JP2008088942A - Stop position control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To ensure high accuracy in controlling a crank stop position while considering the influence of environmental change appropriately in an internal combustion engine to which control of automatically performing the stop and restart of the internal combustion engine is applied regarding a stop position control device for the internal combustion engine. <P>SOLUTION: The stop position control device for the internal combustion engine comprises an engine model 60 including a friction model for computing friction to be input to a crankshaft of the internal combustion engine, and an atmospheric pressure learning means for learning the influence of atmospheric pressure on the crank stop position. When determining the completion of warming up, friction learning is performed, and after determining the completion of the friction learning, atmospheric pressure learning is performed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an internal combustion engine stop position control device, and more particularly, as an apparatus for controlling an internal combustion engine to which control for automatically stopping and restarting an internal combustion engine is applied when a vehicle is temporarily stopped. The present invention relates to a suitable stop position control device for an internal combustion engine.

  Conventionally, for example, Patent Document 1 discloses an engine starter that executes control (eco-run control) for automatically stopping and restarting an internal combustion engine when a vehicle is temporarily stopped. This conventional device controls the engine speed at which the fuel supply is stopped so that the next restart can be performed smoothly, so that the piston stop position (crank stop position) at the time of automatic stop of the internal combustion engine is appropriate. It aims to make it easier.

JP 2004-293444 A JP 2005-16505 A JP-A-2-305342 JP 58-18535 A JP 2006-104955 A

  When the internal combustion engine is automatically stopped, the main factor that causes the crank stop position to deviate from the target stop position is considered to be the influence of friction that is input to the crankshaft. In order to determine the combustion cut rotational speed so that the crank stop position can be accurately converged to a desired position, it is desirable to have a system that can appropriately learn the influence of such friction.

  Further, the crank stop position is greatly affected by changes in atmospheric pressure (environmental changes). Therefore, if the influence of such atmospheric pressure is not properly taken into account, the above-described friction learning accuracy may be deteriorated.

  The present invention has been made to solve the above-described problems. In an internal combustion engine to which control for automatically stopping and restarting the internal combustion engine is applied, the influence of environmental changes is appropriately considered. Another object of the present invention is to provide a stop position control device for an internal combustion engine that can ensure good accuracy of crank stop position control.

According to a first aspect of the present invention, there is provided a friction model for calculating friction that is input to a crankshaft of an internal combustion engine;
Crank position estimating means for acquiring an estimated value of the crank stop position based on predetermined parameters including the friction and atmospheric pressure;
Friction learning means for learning the friction model based on crank angle information of the internal combustion engine;
Atmospheric pressure learning means for learning the influence of atmospheric pressure on the crank stop position;
A warm-up determination means for determining whether the warm-up of the vehicle system is completed;
Learning sequence setting means for performing learning of the friction model when it is determined that the warm-up is completed, and performing learning of the atmospheric pressure after it is determined that learning of the friction model is completed;
It is characterized by providing.

Further, the second invention further comprises system state determining means for determining start and stop of the vehicle system in the first invention,
When it is determined that the vehicle system has stopped, the learning history of the friction model is discarded.

According to a third aspect of the present invention, in the first or second aspect, the internal combustion engine stop position control device controls a crank stop position by controlling a combustion cut rotational speed at which combustion of the internal combustion engine is stopped. Because
When it is determined that the vehicle system is in the warm-up process, updating of the combustion cut speed is prohibited.

Further, a fourth invention further includes an atmospheric pressure information acquisition means for acquiring atmospheric pressure information in any of the first to third inventions,
The friction learning means performs the learning when it is determined that a change in atmospheric pressure is relatively small.

  According to a fifth invention, in any one of the first to fourth inventions, the friction learning means updates the learning value when the learning frequency of the friction model exceeds a predetermined value. And

Further, a sixth aspect of the invention relates to any one of the first to fifth aspects of the present invention, stop position change acquisition means for acquiring a change amount of the crank stop position;
Combustion cut speed correction means for correcting the combustion cut speed so that the crank stop position becomes a target stop position when the change margin of the crank stop position exceeds a predetermined value;
Is further provided.

Further, the seventh invention further comprises driving history acquisition means for acquiring a system driving history after the vehicle system is assembled in the first invention,
The friction learning unit prohibits the learning of the friction model until the system operation history becomes longer than a predetermined determination criterion.

According to an eighth aspect based on the first aspect, clutch engagement state determining means for determining an engagement state of a clutch disposed between the internal combustion engine and the transmission,
A stop position change acquisition means for acquiring a change amount of the crank stop position;
The warm-up determination means determines whether warm-up is completed based on the change margin of the crank stop position,
The change reference value for the change amount of the crank stop position used when the warm-up determination unit determines the warm-up is set to a different value depending on the engagement state of the clutch.

  According to the first invention, even if there is an environmental change (atmospheric pressure change), it is possible to satisfactorily ensure the learning accuracy for the main factors that affect the accuracy of the stop position control.

  According to the second aspect of the present invention, even when a friction change factor such as an oil change occurs during the stop period of the vehicle system, such a friction change affects the accuracy of friction learning. It can be avoided.

  According to the third aspect of the present invention, it is possible to prevent the crank stop position from being corrected to an unintended combustion cut speed during the warm-up process in which the crank stop position is not stable, and to ensure controllability of the crank stop position.

  According to the fourth aspect of the invention, it is possible to ensure a high degree of friction learning accuracy with respect to changes in atmospheric pressure.

  According to the fifth aspect, since the learning value made with a predetermined frequency can be reflected, the re-learning frequency can be lowered, and good learning accuracy can be ensured.

  According to the sixth invention, as an example, in the case where the friction learning is completed and the atmospheric pressure is stable, but the crank stop position is largely deviated. The target crank stop position can be finely adjusted, thereby ensuring the accuracy of crank stop position control.

