JP4600377B2 - Stop position control device for internal combustion engine - Google Patents

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

  As a factor that causes the crank stop position to deviate from the target stop position when the internal combustion engine is automatically stopped, the influence of friction that is input to the crankshaft can be considered. Therefore, in order to determine the target 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.

  When the friction increases, the distance (crank angle) from when the combustion is cut to when the crankshaft is completely stopped is shortened. Therefore, when the friction increases, it is necessary to increase the combustion cut rotational speed so that the crank stop position enters the same target stop region as before the friction increase. However, when a change in friction is recognized, the method of uniquely increasing / decreasing the combustion cut rotational speed with respect to the increase / decrease in friction causes the combustion cut rotational speed to reach a predetermined value when the increase in friction increases. A situation exceeding the idle speed range may occur. As a result, when the internal combustion engine automatically stops, it is necessary to greatly increase the engine rotational speed from the idle rotational speed, and good stop feeling is lost.

  The present invention has been made in order to solve the above-described problems, and in an internal combustion engine to which control for automatically stopping and restarting the internal combustion engine is applied, combustion cut rotation in which the influence of friction is reflected. It is an object of the present invention to provide a stop position control device for an internal combustion engine that can appropriately determine the number, thereby ensuring a good stop feeling when the internal combustion engine is automatically stopped.

A first invention is a stop position control device for an internal combustion engine that controls a crank stop position by controlling a combustion cut rotational speed for stopping combustion of the internal combustion engine.
A friction model that calculates the friction that is input to the crankshaft of the internal combustion engine;
Friction learning means for learning the friction model based on crank angle information of the internal combustion engine;
After the learning of the friction model is executed, based on a predetermined parameter including the friction, a target crank stop position is set as an initial value of a crank angle, and a change in engine speed after combustion is cut off In the reverse direction, a rotational speed calculation means for sequentially calculating the engine rotational speed at the crank angle sequentially updated from the initial value;
Within a predetermined rotational speed range that is the same as or close to the idle rotational speed control range, the engine speed calculated by the rotational speed calculation means is determined at a predetermined crank angle. A rotation speed extraction means for extracting a calculation engine rotation speed;
Combustion cut speed determining means for setting the extracted engine speed close to the current combustion cut speed among the extracted engine speeds extracted by the speed extraction means to be the next combustion cut speed;
It is characterized by providing.

In a second aspect based on the first aspect, the combustion cut rotational speed determining means is
A rotational speed determining means for determining whether or not the extracted engine rotational speed extracted by the rotational speed extracting means has passed the current combustion cut rotational speed;
When the passage is recognized, the difference between the extracted engine speed before the passage and the current combustion cut speed, and the difference between the extracted engine speed after the passage and the current combustion cut speed Difference calculating means for calculating,
A smaller one of the two differences is selected, and a value obtained by reflecting the selected difference in the current combustion cut speed is set as the next combustion cut speed.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the combustion cut rotation speed determining means determines that the current combustion cut rotation speed is a current value near the upper limit of the rotation speed range. The extracted engine rotational speed extracted as a value lower than the combustion cut rotational speed is set as the next combustion cut rotational speed.

A fourth aspect of the invention is a stop position control device for an internal combustion engine that controls a crank stop position by controlling a combustion cut rotational speed for stopping combustion of the internal combustion engine.
A friction model that calculates the friction that is input to the crankshaft of the internal combustion engine;
Friction learning means for learning the friction model based on crank angle information of the internal combustion engine;
After the learning of the friction model is executed, based on a predetermined parameter including the friction, a target crank stop position is set as an initial value of a crank angle, and a change in engine speed after combustion is cut off In a reverse direction, a rotation speed calculation means for sequentially calculating an engine rotation speed at a crank angle that is sequentially updated from the initial value;
A rotation speed extraction means for extracting a calculation engine rotation speed at a predetermined crank angle from the calculation engine rotation speed calculated by the rotation speed calculation means;
A rotational speed determination means for determining whether or not the extracted engine rotational speed extracted by the rotational speed extraction means is within a predetermined combustion cut rotational speed range;
When it is determined that the extracted engine speed is not within the combustion cut speed range, the extracted engine speed is determined based on the relationship between the actual crank stop position and the actual combustion cut speed. A correction amount calculating means for calculating a correction amount to be given to the extraction engine speed so as to be a value within the range;
Combustion cut speed determination means for setting the extracted engine speed corrected based on the correction amount as the next combustion cut speed;
It is characterized by providing.

