in generated torque between cylinders and the difference in friction torque between cylinders, and measures the crankshaft angular speed (crank angle rotational speed) according to the learned values. The value is corrected.

JP-A-4-101071 Japanese Patent Publication No. 3-20590 JP 2002-71000 A

  In order to control the internal combustion engine with high accuracy, means for accurately estimating the combustion state is required. And, when the combustion state is accurately estimated, the effect of friction is large. According to the above-described conventional apparatus, the difference in friction between the cylinders is learned, but the deviation of friction caused by environmental change and secular change is not taken into consideration. For this reason, the above-mentioned conventional apparatus still has room for improvement in constructing a control logic for accurately estimating the combustion state.

  The present invention has been made to solve the above-described problems, and can obtain accurate friction information without depending on secular change or the like, and as a result, an internal combustion engine capable of realizing highly accurate engine control. An object of the present invention is to provide an engine control device.

According to a first aspect of the present invention, there is provided a friction estimation means for estimating the friction of an internal combustion engine based on the engine speed and the engine coolant temperature or the engine speed and the kinematic viscosity of the engine lubricating oil .
Input torque calculating means for calculating the input torque based on the engine speed and / or the measured or estimated value of the crank angle in accordance with a predetermined relational expression that defines the relationship between the crank angle and the input torque input to the crankshaft. When,
Generated torque calculation means for calculating the generated torque of the internal combustion engine based on the input torque calculated by the input torque calculation means, the friction torque calculated by the friction estimation means, and the load torque of the internal combustion engine When,
In-cylinder pressure calculating means for calculating the in-cylinder pressure based on the generated torque according to a predetermined relational expression that defines the relationship between the generated torque and the in-cylinder pressure calculated by the generated torque calculating means;
Combustion state index calculating means for calculating a combustion state index representing the combustion state of each cylinder of the internal combustion engine based on the in-cylinder pressure calculated by the in-cylinder pressure calculating means;
Combustion state index average value calculating means for calculating a combustion state index average value for a predetermined number of cycles for the combustion state index of each cylinder;
Determining means for determining whether the combustion state index average value of all cylinders is within a predetermined range;
When it is determined that the combustion state index average value of all the cylinders is not within the predetermined range, it is determined that there is a deviation in the estimation of the friction by the friction estimation unit.

  The second invention is characterized in that, in the first invention, when it is determined that there is a deviation in the estimation of the friction by the friction estimation means, the friction is learned according to the engine speed. .

A third invention is the crank angle sensor for detecting the rotational position of the crankshaft in the first or second invention, and
Based on the equation of motion of the in-cylinder pressure and crankshaft periphery calculated by the in-cylinder pressure calculation means, the calculation section for calculating an estimated value of the engine rotational speed and or the crank angle,
Feedback means for calculating a feedback correction amount for matching the estimated value calculated by the calculation unit with an actual measurement value detected by the crank angle sensor, and reflecting the feedback correction amount in an input value of the calculation unit; ,
Is further provided .

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the combustion state index is a maximum pressure value of the in-cylinder pressure.

In a fifth aspect based on any one of the first to third aspects, the combustion state index calculating means includes combustion pressure estimating means based on a Weibe function,
The combustion state index is a parameter of a Weibe function calculated by identifying the Weibe function.

According to a sixth aspect of the present invention, there is provided a friction estimating means for estimating the friction of the internal combustion engine based on the engine speed and the engine coolant temperature, or the engine speed and the kinematic viscosity of the engine lubricating oil,
Generated torque calculation means for calculating the generated torque based on the in-cylinder pressure according to a predetermined relational expression defining a relationship between the in-cylinder pressure and the generated torque of the internal combustion engine;
Based on the generated torque calculated by the generated torque calculating means, the friction torque calculated by the friction estimating means, and the load torque of the internal combustion engine, an input torque calculation for calculating an input torque input to the crankshaft Means,
Crank estimated value for calculating an estimated value of the engine speed and / or the crank angle in accordance with a predetermined relational expression that defines the relationship between the input torque calculated by the input torque calculating means, the crank angle, and the engine speed. A calculation means;
A crank angle sensor for detecting the rotational position of the crankshaft;
A feedback correction amount for making the estimated value calculated by the crank estimated value calculating means coincide with the engine speed detected by the crank angle sensor and / or the measured value of the crank angle is set to each cylinder of the internal combustion engine. Combustion state index calculating means for calculating as a combustion state index representing the combustion state of
Combustion state index average value calculating means for calculating a combustion state index average value for a predetermined number of cycles for the combustion state index of each cylinder;
Determining means for determining whether the combustion state index average value of all cylinders is within a predetermined range;
When it is determined that the combustion state index average value of all the cylinders is not within the predetermined range, it is determined that there is a deviation in the estimation of the friction by the friction estimation unit.
The seventh invention is characterized in that, in the sixth invention, when it is determined that there is a deviation in the estimation of the friction by the friction estimation means, the friction is learned according to the engine speed. .
The eighth invention is characterized in that, in the sixth or seventh invention, further comprises feedback means for reflecting the feedback correction amount in the in-cylinder pressure.

  According to the first aspect, since the combustion state of the internal combustion engine is accurately acquired by the combustion state index calculation means, it is possible to accurately determine whether or not there is a deviation in the friction estimation by the friction estimation means. Can do.

  According to the second aspect, since it is learned that there is a deviation in the estimation of the friction, the deviation of the friction due to secular change or the like can be corrected. For this reason, more accurate engine control can be performed.

