JP4788640B2 - In-cylinder pressure estimation method and cylinder pressure estimation apparatus for internal combustion engine - Google Patents

Description

  The present invention relates to an in-cylinder pressure estimation method and an in-cylinder pressure estimation apparatus for an internal combustion engine.

  Japanese Patent Application Laid-Open No. 2004-245173 obtains in-cylinder pressure and unburned gas temperature at a reference crank angle set at a predetermined crank position after compression top dead center from operating conditions of a spark ignition type engine. A technique for calculating a knocking index value using an internal pressure and an unburned gas temperature is disclosed.

JP 2004-245173 A JP 2005-233110 A

  In the above prior art, the in-cylinder pressure at the reference crank angle is estimated from the operating conditions. However, with this method, it is difficult to accurately estimate the in-cylinder pressure.

  In recent years, in order to realize, for example, fuel property detection, misfire detection, control based on the in-cylinder state quantity (combustion ratio, etc.), a request to accurately obtain the in-cylinder pressure with a fine crank angle step size. There is.

  However, the measurement increment of the crank angle sensor is usually as coarse as 10 degrees or 30 degrees. In addition, the crank angle sensor is also noisy due to the influence of individual differences in sensor characteristics, individual differences in rotor dimensions, and the like. For this reason, it is difficult to accurately obtain the in-cylinder pressure with fine crank angle increments.

  Further, since the in-cylinder pressure sensor is expensive, there is a demand to obtain the in-cylinder pressure without installing the in-cylinder pressure sensor if possible.

  The present invention has been made to solve the above-described problems, and provides an in-cylinder pressure estimation method and an in-cylinder pressure estimation device for an internal combustion engine capable of accurately obtaining an in-cylinder pressure estimation value with fine crank angle increments. For the purpose.

In order to achieve the above object, a first invention is a method for estimating an in-cylinder pressure of an internal combustion engine,
In-cylinder pressure acquisition step of acquiring a plurality of in-cylinder pressures between the intake valve closing timing and the exhaust valve opening timing of the internal combustion engine;
Based on the in-cylinder pressure acquired in the in-cylinder pressure acquisition step, a parameter determination step for determining a plurality of undetermined parameters included in the model formula representing the relationship between the in-cylinder heat generation pattern and the in-cylinder pressure;
An in-cylinder pressure estimating step for calculating an in-cylinder pressure estimated value at a predetermined crank angle based on the model formula into which the parameter determined in the parameter determining step is substituted;
It is characterized by providing.

The second invention is the first invention, wherein
The model formula is based on the Wiebe function,
Wherein the plurality of parameters, the shape parameter m, the efficiency parameter k, characterized to include combustion period theta _p and thermogenesis start crank angle theta _b.

The third invention is the first or second invention, wherein
The in-cylinder pressure acquisition step includes:
A crank angular speed acquisition step for acquiring the crank angular speed;
A mechanical loss torque calculating step for calculating a mechanical loss torque generated by the mechanical loss of the internal combustion engine;
An inertial mass torque calculating step for calculating an inertial mass torque generated by the moving member of the internal combustion engine;
An in-cylinder pressure torque calculating step for calculating an in-cylinder pressure torque generated by an in-cylinder pressure based on the crank angular velocity, the mechanical loss torque, and the inertia mass torque;
An in-cylinder volume change rate calculating step for calculating an in-cylinder volume change rate;
An in-cylinder pressure calculating step of calculating an in-cylinder pressure from the in-cylinder pressure torque and the in-cylinder volume change rate;
It is characterized by including.

According to a fourth invention, in any one of the first to third inventions,
The internal combustion engine includes a crank angle sensor that detects a crank angle,
In the in-cylinder pressure obtaining step, the in-cylinder pressure is obtained for each measurement step of the crank angle sensor.

According to a fifth invention, in any one of the first to fourth inventions,
The internal combustion engine has a plurality of cylinders,
The in-cylinder pressure acquisition step includes:
A crank angular speed acquisition step for acquiring the crank angular speed;
A mechanical loss torque calculating step for calculating a mechanical loss torque generated by the mechanical loss of the internal combustion engine;
An inertial mass torque calculating step for calculating an inertial mass torque generated by the moving member of the internal combustion engine;
All-cylinder in-cylinder pressure torque calculating step for calculating all-cylinder in-cylinder pressure torque generated by the in-cylinder pressure of all cylinders based on the crank angular velocity, the mechanical loss torque, and the inertia mass torque;
An in-cylinder volume change rate calculating step for calculating an in-cylinder volume change rate of each cylinder;
A cylinder-specific cylinder pressure calculation step for calculating a cylinder-specific cylinder pressure from the all-cylinder cylinder pressure torque and the cylinder volume change rate of each cylinder;
Including
In the parameter determining step, the undetermined parameter is determined for each cylinder based on the cylinder internal pressure.
In the in-cylinder pressure estimating step, an estimated in-cylinder pressure value at a predetermined crank angle is calculated for each cylinder based on the model formula for each cylinder into which the parameter determined for each cylinder is substituted.

The sixth invention is the fifth invention, wherein
The cylinder-by-cylinder internal pressure calculation step calculates the cylinder-by-cylinder internal pressure based on the assumption that the cylinder-by-cylinder internal pressure does not change for a predetermined time.

The seventh invention is the fifth invention, wherein
The internal combustion engine includes a crank angle sensor that detects a crank angle,
The crank angular velocity acquisition step includes a post-interpolation crank angular velocity calculation step of calculating a post-interpolation crank angular velocity with a step size smaller than the measurement step by interpolating a crank angular velocity acquired at each measurement step of the crank angle sensor. ,
In the cylinder-by-cylinder pressure calculation step, the cylinder-by-cylinder pressure is calculated based on the assumption that the cylinder-by-cylinder pressure does not change for a predetermined time according to the small step size.

An eighth invention is an in-cylinder pressure estimating device for an internal combustion engine,
In-cylinder pressure acquisition means for acquiring a plurality of in-cylinder pressures between the intake valve closing timing and the exhaust valve opening timing of the internal combustion engine;
Based on the in-cylinder pressure acquired by the in-cylinder pressure acquisition unit, a parameter determination unit that determines a plurality of undetermined parameters included in a model expression representing a relationship between the in-cylinder heat generation pattern and the in-cylinder pressure;
In-cylinder pressure estimating means for calculating an estimated value of in-cylinder pressure at a predetermined crank angle based on the model formula into which the parameter determined by the parameter determining means is substituted;
It is characterized by providing.