  According to the seventh aspect, since the friction learning is prohibited under a situation where the driving history of the vehicle system is short and a large friction change is assumed, the influence of the friction is prevented from being erroneously learned during that time. can do.

  According to the eighth aspect, accurate warm-up determination can be performed according to the engagement state of the clutch.

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, the ECU 50 includes an air-fuel ratio sensor 52 for detecting the exhaust air-fuel ratio in the exhaust passage 22, a water temperature sensor 54 for detecting the cooling water temperature of the internal combustion engine 10, and the internal combustion engine 10 A clutch switch 56 is connected for detecting the engagement state of a clutch (not shown) provided between the transmission (not shown). The clutch switch 56 emits an ON signal (clutch engagement) when a clutch pedal (not shown) is depressed, and issues an OFF signal (clutch disengagement) when the clutch pedal is not depressed. . Further, the ECU 50 detects an atmospheric pressure sensor 57 for detecting the atmospheric pressure, an ignition switch (IG switch) 58 for starting and stopping the vehicle system on which the internal combustion engine 10 is mounted, and a vehicle travel distance. A trip meter 59 is connected. The ECU 50 can grasp the starting state of the vehicle system by discriminating such an ON / OFF signal of the IG switch 58. 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, an engine friction model 64, a mission friction model 65, an intake pressure estimation model 66, an in-cylinder pressure estimation model 68, a combustion A waveform calculation unit 70. 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 reflects the influence on the internal friction of the internal combustion engine 10 by the engine friction model 64, and the internal friction of the transmission by the mission friction model 65. The effect on (mainly friction caused by rotation and sliding of the bearing portion) is reflected.

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 rotation 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. Is the moment of inertia around the rotation axis, 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. Note that the inertia moment (transmission-side inertia) related to the transmission is used only during model calculation when it is determined that the clutch is in an engaged state, and when the clutch is determined to be in a non-engaged state. It is zero at the time of model calculation.

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 the friction loss of the piston 12, the crankshaft 16, and the sliding portions of the transmission. This friction torque TRQ _f is a value obtained from the engine friction model 64 and the mission friction model 65. More specifically, the friction torque TRQ _f is calculated using both the engine friction model 64 and the mission friction model 65 when the clutch is in an engaged state, while when the clutch is in an unengaged state. It is calculated using only the engine 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) Engine Friction Model FIG. 4 shows an example of an engine friction map provided for the engine friction model 64 shown in FIG. 2 to acquire the engine friction torque TRQ _{f_EN} . More specifically, FIG. 4A is a diagram conceptually showing the relationship between the first engine friction torque TRQ _{f_map1} and the crank angle rotational speed (dθ / dt) related to the rotational sliding around the crankshaft 16. FIG. 4B is a diagram conceptually showing the relationship between the second engine friction torque TRQ _{f_map2} related to the translational motion of the piston 12 and the piston speed (dXi / dt).

In the system of the present embodiment, in order to improve the model calculation accuracy of the engine model 60, in the routine processing shown in FIG. 7 described later, the engine friction torque TRQ _fEN is changed to the first engine friction torque TRQ _{f_map1} as described above. The second engine friction torque TRQ _{f_map2} may be considered separately.

As shown in FIG. 4A, the first engine friction torque TRQ _{f_map1} relating to the rotational sliding around the crankshaft 16 basically has characteristics that depend on the engine speed (dθ / dt). More specifically, as shown in FIG. _4A , the torque TRQ _{f_map1} increases due to the influence of the maximum static friction coefficient when the engine speed (dθ / dt) is close to zero, and the engine speed When (dθ / dt) begins to increase, the effect of the maximum static friction coefficient is reduced, and once it starts to decrease, but thereafter increases as the engine speed (dθ / dt) increases.

Further, as shown in FIG. 4B, the second engine friction torque TRQ _{f_map2} relating to the translational motion of the piston 12 is the friction between the piston 12 and the cylinder wall surface, and only the contact pressure and the friction coefficient between them are used. Depending on the piston speed (dXi / dt). Further, in the region where the piston speed (dXi / dt) in FIG. 4B is close to zero, the second engine friction torque TRQ _{f_map2} shows a large value. In such a region, the influence of the maximum static friction coefficient becomes large. Because.

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。 Note that the engine friction torque TRQ _{f_EN} tends to increase as the engine coolant temperature decreases. Therefore, the engine friction torque TRQ _{f_EN} is not shown in FIG. 4, but in addition to the relationship with the engine speed Ne (and the piston speed (dXi / dt)), the relationship with the engine coolant temperature is Is also taken into account. Here, in order to reduce the calculation load of the ECU 50, the engine friction model 64 is provided with the friction map as described above, but the configuration of the engine friction model is not limited to this. A relational expression such as the following expression (7) may be used. In the equation (7), the friction torque TRQ _{f_EN} 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) About Mission Friction Model FIG. 5 shows an example of a mission friction map provided for the mission friction model 65 shown in FIG. 2 to acquire the mission friction torque TRQ _{f_MI} . The mission friction torque TRQ _{f_MI} calculated by the mission friction model 65 is a state where the gear is in the neutral position and the clutch is engaged while the vehicle is stopped, that is, the gear of the _transmission is used to drive the power of the internal combustion engine 10. It is the friction torque in the state of rotating without being transmitted to the tire side. Therefore, the mission friction torque TRQ _{f_MI} is determined to have a value corresponding to the internal friction of the transmission (mainly, friction due to rotational sliding of the bearing portion). Therefore, as shown in FIG. 5, the mission friction torque TRQ _{f_MI} has a characteristic that depends on the engine rotational speed (dθ / dt), like the first engine friction torque TRQ _{f_map1} .