  According to the third aspect of the present invention, the friction acting on the crankshaft is accurately estimated using the shaft torque information based on the equation of motion around the crankshaft that is the output shaft of the internal combustion engine, and the deviation of the friction is detected. Can be verified. For this reason, the influence of the friction which occupies for the dispersion | variation in the combustion state of each cylinder can be clarified more.

  According to the fourth aspect of the invention, the combustion state can be accurately acquired using the maximum pressure value of the in-cylinder pressure as the combustion state index.

  According to the fifth aspect of the present invention, the combustion state can be accurately acquired using the parameter of the Weibe function as the combustion state index.

According to the sixth aspect of the present invention, since the combustion state of the internal combustion engine is accurately acquired by the combustion state index calculating means that uses the feedback correction amount as the combustion state index, there is a deviation in the friction estimation by the friction estimation means. It is possible to accurately determine whether or not.
According to the seventh aspect, since it is learned that there is a deviation in the estimation of the friction, the deviation of the friction due to secular change or the like can be corrected. For this reason, more accurate engine control can be performed.
According to the eighth aspect, the friction acting on the crankshaft can be accurately estimated using the shaft torque information, and the deviation of the friction can be verified. For this reason, the influence of the friction which occupies for the dispersion | variation in the combustion state of each cylinder can be clarified more.

Embodiment 1 FIG.
[Configuration of Device of Embodiment 1]
FIG. 1 is a diagram for explaining the configuration of an internal combustion engine 10 to which the stop position control device for an internal combustion engine according to the first embodiment of the present invention is applied. The system of this embodiment includes an internal combustion engine 10. Here, it is assumed that the internal combustion engine 10 is an in-line four-cylinder engine. A piston 12 is provided in the cylinder of the internal combustion engine 10. The piston 12 is connected to the crankshaft 16 via a connecting rod 14. A combustion chamber 18 is formed in the cylinder of the internal combustion engine 10 on the top side of the piston 12. An intake passage 20 and an exhaust passage 22 communicate with the combustion chamber 18.

  A throttle valve 24 is provided in the intake passage 20. The throttle valve 24 is an electronically controlled throttle valve that can control the throttle opening independently of the accelerator opening. In the vicinity of the throttle valve 24, a throttle position sensor 26 for detecting the throttle opening degree TA is disposed. A fuel injection valve 28 for injecting fuel into the intake port of the internal combustion engine 10 is disposed downstream of the throttle valve 24. A spark plug 30 is attached to each cylinder head of the internal combustion engine so as to protrude from the top of the combustion chamber 18 into the combustion chamber 18 for each cylinder. The intake port and the exhaust port are respectively provided with an intake valve 32 and an exhaust valve 34 for bringing the combustion chamber 18 and the intake passage 20 or the combustion chamber 18 and the exhaust passage 22 into a conductive state or a cut-off state.

  The intake valve 32 and the exhaust valve 34 are driven by an intake variable valve operating (VVT) mechanism 36 and an exhaust variable valve operating (VVT) mechanism 38, respectively. The variable valve mechanisms 36 and 38 open and close the intake valve 32 and the exhaust valve 34 in synchronization with the rotation of the crankshaft, and change their valve opening characteristics (valve opening timing, operating angle, lift amount, etc.). can do.

  The internal combustion engine 10 includes a crank angle sensor 40 in the vicinity of the crankshaft. The crank angle sensor 40 is a sensor that reverses the Hi output and the Lo output each time the crankshaft rotates by a predetermined rotation angle. According to the output of the crank angle sensor 40, the rotational position of the crankshaft and its rotational speed (engine rotational speed Ne) can be detected. The internal combustion engine 10 also includes a cam angle sensor 42 in the vicinity of the intake camshaft. The cam angle sensor 42 is a sensor having the same configuration as the crank angle sensor 40. According to the output of the cam angle sensor 42, the rotational position (advance amount) of the intake cam shaft can be detected.

  The system shown in FIG. 1 includes an ECU (Electronic Control Unit) 50. In addition to the various sensors described above, an ECU 50 is connected to an air-fuel ratio sensor 52 for detecting the exhaust air-fuel ratio in the exhaust passage 22 and a water temperature sensor 54 for detecting the cooling water temperature of the internal combustion engine 10. In addition, the above-described various actuators are connected to the ECU 50. The ECU 50 can control the operation state of the internal combustion engine 10 based on the sensor output and the calculation result using the engine model 60 virtually configured in the ECU 50.

[Overview of engine model]
FIG. 2 is a block diagram showing the configuration of the engine model 60 provided in the ECU 50 shown in FIG. As shown in FIG. 2, the engine model 60 includes a motion equation calculation unit 62 around the crankshaft 62, a friction model 64, an intake pressure estimation model 66, an in-cylinder pressure estimation model 68, a combustion waveform calculation unit 70, a large An atmospheric pressure correction term calculation unit 72 and an atmospheric temperature correction term calculation unit 74 are included. Hereinafter, a detailed configuration of each part will be described.

(1) About the equation of motion calculation unit around the crankshaft The equation of motion calculation unit 62 around the crankshaft is used to obtain respective estimated values of the crank angle θ and the engine speed Ne (crank angle rotational speed dθ / dt). It is. The motion equation calculation unit 62 around the crankshaft receives an input of the in-cylinder pressure P of the internal combustion engine 10 from the in-cylinder pressure estimation model 68 or the combustion waveform calculation unit 70, and at the start of the calculation, further includes the initial crank angle θ ₀ and the initial engine. Receives input of rotation speed Ne ₀ .

  The estimated crank angle θ and the estimated engine speed Ne calculated by the motion equation calculation unit 62 around the crankshaft are eliminated from the actual crank angle θ and the actual engine speed Ne by the PID controller 76 shown in FIG. Is feedback controlled. In addition, the calculation result of the motion equation calculation unit 62 around the crankshaft is reflected by the friction model 64 on the influence on the internal friction of the internal combustion engine 10.