The ninth invention is the eighth invention, wherein
The model formula is based on the Wiebe function,
Wherein the plurality of parameters, the shape parameter m, the efficiency parameter k, characterized to include combustion period theta _p and thermogenesis start crank angle theta _b.

The tenth invention is the eighth or ninth invention, wherein
The in-cylinder pressure acquisition means includes
Crank angular velocity acquisition means for acquiring the crank angular velocity;
Mechanical loss torque calculating means for calculating a mechanical loss torque generated by the mechanical loss of the internal combustion engine;
Inertia mass torque calculating means for calculating inertia mass torque generated by the moving member of the internal combustion engine;
In-cylinder pressure torque calculating means for calculating in-cylinder pressure torque generated by the in-cylinder pressure based on the crank angular velocity, the mechanical loss torque, and the inertia mass torque;
An in-cylinder volume change rate calculating means for calculating an in-cylinder volume change rate;
In-cylinder pressure calculating means for calculating in-cylinder pressure from the in-cylinder pressure torque and the in-cylinder volume change rate;
It is characterized by including.

Further, an eleventh aspect of the invention is any one of the eighth to tenth aspects of the invention,
The internal combustion engine includes a crank angle sensor that detects a crank angle,
The in-cylinder pressure acquisition means acquires the in-cylinder pressure at every measurement interval of the crank angle sensor.

In addition, a twelfth aspect of the invention is any one of the eighth to eleventh aspects of the invention.
The internal combustion engine has a plurality of cylinders,
The in-cylinder pressure acquisition means includes
Crank angular velocity acquisition means for acquiring the crank angular velocity;
Mechanical loss torque calculating means for calculating a mechanical loss torque generated by the mechanical loss of the internal combustion engine;
Inertia mass torque calculating means for calculating inertia mass torque generated by the moving member of the internal combustion engine;
All-cylinder in-cylinder pressure torque calculating means for calculating all-cylinder in-cylinder pressure torque generated by the in-cylinder pressure of all cylinders based on the crank angular velocity, the mechanical loss torque, and the inertia mass torque;
An in-cylinder volume change rate calculating means for calculating an in-cylinder volume change rate of each cylinder;
In-cylinder in-cylinder pressure calculating means for calculating in-cylinder in-cylinder pressure from the all-cylinder in-cylinder pressure torque and the in-cylinder volume change rate of each cylinder;
Including
The parameter determination means determines the undetermined parameter for each cylinder based on the cylinder internal pressure.
The in-cylinder pressure estimating means calculates an in-cylinder pressure estimated value at a predetermined crank angle for each cylinder based on the model equation for each cylinder into which the parameter determined for each cylinder is substituted.

The thirteenth invention in the twelfth invention,
The cylinder-specific cylinder pressure calculating means calculates the cylinder-specific cylinder pressure based on the assumption that the cylinder-specific cylinder pressure does not change for a predetermined time.

The fourteenth invention is the twelfth invention,
The internal combustion engine includes a crank angle sensor that detects a crank angle,
The crank angular speed acquisition means includes post-interpolation crank angular speed calculation means for calculating a post-interpolation crank angular speed having a step size smaller than the measurement step by interpolating a crank angular speed acquired at each measurement step of the crank angle sensor. ,
The cylinder-by-cylinder in-cylinder pressure calculating means calculates the cylinder-by-cylinder in-cylinder pressure based on an assumption that the cylinder-by-cylinder in-cylinder pressure does not change for a predetermined time according to the small step size.

  According to the first invention, a plurality of in-cylinder pressures between the intake valve closing timing and the exhaust valve opening timing of the internal combustion engine are acquired, and based on the acquired in-cylinder pressure, the in-cylinder heat generation pattern and A plurality of undetermined parameters included in the model expression representing the relationship with the in-cylinder pressure can be determined. Based on the model formula into which the determined parameter is substituted, the in-cylinder pressure estimated value at a predetermined crank angle can be calculated. For this reason, according to the first aspect, the influence of the noise or the like of the crank angle sensor signal can be corrected by using the above model formula, so that a highly accurate in-cylinder pressure estimated value can be obtained. In addition, the in-cylinder pressure estimated value can be obtained with finer crank angle increments regardless of the measurement increments of the crank angle sensor.

According to the second invention, the estimation accuracy is further improved by using the model equation based on the Wiebe function including the shape parameter m, the efficiency parameter k, the combustion period θ _p and the heat generation start crank angle θ _b. Can do.

  According to the third aspect of the present invention, the in-cylinder pressure torque generated by the in-cylinder pressure is calculated based on the crank angular speed, the mechanical loss torque, and the inertial mass torque. From the in-cylinder pressure torque and the in-cylinder volume change rate, The in-cylinder pressure for determining the parameters of the model formula can be calculated with high accuracy.

  According to the fourth aspect of the present invention, the in-cylinder pressure for determining the parameter of the model formula can be acquired for each measurement step of the crank angle sensor. For this reason, the parameter of the model equation can be determined with higher accuracy.

  According to the fifth aspect of the present invention, the cylinder-by-cylinder in-cylinder pressure is calculated, and the parameters of the model equation can be determined for each cylinder based on the in-cylinder in-cylinder pressure. For this reason, it is possible to accurately calculate the in-cylinder pressure estimated value for each cylinder based on the model formula for each cylinder.

  According to the sixth aspect, the cylinder-by-cylinder pressure is calculated based on the assumption that the cylinder-by-cylinder pressure does not change for a predetermined time. For this reason, the cylinder internal cylinder pressure can be accurately calculated by a simple method.

  According to the seventh aspect, by interpolating the crank angular velocity acquired for each measurement step of the crank angle sensor, the post-interpolation crank angular velocity having a step size smaller than the measurement step can be calculated. Then, the cylinder-by-cylinder pressure is calculated based on the assumption that the cylinder-by-cylinder pressure does not change for a predetermined time corresponding to the small step size. For this reason, according to the seventh aspect, the above assumption can be established with high accuracy even when the measurement increment of the crank angle sensor is large. Therefore, the cylinder internal cylinder pressure can be calculated with higher accuracy.

  According to the eighth invention, a plurality of in-cylinder pressures between the intake valve closing timing and the exhaust valve opening timing of the internal combustion engine are acquired, and based on the acquired in-cylinder pressure, the in-cylinder heat generation pattern and A plurality of undetermined parameters included in the model expression representing the relationship with the in-cylinder pressure can be determined. Based on the model formula into which the determined parameter is substituted, the in-cylinder pressure estimated value at a predetermined crank angle can be calculated. For this reason, according to the eighth aspect of the invention, the influence of noise or the like of the crank angle sensor signal can be corrected by using the above model formula, so that a highly accurate in-cylinder pressure estimated value can be obtained. In addition, the in-cylinder pressure estimated value can be obtained with finer crank angle increments regardless of the measurement increments of the crank angle sensor.