(4) 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).

(5) In-cylinder pressure estimation model The in-cylinder pressure estimation model 68 is a model used to calculate the in-cylinder pressure P in 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.

(6) About 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.

Note that 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. 6 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. 6A, that is, the change in the waveform of the in-cylinder pressure P that changes due to the combustion (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. 6B, 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.

[Calculation method for estimated crank stop position]
In a vehicle including an internal combustion engine, when the vehicle temporarily stops, control (eco-run control) that automatically stops and restarts the internal combustion engine may be executed. Further, even in a hybrid vehicle that drives a vehicle with an internal combustion engine and a motor, control that automatically stops and restarts the internal combustion engine during startup of the vehicle system (including when the vehicle is running) (in this specification, This is also called “eco-run control” in a broad sense).

  In the above-described eco-run control, in order to smoothly restart the internal combustion engine, the stop position of the crankshaft 16 (stop position of the piston 12) when the internal combustion engine is automatically stopped is accurately set to the target stop position. There is a demand for good control. In the engine model 60 described above, the effects of friction, atmospheric pressure, atmospheric temperature, throttle opening, valve timing VVT, etc. (“predetermined parameters” in the present invention) that affect the crank stop position are appropriately modeled. Yes. Therefore, in the system of the present embodiment, the engine model 60 described above is used as a stop position estimation model for estimating the stop position of the crankshaft 16 during the eco-run control. According to the engine model 60 described above, the stop position of the crankshaft 16 when the internal combustion engine 10 is automatically stopped is acquired by acquiring the estimated value of the crank angle θ when the crank angle rotation speed dθ / dt becomes zero. can do. In the present specification, the stop position of the crankshaft 16 may be simply referred to as “crank stop position”.

  More specifically, the estimated value of the crank stop position can be calculated by the following method. When the estimated value of the crank stop position is calculated by the engine model 60, if the clutch is in the engaged state, both the engine friction model 64 and the mission friction model 65 are used as the friction model, When the clutch is in the disengaged state, only the engine friction model 64 is used as the friction model.

The initial value is the average value of the combustion pressure P, the intake pressure P _map , the crank angle θ ₀ , and the engine speed (combustion cut speed) Ne ₀ (= crank angle rotational speed dθ ₀ / dt) acquired in the idle state. Then, the estimated values of the crank angle θ and the crank angle rotation speed dθ / dt are sequentially calculated using the motion equation calculation unit 62 around the crankshaft. Hereinafter, the specific calculation method will be described using the following equations (11) and (12). In this specification, using such a method to solve the engine model 60 in the direction of the arrow shown in FIG. 2 is referred to as “forward model calculation”.

First, in the equation of motion around the crankshaft expressed by the above equation (4e), (∂f (θ) / ∂θ) ≡h (θ) and the input torque TRQ in the equation (4e) After substituting the equation (5), the following equation (11) is obtained by discretizing the equation (4e).

Then, as described above, the crank angle θ ₀ , the crank angle rotational speed dθ ₀ / dt, and the like are given as calculation initial values of the forward model calculation according to the above equation (11). Hereinafter, by sequentially updating the number of steps k, the estimated values of the corresponding crank angle θ and crank angle rotation speed dθ / dt are sequentially calculated. If the number of steps k = 1 is substituted into the above equation (11), it can be expressed as the following equation (12a).

When a part of the crank angle θ (k) in the above equation (12a) is rewritten to the corresponding crank angle rotation speed dθ (k) / dt, it can be expressed as the above equation (12b). Then, when the equation (12b) is developed, the crank angle rotational speed dθ (1) / dt when the number of steps k = 1 is input as the previous time, that is, as an initial value, as in the above equation (12c). It can be expressed using the crank angle θ ₀ and the crank angle rotation speed dθ ₀ / dt. Further, by integrating the equation (12c), the crank angle θ (1) when the number of steps k = 1 can be calculated as the equation (12d).

  Then, when the above processing is repeated until the number of steps k reaches N times, that is, until the crank angle rotation speed reaches dθ (N) / dt = 0, the crank angle rotation speed dθ (N) / dt = 0. , And a crank angle θ (N) are calculated. That is, according to the above processing, the estimated values of the engine speed Ne = 0 when the internal combustion engine 10 is stopped and the crank stop position can be calculated.

[About friction learning]
When the internal combustion engine 10 is automatically stopped, the main factor that causes the crank stop position to deviate from the target stop position may be the influence of friction that is input to the crankshaft 16. Therefore, the engine model 60 of the present embodiment has a configuration that learns friction as appropriate. More specifically, friction learning is performed by the following method.

  FIG. 7 is a diagram for explaining a friction learning method. First, a deviation (hereinafter, may be abbreviated as “rotational speed deviation”) between the actually measured value of the engine rotational speed Ne and the model estimated value is calculated. Then, the PID correction amount calculated by the PID controller 76 as a value obtained by multiplying the rotational speed deviation by a predetermined feedback gain is reflected in the map value of the friction map (see FIG. 4) provided in the engine friction model 64 or the like. I have to.

  FIG. 7 shows how to correct such a friction map. The circles and triangles in FIG. 7 correspond to map values before and after learning at a predetermined engine speed. Further, in FIG. 7, the curve indicated by a broken line passes through each map value before learning, and the curve indicated by a solid line corresponds to each passing through each map value after learning. Yes.

  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).

  In addition, as described above, the engine model 60 considers the difference between the friction and the inertia depending on the engagement state of the clutch, and realizes the adaptive learning control of the crank stop position with high accuracy as described above. A model 64 and a mission friction model 65 are separately provided. When the clutch is engaged when the vehicle is stopped, friction learning is performed using the engine friction model 64 and the mission friction model 65, while the clutch is not engaged when the vehicle is stopped. In some cases, friction learning is performed using only the engine friction model 64.