Next, specific calculation contents executed inside the motion equation calculation unit 62 around the crankshaft will be described.
FIG. 3 is a diagram showing symbols attached to each element around the crankshaft. As shown in FIG. 3, here, A is the surface area of the top of the piston 12 that receives the in-cylinder pressure P. The length of the connecting rod 14 is L, and the crank radius is r. An angle formed by an imaginary line (cylinder axis) connecting the piston attachment point of the connecting rod 14 and the axial center of the crankshaft 16 and the axis of the connecting rod 14 is φ (hereinafter referred to as “connecting rod angle φ”). The angle formed by the cylinder axis and the axis of the crankpin 17 is defined as θ.

In the internal combustion engine 10 having four cylinders, the phase difference of the crank angle between the cylinders is 180 ° CA. Therefore, the relationship of the crank angle between the cylinders can be defined as the following equation (1a). it can. Further, the crank angle rotational speed dθ / dt of each cylinder is a time derivative of the crank angle θ of each cylinder, and can be expressed as the following equation (1b).

  However, in the above formulas (1a) and (1b), the reference numerals 1 to 4 given to the crank angle θ and the crank angle rotational speed dθ / dt are the cylinders in which combustion arrives according to the predetermined explosion order of the internal combustion engine 10. These numbers correspond to the order, and in the mathematical formulas described later, those symbols 1 to 4 may be represented by “i”.

ただし、上記（２）式において、dXi/dtはピストン速度である。 In the piston / crank mechanism shown in FIG. 3, the crank angle θi and the connecting rod angle φi have a relationship represented by the following equation (2).

However, in the above equation (2), dXi / dt is the piston speed.

Further, the total kinetic energy T around the crankshaft can be expressed as the following equation (3). When formula (3) is expanded, various parameters of each term in formula (3) can be collected as a coefficient of 1/2 (dθ / dt) ² . Here, the coefficients summarized in this way are expressed as a function f (θ) of the crank angle θ.

However, in the above equation (3), the first term on the right side is the kinetic energy related to the rotational motion of the crankshaft 16, the second term on the right side is the kinetic energy related to the linear motion of the piston 12 and the connecting rod 14, and the third term on the right side is the connecting rod 14. Respectively corresponding to the kinetic energy related to the rotational motion of the. In the above equation (3), I _k is the moment of inertia around the axis of the crankshaft 16, I _fl is the moment of inertia around the rotation axis of the flywheel, and I _mi is the transmission combined with the internal combustion engine 10. It is the moment of inertia around the rotation axis of the following rotating part (that is, transmission, drive shaft, tire, etc.), and I _c is the moment of inertia related to the connecting rod. Also, m _p is the displacement of the piston 12, m _c is the displacement of the connecting rod 14.

Next, Lagrangian L is defined as the following equation (4a) as the deviation between the total kinetic energy T and the potential energy U of the system. If the input torque acting on the crankshaft 16 is TRQ, the relationship between the Lagrangian L, the crank angle θ, and the input torque TRQ can be expressed by the following equation (4b) using the Lagrangian equation of motion. it can.

  Here, in the above equation (4a), the influence of the potential energy U is smaller than the influence of the kinetic energy T, and the influence can be ignored. Therefore, the first term on the left side of the equation (4b) is a function of the crank angle θ by differentiating the value obtained by partial differentiation of the equation (3) with respect to the crank angle rotation speed (dθ / dt). Can be expressed as the following equation (4c). Further, the second term on the left side of the above equation (4b) can be expressed as the following equation (4d) as a function of the crank angle θ by partially differentiating the above equation (3) with respect to the crank angle θ. .

Therefore, the above equation (4b) can be expressed as the following equation (4e), whereby the relationship between the crank angle θ and the input torque TRQ can be obtained. Further, here, the input torque TRQ is defined as consisting of three parameters as shown in the following equation (5).

However, in the above equation (5), TRQ _e is the engine generated torque, more specifically, the torque acting on the crankshaft 16 from the piston 12 that receives the gas pressure (in-cylinder pressure P). TRQ _L is a load torque, and is stored in the ECU 50 as a known value that varies depending on the characteristics of the vehicle on which the internal combustion engine 10 is mounted. TRQ _f is a friction torque, that is, a torque corresponding to a friction loss of sliding portions such as the piston 12 and the crankshaft 16. This friction torque TRQ _f is a value obtained from the friction model 64.

Next, the engine generated torque TRQ _e can be calculated according to the following equations (6a) to (6c). That is, first, the force F _c acting on the connecting rod 14 based on the in-cylinder pressure P can be expressed as the equation (6a) as the axial component of the connecting rod 14 of the force PA acting on the top of the piston 12. . As shown in FIG. 3, the angle α formed between the axis of the connecting rod 14 and the tangent to the locus of the crankpin 17 is {π / 2− (φ + θ)}. The force F _k acting in the tangential direction of the trajectory can be expressed as the equation (6b) using the force F _c acting on the connecting rod 14. Therefore, since the engine generated torque TRQ _e is the product of the force F _k acting in the tangential direction of the locus of the crank pin 17 and the rotation radius r of the crank, using the equations (6a) and (6b), 6c) can be expressed as:

  According to the configuration of the motion equation calculation unit 62 around the crankshaft described above, the in-cylinder pressure P is acquired by the in-cylinder pressure estimation model 68 or the combustion waveform calculation unit 70, whereby the equations (6c) and (5) are obtained. Input torque TRQ can be obtained. Then, by solving the equation (4e), it is possible to obtain the crank angle θ and the crank angle rotation speed dθ / dt.

