JP2007211685A - Oil degradation determining device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately determine the degradation of oil without limiting the operating conditions of an internal combustion engine in an oil degradation determining device for the internal combustion engine. <P>SOLUTION: An engine model 60 constructed comprises an equation of motion calculation part 62 around a crankshaft, a friction model 64, an intake pressure estimating model 66, a cylinder pressure estimating model 68, a combustion waveform calculation part 70, an atmospheric pressure correction item calculation part 72, and an atmospheric temperature correction item calculation part 74. The friction model 64 is learned based on the estimated values of the crank angle θ and the crank angle rotating speed dθ/dt calculated by the engine model 60 and the actually measured values thereof. When the margin of degradation of fuel economy acquired by the relation between a friction and an engine rotational speed Ne is larger than a predetermined value, the oil is determined to be degraded. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an oil deterioration determination device for an internal combustion engine that determines deterioration of oil used for lubricating an internal combustion engine.

  Conventionally, for example, Patent Document 1 discloses a friction estimation apparatus that estimates the friction of an internal combustion engine. Specifically, in this device, when the operation of the internal combustion engine is stopped, whether or not the friction has increased by calculating the speed of decrease of the engine speed and comparing the calculated speed of decrease of the engine speed with the judgment value. Is determined.

JP 2001-98997 A JP 2002-266617 A

  In the conventional technique described above, the friction is directly estimated based on the decrease speed of the engine speed. However, the friction depends on the difference in operating conditions, and the conventional method does not consider the relationship between the friction and the operating conditions, so that the region where the friction can be accurately estimated is limited. For this reason, according to the above-described conventional method, there is a possibility that sufficient determination accuracy cannot be ensured when determining oil deterioration of the internal combustion engine based on friction.

  The present invention has been made to solve the above-described problems, and provides an oil deterioration determination device for an internal combustion engine that can accurately determine oil deterioration without being restricted by operating conditions of the internal combustion engine. With the goal.

In order to achieve the above object, the first invention provides a friction model for calculating the friction of the internal combustion engine,
Crank information estimating means for obtaining an estimated value of a crank angle and / or a crank angle rotation speed based on a predetermined parameter including the friction;
Crank information measuring means for obtaining an actual measurement value of the crank angle and / or the crank angle rotation speed;
Friction learning means for learning the friction model based on a deviation between the estimated value and the measured value;
Oil deterioration determination means for determining oil deterioration based on the relationship between the degree of deterioration of fuel consumption of the internal combustion engine and the friction;
It is characterized by providing.

  According to a second aspect, in the first aspect, the oil deterioration determining means determines that the oil has deteriorated when the degree of deterioration of the fuel consumption exceeds a predetermined threshold.

According to a third aspect of the present invention, the first or second aspect of the present invention further includes feedback means for calculating a correction amount based on the deviation and correcting the estimated value based on the correction amount so that the deviation is eliminated. ,
The friction learning means is characterized in that when learning of the friction model is executed during the stop process of the internal combustion engine, the feedback is executed by specifying an engine speed region.

According to a fourth aspect of the present invention, in the first or second aspect of the invention, a feedback unit that calculates a correction amount based on the deviation and corrects the estimated value so that the deviation is eliminated based on the correction amount;
Separating means for separating the correction amount into a variation due to combustion pressure and a variation due to friction;
The feedback learning unit is configured to learn the friction model based on a variation due to the friction when the friction model is learned during steady operation of the internal combustion engine.

  According to the first invention, an estimated value of the crank angle and / or the crank angle rotational speed is acquired based on a predetermined parameter including friction, and is learned based on a deviation between the estimated value and an actually measured value. Based on the friction, the degree of deterioration of fuel consumption is acquired. If deterioration of fuel consumption due to increased friction is recognized, it can be determined that the oil has deteriorated. For this reason, it is possible to accurately determine the oil deterioration based on the friction based on various influences of the internal combustion engine, without being limited by the operating conditions.

  According to the second invention, it is determined that the oil has deteriorated when the deterioration degree of the fuel consumption determined in relation to the friction to be learned exceeds a threshold value. For this reason, oil deterioration can be determined accurately.