According to a fifth aspect of the present invention based on the fourth aspect, the correction amount calculating means calculates the change in the combustion cut speed corresponding to a predetermined crank angle width as the actual crank angle and the actual combustion cut speed. Calculated as the correction amount based on the relationship,
The crank angle width is a change amount necessary for changing a crank angle corresponding to a target stop region of a piston included in one cylinder to a crank angle corresponding to a target stop region of a piston included in another cylinder. It is characterized by that.

  According to the first invention, the combustion cut rotational speed is converged to a value within a desired rotational speed range based on the extracted engine rotational speed extracted from the arithmetic engine rotational speed reflecting the friction learning result. Can do. For this reason, according to the present invention, when the internal combustion engine is automatically stopped from the idling state, it is not necessary to greatly increase the idling speed, and a good stop feeling can be ensured. This makes it possible to achieve both controllability of the crank stop position and ensuring drivability of the internal combustion engine.

  According to the second invention, based on the selected difference, the extraction engine speed closest to the current combustion cut speed can be set as the next combustion cut speed, thereby the combustion cut speed. Can be converged to a value within a desired rotational speed range.

  According to the third aspect of the invention, when the current ignition cut speed is a value near the upper limit value of the speed range, it is possible to avoid correcting the combustion cut speed to a larger value. For this reason, when the internal combustion engine is automatically stopped from the idling state, it is possible to prevent the idling speed from greatly increasing.

  According to the fourth invention, by using the correction amount that utilizes the relationship between the actual crank stop position and the actual combustion cut rotation speed, while reducing the number of calculation of the calculation engine speed that reflects the friction learning result, The combustion cut rotational speed can be converged to a value within a desired combustion cut rotational speed range. According to the present invention, when the internal combustion engine is automatically stopped from the idling state, it is not necessary to greatly increase the idling speed, and a good stop feeling can be ensured. This makes it possible to achieve both controllability of the crank stop position and ensuring drivability of the internal combustion engine.

  According to the fifth aspect of the present invention, when the extraction engine speed that allows a piston included in one cylinder to be put in the target stop region can be acquired, a piston provided in another cylinder can be put in the target stop region. The correction of the extracted engine speed is corrected so that the extracted engine speed becomes a value within the desired combustion cut speed range, and the calculation of the calculation engine speed reflecting the friction learning result is continued. It can be executed without necessity, that is, without increasing the calculation load.

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 and the like for detecting the engagement state of a clutch (not shown) provided between the transmission (not shown) and the like are connected. 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. . 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, 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. Motion equation calculating section 62 around the crankshaft, receives 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, at the time of operation start, further, the initial crank angle theta ₀ and an 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 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. 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) starts to increase, the influence of the maximum static friction coefficient is reduced, so it temporarily 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 shown. Depending on the piston speed (dXi / dt). Further, in the region where the piston speed (dXi / dt) in FIG. 4 (B) 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.

(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.

[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 (13) and (14). 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) and discretizing the equation (4e), the following equation (13) is obtained.

上記（１４ａ）式中のクランク角度θ(k)の一部を対応するクランク角回転速度dθ(k)/dtに書き直すと、上記（１４ｂ）式のように表すことができる。そして、その（１４ｂ）式を展開すると、ステップ数k＝1のときのクランク角回転速度dθ(1)/dtは、上記（１４ｃ）式のように、前回、すなわち、初期値として入力されたクランク角度θ₀およびクランク角回転速度dθ₀/dtを用いて表すことができる。更に、上記（１４ｃ）式を積分することにより、ステップ数k＝1のときのクランク角度θ(1)を、上記（１４ｄ）式のように算出することができる。 Then, as described above, the crank angle θ ₀ , the crank angle rotation speed dθ ₀ / dt, and the like are given as the initial calculation values of the forward model calculation according to the above equation (13). 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 (13), it can be expressed as the following equation (14a).