(2) About Friction Model FIG. 4 shows an example of a friction map provided for the friction model 64 shown in FIG. 2 to acquire the friction torque TRQ _f . In the friction map shown in FIG. 4, the friction torque TRQ _f is determined by the relationship between the engine speed Ne and the engine coolant temperature. Such a characteristic of the friction map is determined in advance by experiments or the like, and the friction torque TRQ _f tends to increase as the engine coolant temperature decreases.

ただし、上記（７）式において、C₁、C₂、C₃は、それぞれ実験等により適合される係数である。 Here, in order to reduce the calculation load of the ECU 50, the friction model 64 is provided with the friction map as described above, but the configuration of the friction model is not limited to this, and the following A relational expression such as the expression (7) may be used. In the equation (7), the friction torque TRQ _f is configured to be a function having the engine speed Ne and the kinematic viscosity ν of the lubricating oil of the internal combustion engine 10 as parameters.

However, in the above equation (7), C ₁ , C ₂ , and C ₃ are coefficients that are adapted by experiments or the like.

(3) Intake Pressure Estimation Model The intake pressure estimation model 66 includes an intake pressure map (not shown) for estimating the intake pressure. This intake pressure map defines the intake pressure in relation to the throttle opening degree TA, the engine speed Ne, and the valve timing VVT of the intake and exhaust valves. According to such a configuration of the intake pressure estimation model, it is possible to acquire the intake pressure while keeping the calculation load of the ECU 50 low. When the intake pressure is calculated in detail, a throttle model that estimates the air flow rate that passes through the throttle valve 24 and the air flow rate that passes around the intake valve 32 without using the intake pressure map as described above. An intake pressure estimation model may be configured using a valve model that estimates (in-cylinder intake air flow rate).

(4) In-cylinder pressure estimation model The in-cylinder pressure estimation model 68 is a model used to calculate the in-cylinder pressure P under a situation where combustion is not performed. In this in-cylinder pressure estimation model 68, the in-cylinder pressure P in each stroke of the internal combustion engine 10 is calculated using the following equations (8a) to (8d). That is, first, the in-cylinder pressure P during the intake stroke is obtained from the in-cylinder pressure map value P _map obtained from the intake pressure map of the intake pressure estimation model 66 described above, as shown by the equation (8a). I am doing so.

Next, the in-cylinder pressure P during the course of the compression stroke can be expressed as in equation (8b) based on the equation for reversible adiabatic change of gas.
However, in the above equation (8b), V _BDC is the stroke volume V when the piston 12 is at the intake bottom dead center, and κ is the specific heat ratio.

Further, the in-cylinder pressure P during the expansion stroke can also be expressed as in the equation (8c) in the same manner as in the compression stroke.
However, in the above equation (8c), V _TDC is the stroke volume V when the piston 12 is at the compression top dead center, and P _c is the in-cylinder pressure at the end of the compression stroke.

Further, the in-cylinder pressure P during the exhaust stroke is assumed to be the pressure P _ex in the exhaust passage 22 as shown by the equation (8d). This pressure P _ex can be regarded as substantially equal to the atmospheric pressure P _air . Therefore, here, the atmospheric pressure P _air is used as the in-cylinder pressure P during the exhaust stroke.

(5) Combustion waveform calculation unit The combustion waveform calculation unit 70 is a model used to calculate the in-cylinder pressure (combustion pressure) P during the period in which combustion is performed from the middle of the compression stroke to the middle of the expansion stroke. It is. In the combustion waveform calculation unit 70, an estimated value of the combustion pressure P is calculated using an equation (9a) that is a relational expression using the Weibe function and an equation (10) described later.

More specifically, the combustion waveform calculation unit 70 first calculates the heat generation rate dQ / dθ corresponding to the current crank angle θ using the equation (9a).
However, in the above equation (9a), m is the shape factor, k is the combustion efficiency, θ _b is the ignition delay period, and a is the combustion rate (here, fixed value 6.9). For each of these parameters, pre-adapted values are used. Q is the calorific value.

  In order to calculate the heat generation rate dQ / dθ using the above equation (9a), it is necessary to calculate the calorific value Q. The calorific value Q can be calculated by solving the equation (9a) which is a differential equation. Therefore, first, in the equation (9b), the part corresponding to the Weibe function in the equation (9a) is replaced with g (θ). If it does so, it will become possible to express (9a) Formula like (9c) Formula. Next, after integrating both sides of the formula (9c) with the crank angle θ, the calorific value Q can be expressed as the formula (9d) by developing the formula (9c). Next, the heat generation rate dQ / dθ is calculated by substituting the calorific value Q calculated according to the equation (9d) into the equation (9a) again.

The heat release rate dQ / dθ and the in-cylinder pressure (combustion pressure) P can be expressed as in equation (10) using a relational expression based on the law of conservation of energy. Therefore, the combustion pressure P can be calculated by substituting the heat release rate dQ / dθ calculated according to the equation (9a) and solving the equation (10).

  According to the in-cylinder pressure estimation model 68 and the combustion waveform calculation unit 70 described above, the in-cylinder pressure P is calculated using the in-cylinder pressure estimation model 68 in a state where combustion is not performed, and the combustion waveform calculation unit 70 is calculated. By calculating the in-cylinder pressure P during the period during which combustion is performed, the history of the in-cylinder pressure P of the internal combustion engine 10 can be acquired regardless of whether combustion is performed.