[Calculation of combustion cut speed]
There is known a method for controlling the engine speed (combustion cut speed) for cutting off the ignition and fuel supply so that the actual crank stop position becomes the target crank stop position when the internal combustion engine is automatically stopped. . In the following specification, the combustion cut speed is also referred to as “ignition cut speed” as appropriate.

FIG. 8 is a block diagram for explaining a method of calculating the combustion cut rotational speed used in the system of the present embodiment. In the present embodiment, as shown in FIG. 8, the ignition cut speed is calculated by the inverse model calculation of the engine model 60. The inverse model calculation is a calculation method for solving the engine model 60 in the opposite direction to the above-described forward model calculation. According to the engine model 60 described above, the target crank stop position (crank angle) of the crankshaft 16 and the initial engine speed (= 0 rotation) are input as initial values, and the engine model 60 is subjected to inverse model calculation, A target ignition cut rotational speed (corresponding to the initial crank angle rotational speed dθ ₀ / dt in the forward model calculation) for making the actual crank stop position the desired target crank stop position can be calculated. Further, according to such a method, it is possible to acquire the ignition cut speed that reflects the influence of friction that is appropriately learned.

  In the present embodiment, the ignition cut speed calculated by the inverse model calculation is corrected according to the magnitude of the stop position error between the estimated value of the crank stop position calculated by the engine model 60 and the actual crank stop position. Like to do. More specifically, as shown in FIG. 8, a new target ignition cut speed is obtained by reflecting the correction amount calculated by the PI control based on the stop position error in the ignition cut speed by the inverse model calculation. Is done.

[About atmospheric pressure learning]
FIG. 9 is a block diagram for explaining an atmospheric pressure learning method using the engine model 60 in the present embodiment. In FIG. 9, a part of the configuration of the engine model 60 shown in FIG. 2 necessary for explaining the atmospheric pressure learning method is extracted and shown in a simplified manner.
When the internal combustion engine 10 is automatically stopped by the eco-run control, as shown in FIG. 9, the motion equation calculation unit 62 around the crankshaft reflects the learning result of the friction map (the engine friction model 64 and the mission friction model 65). An estimate of the angle is calculated. Then, an error (stop position error between the model and the actual measurement) between these estimated values and the actual crank angle is calculated.

  In the present embodiment, the atmospheric pressure correction coefficient is corrected by PI control based on the stop position error. This atmospheric pressure correction coefficient is a coefficient for correcting the atmospheric pressure used for estimating the intake pressure and the in-cylinder pressure.

[Characteristics of this embodiment]
FIG. 10 is a diagram showing the relationship between the amount of deviation of the crank stop position and the atmospheric pressure (elevation). According to the system of the present embodiment described above, the friction learning is appropriately performed according to the difference between the measured value of the crank stop position and the model estimated value. The accuracy of position control can be ensured. However, the crank stop position is greatly influenced by changes in atmospheric pressure in addition to changes in friction. More specifically, as shown in FIG. 10, the larger the change amount of atmospheric pressure (the change amount of altitude), the greater the shift amount of the crank stop position. The reason is that when the atmospheric pressure changes, the pump loss of the internal combustion engine 10 changes. Therefore, if the influence of such atmospheric pressure change (environmental change) is not properly taken into account, erroneous learning of friction may be caused, and the learning accuracy may be deteriorated.

  Therefore, in this embodiment, the timing for learning the influence of friction and the influence of atmospheric pressure is separated. More specifically, after the warm-up of the internal combustion engine 10 and the transmission is completed, the friction learning is first performed, and then the atmospheric pressure learning is performed.

  FIG. 11 is a flowchart of a routine executed by the ECU 50 in the first embodiment to realize the above function. In the routine shown in FIG. 11, it is first determined whether or not the IG switch 58 is ON (step 100). As a result, when the IG switch 58 is ON, the latest ignition cut speed stored in the ECU 50 is acquired (step 102).

1. Complete warm-up completion determination Next, it is determined whether or not the complete warm-up of the vehicle system (engine coolant temperature, engine oil temperature, and mission oil temperature is stable) is completed (step 104). In this step 104, whether or not complete warm-up has been completed is based on the output of the sensors provided with the sensors for detecting the engine coolant temperature, the engine oil temperature, and the like. The determination can be made based on whether the temperature change is within the reference range. In contrast to such a method, a complete warm-up determination method that does not rely on these sensors is used in step 104 and steps 106 to 112 described later.

  Specifically, first, in step 104, the total engine speed, the total intake air amount, the travel distance, and the travel distance after the IG switch 58 is turned on are compared with the respective reference values, and the complete warm-up is completed. Whether or not is completed. If it is determined that the complete warm-up has not been completed based on the information, it is determined whether the complete warm-up has been completed in accordance with the processing in steps 106 to 112.

  FIG. 12 is a graph showing the change in the crank stop position after the vehicle system is started, in relation to the change in the engine oil temperature and the mission (MT) oil temperature. It is. As shown in FIG. 12, after the IG switch 58 is turned ON, the mission oil temperature gradually rises compared to the engine oil temperature, and both temperatures thereafter become stable. In such a warm-up process, the friction changes greatly under the influence of the oil temperature. As a result, as shown in FIG. 12, the amount of change in the crank stop position also changes with the progress of warm-up, and after the warm-up is completed, the crank stop position is stabilized within a predetermined variation range. In the subsequent processing of steps 106 to 112, complete warm-up determination is performed using the characteristics of the change in the crank stop position during such warm-up process.

