JP2008223688A - Ignition timing control system of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ignition timing control system of an internal combustion engine wherein a quantity of state of combustion (8° combustion rate) to the present combustion stroke for the ignition timing control is accurately estimated before determination of ignition-timing thereby correctly controlling the ignition timing even in a transient operation state. <P>SOLUTION: By this control system, ignition timing SA is controlled in the following procedure by which a calculated combustion-rate MFB8 cal(k) is predicted by an MFB calculation model A2, and the predicted value is corrected by a correction value HMFB so that the corrected combustion-rate MFB8mfd(k) becomes made a command correction-rate MFB8tgt. A real MFB calculation-means A7 calculates a previous real combustion-rate MFB8act(k-1) from the cylinder pressure indicated by a cylinder-pressure sensor 65. A correction base-quantity calculation means A9 obtains a correction base-quantity eMDL by subtracting the previous corrected combustion-rate MFB8mfd(k-1) from the real combustion-rate MFB8act(k-1). A low-pass filter A10 calculates a correction HMFB from the correction base quantity eMDL. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ignition timing control device for an internal combustion engine that acquires a combustion state quantity representing a combustion state in a combustion stroke and controls an ignition timing based on the combustion state quantity.

  Conventionally, a combustion ratio MFB (Mass Fraction Burned) is calculated as an amount representing the “combustion state” based on the in-cylinder pressure (pressure in the combustion chamber) detected by the in-cylinder pressure detecting means, and the combustion ratio MFB at a predetermined crank angle is calculated. 2. Description of the Related Art A control device for an internal combustion engine that controls ignition timing (combustion start timing) so as to match a target combustion ratio is known. One of such devices, for example, obtains a combustion rate MFB8 at a crank angle of 8 ° after compression top dead center, and controls the ignition timing SA so that the combustion rate MFB8 becomes a target value (for example, 50%). It is like that. Thereby, even when there are individual differences in the internal combustion engine, the ignition timing is appropriately controlled according to the individual engine. As a result, the combustion efficiency is improved and the output torque of the internal combustion engine can be increased (see, for example, Patent Document 1). The combustion ratio MFB8 is a combustion state quantity at a specific timing (crank angle 8 ° after compression top dead center) in the combustion stroke, and is also referred to as an 8 ° combustion ratio.

Here, the combustion ratio MFB is a value substantially equivalent to the ratio of the indicated heat quantity. Therefore, the ratio of the indicated heat quantity is one of the quantities representing the combustion state. The ratio of the indicated amount of heat is as follows: “With respect to a single combustion stroke, the combustion chamber has a predetermined timing with respect to the total amount Qtotal of heat generated by all fuel combusted in the combustion chamber and converted into work for the piston. Is defined as the ratio Qsum / Qtotal of the cumulative amount Qsum of heat converted into work for the piston among the heat generated by the fuel combusted in FIG. The combustion ratio MFB is “of the fuel that contributed to work for the piston among the fuel burned in the combustion chamber by a predetermined timing relative to the total amount of fuel that contributed to work for the piston among all the fuel burned in the combustion chamber”. It is defined as “the percentage of the integrated amount”.
JP 2006-144645 A

  By the way, the 8 ° combustion ratio MFB8 is obtained based on the detection value of the in-cylinder pressure sensor in the combustion stroke. Accordingly, in the conventional apparatus, the ignition timing for the next combustion stroke (current combustion stroke) is feedback controlled so that the 8 ° combustion ratio MFB in the previous combustion stroke matches the target value. For this reason, there is a problem that the ignition timing cannot be appropriately controlled in a transient operation state such as an acceleration at which the combustion state greatly changes.

  The present invention has been made to cope with the above problems. That is, an object of the present invention is to predict the combustion state quantity for the current combustion stroke with high accuracy in advance, and determine the ignition timing based on the predicted combustion state quantity (predicted combustion state quantity), thereby enabling transient operation. An object of the present invention is to provide an ignition timing control device for an internal combustion engine that can appropriately control the ignition timing even in a state.

  To achieve the above object, an ignition timing control device according to the present invention comprises a combustion state detection sensor, an actual combustion state amount acquisition means, an operating state amount acquisition means, a predicted combustion state amount acquisition means, and a predicted combustion state amount correction. Means, correction amount calculating means, and ignition timing control means.

  The combustion state detection sensor actually detects a physical quantity that changes in accordance with the combustion state of the air-fuel mixture in the combustion chamber of the engine. An example of the combustion state detection sensor is an in-cylinder pressure sensor. The in-cylinder pressure sensor detects the pressure in the combustion chamber (in-cylinder pressure) as a physical quantity that changes according to the combustion state of the air-fuel mixture in the combustion chamber.

  The actual combustion state quantity acquisition means acquires an amount representing the combustion state at a specific timing of the combustion stroke as the actual combustion state quantity based on the physical quantity detected by the combustion state detection sensor. An example of the actual combustion state quantity is the above-described 8 ° combustion ratio MFB8.

  Thus, the actual combustion state quantity is acquired based on the physical quantity actually detected by the combustion state detection sensor. Therefore, the latest actual combustion state quantity that can be used when determining the ignition timing for the current combustion stroke is the actual combustion state quantity in the previous (immediate) combustion stroke.