When a part of the crank angle θ (k) in the above equation (14a) is rewritten to the corresponding crank angle rotation speed dθ (k) / dt, it can be expressed as the above equation (14b). When the equation (14b) 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 (14c). It can be expressed using the crank angle θ ₀ and the crank angle rotation speed dθ ₀ / dt. Further, by integrating the equation (14c), the crank angle θ (1) when the number of steps k = 1 can be calculated as the equation (14d).

  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, a 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 for appropriately learning the friction. 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 present specification, the combustion cut speed is also referred to as “ignition cut speed” as appropriate.

According to the engine model 60 described above, the target crank stop position (crank angle) of the crankshaft 16 and the engine speed at the time of stop (= 0 rotation) are input as initial values, and the engine model 60 is subjected to the forward model calculation described above. (Inverse model calculation), the target ignition cut speed for making the actual crank stop position the desired target crank stop position (the initial crank angle rotation speed dθ _{0 in} the case of forward model calculation) / corresponding to / dt) can be calculated. Further, according to such a method, it is possible to acquire the target ignition cut speed that reflects the influence of friction that is appropriately learned.

[Characteristics of this embodiment]
FIG. 8 is a diagram showing the relationship between the distance (crank angle) from when the ignition is cut to when the internal combustion engine 10 is automatically stopped until the crankshaft is completely stopped, and the friction variation (increase). FIG. 9 is a diagram showing the relationship between the distance to the stop and the ignition cut speed.

  When the friction increases, as shown in FIG. 8, the distance (crank angle) from when the ignition is cut until the crankshaft is completely stopped is shortened. Further, the higher the ignition cut speed, the longer the distance to the stop. Therefore, when the friction increases, it is necessary to increase the ignition cut speed so that the actual crank stop position enters the same target stop region as before the friction increase. On the other hand, when the friction decreases, it is necessary to lower the ignition cut speed. If there is no restriction on the value of the ignition cut speed, it can be said that there is no problem with such a method.

  However, during the eco-run control, the internal combustion engine 10 is normally automatically stopped from the idle state. For this reason, when a change in friction is recognized, the method of uniquely increasing / decreasing the ignition cut speed as described above with respect to the increase / decrease of the friction causes the ignition cut when the increase in the friction increases. A situation may occur in which the rotational speed exceeds a predetermined idle rotational speed region. As a result, when the internal combustion engine automatically stops, it is necessary to greatly increase the engine speed from the idle speed. As a result, the idling speed becomes unstable, and a good stop feeling is lost.

  Therefore, in the present embodiment, when it is recognized that the shift of the crank stop position due to the change in friction has occurred, after the friction learning is appropriately performed, the stop feeling during the automatic stop of the internal combustion engine 10 is improved. In order to keep the ignition cut speed within an idle speed control range that can be secured (the predetermined speed range in the first and third inventions), the next time according to the technique shown with reference to FIG. Changed the ignition cut speed. In this embodiment, the idle speed control range is set to 700 rpm to 800 rpm as an example, but such a numerical range varies depending on the specifications of the internal combustion engine, and is limited to such a numerical range. Is not to be done.

  FIG. 10 is a diagram for explaining a characteristic method used for determining the ignition cut speed in the present embodiment. More specifically, FIG. 10 (A) is a diagram showing the time change of the crank angle when the internal combustion engine 10 is automatically stopped (corresponding to the model calculation crank angle at the time of inverse model calculation). FIG. 10B is a diagram showing the change over time of the engine speed when the internal combustion engine 10 is automatically stopped (also corresponding to the model calculation engine speed at the time of inverse model calculation). Note that the periodic change in the crank angle shown in FIG. 10 (A) is a simplified version of the actual one with a finer period from the viewpoint of easy understanding.

  In the technique shown in FIG. 10, the ignition cut speed after friction learning is calculated by inverse model calculation. In FIG. 10, an arrow showing the direction opposite to the time axis indicates the calculation direction of such inverse model calculation. The forward model calculation of the engine model 60 described above performs ignition cut determination (in terms of crank angle, 90 ° CA (90 ° ATDC) after compression top dead center in the ignition cut start cylinder) when the internal combustion period 10 is automatically stopped. Started after implementation. The internal combustion engine 10 is a four-cylinder engine, and the crank angle phase difference between the cylinders is 180 ° CA. Accordingly, the crank angle at the time of execution of the ignition cut determination in each cylinder is 90, 270, 450, 630 (° with the compression top dead center of a certain cylinder being 0 ° CA, as shown in FIG. CA).