According to the ninth invention, the estimation accuracy is further improved by using the model formula based on the Wiebe function including the shape parameter m, the efficiency parameter k, the combustion period θ _p and the heat generation start crank angle θ _b. Can do.

  According to the tenth aspect of the invention, the in-cylinder pressure torque generated by the in-cylinder pressure is calculated based on the crank angular velocity, the mechanical loss torque, and the inertia mass torque, and the above-mentioned in-cylinder pressure torque and the in-cylinder volume change rate are The in-cylinder pressure for determining the parameters of the model formula can be calculated with high accuracy.

  According to the eleventh aspect, the in-cylinder pressure for determining the parameters of the model equation can be acquired for each measurement step of the crank angle sensor. For this reason, the parameter of the model equation can be determined with higher accuracy.

  According to the twelfth aspect, the cylinder-by-cylinder internal pressure can be calculated, and the parameter of the model equation can be determined for each cylinder based on the cylinder-by-cylinder internal pressure. For this reason, it is possible to accurately calculate the in-cylinder pressure estimated value for each cylinder based on the model formula for each cylinder.

  According to the thirteenth invention, the cylinder-by-cylinder pressure is calculated based on the assumption that the cylinder-by-cylinder pressure does not change for a predetermined time. For this reason, the cylinder internal cylinder pressure can be accurately calculated by a simple method.

  According to the fourteenth aspect of the present invention, by interpolating the crank angular velocity acquired for each measurement step of the crank angle sensor, the post-interpolation crank angular velocity having a step size smaller than that measurement step can be calculated. Then, the cylinder-by-cylinder pressure is calculated based on the assumption that the cylinder-by-cylinder pressure does not change for a predetermined time corresponding to the small step size. Therefore, according to the fourteenth aspect, the above assumption can be established with high accuracy even when the measurement increment of the crank angle sensor is large. Therefore, the cylinder internal cylinder pressure can be calculated with higher accuracy.

Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. As shown in FIG. 1, the system of the present embodiment includes an internal combustion engine 10.

  An intake passage 12 and an exhaust passage 14 communicate with each other in the cylinder of the internal combustion engine 10. An air flow meter 16 that detects an intake air amount Ga is disposed in the intake passage 12. A throttle valve 18 is disposed downstream of the air flow meter 16. The opening degree of the throttle valve 18 is adjusted by the operation of the throttle motor 20. A throttle position sensor 22 for detecting the opening degree of the throttle valve 18 is disposed in the vicinity of the throttle valve 18. An accelerator position sensor 24 that detects the amount of depression of the accelerator pedal is provided in the vicinity of the accelerator pedal.

  A fuel injector 26 for injecting fuel into the intake port 11 is disposed in the cylinder of the internal combustion engine 10. The cylinder of the internal combustion engine 10 is further provided with an intake valve 28, a spark plug 30, an exhaust valve 32, and a piston 34. The internal combustion engine according to the present invention is not limited to the port injection type as shown in the figure, but may be an in-cylinder direct injection type that directly injects fuel into the cylinder, and further includes port injection and in-cylinder injection. It may be used in combination.

  Further, the system of the present embodiment includes a crank angle sensor 38 that detects a rotation angle (rotation position) of the crankshaft 36, that is, a crank angle θ, an oil temperature sensor 42 that detects the temperature of engine oil, and an ECU (Electronic Control). Unit) 50. The ECU 50 is electrically connected to the various sensors and actuators described above.

[Features of Embodiment 1]
In the present embodiment, in addition to the output of the crank angle sensor 38, a highly accurate in-cylinder pressure estimated value is calculated by using a model formula using a Wiebe function that is a heat generation pattern model. The specific procedure will be described below. 2 and 3 are flowcharts of routines executed by the ECU 50 in the present embodiment in order to calculate the in-cylinder pressure estimated value.

  According to these routines, first, the history of the crank angular speed ω is detected. Specifically, the history of the crank angle θ is acquired as a function θ (t) of the time t based on the output of the crank angle sensor 38 (steps 100 and 102 in FIG. 2). Next, the crank angular speed history ω (t) is calculated by differentiating θ (t) with respect to time t (step 104), and by converting the ω (t) into a function of the crank angle θ, the crank angular speed history is calculated. ω (θ) is calculated (step 106).

  Along with this, a history of the load factor KL is detected. Specifically, the load factor history KL (t) is calculated based on the intake air amount Ga detected by the air flow meter 16 (steps 108 and 110), and the KL (t) is converted into a function of θ. A load factor history KL (θ) is calculated (step 112).

Moreover, the history of the engine oil temperature T _o is detected. Specifically, based on the output of the oil temperature sensor 42, an engine oil temperature history T _o (t) is calculated (step 114, 116), by converting the T _o (t) is a function of theta, engine oil temperature history T _o (theta) is calculated (step 118).

Subsequently, calculated over the crank angular history omega (theta), load factor history KL (theta) and using the engine oil temperature history T _o (theta), mechanical loss of the engine 10 (the piston 34, the crankshaft 36 or the like The history of the mechanical loss torque T _f generated by the friction (step 120) is calculated (step 120). The mechanical loss torque T _f, larger as the crank angular velocity ω is high, also as the load factor KL is high increases further, larger as the engine oil temperature T _o is low. The ECU 50 stores a map representing these tendencies in advance, and in step 120, the mechanical loss torque history T _f (θ) is calculated based on the map.

Further, according to the routine shown in FIG. 2, further, a history of the moment of inertia J of the engine 10, and the history of the inertial mass torque T _m generated by the inertia of the moving member of the internal combustion engine 10 (piston 34 or the like) is calculated (Steps 122 and 124). The inertia moment J and the inertia mass torque T _m can be obtained from the design values as a function of the crank angle θ. Therefore, in steps 122 and 124, the inertia moment history J (θ) and the inertia mass torque history T _m (θ) are calculated based on a map or mathematical formula stored in advance in the ECU 50.

Here, assuming that the torque generated by the force exerted on the piston 34 by the in-cylinder pressure P _c of the internal combustion engine 10 (hereinafter referred to as “in-cylinder pressure torque”) is T _p , the equation of motion of the crankshaft 36 is expressed by the following equation (1). Is done. Therefore, the in-cylinder pressure torque T _p is expressed by the following equation (2).