  According to the third aspect of the present invention, it is possible to avoid the deviation between the estimated value and the measured value from accumulating when the engine speed decreases due to the stop process of the internal combustion engine. For this reason, the adaptive accuracy of friction can be ensured satisfactorily.

  According to the fourth aspect of the invention, even when the combustion of the internal combustion engine is being executed, the variation caused by the combustion pressure is removed, and the friction model is accurately learned based on the variation caused by the friction. Can do. For this reason, it is possible to accurately determine oil deterioration without being restricted by operating conditions.

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. .

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.

[Oil deterioration judgment using engine model]
The system of the present embodiment uses the engine model 60 described above to determine engine oil deterioration without using a special sensor for detecting oil deterioration. Specifically, oil deterioration is determined based on the estimated value of friction (friction torque TRQ _f ) obtained by the friction model 64.

  Friction varies greatly due to differences in operating conditions (cooling water temperature, engine speed Ne, etc.). Therefore, in order to accurately estimate the friction, it is necessary to consider the influence of operating conditions. Therefore, in the present embodiment, the ECU 50 is caused to execute the routine shown in FIG. 6 below in order to accurately determine the oil deterioration using the engine model 60.

[Specific Processing in Embodiment 1]
FIG. 6 is a flowchart of a routine executed by the ECU 50 in the first embodiment to realize the above object. The routine shown in FIG. 6 is a routine that is executed in response to the start of an engine stop process for stopping the internal combustion engine 10 by the operation of the driver or automatically.

In this routine, first, estimated values of the engine speed Ne (crank angle rotational speed dθ / dt) and the crank position (crank angle θ) are calculated (step 100). Specifically, in step 100, the engine speed Ne ₀ (crank angle rotation speed dθ ₀ / dt) and the crank angle θ ₀ at the start of the engine stop process are input to the engine model 60 described above as initial values. Thus, the estimated values of the engine speed Ne and the crank angle θ are sequentially calculated.

  Next, deviations between the estimated values of the engine speed Ne and the crank angle θ calculated in step 100 and the actually measured values of the engine speed Ne and the crank angle θ are calculated (step 102).

  Next, learning of the friction model 64 is executed based on the deviation calculated in step 102 (step 104). FIG. 7 is a diagram for explaining the friction learning method in step 104. In step 104, the PID controller 76 calculates a value obtained by multiplying the deviation of the engine speed Ne calculated in step 102 (hereinafter, may be abbreviated as “rotational speed deviation”) 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. 7A shows how to correct such a friction map. In FIG. 7A, 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. Also, the circles and triangles on the waveform in FIG. 7A correspond to the map values before and after learning, respectively.

  As shown in FIG. 7A, the PID correction amount is an average of the correction amounts calculated in the area in consideration of a predetermined area for each map point in order to remove noise behavior. It is calculated as a value or an integral value over time. 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).

  Further, in step 104, the following correction is performed in order to reduce the estimation error of the engine speed Ne by the engine model 60. FIG. 7B shows a state in which the engine speed Ne decreases after the engine stop process is started. In FIG. 7B, the waveform represented by the solid line represents the measured value of the engine speed Ne, and the waveform represented by the broken line represents the estimated value of the engine speed Ne when the friction of this step 104 is not well applied. Represents each.

As shown in FIG. 7B, in a state where the friction is not applied well, the rotational speed deviation generated at the initial stage of the engine stop process is accumulated as the engine rotational speed Ne decreases. This is due to the following reason. The variation in the friction torque TRQ _f affects the crank angular acceleration (that is, the engine speed reduction speed) d ² θ / dt ² . _If an error occurs in the crank angular acceleration d ² θ / dt ^{2 due} to variations in the friction torque TRQ _f , the engine speed Ne is expressed as a temporal integral value of the crank angular acceleration (d ² θ / dt ² ). The effect is reflected. As a result, at the beginning of the engine stop process, even if there is only a certain rotational speed deviation, the rotational speed deviation increases with time.