  In the method shown in FIG. 10A, the crank angle (90, 270, 450, 630 (°) at the time of ignition cut determination in each cylinder is selected from the “model calculation engine speed” calculated by the inverse model calculation. CA) (see crank angle indicated by white circle in FIG. 10A)) is extracted and acquired as “model extraction engine speed” (see crank angle indicated by white circle in FIG. 10B). I did it.

  Then, when the model extraction engine speed extracted in this way is within a predetermined idle speed control range (700 rpm to 800 rpm), the model extraction engine speed close to the current ignition cut speed is set next time. The ignition cut speed was determined as follows. More specifically, when the model extraction engine speed has passed the current ignition cut speed, the difference between each model extraction engine speed before and after the passage and the current ignition cut speed is calculated, The smaller absolute value of these differences was selected, and the selected difference was added to the current ignition cut speed to obtain the next ignition cut speed.

FIG. 11 is a flowchart of a routine executed by the ECU 50 in the first embodiment to realize the above function. It is assumed that this routine is started after the friction learning is executed.
In the routine shown in FIG. 11, first, 1000 rpm is given as an initial value of the difference dlt2, which is the difference between the model extraction engine speed and the current ignition cut speed (step 100).

  Next, the inverse model calculation is started (step 102). As described above with reference to FIG. 10, the inverse model calculation is performed with the crank angle θ at the target stop position as an initial value. When the inverse model calculation is started, it is then determined whether or not the calculated model calculation engine speed is greater than 700 rpm (step 104). As a result, when it is determined that the model calculation engine speed has not yet reached 700 rpm, the crank angle previously calculated by the inverse model calculation is replaced with the crank angle calculated this time (step 106). ), The inverse model calculation is repeatedly executed.

  On the other hand, if it is determined in step 104 that the model calculation engine speed has exceeded 700 rpm, then the previous model calculation crank angle is greater than any of 90, 270, 450, and 630 (° CA). In addition, it is determined whether or not the current model calculation crank angle is smaller than any one of those 90, 270, 450, and 630 (° CA) (step 108). According to such discrimination processing, whether the model calculation crank angle has passed 90, 270, 450, or 630 (° CA) during the change from the previous value to the current value, that is, each cylinder It is possible to determine whether or not the crank angle at the time of execution of the ignition cut determination at is passed.

  Until the determination in step 108 is established, the inverse model calculation is repeatedly executed while the model calculation crank angle is updated in step 106. On the other hand, if the determination in step 108 is established, it is then determined whether or not the current model calculation engine speed (= model extraction engine speed) is smaller than the current ignition cut speed (step 110). ).

  As a result, when it is determined that the current model extraction engine speed <the current ignition cut speed is satisfied, that is, it is recognized that the engine speed calculated by the inverse model has not yet reached the current ignition cut speed. In this case, the difference between the current model extraction engine speed and the current ignition cut speed is stored in the difference dlt1 (step 112). The difference dlt1 is a negative value. Next, it is determined whether or not the current model calculation engine speed is greater than 800 rpm (step 114). As a result, if the model calculation engine speed is 800 rpm or less, the inverse model calculation is repeatedly executed while the model calculation crank angle is updated in step 106.

  On the other hand, if it is determined in step 110 that the current model calculation engine speed <the current ignition cut speed is not satisfied, that is, the engine speed calculated in the reverse model passes the current ignition cut speed. If it is determined that the difference has occurred, the difference between the current model extraction engine speed and the current ignition cut speed is stored in the difference dlt2 (step 116). The difference dlt2 is a positive value.

  Next, in the routine shown in FIG. 11, if the determination in step 114 is established, or if the difference dlt2 is calculated in step 116, the absolute value of each of the differences dlt1 and dlt2 Is selected as a correction amount edlt_igtcutref for the current ignition cut speed (step 118). Then, the next ignition cut speed is calculated by adding the correction amount edlt_igtcutref to the current ignition cut speed (step 120).