According to the routine shown in FIG. 2, the crank angular velocity history ω (θ), mechanical loss torque history T _f (θ), inertia moment history J (θ), and inertia mass torque history T _m (θ ) Is substituted into the above equation (2) to calculate the in-cylinder pressure torque history T _p (θ) (step 126).

  Subsequently, a history of the rate of change dV (θ) / dθ of the in-cylinder volume V with respect to the crank angle θ is calculated (step 128). Since the in-cylinder volume change rate dV (θ) / dθ is geometrically determined according to the crank angle θ, it can be obtained from the design value. Therefore, in step 128, the in-cylinder volume change rate history dV (θ) / dθ is calculated based on a map or mathematical expression stored in advance in the ECU 50.

Subsequently, the in-cylinder pressure history P _c (θ) is calculated (step 130). The following formula (3) is established in terms of dynamics between the in-cylinder pressure P _c , the in-cylinder pressure torque T _p, and the in-cylinder volume change rate dV (θ) / dθ. Therefore, in step 130, the in-cylinder pressure is substituted by substituting T _p (θ) obtained in step 126 and dV (θ) / dθ obtained in step 128 into the following equation (3). A history P _c (θ) is calculated.

Here, the model formula using the Wiebe function used in the present embodiment will be described. According to the Wiebe function, the mass combustion ratio _{Xb at} the crank angle θ can be expressed by the following equation (4).

Here, θ _b is a crank angle at which heat generation starts, θ _p is a combustion period, m is a shape parameter, and a is a predetermined constant.

  Further, assuming that the amount of heat generated by the combustion of fuel is Q, the heat generation rate dQ / dθ can be expressed by the following equation (5) by using an equation obtained by differentiating the above equation (4).

However, Q _f is an amount of heat that the fuel supplied into the cylinder has, and k is an efficiency parameter that represents the efficiency with which the amount of heat Q _f of the fuel is actually converted into heat.

  The following equation (7) is obtained from the above equation (5) and the first law of thermodynamics expressed by the following equation (6).

However, (gamma) is a specific heat ratio. The above equation (7) is a model equation used in this embodiment. In this model equation, the heat quantity Q _f of the fuel can be calculated based on the air-fuel ratio or the fuel injection amount. The specific heat ratio γ is a known value. In the present embodiment, a is a predetermined constant (for example, 6.9) as described above. Then, dθ / dt (= ω), the in-cylinder volume change rate dV (θ) / dθ, and the in-cylinder volume V (θ) are the history of the crank angular velocity ω calculated in the above-described process and the in-cylinder volume change rate dV. It can be obtained from the history of (θ) / dθ. Therefore, there are four undetermined parameters in the above model equation: efficiency parameter k, shape parameter m, heat generation start crank angle θ _b, and combustion period θ _p .

After the in-cylinder pressure history P _c (θ) is calculated in step 130, the intake valve closing timing of the last (most recent) cycle is determined in order to determine the values of the undetermined parameters k, m, θ _b and θ _p. A plurality of in-cylinder pressures P _c (θ) from (hereinafter referred to as “IVC”) to the exhaust valve opening timing (hereinafter referred to as “EVO”) are extracted (step 132 in FIG. 3).

The crank angle sensor 38 detects the crank angle θ every predetermined measurement interval Δθ (for example, 10 degrees or 30 degrees). In step 132, the in-cylinder pressure P _c (θ) for each measurement increment Δθ from IVC to EVO is extracted from the in-cylinder pressure history P _c (θ) calculated in step 130. Therefore, the number n of data extracted here is equal to the quotient obtained by dividing the crank angle period from IVC to EVO by the measurement increment Δθ. In the present embodiment, the number of data n may be equal to or greater than the number of undetermined parameters in the model formula, that is, 4 or more.

When n pieces of data of the in-cylinder pressure P _c (θ) are extracted in the above step 132, the respective undetermined parameters k, m, θ _b and θ _p are substituted by substituting each data into the above equation (7). Are generated as variables (n ≧ 4) (step 134). K, m, θ _b and θ _p are respectively calculated by solving these n equations as simultaneous equations or using the least square method (step 136).

The k, m, θ _b and θ _p calculated in step 136 are substituted into the following equation (8) (step 138).

The above equation (8) is an equation in which the in-cylinder pressure P _c (θ) in the above equation (7) is replaced with the corrected in-cylinder pressure P _w (θ). By solving the equation (8) as a differential equation of P _w (θ), a corrected in-cylinder pressure history P _w (θ) is calculated (step 140).

The corrected in-cylinder pressure history P _w (θ) calculated in this way can be used as a highly accurate in-cylinder pressure estimation value. That is, the in-cylinder pressure history P _c (θ) calculated in step 130 includes an error due to the noise of the crank angle sensor 38, but is calculated using the above model formula using the Wiebe function. In the corrected in-cylinder pressure history P _w (θ), the error due to the noise of the crank angle sensor 38 is corrected with high accuracy. Further, according to the corrected in-cylinder pressure history P _w (theta), it is possible to accurately calculate the desired the corrected in (any) crank angle theta cylinder pressure P _w (theta). For this reason, the corrected in-cylinder pressure P _w (θ) can be accurately calculated with finer crank angle increments regardless of the magnitude of the measurement increment Δθ of the crank angle sensor 38.

Therefore, in the present embodiment, by using the corrected in-cylinder pressure P _w (θ) as the in-cylinder pressure estimation value, for example, control based on fuel property detection, misfire detection, in-cylinder state quantity (combustion ratio, etc.) Control using the in-cylinder pressure can be executed with high accuracy.

  In the first embodiment described above, the ECU 50 executes the processes of steps 100 to 132, so that the “cylinder pressure acquisition means” in the eighth aspect of the invention executes the processes of steps 134 and 136. As a result, the “parameter determining means” in the eighth invention executes the processes in steps 138 and 140, whereby the “in-cylinder pressure estimating means” in the eighth invention executes the processes in steps 100 to 106. As a result, the “crank angular velocity acquisition means” in the tenth aspect of the invention executes the processing of steps 108 to 120, so that the “mechanical loss torque calculation means” in the tenth aspect of the invention performs the processing of step 124. By executing the “inertial mass torque calculating means” in the tenth aspect of the invention, By executing the process of step 126, the “in-cylinder pressure torque calculating means” in the tenth aspect of the invention is executed, and by executing the processing of step 128, the “in-cylinder volume change rate calculating means” in the tenth aspect of the invention is executed. The “in-cylinder pressure calculating means” according to the tenth aspect of the present invention is implemented by executing the processing of step 130 described above.