  That is, first, it is determined whether or not the internal combustion engine 10 has been automatically stopped (step 106). If it is determined in step 106 that the internal combustion engine 10 has not been automatically stopped, the process of step 100 is performed again. On the other hand, if it is determined that the internal combustion engine 10 has been automatically stopped, then Then, it is determined whether or not the clutch signal of the clutch switch 56 is ON (step 108).

  If it is determined in step 108 that the clutch signal is ON, the Δ stop position, which is the amount of change between the previous value and the current value of the actual crank stop position, is determined when the clutch is not engaged. It is determined whether or not it is smaller than a predetermined reference value 1ON to be used (step 110). On the other hand, when it is determined that the clutch signal is OFF, it is determined whether or not the Δ stop position is smaller than a predetermined reference value 1OFF used when the clutch is engaged (step 112). Whether or not it is affected by the friction in the transmission changes depending on whether or not the clutch is engaged when the internal combustion engine 10 is automatically stopped. More specifically, if the clutch is in the disengaged state, the crank stop position is not affected by the mission oil temperature, but only by the engine oil temperature. Therefore, in the above steps 110 and 112, the reference value for determination is varied according to the engagement state of the clutch.

  If the determination in step 110 or 112 is not established, that is, if a large change in the crank stop position is recognized, it is determined that the engine is still warming up. In this case, the process in step 100 is performed again. Return. On the other hand, if the determination in step 110 or 112 is satisfied, that is, if it is recognized that the amount of change in the crank stop position has decreased, the warm-up determination by the method in step 104 is not satisfied. However, it can be determined that the complete warm-up has been completed because the change in the crank stop position is stable. Therefore, in this case, the process proceeds to the next step 114.

2. Friction learning In the routine shown in FIG. 11, the atmospheric pressure is acquired based on the output of the atmospheric pressure sensor 57 (step 114). Next, it is determined whether or not the friction learning (mechanical μ learning) is completed, more specifically, whether or not the μ learning completion flag is ON (step 116).

  If it is determined in step 116 that the friction learning has been completed, it is determined whether or not the internal combustion engine 10 has been automatically stopped (step 118). As a result, if it is determined that the internal combustion engine 10 has automatically stopped, friction learning is executed using the above-described method described with reference to FIG. 7 (step 120). Thus, in this routine, the friction learning is started only after the complete warm-up is completed. Note that, as described above, the friction learning is performed in a state where a friction model corresponding to the engagement state of the clutch is used.

  Next, it is determined whether or not the pressure change ΔP between the current atmospheric pressure acquired in step 114 and the atmospheric pressure at the previous automatic stop is smaller than a predetermined P reference value 1 (step 122). As a result, when ΔP <P reference value 1 is satisfied, that is, when it is recognized that the atmospheric pressure is stable, a counter value for counting the number of times of friction learning is counted up (step 124). On the other hand, when ΔP <P reference value 1 is not established, the friction learning is performed under a situation where the atmospheric pressure is not stable. In this case, the number of times of friction learning is not counted up.

  If the number of times of friction learning is counted up in step 124, it is then determined whether or not the number of times of friction learning (count-up number CU) is greater than N (step 126). As a result, if CU> N times is established, the friction learning is updated (stored) based on the friction learning results for N times so far (step 128). More specifically, the friction maps shown in FIGS. 4 and 5 are updated based on the learning result.

  As described above, when the friction learning is updated, the friction learning completion flag is set to ON (step 130). Next, the ignition cut speed reflecting the latest friction learning is calculated using inverse model calculation (step 132).

3. Atmospheric Pressure Learning In the routine shown in FIG. 11, it is next determined whether or not the internal combustion engine 10 has been automatically stopped (step 134). As a result, when it is determined that the internal combustion engine 10 has been automatically stopped, the atmospheric pressure change ΔP between the current atmospheric pressure acquired in step 114 and the atmospheric pressure at the previous automatic stop is acquired (step 136).

  Next, it is determined whether or not the atmospheric pressure change ΔP is larger than a predetermined P reference value 2 (step 138). As a result, when it is determined that ΔP> P reference value 2 is satisfied, that is, when an atmospheric pressure change larger than P reference value 2 is recognized, the influence of the atmospheric pressure change on the estimation of the crank stop position is learned. The learning value is updated (step 140). The atmospheric pressure learning in step 140 is executed based on the above-described method described with reference to FIG.

4). On the other hand, if it is determined in step 138 that ΔP> reference value P2 is not established, that is, if it is determined that the atmospheric pressure is stable. Next, it is determined whether or not the latest Δ stop position is smaller than a predetermined reference value 2 (step 142). More specifically, the process of step 142 is compared with a reference value (2ON or 2OFF) having a different Δ stop position depending on the engagement state of the clutch. Since this is the same as steps 108 to 112 described above, the description of the flowchart and the description thereof will be simplified here.

  If it is determined in step 142 that Δstop position <reference value 2 is satisfied, the amount of deviation of the crank stop position is reduced under the condition that the friction learning is completed and the atmospheric pressure is stable. Since it can be determined that it is small, the current processing cycle is promptly terminated thereafter.

  On the other hand, if it is determined in step 142 that Δstop position <reference value 2 is not established, that is, the friction learning is completed and the atmospheric pressure is stable. If a shift exceeding the reference value 2 is recognized at the crank stop position, the ignition cut speed adjustment term is then updated (step 144). The adjustment term here refers to the feedback gain of the PI control shown in FIG. 8. More specifically, in this step 144, the target crank stop position is set so that the shift of the crank stop position is eliminated. The control center is corrected by fine adjustment of the feedback gain.