  The case where the model calculation engine speed sequentially calculated by the inverse model calculation passes (strides) the current ignition cut speed is the case where the process proceeds to step 118 via step 116. On the other hand, if the current ignition cut speed slightly exceeds 800 rpm, the process may proceed to step 118 without calculating the difference dlt2 in step 116. In this routine, a sufficiently large initial value of, for example, 1000 rpm is given to the difference dlt2 in step 100 above. For this reason, when the current ignition cut speed is over 800 rpm which is the upper limit value of the target idle speed control range, it is possible to avoid the ignition cut speed being corrected to a larger value.

  According to the routine shown in FIG. 11 described above, the model calculation engine speed that is a candidate for the next ignition cut speed is extracted at a predetermined crank angle (90 ° CA, etc.) by inverse model calculation. Only when the engine speed calculated by the inverse model is between 700 and 800 rpm, the differences dlt1 and dlt2 that are correction amounts of the current ignition cut speed are calculated. Then, within such a rotational speed range, the model calculation engine rotational speed closest to the current ignition cut rotational speed is selected as the next ignition cut rotational speed. Further, according to the above routine, when the current ignition cut rotational speed has already slightly exceeded the upper limit value, it is possible to avoid correcting the ignition cut rotational speed to a larger value.

  For this reason, according to the method of the present embodiment, the calculated correction amount edlt_igtcutref is limited, and the ignition cut speed can be converged to a value within a desired idle speed control range. When the internal combustion engine 10 is automatically stopped, it is not necessary to greatly increase the idle rotation speed, and a good stop feeling can be ensured. Thereby, both controllability of the crank stop position and securing of drivability of the internal combustion engine 10 can be achieved.

  By the way, in Embodiment 1 mentioned above, although the predetermined rotation speed range (700-800 rpm) which restrict | limits correction | amendment of ignition cut rotation speed is demonstrated as an idle rotation speed control range, the rotation speed range in this invention is demonstrated. May not necessarily be the same as the idle speed control range, but may be a range in the vicinity thereof.

  Further, in the routine of FIG. 11 in the above-described first embodiment, a large value is given in advance to the initial value of the difference dlt2, so that the current ignition cut speed is the upper limit value of the target idle speed control range. When the rotation speed exceeds 800 rpm, the difference dlt1 for correcting the ignition cut rotational speed to the lower side is easily selected. However, the present invention is not limited to such a method, and even if the current ignition cut speed does not exceed the upper limit value, similarly, if the upper limit value is close to the upper limit value, the ignition is similarly performed. In order to avoid the correction of the cut rotation speed to a larger value, a process for urging the correction to the side where the ignition cut rotation speed is lowered may be performed.

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 executes the friction learning according to the method shown in FIG. 7, the “friction learning means” in the first invention repeatedly executes the processes of the steps 102 and 106 to thereby execute the first invention. The “revolution number calculating means” in the first embodiment executes the process of step 108, so that the “revolution number extracting means” in the first aspect of the invention executes the processes of steps 110 to 120. The “combustion cut rotational speed determination means” in FIG.
Further, when the ECU 50 executes the process of step 110 described above, the “rotational speed discriminating means” in the second invention executes the processes of steps 112 and 116 described above, thereby executing “difference calculation” in the second invention. Each means is realized.

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. 14 described later instead of the routine shown in FIG. It can be realized.

[Features of Embodiment 2]
In the first embodiment described above, until the model calculation (extraction) engine speed by the inverse model calculation passes the current ignition cut speed, or if it does not pass, the model calculation (extraction) engine speed Until it reaches 800rpm, the inverse model calculation is repeated sequentially. According to such a method, it is possible to correct the ignition cut speed to a value within a desired idle speed control range while reflecting friction learning. However, such an inverse model calculation has a high calculation load on the ECU 50. The system of this embodiment is intended to correct the ignition cut speed to a value within a desired combustion cut speed range after friction learning is performed while reducing the calculation load of the ECU 50.
In the present embodiment, the “combustion cut rotational speed range” is defined as a rotational speed range narrower than the idle rotational speed control range (700 to 800 rpm) (720 to 780 rpm in the example of the present embodiment). I decided to. Further, the combustion cut rotational speed range varies depending on the specifications of the internal combustion engine, and is not limited to the numerical range such as 720 to 780 rpm.