In addition, the method of acquiring the history of the in-cylinder pressure P of the internal combustion engine 10 is not limited to the above method, and may be a method as shown with reference to FIG.
FIG. 5 is a diagram for explaining a method of such a modification. In this method, the combustion pressure P is not calculated for each predetermined crank angle θ using the above equations (9a) and (10), but the above equations (9a) and (10) are calculated in advance. Using the equation, only the combustion pattern as shown in FIG. 5A, that is, the change in the waveform of the in-cylinder pressure P that changes as a result of being applied to combustion (the pressure increase due to combustion) is calculated in advance. .

More specifically, there are three parameters that determine such a combustion pattern: ignition delay period, combustion period, and ΔP _max (deviation between maximum pressure P _max during combustion and maximum pressure P _max0 without combustion). Are stored in relation to the engine speed Ne, the air filling rate KL, the valve timing VVT of the intake and exhaust valves, and the ignition timing. Then, in order to calculate the waveform corresponding to the pressure increase due to combustion as a waveform approximated by combining simple functions such as a quadratic function, each coefficient of the approximate waveform is related to the engine speed Ne. Map it with. Then, as shown in FIG. 5B, the waveform of the pressure increase due to combustion obtained by referring to such a map is added to the value of the in-cylinder pressure P calculated by the in-cylinder pressure estimation model 68. Thus, the combustion pressure P is acquired.

(6) The atmospheric pressure correction term calculation unit atmospheric pressure correction term calculation unit 72, a model for estimating the in-cylinder charged air amount M _c is taken into the cylinder (referred to herein as "air model") contains. In this air model, it has decided to calculate the in-cylinder charged air amount M _c according to the following equation (11).

However, in the above equation (11), a and b are coefficients adapted according to operating conditions (engine speed Ne, valve timing VVT, etc.), respectively. Note that P _m is the intake pressure, and for example, a value calculated by the intake pressure estimation model 66 described above can be used.

Further, the atmospheric pressure correction term calculation unit 72 (here referred to as "fuel model") model for estimating the fuel quantity f _c drawn into the cylinder contains. Considering the behavior of the fuel after being injected from the fuel injection valve 28, that is, taking into account the phenomenon of part of the injected fuel adhering to the inner wall of the intake port and the vaporization of the adhering fuel, the k-th cycle When the fuel adhering to the wall surface at the start of fuel injection is f _w (k) and the actual fuel injection amount in the k-th cycle is f _i (k), the wall surface adhering after the end of the k-th cycle The fuel amount f _w (k + 1) and the fuel amount f _c sucked into the cylinder in the k-th cycle can be expressed as the following equations (12a) and (12b).

However, in the above (12), P is, deposition rate, and more specifically, the ratio of the amount of fuel adhering to the inner wall of the intake port of the fuel injection amount f _i. R is the residual percentage, more specifically, adherent fuel amount f _w after execution of the intake stroke is the fraction that remains in a state adhered to the wall surface or the like.
According to the above (12), the adhesion rate P and the residual rate R as a parameter, it is possible to calculate the fuel quantity f _c for each individual cycle.

Therefore, the estimated value of the air-fuel ratio A / F can be calculated using the calculation results of the air model and the fuel model. Next, the atmospheric pressure correction term calculation unit 72 detects the estimated air / fuel ratio A / F and the air / fuel ratio detected at a timing considering the transport delay until the injected fuel reaches the air / fuel ratio sensor 52 after being subjected to combustion. The steady deviation from the actual measurement value of the fuel ratio A / F is calculated. Then, the steady state error for the error of the in-cylinder charged air amount M _c, when the steady-state deviation is large, the assumption that the atmospheric pressure is deviated, calculates the atmospheric pressure correction coefficient k _airp. Specifically, calculated back to the intake pressure P _m above the air model, we calculate the atmospheric pressure correction coefficient k _airp as a correction factor for the standard atmospheric pressure P _a0 based on the intake air pressure P _m. The atmospheric pressure correction coefficient k _airp is used for correcting the intake pressure P _map and the exhaust pressure (atmospheric pressure P _air ) in the intake pressure estimation model 66 and the in-cylinder pressure estimation model 68 described above.

(7) About the atmospheric temperature correction term calculation unit In the atmospheric temperature correction term calculation unit 74, the stroke volume V during the exhaust stroke, the residual gas mass (calculated based on the clearance volume V _c at the exhaust top dead center) m, the residual gas The in-cylinder pressure P _th is calculated by substituting the measured values of the gas constant R of (burnt gas) and the atmospheric temperature T _air into the ideal gas equation of state. A deviation between the in-cylinder pressure P _th and the in-cylinder pressure P calculated by the in-cylinder pressure estimation model 68 is calculated. If the deviation is large, a correction coefficient is calculated based on the deviation. This correction coefficient is used to correct the intake pressure P _map in the intake pressure estimation model 66 described above.

[Friction model learning]
In the internal combustion engine 10, in order to achieve highly accurate air-fuel ratio control and good drivability, a means for accurately estimating the combustion state is required. According to the engine model 60 described above, the maximum pressure value P _max of the in-cylinder pressure P can be calculated as an index representing the combustion state. In order to accurately estimate the combustion state, the effect of friction is significant.

  In order to clarify the influence of such friction, it is desirable to take into account the deviation of friction caused by environmental changes and secular changes. Therefore, in the system of the present embodiment, the ECU 50 is caused to execute the following routine shown in FIG. 6 so that accurate friction information can be obtained without depending on secular change or the like.

  FIG. 6 is a flowchart of a routine executed by the ECU 50 in the first embodiment to realize the above object. Note that this routine is executed in a state where the friction is adapted so that the processing is performed in a state where the engine model 60 exhibits high calculation accuracy. The state in which the friction is adapted here means a state in which the deviation between the estimated crank angle θ and the estimated engine speed Ne calculated by the engine model 60 and the actual crank angle θ and the actual engine speed Ne is sufficiently small. Say.