  Next, it is determined whether or not the adjustment term is larger than a reference value FB (step 146). Specifically, in this step 146, it is determined whether or not the correction of the ignition cut speed is within the fine adjustment range. As a result, when it is determined that the adjustment term> the reference value FB is satisfied, that is, in a situation where the friction learning is completed and the atmospheric pressure is stable, in order to eliminate the shift of the crank stop position, When it is recognized that it is necessary to greatly change the ignition cut speed beyond the fine adjustment range, it is determined that the friction learning performed this time was not effective, and the latest friction learning history is discarded (step S1). 148). More specifically, the value of the friction map is returned to the updated value of the previous friction learning.

5. Processing at ON / OFF of IG Switch Also, in the routine shown in FIG. 11, when it is determined in step 100 that the IG switch 58 is not ON, that is, an operation to turn the IG switch 58 from ON to OFF. If it is determined that there has been, the latest friction learning history is discarded (step 150). More specifically, also in this case, the value of the friction map is returned to the updated value of the previous friction learning.

  According to the routine shown in FIG. 11 described above, the friction learning is performed after the complete warm-up is completed, and then the influence of the atmospheric pressure on the crank stop position is learned. By learning the main factors that affect the crank stop position in this order, first, it is possible to avoid erroneous learning of friction changes due to changes in engine oil temperature and mission oil temperature during the warm-up process. be able to. In addition, erroneous learning of friction can be avoided by updating the friction learning value only under the condition where the atmospheric pressure is stable after completion of complete warm-up. Further, after learning the influence of friction, learning about the influence of atmospheric pressure can be performed separately without mixing the influence of friction and the influence of atmospheric pressure. As described above, according to the learning in the above order, even when there is an environmental change (a change in atmospheric pressure), it is possible to satisfactorily ensure the learning accuracy for the main factors that affect the accuracy of the stop position control. .

  Further, according to the above routine, when it is recognized that there has been an operation of turning the IG switch 58 from ON to OFF, the latest friction learning history is discarded. According to such processing, the friction learning value is updated because the N times of friction learning are all performed in one trip (the vehicle travel period from when the IG switch 58 is turned on to when it is turned off thereafter). ) Can be limited only to be performed within. Thus, even when a friction change factor such as oil change occurs during the OFF period of the IG switch 58, it is possible to avoid such a friction change from affecting the accuracy of friction learning. it can.

  Further, according to the above routine, until the complete warm-up is completed, the latest ignition cut speed stored in the ECU 50 is used when the internal combustion engine 10 is automatically stopped. In this case, correction (update) of the ignition cut speed based on the stop position error is prohibited. According to such a process, it is possible to avoid control of the unintended ignition cut speed during the warm-up process in which the crank stop position is not stable, and to ensure controllability of the crank stop position.

  Further, according to the above routine, the friction learning is executed only under a situation where the atmospheric pressure change ΔP is relatively small, that is, only under a situation where the atmospheric pressure change is not affected as much as possible. According to such processing, it is possible to ensure a high degree of friction learning accuracy with respect to changes in atmospheric pressure.

  Further, according to the above routine, the learning value is updated (learning completion determination) only when the number of times of friction learning reaches N, that is, only when the learning frequency exceeds a predetermined value. According to such a process, the learning value that has been made N times can be reflected in the friction map, so that the relearning frequency can be reduced and good learning accuracy can be ensured. .

  Further, according to the above routine, even when the friction learning is completed and the atmospheric pressure is stable, a deviation exceeding the reference value 2 is recognized at the crank stop position. In order to obtain the target crank stop position, the ignition cut speed is corrected in the form of fine adjustment of the feedback gain. According to such processing, the target crank stop position can be finely adjusted, thereby ensuring the accuracy of crank stop position control.

  Further, according to the above routine, the reference value 1 for evaluating the shift amount of the crank stop position during the warm-up process is changed according to the engagement state of the clutch. According to such processing, it is possible to carry out accurate warm-up determination according to the engagement state of the clutch.

  By the way, in the first embodiment described above, the atmospheric pressure sensor 57 is provided. However, as a technique for obtaining the atmospheric pressure by numerical calculation without using such an atmospheric pressure sensor 57, for example, the following A method can be considered. That is, the amount of air and the amount of fuel supplied into the cylinder are calculated by numerical calculation, and the estimated value of the air-fuel ratio is calculated based on these. Then, the atmospheric pressure correction coefficient with respect to the standard atmospheric pressure is calculated by using an error between the estimated value and the actual measured value of the air / fuel ratio by the air / fuel ratio sensor as a deviation of the atmospheric pressure.

  The atmospheric pressure acquired by the numerical calculation as described above is less accurate than the atmospheric pressure detected by the atmospheric pressure sensor 57. For example, in the case of a system that does not include the atmospheric pressure sensor 57 and acquires the atmospheric pressure by the above-described method, the following routine processing shown in FIG. 13 may be executed. The routine shown in FIG. 13 is the same as the routine shown in FIG. 11 described above except that the processing in step 148 is replaced with step 152, and only the difference will be described here.

  That is, in the routine shown in FIG. 13, when it is determined in step 146 that the adjustment term> the reference value FB is satisfied, that is, in a situation where the friction learning is completed and the atmospheric pressure is stable. When a deviation exceeding the reference value 2 is recognized at the crank stop position, in order to eliminate such a deviation of the crank stop position, it is necessary to greatly change the ignition cut speed beyond the fine adjustment range. When it is recognized, only the atmospheric pressure learning value is discarded without discarding the friction learning history (step 152).

  In other words, according to the repair as described above, the friction learning value based on the learning value made N times in advance is the atmospheric pressure acquired by a method with lower accuracy than the atmospheric pressure sensor 57. Emphasis on the atmospheric pressure learning value based on. For this reason, in a system that does not include the atmospheric pressure sensor 57, it is possible to satisfactorily suppress a decrease in learning accuracy.