  In this step 104, in order to eliminate such accumulation of rotational speed deviation, a predetermined engine rotational speed region is specified, and the PID correction amount calculated by the PID controller 76 is input to the motion equation calculation unit 62 around the crankshaft. Thus, the estimated value of the engine speed Ne calculated by the engine model 60 is corrected so as to eliminate the engine speed deviation. FIG. 7C is a diagram for explaining the timing for performing such feedback control. In FIG. 7C, the waveform represented by the solid line represents the measured value of the engine speed Ne, and the waveform represented by the broken line represents the estimated value of the engine speed Ne. As shown in FIG. 7C, the calculation of the PID correction amount is performed by specifying the timing at which the degree of decrease increases when the engine speed Ne decreases.

  More specifically, the degree of decrease in the engine speed Ne is greatest at the timing when the piston 12 is positioned around 90 ° CA after top dead center in the expansion stroke. In this step 104, therefore, a PID correction amount is calculated for each cylinder every time such timing arrives, and each time the PID correction amount is fed back to the motion equation calculation unit 62 around the crankshaft. Yes. According to such a process, it is possible to avoid the accumulation of rotational speed deviations as the engine rotational speed Ne decreases.

In the routine shown in FIG. 6, the fuel efficiency deterioration margin of the internal combustion engine 10 is then calculated based on the friction torque TRQ _f estimated by the friction model 64 learned and updated by the processing of step 104 (step 106). . As shown in FIG. 8, the ECU 50 stores a map in which the relationship between the deterioration rate of fuel consumption (degree of deterioration of fuel consumption) and the friction torque TRQ _f and the engine speed Ne are determined in advance. In step 106, the fuel consumption deterioration margin is calculated with reference to this map.

  Next, it is determined whether or not the fuel consumption deterioration calculated in step 106 is greater than a predetermined threshold (step 108). As a result, when it is determined that the fuel consumption deterioration margin is larger than the threshold value, it is determined that the oil has deteriorated, and the oil change lamp is lit to notify the driver of the oil deterioration at the next start of the internal combustion engine 10. (Step 110).

  According to the routine shown in FIG. 8 described above, it is possible to determine the oil deterioration without using a special sensor for detecting the oil deterioration.

  Further, according to the engine model 60 described above, the influence of the operating conditions and environmental conditions of the internal combustion engine 10 such as atmospheric pressure, atmospheric temperature, throttle opening, valve timing VVT, etc. (“predetermined parameters” in the present invention) is appropriate. Has been modeled. According to the engine model 60, learning of the friction model 64 constructed in consideration of the operating conditions of the engine speed Ne and the coolant temperature is performed by estimating and measuring the engine speed Ne and the crank angle θ. Based on the deviation from the value (that is, based on the PID correction amount), it is performed on the engine model 60 in which the above operating conditions and environmental conditions are taken into consideration. For this reason, according to the engine model 60, the adaptive accuracy of friction can be improved, and accurate oil determination can be performed without being restricted by operating conditions.

  Furthermore, according to the engine model 60, since the friction model 64 is sequentially learned, it is possible to eliminate prior adaptation.

In the first embodiment described above, the ECU 50 executes the processing of step 100, so that the “crank information estimating means” in the first aspect of the invention is based on the output of the crank angle sensor 40. Or by obtaining the crank angle rotation speed dθ / dt, the “crank information measuring means” in the first invention performs the processing of step 104, and the “friction learning means” in the first invention By executing the processing of steps 106 to 110, the “oil deterioration determination means” in the first invention is realized.
Further, the “feedback means” in the third aspect of the present invention is realized by giving a command to the PID controller 76 so that the ECU 50 reflects the PID correction amount in the motion equation calculation unit 62 around the crankshaft.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG. 9 and 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, the oil deterioration determination using the engine model 60 is performed at the timing when the engine stop process is started. In contrast, the present embodiment is characterized in that the oil deterioration determination using the engine model 60 is performed during the steady operation of the internal combustion engine 10.

[Specific Processing in Second Embodiment]
FIG. 9 is a flowchart of a routine executed by the ECU 50 in the second embodiment in order to determine oil deterioration during steady operation. 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. The routine shown in FIG. 9 is executed at a predetermined timing (predetermined engine speed Ne) during the period in which the combustion of the internal combustion engine 10 is being executed, and the learning process (step 200) of the friction model 64 is performed. This is different from the learning process (step 104) in the first embodiment described above.