  In the routine shown in FIG. 6, first, the actual engine speed Ne and the actual crank angle θ are detected every 30 ° CA (step 100). Next, it is determined whether or not the current operating state of the internal combustion engine 10 is in a steady state (step 102).

If it is determined in step 102 that the internal combustion engine 10 is in a steady state, the combustion pressure P is calculated using the engine model 60 (step 104). More specifically, in step 104, first, the actual engine speed Ne and the actual crank angle θ detected in step 100 are input to the engine model 60 as initial values. Next, the input torque TRQ is calculated by substituting the estimated values of the engine speed Ne and the crank angle θ calculated by the engine model 60 into the above equation (4e). Further, the friction torque TRQ _f can be obtained from the friction model 64, and the load torque TRQ _L is stored in the ECU 50. Therefore, the engine generated torque TRQ _e can be calculated using the above equation (5). As a result, the combustion pressure P can be calculated according to the above equation (6c). More specifically, here, the combustion pressure P is calculated as a pressure history with respect to the crank angle θ.

Next, for each cylinder, an average value of the maximum pressure value _{Pmax with} respect to a predetermined number of cycles is calculated (step 106). More specifically, in this step 106, the maximum pressure value P _{max of} each cylinder is specified based on the information of the crank angle θ from the history of the combustion pressure P calculated in the above step 104. For each cylinder, the average value of the maximum pressure value P _max for a predetermined number of cycles is calculated.

Next, it is determined for each cylinder whether or not the average value of the maximum pressure value P _max calculated in step 106 is within a predetermined range (step 108). As a result, when it is determined that the average value is within the predetermined range, it is determined that there is no cylinder in which the combustion state is deteriorated, and the processing of this routine is immediately terminated.

  On the other hand, if it is determined in step 108 that there is a cylinder whose average value is out of the predetermined range, it is determined that the combustion state of the corresponding cylinder is deteriorated, and The ignition timing is corrected (step 110).

  Next, it is determined whether or not the average value is out of a predetermined range in all cylinders (step 112). As a result, if it is determined that the average value is out of the predetermined range in all the cylinders, it is determined that a frictional deviation has occurred. In this routine, therefore, friction learning is executed using the engine model 60 according to the engine speed Ne (step 114).

  FIG. 7 is a diagram for explaining the friction learning method in step 114. In this step 114, the PID controller 76 calculates a value obtained by multiplying the deviation between the actual engine speed Ne calculated in step 100 and the estimated engine speed Ne calculated by the engine model 60 by a predetermined feedback gain. The PID correction amount is reflected in the map value of the friction map (see FIG. 4) provided in the friction model 64.

  FIG. 7 shows how to correct such a friction map. In FIG. 7, the waveform indicated by the broken line corresponds to the map value before learning in step 104, and the waveform indicated by the solid line corresponds to the map value after learning. 7 in the waveform correspond to map values before and after learning, respectively.

  As shown in FIG. 7, the PID correction amount is calculated by taking into account a predetermined region for each map point in order to eliminate noise-like behavior, and the average value and time of the correction amount calculated in the region. It is calculated as an integral value. By reflecting such a PID correction amount on each map value (circled value), the friction value is learned and updated to a new map value (triangled value).

  According to the routine shown in FIG. 6 described above, since the combustion state of the internal combustion engine 10 is accurately acquired using the engine model 60, it is accurately determined whether or not the friction model 64 is displaced. be able to. Then, based on such accurate determination, the deviation of the friction model 64 can be learned, and the output of the friction model 64 can be updated. For this reason, it is possible to correct the deviation of the friction model 64 caused by the secular change and the environmental change. As a result, it is possible to perform more accurate engine control based on the engine model 60 in which the accurate output value of the friction model 64 is reflected.

  By the way, a method for estimating a combustion state based on an output value of an in-cylinder pressure sensor that detects an in-cylinder pressure is conventionally known. According to the technique using the in-cylinder pressure sensor, the indicated torque of the internal combustion engine 10 can be obtained, but the axial torque of the crankshaft 16 that is the output shaft cannot be obtained from the technique. Whether or not the friction information output from the friction model 64 is accurate cannot be accurately determined unless it depends on the shaft torque, not the indicated torque.

  In contrast to the above-described method using the in-cylinder pressure sensor, according to the method using the engine model 60 of the present embodiment, the combustion pressure is calculated from the engine speed Ne and the crank angle θ of the actual machine as described in the routine shown in FIG. P will be calculated backwards. According to such a method, the combustion pressure P can be calculated based on the input torque TRQ of the crankshaft 16 that reflects the influence of friction, that is, the shaft torque.

That is, according to the method of this embodiment, since making a motion equation around the crank shaft 16 as an output shaft of the internal combustion engine 10, in terms of estimated accurately friction torque TRQ _f acting on the crankshaft 16 The variation of the friction is verified. For this reason, the influence of friction can be clarified as compared with the method using the in-cylinder pressure sensor. Thus, according to the method of the present embodiment, it is possible to perform more accurate engine control without requiring an expensive sensor.