  Specifically, in this embodiment, when the model extraction engine rotational speed is acquired at a rotational speed higher than 700 rpm, the inverse model calculation with a high calculation load is terminated at that time. When the model extraction engine speed falls within the desired combustion cut speed range (720 to 780 rpm), the model extraction engine speed is used as it is as the next ignition cut speed. When the model extraction engine speed is 700 to 720 rpm or more than 780 rpm, the current ignition cut is performed by a method using the relationship shown in FIGS. 12 and 13 (see step 206 in FIG. 14). The rotation speed was corrected.

  FIG. 12 is a view showing a target stop region of the crankshaft 16 (piston 12 of each cylinder). There is a region at the crank stop position that is desirable for satisfactorily restarting the internal combustion engine 10 when the eco-run control is executed. The target stop area hatched in FIG. 12 corresponds to such an area. More specifically, a region 1 where the crank angle corresponding to the piston stop position of a certain cylinder is from the intake top dead center (0 ° ATDC) to a little less than 90 ° ATDC corresponds to the target stop region, and 4 equal explosions. In the internal combustion engine 10 which is a cylinder engine, the target stop region of the piston 12 in the other cylinders is also obtained in the region 2 which is reversed by 180 ° CA obtained by dividing 720 ° CA by the number of cylinders 4 with respect to the region 1. It corresponds to.

  FIG. 13 is a diagram showing the relationship between the actual crank stop position and the actual ignition cut speed. FIG. 13 is a plot of 10 points of actual crank stop position and actual ignition cut speed data as an example. There is a correlation between them, and it can be approximated by a single straight line as shown in FIG. Here, the inclination of the approximate straight line is referred to as “dlt_hosei”. According to the relationship shown in FIG. 13, it is possible to calculate the correction amount of the ignition cut speed necessary for shifting the crank stop position by a desired crank angle width. Note that the relationship shown in FIG. 13 indicates that when forward model calculation is performed, the relationship between the actual ignition cut speed at which ignition was actually cut and the actual crank stop position at that time is N times (here 10 times). It can be obtained only by storing it as a map in the ECU 50. In addition, since the slope dlt_hosei changes when the friction changes, the slope dlt_hosei is updated at any time with the latest data using the ignition cut speed reflecting the learning result of the friction. .

  FIG. 14 is a flowchart of a routine executed by the ECU 50 in the second embodiment to realize the above object. In FIG. 14, the same steps as those shown in FIG. 11 in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 14, in step 108, the previous model calculation crank angle is larger than any of 90, 270, 450, and 630 (° CA), and the current model calculation crank angle is those 90, 270. , 450, and 630 (° CA), the difference between the current model calculation (extraction) engine speed and the current ignition cut speed is immediately stored in the difference dlt. (Step 200).

  Next, it is determined whether or not the current model extraction engine speed is higher than 720 rpm and lower than 780 rpm (step 202). As a result, when it is determined that 720 <model extraction engine speed <780 is established, that is, when it is confirmed that the model extraction engine speed calculated this time is within the target combustion cut speed range In this case, the current model extraction engine speed is set as the next ignition cut speed (step 204).

On the other hand, if it is determined in step 202 that 720 <model extraction engine speed <780 is not satisfied, that is, the model extraction engine speed is in the range of 700 to 720 rpm, or is 780 rpm or more. Is recognized, the correction amount edlt_igtcutref to the current ignition cut speed is calculated by the following equation.
edlt_igtcutref = dlt + dlt_hosei × 180 (1)
The coefficient dlt_hosei in the above equation (1) is stored as a map in the ECU 50 as described above. The coefficient 180 in the above equation (1) means the crank angle width.