  FIG. 10 is a diagram for explaining the processing of step 200. At the time of steady operation in which combustion is performed, two factors that greatly affect the estimation result of the engine model 60 are a variation due to the combustion pressure P and a variation due to friction. Therefore, in order to learn the friction model 64 with high accuracy during such combustion execution, it is necessary to separate these two factors. In the case of a four-cylinder engine such as the internal combustion engine 10, the in-cylinder pressure P varies due to combustion at intervals of 180 ° CA. Therefore, for example, when the engine speed Ne is 1800 rpm, a fluctuation in the in-cylinder pressure P with a frequency of 60 Hz occurs.

  FIG. 10A shows how the PID correction amount calculated by the PID controller 76 varies. That is, the PID correction amount (FB correction amount) also varies due to the variation in the in-cylinder pressure P. Therefore, in this step 200, the PID correction amount is passed through a high-pass filter (HPF) provided in the ECU 50, so that the PID correction amount and the fluctuation caused by the combustion pressure P and the friction are shown in FIG. It is made to isolate | separate into the fluctuation part resulting from. For example, when learning of the friction model 64 is performed at 1800 rpm, an HPF having a cutoff frequency of 60 Hz is provided. According to such a method, the high frequency component separated by the HPF corresponds to the fluctuation caused by the combustion pressure, and the low frequency component becomes the fluctuation caused by the friction. Therefore, in this step 200, only the low frequency component of the PID correction amount is reflected as the learning amount of the friction model 64. Subsequent learning processing of the friction model 64 is the same as the processing in step 104 described above, and thus detailed description thereof is omitted here.

  In the routine shown in FIG. 9, if it is determined that the fuel consumption deterioration margin is larger than the threshold value (step 108), it is determined that the oil has deteriorated. In this case, the internal combustion engine 10 is in operation. The oil change lamp is immediately turned on (step 202).

  According to the routine shown in FIG. 9 described above, the friction model 64 is learned based on the PID correction amount from which the fluctuation due to the combustion pressure P is separated by the high-pass filter. For this reason, the adaptive accuracy of friction can be improved even during steady operation, and accurate oil determination can be performed.

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 technique of the friction learning in step 104 of the routine shown in FIG. It is an example of the map referred in the routine shown in FIG. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a figure for demonstrating the process of step 200 of the routine shown in FIG.

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 (4)

A friction model for calculating the friction of the internal combustion engine;
Crank information estimating means for obtaining an estimated value of a crank angle and / or a crank angle rotation speed based on a predetermined parameter including the friction;
Crank information measuring means for obtaining an actual measurement value of the crank angle and / or the crank angle rotation speed;
Friction learning means for learning the friction model based on a deviation between the estimated value and the measured value;
Oil deterioration determination means for determining oil deterioration based on the relationship between the degree of deterioration of fuel consumption of the internal combustion engine and the friction;
An oil deterioration determination device for an internal combustion engine, comprising:   2. The oil deterioration determining apparatus for an internal combustion engine according to claim 1, wherein the oil deterioration determining means determines that the oil has deteriorated when the degree of deterioration of the fuel consumption exceeds a predetermined threshold value. Feedback means for calculating a correction amount based on the deviation and correcting the estimated value so that the deviation is eliminated based on the correction amount;
3. The internal combustion engine according to claim 1, wherein the friction learning unit executes the feedback by specifying an engine speed region when performing the learning of the friction model during a stop process of the internal combustion engine. Engine oil deterioration judgment device. Feedback means for calculating a correction amount based on the deviation and correcting the estimated value so that the deviation is eliminated based on the correction amount;
Separating means for separating the correction amount into a variation due to combustion pressure and a variation due to friction;
The said feedback learning means learns the said friction model based on the fluctuation | variation resulting from the said friction, when learning the said friction model at the time of steady operation of an internal combustion engine. 3. An oil deterioration determination device for an internal combustion engine according to 2.

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