  Further, in the first embodiment described above, the change amount of the crank stop position when the internal combustion engine 10 automatically stops based on the Δ stop position that is the amount of change between the previous value and the current value of the actual crank stop position. Try to get. However, the change margin of the crank stop position in the present invention is not limited to such a method. For example, the difference between the model estimated value of the crank stop position calculated by the engine model 60 and the actual crank stop position (stop position error). It may be calculated based on the above.

In the first embodiment described above, the engine friction model 64 and the mission friction model 65 correspond to the “friction model” in the first invention. Further, when the ECU 50 calculates the estimated value of the crank stop position by the forward model calculation of the engine model 60, the “crank position estimating means” in the third aspect of the invention executes the processing of the above steps 114 to 132. The “friction learning means” in the first invention executes the processes in steps 134 to 140, and the “atmospheric pressure learning means” in the first invention executes the processes in steps 104 to 112. Thus, the “warm-up determination means” in the first invention realizes the “learning order setting means” in the first invention by executing the processing of each step according to the routine procedure shown in FIG. Yes.
Further, the “system state discriminating means” according to the second aspect of the present invention is realized by the ECU 50 executing the processing of step 100 described above.
Further, the “atmospheric pressure information acquisition means” according to the fourth aspect of the present invention is realized by the ECU 50 executing the process of step 114 described above.
In addition, when the ECU 50 executes the process of step 142, the “stop position change acquisition unit” in the sixth or eighth invention executes the process of step 144, so that “ Each of the “combustion cut speed correction means” is realized.
Further, the “clutch engagement state discriminating means” according to the eighth aspect of the present invention is realized by the ECU 50 executing the processing of step 108.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIGS.
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. 15 described later instead of the routine shown in FIG. It can be realized.

[Features of Embodiment 2]
FIG. 14 is a graph showing the relationship between the friction torque and the friction time of a new internal combustion engine at the time of shipment from the factory. According to the test data shown in FIG. 14, in the initial stage of factory shipment, that is, in the initial stage where the rubbing time after the internal combustion engine is assembled is short, the friction until the sliding part inside the internal combustion engine gets used thereafter. Can be seen to change significantly. In the present embodiment, in order to prevent erroneous learning of the friction, the friction time after the assembly of the internal combustion engine is short, that is, until the operation history of the internal combustion engine becomes longer than a predetermined criterion. Learning was prohibited.

  FIG. 15 is a flowchart of a routine executed by the ECU 50 in the second embodiment to realize the above function. In the routine shown in FIG. 15, it is first determined whether or not the IG switch 58 is ON (step 200). As a result, if the IG switch 58 is ON, the internal combustion engine 10 is automatically stopped. It is determined whether or not it has been performed (step 202).

  If it is determined in step 202 that the internal combustion engine 10 has automatically stopped, the elapsed time from the previous automatic stop point is acquired (step 204). Next, the actual crank stop position when the internal combustion engine 10 is automatically stopped is acquired (step 206).

  Next, it is determined whether or not a predetermined time α has elapsed since the previous automatic stop (step 208). As shown in FIG. 14, the friction change is large until the internal combustion engine 10 is new and exceeds a certain period of use. In such a stage, when comparing the Δ stop position, which is the amount of deviation between the previous value and the current value of the actual crank stop position, if the automatic stop is performed continuously in a relatively short time, the Δ stop The position is a small value. In other words, if the time interval for calculating the Δ stop position is not set appropriately, it is impossible to accurately evaluate whether the period of use of the internal combustion engine 10 is shallow according to the value of the Δ stop position. Therefore, in this routine, the time interval when the Δ stop position is calculated is grasped by the processing of step 208.

  If it is determined in step 208 that the predetermined time α has elapsed, then whether the Δ stop position, which is the amount of change between the previous value and the current value of the actual crank stop position, is smaller than the predetermined reference value 3 or not. Is determined (step 210). More specifically, the processing in step 210 is compared with a reference value (3ON or 3OFF) having a different Δ stop position depending on the clutch engagement state, as in the routine processing shown in FIG. Is done.

  If it is determined in step 210 that Δstop position <reference value 3 is satisfied, that is, if it is determined that the Δ stop position is smaller than the reference value 3 while the predetermined time α has elapsed. Therefore, it is determined that a new article period with a large friction change has passed. In this case, the execution of friction learning is permitted (step 212).

  In the routine shown in FIG. 15, if it is determined in step 202 that the internal combustion engine 10 has not been automatically stopped, then the elapsed time from when the engine is shipped from the factory to the present is acquired ( Step 214). Next, it is determined whether or not the elapsed time is longer than the predetermined time β (step 216). The predetermined time β is set to a time at which it can be determined that a significant friction change when the internal combustion engine 10 is new is settled. Next, if it is determined in step 216 that the elapsed time> predetermined time β is satisfied, the execution of friction learning is permitted (friction learning permission flag ON) (step 212).

  According to the routine shown in FIG. 15 described above, when the internal combustion engine 10 is automatically stopped, paying attention to the characteristic of a large friction change when the internal combustion engine 10 is in a new state, the internal combustion engine 10 It is possible to accurately determine the operation history at the beginning of shipment and to appropriately determine the timing at which the friction learning execution is permitted. Further, even when the internal combustion engine 10 is not automatically stopped, the operation history at the initial shipment of the internal combustion engine 10 is accurately determined based on the elapsed time from the factory shipment, and the friction learning execution is permitted. The timing to do can be determined appropriately. As described above, according to the method of the present embodiment, the friction learning is prohibited under a situation where the operation history of the internal combustion engine 10 is short and a large friction change at the beginning of shipment is assumed. It is possible to prevent the learning effect from being mislearned.

  Incidentally, in the second embodiment described above, a configuration is described in which friction learning is prohibited until the operation history of the internal combustion engine becomes longer than a predetermined criterion. Such a configuration may be combined with the configuration of the first embodiment described above as shown in FIG.