  According to the above equation (1), the correction amount edlt_igtcutref is calculated as a value obtained by adding the difference dlt calculated in step 200 to the engine speed corresponding to the crank angle width of 180 ° CA. More specifically, when the model extraction engine speed is 700 to 720 rpm, the correction amount edlt_igtcutref is corrected to a value shifted by 180 ° CA in the crank angle toward the higher ignition cut speed, When the model extraction engine rotational speed is 780 rpm or more, the value is corrected to a value shifted by 180 ° CA in the crank angle toward the side where the ignition cut rotational speed becomes lower. According to such a method, when the model extraction engine speed obtained through the inverse model calculation is close to the upper and lower limit values of the desired idle speed control range (700 to 800 rpm), the crank angle width is 180 ° CA. By giving the model extraction engine speed a correction amount edlt_igtcutref that gives an inverted piston stop position, it is not necessary to continue the inverse model calculation with a high computational load, and the target engine cuts off the target model extraction engine speed. It can correct | amend so that it may enter into rotation speed range (720-780rpm).

  Next, the next ignition cut rotational speed is calculated by adding the correction amount edlt_igtcutref to the current ignition cut rotational speed (step 120).

  According to the routine shown in FIG. 14 described above, if the model extraction engine speed is acquired as an engine speed higher than 700 rpm, the next ignition is performed without continuing the inverse model calculation with a high calculation load. The cutting speed is determined. That is, according to the processing of the above routine, when the model extraction engine speed obtained by the inverse model calculation is within the desired combustion cut speed range (720 to 780 rpm), the acquired model extraction engine speed is It is used as it is as the next ignition cut speed. Then, when the acquired model extraction engine speed is close to the upper and lower limits of the speed range, the current ignition cut speed is corrected so as to fall within the combustion cut speed range according to the relationship shown in FIG. .

  For this reason, according to the system of the present embodiment, the ignition cut speed can be converged to a value within the desired combustion cut speed range after the friction learning is performed while reducing the calculation load of the ECU 50. As a result, not only during the engine automatic stop with a low operation rate of the ECU 50, but before starting the ignition cut by the eco-run control, the inverse model calculation is performed to calculate a new ignition cut rotational speed reflecting the friction learning result. It can be made easy.

  By the way, in Embodiment 2 mentioned above, when the model extraction engine speed acquired through the inverse model calculation is close to the upper and lower limit values of a desired idle speed control range (700 to 800 rpm), the crank angle width is 180 °. A correction amount edlt_igtcutref that gives a piston stop position inverted by CA is given to the model extraction engine speed. However, in the present invention, based on the relationship between the actual crank angle and the actual combustion cut speed, the crank angle width used for calculating the correction amount so that the extracted engine speed becomes a value within the combustion cut speed range. Is a change amount necessary for changing the crank angle corresponding to the target stop region of the piston included in one cylinder to the crank angle corresponding to the target stop region of the piston included in the other cylinder. In the case of the engine 10, it is not limited to 180 ° CA, and may be a multiple of 180 °. The internal combustion engine that is the subject of the present invention is not limited to a four-cylinder engine. Therefore, for example, in the case of an equal explosion multi-cylinder internal combustion engine, the crank angle width used for calculating such a correction amount is a multiple of a value obtained by dividing 720 ° CA by the number of cylinders of the internal combustion engine. It is good.

  In the second embodiment, the engine friction model 64 and the mission friction model 65 correspond to the “friction model” in the fourth aspect of the invention. Further, when the ECU 50 executes the friction learning according to the method shown in FIG. 7, the “friction learning means” in the fourth invention repeatedly executes the processes of the steps 102 and 106 to thereby execute the fourth invention. The “revolution number calculation means” in the above-mentioned step 108 executes the process of step 108, and the “revolution number extraction means” in the fourth aspect of the invention executes the process of step 202. When the "rotational speed discriminating means" executes the process of step 206, the "correction amount calculating means" according to the fourth aspect of the invention executes the process of step 120, thereby causing the "combustion cut" according to the fourth aspect of the invention. "Rotational speed determination means" is realized respectively.