Embodiment 2. FIG.
Next, the second embodiment of the present invention will be described with reference to FIG. 4 to FIG. 6. The description will focus on the differences from the first embodiment described above, and the same matters will be described. Simplify or omit.

[Features of Embodiment 2]
In the internal combustion engine 10 having a plurality of cylinders, the in-cylinder pressure torque T _p calculated by the above equation (2) is the sum of the in-cylinder pressure torques of the plurality of cylinders. For this reason, in the above equation (3), the in-cylinder pressure _Pc cannot be calculated for each cylinder. In this embodiment, the first embodiment is improved so that the in-cylinder pressure for each cylinder can be calculated. In the following description, it is assumed that the internal combustion engine 10 has four cylinders # 1 to # 4. In the following description, the subscript i of each symbol represents a cylinder number. That is, (i = 1, 2, 3, 4).

  FIGS. 4 to 6 are flowcharts of routines executed by the ECU 50 in the present embodiment in order to calculate the estimated cylinder pressure for each cylinder.

According to these routines, first, the in-cylinder pressure torque history T _p (θ) is calculated (step 142 in FIG. 4). The processing in step 142 is the same as the processing in steps 100 to 126 in the first embodiment described above.

Subsequently, the cylinder volume change rate history dV ₁ (θ) / dθ of the # 1 cylinder, the cylinder volume change rate history dV ₂ (θ) / dθ of the # 2 cylinder, and the cylinder volume change rate of the # 3 cylinder The history dV ₃ (θ) / dθ and the cylinder volume change rate history dV ₄ (θ) / dθ of the # 4 cylinder are respectively calculated (steps 144, 146, 148, 150). In this case, the in-cylinder volume change rate dV (θ) / dθ of each cylinder can be calculated based on a map or formula for each cylinder stored in advance in the ECU 50.

Here, assuming that the in-cylinder pressures of the cylinders # 1 to # 4 are P _c1 , P _c2 , P _c3 , and P _c4 and the current crank angle is θ ₀ , the current in-cylinder pressure torque T _p (θ ₀ ) Can be represented by the following formula (9).

Similarly, the in-cylinder pressure torque T _p (θ ₀ −Δθ) before one measurement step of the crank angle sensor 38, the in-cylinder pressure torque T _p (θ ₀ −2Δθ) before the measurement step, and the in-cylinder pressure before three measurement steps. The torque T _p (θ ₀ −3Δθ) can be expressed by the following equations (10) to (12), respectively.

In the above equations (9) to (12), dV _i (θ ₀ ) / dθ, dV _i (θ ₀ −Δθ) / dθ, dV _i (θ ₀ −2Δθ) / dθ, dV _i (θ ₀ − 3Δθ) / dθ (i = 1, 2, 3, 4) can be extracted from the in-cylinder volume change rate dV _i (θ) / dθ calculated in steps 144 to 150, respectively.

Here, in the present embodiment, it is assumed that the in-cylinder pressure P _{ci of} each cylinder does not change for a certain period of time, specifically, for (θ ₀ −3Δθ) ≦ θ ≦ θ ₀ . That is, the following equation (13) is assumed.

In the present embodiment, the in-cylinder pressure P _ci (θ ₀ ) of each cylinder is calculated under the assumption of the above equation (13). That is, first, P _ci (θ ₀ −Δθ), P _ci (θ ₀ −2Δθ), P _ci (θ ₀ −3Δθ) is obtained by substituting the above equation (13) into the above equations (9) to (12). ) (I = 1, 2, 3, 4) is deleted (step 152 in FIG. 5).

As a result, the above equations (9) to (12) become four equations including four unknowns P _ci (θ ₀ ) (i = 1, 2, 3, 4), so these are solved as simultaneous equations. Thus, P _ci (θ ₀ ) (i = 1, 2, 3, 4), that is, the current cylinder-by-cylinder pressure for the cylinders # 1 to # 4 can be calculated (step 154).

Subsequently, the current crank angle θ ₀ is updated by the following equation (14) (step 156), and the processing of step 154 is executed again. That is, after the current crank angle θ ₀ is advanced by one measurement increment Δθ of the crank angle sensor 38, the cylinder internal cylinder pressure P _ci (θ ₀ ) (i = 1, 2, 3, 4) is calculated again. The
θ ₀ = θ ₀ + Δθ (14)

Then, the loop of steps 152 to 156 acquires the cylinder internal cylinder pressure P _ci (θ ₀ ) (i = 1, 2, 3, 4) for one cycle of the internal combustion engine 10, that is, the crank angle of 720 degrees. Until it is executed repeatedly.

Next, when the cylinder for which the cylinder internal pressure estimate for each cylinder is to be calculated accurately (here, the cylinder that finally reached EVO) is #i cylinder, from the last cycle IVC to EVO of this #i cylinder The in-cylinder pressure P _ci (θ) at the point n _i is extracted from the data calculated by the above-described processes 152 to 156 (step 158). This number of data n _i is the quotient when the crank angle period from the last IVC of the #i cylinder to EVO is divided by the measurement increment Δθ, as in the first embodiment, and is equal to or greater than the number of undetermined parameters in the model formula. That is, it may be 4 or more.

Subsequently, the n _i pieces of data extracted in step 158 are substituted into the following equation (15) (step 160 in FIG. 6).

The above equation (15) is a model equation used in the present embodiment, and is the same as the equation (7) in the first embodiment. By the process of step 160, n _i (n _i ≧ 4) expressions including four undetermined parameters k _i , m _i , θ _bi and θ _pi as variables are generated. By solving these n _i equations as simultaneous equations or using the least squares method, k _i , m _i , θ _bi and θ _pi in the model equation of the #i cylinder are respectively calculated (step 162). .

The k _i , m _i , θ _bi and θ _pi calculated in step 162 are substituted into the following equation (16) (step 164).

The above expression (16) is an expression in which the in-cylinder pressure P _ci (θ) in the above expression (15) is replaced with the corrected in-cylinder pressure P _wi (θ). By solving the equation (16) as a differential equation of P _wi (θ), a corrected in-cylinder pressure history P _wi (θ) of the #i cylinder is calculated (step 166).

As described above, according to this embodiment, it is possible to calculate the cylinder pressure estimated value (corrected cylinder pressure history P _wi (θ)) for each cylinder of the internal combustion engine 10 having a plurality of cylinders with high accuracy.