  The routine shown in FIG. 16 is basically a combination of the routine shown in FIG. 11 and the routine shown in FIG. In the routine shown in FIG. 16, when the IG switch 58 is ON (step 100), first, the complete warm-up completion determination (steps 104 to 112) is executed, and then the friction learning permission flag is turned ON. It is determined whether or not (step 218).

  In step 218, if the friction learning permission flag is not ON, it is determined that the internal combustion engine 10 is in a new state with a short use period, and then it is determined whether or not the friction learning may be permitted. Therefore, the processing of steps 202 to 216 of the routine shown in FIG. 15 is executed.

If the friction learning permission flag is ON in step 218, friction learning (steps 114 to 132) is executed. Next, atmospheric pressure learning (steps 134 to 140), or correction of ignition cut speed and determination of the effectiveness of friction learning (steps 142 to 148) are executed.
In addition, when it is recognized that there has been an operation of turning the IG switch 58 from ON to OFF (step 100), the latest friction learning history is discarded as in the case of the routine shown in FIG. Step 150).

  In the second embodiment described above, the “operating history acquisition means” according to the seventh aspect of the present invention is realized by the ECU 50 executing the series of processes in steps 204 to 210 or the processes in steps 214 and 216. Has been.

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 is a diagram showing an example of an engine friction map provided for the engine friction model shown in FIG. 2 to acquire engine friction torque TRQ _{f_EN} . FIG. 3 is a diagram illustrating an example of a mission friction map provided for the mission friction model shown in FIG. 2 to acquire a mission friction torque TRQ _{f_MI} . FIG. 6 is a diagram for explaining a modified technique for obtaining a history of in-cylinder pressure P. It is a figure for demonstrating the technique of friction learning. It is a block diagram for demonstrating the calculation method of the combustion cut rotation speed used in the system of Embodiment 1 of this invention. It is a block diagram for demonstrating the atmospheric pressure learning method using the engine model 60 in Embodiment 1 of this invention. It is the figure which showed the relationship between the deviation | shift amount of a crank stop position, and atmospheric pressure (altitude). It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a figure showing the change of the crank stop position after vehicle system starting by the relationship with the change of an engine oil temperature and a mission (MT) oil temperature. It is a flowchart of the routine performed in the modification of Embodiment 1 of this invention. It is a figure showing the relationship between friction torque and the rubbing time of a new internal combustion engine at the time of factory shipment. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a flowchart of the routine performed in the modification of Embodiment 2 of this 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 56 Clutch switch 57 Atmospheric pressure sensor 58 IG switch 59 Trip meter 60 Engine model 62 Motion equation calculation unit around the crankshaft 64 Engine friction model 65 Mission friction model 66 Intake pressure estimation model 68 In-cylinder pressure estimation model 70 Combustion waveform calculation unit 72 Atmospheric pressure correction term calculation unit 74 Atmospheric temperature correction term calculation unit 76 PID controller
dQ / dθ Heat release rate
dθ / dt Crank angle rotation speed

Claims (8)

A friction model that calculates the friction that is input to the crankshaft of the internal combustion engine;
Crank position estimating means for acquiring an estimated value of the crank stop position based on predetermined parameters including the friction and atmospheric pressure;
Friction learning means for learning the friction model based on crank angle information of the internal combustion engine;
Atmospheric pressure learning means for learning the influence of atmospheric pressure on the crank stop position;
A warm-up determination means for determining whether the warm-up of the vehicle system is completed;
Learning sequence setting means for performing learning of the friction model when it is determined that the warm-up is completed, and performing learning of the atmospheric pressure after it is determined that learning of the friction model is completed;
A stop position control device for an internal combustion engine, comprising: A system state determining means for determining start and stop of the vehicle system;
2. The stop position control device for an internal combustion engine according to claim 1, wherein when it is determined that the vehicle system has stopped, the learning history of the friction model is discarded. The internal combustion engine stop position control device controls a crank stop position by controlling a combustion cut rotational speed for stopping combustion of the internal combustion engine,
3. The stop position control device for an internal combustion engine according to claim 1, wherein, when it is determined that the vehicle system is in a warm-up process, updating of the combustion cut speed is prohibited. It further comprises atmospheric pressure information acquisition means for acquiring atmospheric pressure information,
4. The stop position control device for an internal combustion engine according to claim 1, wherein the friction learning unit performs the learning when it is determined that a change in atmospheric pressure is relatively small. 5.   The stop position control of the internal combustion engine according to any one of claims 1 to 4, wherein the friction learning means updates a learning value when a learning frequency of the friction model exceeds a predetermined value. apparatus. Stop position change acquisition means for acquiring a change margin of the crank stop position;
Combustion cut speed correction means for correcting the combustion cut speed so that the crank stop position becomes a target stop position when the change margin of the crank stop position exceeds a predetermined value;
The stop position control device for an internal combustion engine according to any one of claims 1 to 5, further comprising: It further comprises driving history acquisition means for acquiring a system driving history after the vehicle system is assembled,
2. The stop position control apparatus for an internal combustion engine according to claim 1, wherein the friction learning unit prohibits the learning of the friction model until the system operation history becomes longer than a predetermined determination criterion. Clutch engagement state determining means for determining an engagement state of a clutch disposed between the internal combustion engine and the transmission;
A stop position change acquisition means for acquiring a change amount of the crank stop position;
The warm-up determination means determines whether warm-up is completed based on the change margin of the crank stop position,
2. The internal combustion engine according to claim 1, wherein a determination reference value of the change allowance of the crank stop position used when the warm-up determination unit determines warm-up is set to a different value depending on an engagement state of the clutch. Stop position control device.

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