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 figure showing the relationship between the distance (crank angle) from the time when ignition is cut to the time when the crankshaft is completely stopped during the automatic stop of the internal combustion engine, and the variation allowance (increase allowance). It is a figure showing the relation between the distance (crank angle) from the time when ignition is cut to the time when the crankshaft is completely stopped and the ignition cut speed when the internal combustion engine is automatically stopped. It is a figure for demonstrating the characteristic method used for determination of the ignition cut rotation speed in Embodiment 1 of this invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is the figure which showed the target stop area | region of a crankshaft (piston of each cylinder). It is a figure showing the relationship between a real crank stop position and a real ignition cut rotation speed. It is a flowchart of the routine performed in 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 60 Engine model 62 Motion equation calculation unit around 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 Ambient temperature correction term calculation unit 76 PID controller
dQ / dθ Heat release rate
dθ / dt Crank angle rotation speed

Claims (5)

A stop position control device for an internal combustion engine for controlling a crank stop position by controlling a combustion cut rotational speed for stopping combustion of the internal combustion engine,
A friction model that calculates the friction that is input to the crankshaft of the internal combustion engine;
Friction learning means for learning the friction model based on crank angle information of the internal combustion engine;
After the learning of the friction model is executed, based on a predetermined parameter including the friction, a target crank stop position is set as an initial value of a crank angle, and a change in engine speed after combustion is cut off In the reverse direction, a rotational speed calculation means for sequentially calculating the engine rotational speed at the crank angle sequentially updated from the initial value;
Within a predetermined rotational speed range that is the same as or close to the idle rotational speed control range, the engine speed calculated by the rotational speed calculation means is determined at a predetermined crank angle. A rotation speed extraction means for extracting a calculation engine rotation speed;
Combustion cut speed determining means for setting the extracted engine speed close to the current combustion cut speed among the extracted engine speeds extracted by the speed extraction means to be the next combustion cut speed;
A stop position control device for an internal combustion engine, comprising: The combustion cut rotational speed determining means is
A rotational speed determining means for determining whether or not the extracted engine rotational speed extracted by the rotational speed extracting means has passed the current combustion cut rotational speed;
When the passage is recognized, the difference between the extracted engine speed before the passage and the current combustion cut speed, and the difference between the extracted engine speed after the passage and the current combustion cut speed Difference calculating means for calculating,
The smaller one of the two differences is selected, and a value obtained by reflecting the selected difference in the current combustion cut speed is set as the next combustion cut speed. A stop position control device for an internal combustion engine.   When the current combustion cut rotation speed is a value near the upper limit of the rotation speed range, the combustion cut rotation speed determination means determines the extracted engine rotation speed extracted as a value lower than the current combustion cut rotation speed. The stop position control device for an internal combustion engine according to claim 1 or 2, wherein the next combustion cut rotational speed is used. A stop position control device for an internal combustion engine for controlling a crank stop position by controlling a combustion cut rotational speed for stopping combustion of the internal combustion engine,
A friction model that calculates the friction that is input to the crankshaft of the internal combustion engine;
Friction learning means for learning the friction model based on crank angle information of the internal combustion engine;
After the learning of the friction model is executed, based on a predetermined parameter including the friction, a target crank stop position is set as an initial value of a crank angle, and a change in engine speed after combustion is cut off In the reverse direction, a rotational speed calculation means for sequentially calculating the engine rotational speed at the crank angle sequentially updated from the initial value;
A rotation speed extraction means for extracting a calculation engine rotation speed at a predetermined crank angle from the calculation engine rotation speed calculated by the rotation speed calculation means;
A rotational speed determining means for determining whether or not the extracted engine rotational speed extracted by the rotational speed extracting means is within a predetermined combustion cut rotational speed range;
When it is determined that the extracted engine speed is not within the combustion cut speed range, the extracted engine speed is determined based on the relationship between the actual crank stop position and the actual combustion cut speed. Correction amount calculating means for calculating a correction amount to be given to the extraction engine speed so as to be a value within the range;
Combustion cut speed determining means for setting the extracted engine speed corrected based on the correction amount as the next combustion cut speed;
A stop position control device for an internal combustion engine, comprising: The correction amount calculating means calculates a change in the combustion cut speed corresponding to a predetermined crank angle width as the correction amount based on the relationship between the actual crank angle and the actual combustion cut speed. There,
The crank angle width is a change amount necessary for changing a crank angle corresponding to a target stop region of a piston included in one cylinder to a crank angle corresponding to a target stop region of a piston included in another cylinder. The stop position control device for an internal combustion engine according to claim 4, wherein

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