  In the second embodiment described above, the ECU 50 executes the process of step 142, whereby the “all-cylinder in-cylinder pressure torque calculating means” in the twelfth aspect of the invention executes the processes of steps 144 to 150. As a result, the “cylinder volume change rate calculating means” in the twelfth aspect of the invention realizes the “cylinder-specific in-cylinder pressure calculating means” of the twelfth aspect of the invention by executing the processing of steps 152 to 156, respectively. Has been.

Embodiment 3 FIG.
Next, the third embodiment of the present invention will be described with reference to FIG. 7 to FIG. 10. The description will focus on the differences from the first embodiment described above, and the same matters will be described. Simplify or omit.

[Features of Embodiment 3]
The assumption of the above equation (13) in the second embodiment is difficult to be established when the measurement increment Δθ of the crank angle sensor 38 is large. For this reason, the estimation accuracy of the cylinder-specific in-cylinder pressure estimation value (P _wi ) may not be sufficiently secured. In this embodiment, in order to obtain sufficient estimation accuracy even in such a case, the crank angular increment is reduced by interpolating the waveform of the crank angular velocity ω (θ) using an appropriate function. It was decided.

  FIGS. 7 to 10 are flowcharts of routines executed by the ECU 50 in the present embodiment in order to calculate the estimated cylinder pressure for each cylinder.

  According to these routines, first, the crank angular velocity history ω (θ) is calculated (step 168 in FIG. 7). This processing is the same as the processing in steps 100 to 106 of the first embodiment described above.

  In this embodiment, the waveform of the crank angular velocity ω (θ) is interpolated by the cubic function of the following equation (17).

Subsequent to the processing of step 168, in order to determine the four undetermined coefficients α ₃ , α ₂ , α ₁ , α ₀ in the equation (17), the current crank angle θ ₀ and one measurement of the crank angle sensor 38 are measured. Crank angle speed ω at four points of time: crank angle before ticking (θ ₀ −Δθ), crank angle before ticking (θ ₀ −2Δθ), crank angle before ticking (θ ₀ −3Δθ), Extracted from the crank angular speed history (step 170). That is, ω (θ ₀ −3Δθ), ω (θ ₀ −2Δθ), ω (θ ₀ −Δθ), and ω (θ ₀ ) are extracted.

Subsequently, the values of ω (θ ₀ −3Δθ), ω (θ ₀ −2Δθ), ω (θ ₀ −Δθ), and ω (θ ₀ ) extracted in step 170 are substituted into the equation (17). (Step 172). As a result, simultaneous equations of unknown number 4 and equation number 4 are obtained, and the values of coefficients α ₃ , α ₂ , α ₁ and α ₀ can be calculated by solving the simultaneous equations (step 174).

Next, the calculated values of the coefficients α ₃ , α ₂ , α ₁ , α ₀ are substituted into the following equation (18) (step 176).

In the above equation (18), ω _c is the post-interpolation crank angular velocity. According to the equation (18), the post-interpolation crank angular velocity ω _c is accurately calculated with a calculation step Δθ _c (for example, Δθ _c = 0.1 degree) that is significantly smaller than the measurement step Δθ of the crank angle sensor 38. be able to.

In this embodiment, in order to further improve the accuracy, the interpolation of the above equation (18) obtained using four points (θ ₀ −3Δθ), (θ ₀ −2Δθ), (θ ₀ −Δθ), and θ ₀ is performed. of the rear crank angular speed omega _c, it was decided to use the up (θ ₀ -Δθ) from (θ ₀ -2Δθ). Therefore, in this embodiment, following the process in step 176, the above equation (18), (θ ₀ -2Δθ) from to (θ ₀ -Δθ), after interpolation for every calculation increments [Delta] [theta] _c crank angular speed omega _c Is calculated (step 178). That is, the post-interpolation crank angular velocity ω _c when θ = (θ ₀ −2Δθ, θ ₀ −2Δθ + Δθ _c , θ ₀ −2Δθ + 2Δθ _c ,..., Θ ₀ −Δθ) is calculated.

Subsequently, the current crank angle θ ₀ is updated by the following equation (19) (step 180), and the processing of steps 170 to 180 is executed again. That is, the current crank angle theta _0, after being advanced by one measurement increment Δθ min crank angle sensor 38, (θ ₀ -2Δθ) from (θ ₀ -Δθ) to the interpolated crank angular omega _c is calculated increments Δθ Calculated every _c .
θ ₀ = θ ₀ + Δθ (19)

The loop of steps 170 to 180 is repeatedly executed for one cycle of the internal combustion engine 10, that is, for a crank angle of 720 degrees. Thereby, a history of the post-interpolation crank angular velocity ω _c for 720 degrees for each calculation step Δθ _c can be acquired.

Along with the above processing, the load factor history KL (θ) is calculated (step 182 in FIG. 8). This calculation processing is the same as the processing in steps 108 to 112 of the first embodiment described above. The engine oil history T _o (theta) is calculated (step 184). This calculation processing is the same as the processing in steps 148 to 118 of the first embodiment described above.

Subsequently, the above history interpolated crank angular omega _c calculated by the processing, the load factor history KL (theta), based on the engine oil temperature history T _o (theta), the history of the mechanical loss torque T _f Is calculated for each calculation step Δθ _c (step 186). This calculation process is the same as the process in step 120 of the first embodiment.

Subsequently, a history of in-cylinder pressure torque T _p (θ) for each calculation step Δθ _{c is} calculated based on the following equation (20) (step 188). The following equation (20) is the same as the equation (2) described in the first embodiment.

Assuming that the cylinder pressures of the cylinders # 1 to # 4 are P _c1 , P _c2 , P _c3 , and P _c4 , respectively, the cylinder pressure torque T _p (θ ₀₀ ) at the crank angle θ ₀₀ , one calculation step Δθ _c cylinder pressure torque _{T p (θ 00 -Δθ c)} , 2 calculated increment [Delta] [theta] _c before the in-cylinder pressure torque _{T p (θ 00 -2Δθ c)} , 3 calculates increment [Delta] [theta] _c before the in-cylinder pressure torque T _p (θ ₀₀ -3Δθ _c ) can be represented by the following formulas (21) to (24), respectively.

Here, in the present embodiment, it is assumed that the in-cylinder pressure P _{ci of} each cylinder does not change for a certain period of time, specifically, (θ ₀₀ -3Δθ _c ) ≦ θ ≦ θ ₀₀ . That is, the following equation (25) is assumed.

In the present embodiment, as described above, the calculation step Δθ _c can be made extremely small. For this reason, the assumption of the above equation (25) is established with high accuracy regardless of the magnitude of the measurement increment Δθ of the crank angle sensor 38.