In the first embodiment described above, the ECU 50 executes the process of step 104, so that the “combustion state index calculating means” in the first invention executes the process of step 106. The “determination means” according to the first aspect of the present invention is realized by executing the processing of the above step 112 by the “combustion state index average value calculation means” according to the first aspect of the invention. The friction model 64 corresponds to the “friction estimation means” in the first aspect of the present invention.
In the first embodiment described above, the motion equation calculation unit 62 around the crankshaft is the “calculation unit” in the third invention, and the PID correction amount is the “feedback correction amount” in the third invention. The PID controller 76 corresponds to the “feedback means” in the third invention.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG.
The system of the present embodiment uses the hardware configuration shown in FIG. 1 and the configuration of the engine model 60 shown in FIG. 2 to cause the ECU 50 to execute a routine shown in FIG. 8 described later instead of the routine shown in FIG. It can be realized.

In the first embodiment described above, the maximum pressure value P _max is used as an index representing the combustion state. On the other hand, the present embodiment is characterized in that the parameter of the Weibe function described above (see the above equation (9a)) is used as an index representing the combustion state.

[Specific Processing in Second Embodiment]
FIG. 8 is a flowchart of a routine executed by the ECU 50 in the second embodiment in order to perform friction learning based on the combustion state of each cylinder. In FIG. 8, the same steps as those shown in FIG. 6 in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified. This routine is also executed in a state where the friction is adapted.

  In the routine shown in FIG. 8, after the combustion pressure P is calculated backward using the engine model 60 (step 104), the combustion waveform calculation unit (combustion model) 70 is then used to determine the parameter of the Weibe function for each cylinder. An average value is calculated (step 200).

  More specifically, in step 200, the combustion pressure P calculated by the combustion waveform calculation unit 70 using the above equations (9a) and (10) is calculated by the back calculation of the combustion pressure P by the processing of step 104. The parameters of the Weibe function (such as the above-described shape factor m, combustion efficiency k, etc.) for matching are calculated by identifying the Weibe function using the least square method. In this step 200, such identification of the parameter of the Weibe function is executed over a predetermined number of cycles for each cylinder. Then, the average value of the parameters identified for each cylinder is calculated for a predetermined number of cycles.

  Next, it is determined for each cylinder whether or not the average value of the parameter of the Wiebe function calculated in step 200 is within a predetermined range (step 202). As a result, when it is determined that the average value is within the predetermined range, it is determined that there is no cylinder in which the combustion state is deteriorated, and the processing of this routine is immediately terminated.

  On the other hand, when it is determined in step 202 that there is a cylinder whose average value is out of the predetermined range, it is determined that the combustion state of the corresponding cylinder is deteriorated, and The ignition timing is corrected (step 110).

  Next, it is determined whether or not the average value is out of a predetermined range in all cylinders (step 204). As a result, when it is determined that the average value is out of the predetermined range in all the cylinders, it is determined that a frictional deviation has occurred. In this routine, therefore, friction learning is executed using the engine model 60 according to the engine speed Ne (step 114).

  As described with reference to the routine shown in FIG. 8, the combustion state of the internal combustion engine 10 can be determined based on the axial torque information using the engine model 60 also by the method using the parameter of the Weibe function as an index representing the combustion state. Since it has been acquired accurately, it can be accurately determined whether or not the friction model 64 is displaced.

  In the second embodiment described above, the combustion waveform calculation unit 70 corresponds to the “combustion pressure estimating means” in the fourth invention.

Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described with reference to FIG.
The system of this embodiment uses the hardware configuration shown in FIG. 1 and the configuration of the engine model 60 shown in FIG. 2 to cause the ECU 50 to execute a routine shown in FIG. 9 described later instead of the routine shown in FIG. It can be realized.

In the first embodiment described above, as an index representing the combustion state, using a maximum pressure value P _max. In contrast, the present embodiment is characterized in that the PID correction amount calculated by the PID controller 76 is used as an index representing the combustion state.

[Specific Processing in Embodiment 3]
FIG. 9 is a flowchart of a routine executed by the ECU 50 in the third embodiment in order to perform friction learning based on the combustion state of each cylinder. In FIG. 9, the same steps as those shown in FIG. 6 in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified. This routine is also executed in a state where the friction is adapted.

  In the routine shown in FIG. 9, when it is determined that the current operating state of the internal combustion engine 10 is in a steady state (step 102), the actual engine speed Ne calculated in step 100 and the engine model 60 are used. The PID correction amount is calculated by the PID controller 76 as a value obtained by multiplying the deviation from the calculated estimated engine speed Ne by a predetermined coefficient (step 300). The PID correction amount calculated here is a correction amount for feeding back the deviation of the engine speed Ne to the in-cylinder pressure P.

  Next, the PID correction amount calculated in step 300 is integrated between predetermined cycles for each cylinder, and an average value of the PID correction amounts is calculated for each cylinder (step 302).

  Next, it is determined for each cylinder whether or not the average value of the PID correction amount calculated in step 302 is within a predetermined range (step 304). As a result, when it is determined that the average value is within the predetermined range, it is determined that there is no cylinder in which the combustion state is deteriorated, and the processing of this routine is immediately terminated.

  On the other hand, if it is determined in step 304 that there is a cylinder whose average value is out of the predetermined range, it is determined that the combustion state of the corresponding cylinder is deteriorated, and The ignition timing is corrected (step 110).

  Next, it is determined whether or not the average value is out of a predetermined range in all cylinders (step 306). As a result, when it is determined that the average value is out of the predetermined range in all the cylinders, it is determined that a frictional deviation has occurred. In this routine, therefore, friction learning is executed using the engine model 60 according to the engine speed Ne (step 114).

  As described with reference to the routine shown in FIG. 9, the engine model 60 is also used by a method of using the PID correction amount based on the output of the motion equation calculation unit 62 around the crankshaft as an index representing the combustion state. Since the combustion state of the internal combustion engine 10 is accurately acquired based on the shaft torque information, it is possible to accurately determine whether or not the friction model 64 has shifted.