In order to calculate the in-cylinder pressure P _ci (θ ₀ ) of each cylinder under the assumption of the above equation (25), P _ci is substituted by substituting the above equation (25) into the above equations (21) to (24). (θ ₀₀ −Δθ _c ), P _ci (θ ₀₀ −2Δθ _c ), P _ci (θ ₀₀ −3Δθ _c ) (i = 1, 2, 3, 4) are deleted (step 190 in FIG. 9).

As a result, the above equations (21) to (24) become four equations including four unknowns P _ci (θ ₀₀ ) (i = 1, 2, 3, 4), so that these are solved as simultaneous equations. Thus, the cylinder internal pressure P _ci (θ ₀₀ ) (i = 1, 2, 3, 4) of the cylinders # 1 to # 4 at the crank angle θ ₀₀ can be calculated (step 192).

Subsequently, the crank angle θ ₀₀ is updated by the following equation (26) (step 194), and the process of step 190 is executed again. That is, after the crank angle θ ₀₀ is advanced by one calculation step Δθ _c , the cylinder internal pressure P _ci (θ ₀₀ ) (i = 1, 2, 3, 4) of each cylinder is calculated again.
θ ₀₀ = θ ₀₀ + Δθ _c (26)

Until the loop of steps 190 to 194 obtains the cylinder internal cylinder pressure P _ci (θ ₀₀ ) (i = 1, 2, 3, 4) for one cycle of the internal combustion engine 10, that is, the crank angle of 720 degrees. , Repeatedly executed.

Next, when the cylinder for which the cylinder internal pressure estimate for each cylinder is to be calculated accurately (here, the cylinder that finally reached EVO) is #i cylinder, from the last cycle IVC to EVO of this #i cylinder The in-cylinder pressure P _ci (θ) at point n _i is extracted from the data calculated by the processing of 190 to 194 (step 196). This data number n _i is a quotient obtained by dividing the crank angle period from the last IVC of the #i cylinder to EVO by the calculation step Δθ _c .

Subsequently, the n _i pieces of data extracted in step 196 are substituted into a model equation similar to the equation (15) of the second embodiment (step 198 in FIG. 10).

By the processing in step 198, n _i (n _i ≧ 4) expressions are generated that include four undetermined parameters of k _i , m _i , θ _bi and θ _pi as variables. By solving these n _i equations as simultaneous equations or using the least square method, k _i , m _i , θ _bi and θ _pi in the model equation of the #i cylinder are respectively calculated (step 200). .

The k _i , m _i , θ _bi and θ _pi calculated in step 200 are substituted into the same equation as the equation (16) of the second embodiment (step 202). By solving this equation as a differential equation of P _wi (θ), the corrected in-cylinder pressure history P _wi (θ) of the #i cylinder is calculated (step 204).

As described above, in this embodiment, the calculation step Δθ _c can be made extremely small, so that the assumption of the above equation (25) is established with high accuracy. For this reason, the cylinder pressure estimated value (corrected cylinder pressure history P _wi (θ)) for each cylinder of the internal combustion engine 10 having a plurality of cylinders can be calculated with higher accuracy.

  In the third embodiment described above, the ECU 50 executes the processes in steps 168 to 180, so that the “crank angular velocity acquisition means” in the fourteenth aspect executes the processes in steps 170 to 180. As a result, the “post-interpolation crank angular velocity calculating means” in the fourteenth aspect of the invention executes steps 182 to 188, whereby the “all cylinder cylinder pressure torque calculating means” in the fourteenth aspect of the invention is the step 190. The “cylinder-by-cylinder in-cylinder pressure calculating means” according to the fourteenth aspect of the present invention is implemented by executing the processes of.

  In Embodiment 3 described above, the waveform of the crank angular velocity ω (θ) is interpolated using a cubic function. However, the function used for this interpolation is not limited to this. For example, a spline function is used. Etc. may be used.

Further, in each of the above-described embodiments, the in-cylinder pressure history P _c (θ) is obtained from the in-cylinder pressure torque T _p (θ) obtained using the equation of motion of the crankshaft 36 such as the above equation (1). However, in the present invention, a cylinder pressure sensor may be provided, and the cylinder pressure history P _c (θ) may be obtained from the output of the cylinder pressure sensor.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a flowchart of the routine performed in Embodiment 3 of the present invention. It is a flowchart of the routine performed in Embodiment 3 of the present invention. It is a flowchart of the routine performed in Embodiment 3 of the present invention. It is a flowchart of the routine performed in Embodiment 3 of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 11 Intake port 12 Intake passage 14 Exhaust passage 16 Air flow meter 18 Throttle valve 26 Fuel injector 30 Spark plug 36 Crankshaft 38 Crank angle sensor 42 Water temperature sensor 50 ECU

Claims (12)

In-cylinder pressure acquisition step of acquiring a plurality of in-cylinder pressures between the intake valve closing timing and the exhaust valve opening timing of the internal combustion engine;
Based on the in-cylinder pressure acquired in the in-cylinder pressure acquisition step, a parameter determination step for determining a plurality of undetermined parameters included in the model formula representing the relationship between the in-cylinder heat generation pattern and the in-cylinder pressure;
An in-cylinder pressure estimating step for calculating an in-cylinder pressure estimated value at a predetermined crank angle based on the model formula into which the parameter determined in the parameter determining step is substituted;
Equipped with a,
The in-cylinder pressure acquisition step includes:
A crank angular speed acquisition step for acquiring the crank angular speed;
A mechanical loss torque calculating step for calculating a mechanical loss torque generated by the mechanical loss of the internal combustion engine;
An inertial mass torque calculating step for calculating an inertial mass torque generated by the moving member of the internal combustion engine;
An in-cylinder pressure torque calculating step for calculating an in-cylinder pressure torque generated by an in-cylinder pressure based on the crank angular velocity, the mechanical loss torque, and the inertia mass torque;
An in-cylinder volume change rate calculating step for calculating an in-cylinder volume change rate;
An in-cylinder pressure calculating step of calculating an in-cylinder pressure from the in-cylinder pressure torque and the in-cylinder volume change rate;
A method for estimating an in-cylinder pressure of an internal combustion engine , comprising : The model formula is based on the Wiebe function,
Wherein the plurality of parameters, the shape parameter m, the efficiency parameter k, the cylinder pressure estimation method for an internal combustion engine according to claim 1, characterized in that it includes combustion period theta _p and thermogenesis start crank angle theta _b. The internal combustion engine includes a crank angle sensor that detects a crank angle,
The method for estimating an in-cylinder pressure of an internal combustion engine according to claim 1 or 2, wherein, in the in-cylinder pressure acquisition step, an in-cylinder pressure is acquired for each measurement step of the crank angle sensor. The internal combustion engine has a plurality of cylinders,
The in-cylinder pressure acquisition step includes:
A crank angular speed acquisition step for acquiring the crank angular speed;
A mechanical loss torque calculating step for calculating a mechanical loss torque generated by the mechanical loss of the internal combustion engine;
An inertial mass torque calculating step for calculating an inertial mass torque generated by the moving member of the internal combustion engine;
All-cylinder in-cylinder pressure torque calculating step for calculating all-cylinder in-cylinder pressure torque generated by the in-cylinder pressure of all cylinders based on the crank angular velocity, the mechanical loss torque, and the inertia mass torque;
An in-cylinder volume change rate calculating step for calculating an in-cylinder volume change rate of each cylinder;
A cylinder-specific cylinder pressure calculation step for calculating a cylinder-specific cylinder pressure from the all-cylinder cylinder pressure torque and the cylinder volume change rate of each cylinder;
Including
In the parameter determining step, the undetermined parameter is determined for each cylinder based on the cylinder internal pressure.
2. The in-cylinder pressure estimating step calculates an in-cylinder pressure estimated value at a predetermined crank angle for each cylinder based on the model formula for each cylinder into which the parameter determined for each cylinder is substituted. The in-cylinder pressure estimation method for an internal combustion engine according to any one of claims 1 to 3 . The in-cylinder in-cylinder pressure estimation method for an internal combustion engine according to claim 4, wherein in the in-cylinder in-cylinder pressure calculation step, the in-cylinder in-cylinder pressure is calculated based on an assumption that the in-cylinder in-cylinder pressure does not change for a predetermined time. . The internal combustion engine includes a crank angle sensor that detects a crank angle,
The crank angular velocity acquisition step includes a post-interpolation crank angular velocity calculation step of calculating a post-interpolation crank angular velocity with a step size smaller than the measurement step by interpolating a crank angular velocity acquired at each measurement step of the crank angle sensor. ,
In the cylinder cylinder pressure calculating step, cylinder-cylinder pressure, based on the assumption that no change for a predetermined period of time corresponding to the small step size, according to claim 4, characterized in that to calculate the cylinder-cylinder pressure The in-cylinder pressure estimation method of an internal combustion engine as described. In-cylinder pressure acquisition means for acquiring a plurality of in-cylinder pressures between the intake valve closing timing and the exhaust valve opening timing of the internal combustion engine;
Based on the in-cylinder pressure acquired by the in-cylinder pressure acquisition unit, a parameter determination unit that determines a plurality of undetermined parameters included in a model expression representing a relationship between the in-cylinder heat generation pattern and the in-cylinder pressure;
In-cylinder pressure estimating means for calculating an estimated value of in-cylinder pressure at a predetermined crank angle based on the model formula into which the parameter determined by the parameter determining means is substituted;
Equipped with a,
The in-cylinder pressure acquisition means includes
Crank angular velocity acquisition means for acquiring the crank angular velocity;
Mechanical loss torque calculating means for calculating a mechanical loss torque generated by the mechanical loss of the internal combustion engine;
Inertia mass torque calculating means for calculating inertia mass torque generated by the moving member of the internal combustion engine;
In-cylinder pressure torque calculating means for calculating in-cylinder pressure torque generated by the in-cylinder pressure based on the crank angular velocity, the mechanical loss torque, and the inertia mass torque;
An in-cylinder volume change rate calculating means for calculating an in-cylinder volume change rate;
In-cylinder pressure calculating means for calculating in-cylinder pressure from the in-cylinder pressure torque and the in-cylinder volume change rate;
An in-cylinder pressure estimating device for an internal combustion engine , comprising: The model formula is based on the Wiebe function,
Wherein the plurality of parameters, the shape parameter m, the efficiency parameter k, the cylinder pressure estimation apparatus for an internal combustion engine according to claim 7, wherein to include combustion period theta _p and thermogenesis start crank angle theta _b. The internal combustion engine includes a crank angle sensor that detects a crank angle,
The in-cylinder pressure estimating device for an internal combustion engine according to claim 7 or 8, wherein the in-cylinder pressure acquisition means acquires an in-cylinder pressure for each measurement step of the crank angle sensor. The internal combustion engine has a plurality of cylinders,
The in-cylinder pressure acquisition means includes
Crank angular velocity acquisition means for acquiring the crank angular velocity;
Mechanical loss torque calculating means for calculating a mechanical loss torque generated by the mechanical loss of the internal combustion engine;
Inertia mass torque calculating means for calculating inertia mass torque generated by the moving member of the internal combustion engine;
All-cylinder in-cylinder pressure torque calculating means for calculating all-cylinder in-cylinder pressure torque generated by the in-cylinder pressure of all cylinders based on the crank angular velocity, the mechanical loss torque, and the inertia mass torque;
An in-cylinder volume change rate calculating means for calculating an in-cylinder volume change rate of each cylinder;
In-cylinder in-cylinder pressure calculating means for calculating in-cylinder in-cylinder pressure from the all-cylinder in-cylinder pressure torque and the in-cylinder volume change rate of each cylinder;
Including
The parameter determination means determines the undetermined parameter for each cylinder based on the cylinder internal pressure.
The cylinder pressure estimation means, based on the parameter that was assigned cylinder of the model formula determined for each cylinder, according to claim 7, characterized in that for calculating the cylinder pressure estimate value at a predetermined crank angle cylinder The in-cylinder pressure estimating device for an internal combustion engine according to any one of claims 1 to 9 . 11. The in-cylinder in-cylinder pressure estimation device for an internal combustion engine according to claim 10, wherein the in-cylinder in-cylinder pressure calculation means calculates the in-cylinder in-cylinder pressure based on an assumption that the in-cylinder in-cylinder pressure does not change for a predetermined time. . The internal combustion engine includes a crank angle sensor that detects a crank angle,
The crank angular speed acquisition means includes post-interpolation crank angular speed calculation means for calculating a post-interpolation crank angular speed having a step size smaller than the measurement step by interpolating a crank angular speed acquired at each measurement step of the crank angle sensor. ,
The cylinder cylinder pressure calculation means, cylinder-cylinder pressure, based on the assumption that no predetermined time varies depending on the small step size, according to claim 10, characterized in that to calculate the cylinder-cylinder pressure The in-cylinder pressure estimating device for an internal combustion engine as described.

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