It is a figure for demonstrating the structure of the internal combustion engine to which the stop position control apparatus of the internal combustion engine of Embodiment 1 of this invention was applied. It is a block diagram which shows the structure of the engine model with which ECU shown in FIG. 1 is provided. It is a figure which shows the symbol attached | subjected to each element around a crankshaft. FIG. 3 shows an example of a friction map provided for the friction model shown in FIG. 2 to acquire the friction torque TRQ _f . FIG. 6 is a diagram for explaining a modified technique for obtaining a history of in-cylinder pressure P. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a figure for demonstrating the friction learning method in step 114 of the routine shown in FIG. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a flowchart of the routine performed in Embodiment 3 of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Piston 14 Connecting rod 16 Crankshaft 24 Throttle valve 26 Throttle position sensor 40 Crank angle sensor 42 Cam angle sensor 50 ECU (Electronic Control Unit)
52 Air-fuel ratio sensor 54 Water temperature sensor 60 Engine model 62 Equation of motion calculation section around crankshaft 64 Friction model 66 Intake pressure estimation model 68 In-cylinder pressure estimation model 70 Combustion waveform calculation section 72 Atmospheric pressure correction term calculation section 74 Atmospheric temperature correction term calculation 76 PID controller
dQ / dθ Heat release rate
dθ / dt Crank angle rotation speed

Claims (8)

Friction estimation means for estimating the friction of the internal combustion engine based on the engine speed and the engine coolant temperature or the kinematic viscosity of the engine speed and the engine lubricating oil ;
Input torque calculating means for calculating the input torque based on the engine speed and / or the measured or estimated value of the crank angle in accordance with a predetermined relational expression that defines the relationship between the crank angle and the input torque input to the crankshaft. When,
Generated torque calculation means for calculating the generated torque of the internal combustion engine based on the input torque calculated by the input torque calculation means, the friction torque calculated by the friction estimation means, and the load torque of the internal combustion engine When,
In-cylinder pressure calculating means for calculating the in-cylinder pressure based on the generated torque according to a predetermined relational expression that defines the relationship between the generated torque and the in-cylinder pressure calculated by the generated torque calculating means;
Combustion state index calculating means for calculating a combustion state index representing the combustion state of each cylinder of the internal combustion engine based on the in-cylinder pressure calculated by the in-cylinder pressure calculating means;
Combustion state index average value calculating means for calculating a combustion state index average value for a predetermined number of cycles for the combustion state index of each cylinder;
Determining means for determining whether the combustion state index average value of all cylinders is within a predetermined range;
A control device for an internal combustion engine, wherein when it is determined that the combustion state index average value of all cylinders is not within the predetermined range, it is determined that there is a deviation in the estimation of the friction by the friction estimation means .   2. The control apparatus for an internal combustion engine according to claim 1, wherein when it is determined that there is a deviation in the estimation of the friction by the friction estimation means, the friction is learned according to the engine speed. A crank angle sensor for detecting a rotational position of the crankshaft,
Based on the equation of motion of the in-cylinder pressure and crankshaft periphery calculated by the in-cylinder pressure calculation means, the calculation section for calculating an estimated value of the engine rotational speed and or the crank angle,
Feedback means for calculating a feedback correction amount for matching the estimated value calculated by the calculation unit with an actual measurement value detected by the crank angle sensor, and reflecting the feedback correction amount in an input value of the calculation unit; ,
The control apparatus for an internal combustion engine according to claim 1, further comprising:   The internal combustion engine control device according to any one of claims 1 to 3, wherein the combustion state index is a maximum pressure value of in-cylinder pressure. The combustion state index calculation means includes combustion pressure estimation means by a Weibe function,
4. The control apparatus for an internal combustion engine according to claim 1, wherein the combustion state index is a parameter of a Weibe function calculated by identifying the Weibe function. Friction estimation means for estimating the friction of the internal combustion engine based on the engine speed and the engine coolant temperature or the kinematic viscosity of the engine speed and the engine lubricating oil;
Generated torque calculation means for calculating the generated torque based on the in-cylinder pressure according to a predetermined relational expression defining a relationship between the in-cylinder pressure and the generated torque of the internal combustion engine;
Based on the generated torque calculated by the generated torque calculating means, the friction torque calculated by the friction estimating means, and the load torque of the internal combustion engine, an input torque calculation for calculating an input torque input to the crankshaft Means,
Crank estimated value for calculating an estimated value of the engine speed and / or the crank angle in accordance with a predetermined relational expression that defines the relationship between the input torque calculated by the input torque calculating means, the crank angle, and the engine speed. A calculation means;
A crank angle sensor for detecting the rotational position of the crankshaft;
A feedback correction amount for making the estimated value calculated by the crank estimated value calculating means coincide with the engine speed detected by the crank angle sensor and / or the measured value of the crank angle is set to each cylinder of the internal combustion engine. Combustion state index calculating means for calculating as a combustion state index representing the combustion state of
Combustion state index average value calculating means for calculating a combustion state index average value for a predetermined number of cycles for the combustion state index of each cylinder;
Determining means for determining whether the combustion state index average value of all cylinders is within a predetermined range;
A control apparatus for an internal combustion engine, wherein when it is determined that the combustion state index average value of all cylinders is not within the predetermined range, it is determined that there is a deviation in the estimation of the friction by the friction estimation means . 7. The control apparatus for an internal combustion engine according to claim 6, wherein when it is determined that there is a deviation in the estimation of the friction by the friction estimation means, the friction is learned according to the engine speed. 8. The control apparatus for an internal combustion engine according to claim 6, further comprising feedback means for reflecting the feedback correction amount to the in-cylinder pressure.

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