  The operating state quantity acquisition means acquires an operating state quantity that is a physical quantity that is different from the physical quantity detected by the combustion state detection sensor and represents the operating state of the engine. This amount of operating state is an amount that affects the combustion state, such as the engine load for the current combustion stroke, the engine speed for the current combustion stroke, the VVT advance amount for the current combustion stroke, etc. It is not limited to. The advance amount of VVT is the intake valve opening timing based on the case where the intake valve opening timing is set to the most retarded angle when the opening timing and closing timing of the exhaust valve are constant. Is the advance amount. The larger the VVT advance amount, the longer the overlap period, and the amount of burned gas (internal EGR gas amount) increases. Therefore, instead of the VVT advance amount, an overlap period or an internal EGR gas amount may be adopted as one of the operation state amounts. The overlap period is a period during which both the intake valve and the exhaust valve are maintained in the open state in the latter stage of the exhaust stroke. The advance amount of VVT, the overlap period, the internal EGR gas amount, and the like can be omitted particularly when the overlap period is not changed.

  The predicted combustion state quantity acquisition means includes a combustion state model that describes the relationship between the operation state quantity and the quantity representing the combustion state at a predetermined timing of the combustion stroke. The predicted combustion state quantity acquisition means acquires the quantity representing the combustion state at a specific timing of the combustion stroke as the predicted combustion state quantity by applying the operation state quantity acquired by the operation state quantity acquisition means to the combustion state model. . An example of the combustion state model is a well-known Wiebe function that describes the relationship between the operation state amount and the combustion ratio MFB.

  Thus, the predicted combustion state quantity is acquired based on the combustion state model. Therefore, by applying the operation state quantity in the current combustion stroke to the combustion state model, the current predicted combustion state quantity can be obtained before the current combustion stroke (before the ignition timing and before the ignition timing is determined). However, the combustion state model cannot be a perfect model. Therefore, the predicted combustion state quantity includes a prediction error based on the model error of the combustion state model. This error is reduced by a predicted combustion state amount correcting means, a correction amount calculating means, and an ignition timing control means described below.

The predicted combustion state quantity correction means acquires the corrected predicted combustion state quantity by correcting the predicted combustion state quantity with the correction amount. This correction amount is updated by the correction amount calculation means.
The correction amount calculation means is the same as the corrected predicted combustion state quantity acquired for the previous combustion stroke by the predicted combustion state quantity acquisition means and the predicted combustion state quantity correction means by the actual combustion state quantity acquisition means. The correction amount is calculated based on a difference from the actual combustion state amount acquired with respect to the previous combustion stroke.

  The latest value of the actual combustion state quantity is a value acquired for the previous combustion stroke. Therefore, the correction amount calculation means includes the corrected predicted combustion state amount for the previous combustion stroke used when determining the ignition timing for the previous combustion stroke, and the actual combustion state amount acquired for the previous combustion stroke. Based on the difference between and, the correction amount for reducing the difference is calculated.

  Then, the ignition timing control means obtains the “current combustion stroke obtained by correcting the predicted combustion state quantity with respect to the current combustion stroke obtained by the predicted combustion state quantity obtaining means by the calculated correction amount. The ignition timing of the engine is controlled based on the “corrected predicted combustion state quantity for”. In this case, for example, the ignition timing control means may feedback control the ignition timing of the engine so that the “corrected predicted combustion state quantity for the current combustion stroke” matches the “predetermined target combustion state quantity”. desirable.

  Thus, the accuracy of the corrected predicted combustion state quantity used when determining the ignition timing for the current combustion stroke is such that the actual combustion state quantity for the previous combustion stroke and the corrected predicted combustion state quantity for the previous combustion stroke are Improved based on As a result, even in the transient operation state of the engine, the combustion state quantity for the current combustion stroke is accurately predicted, so the ignition timing determined based on the predicted combustion state quantity approaches the optimal ignition timing.

  In this case, the predicted combustion state quantity acquisition means calculates the ignition state for the previous combustion stroke and the operation state quantity other than the ignition timing for the current combustion stroke acquired by the operation state quantity acquisition means. By applying to the above, the predicted combustion state quantity for the current combustion stroke can be obtained. In other words, when the operation state quantity other than the ignition timing changes, it is predicted what the combustion state quantity in the current combustion stroke will be, and the current ignition timing is corrected based on the predicted value. As a result, the ignition timing can be appropriately controlled.

  On the other hand, another ignition timing control device according to the present invention includes a combustion state detection sensor, an actual combustion state amount acquisition unit, an operation state amount acquisition unit, a previous predicted combustion state amount acquisition unit, a model error amount acquisition unit, This time, a predicted combustion state quantity acquisition means, a model error compensation means, and an ignition timing control means are provided.

  The combustion state detection sensor, the actual combustion state amount acquisition unit, and the operation state amount acquisition unit are as described above.

  The previous predicted combustion state quantity acquisition means includes a combustion state model that describes the relationship between the operating state quantity and the quantity representing the combustion state at a predetermined timing of the combustion stroke. An example of the combustion state model is the above-described known Wiebe function that describes the relationship between the operation state amount and the combustion ratio MFB. Further, the previous predicted combustion state quantity acquisition means applies the operation state quantity for the previous combustion stroke acquired by the operation state quantity acquisition means to the combustion state model, thereby determining the combustion state at the specific timing of the previous combustion stroke. The amount to be represented is acquired as the previous predicted combustion state amount.

  The model error amount acquisition unit acquires a difference between the acquired previous predicted combustion state amount and the actual combustion state amount with respect to the previous combustion stroke acquired by the actual combustion state amount acquisition unit as a model error amount. The previous predicted combustion state quantity is a value obtained by adding no correction to the value obtained based on the combustion state model. Therefore, the difference between the previous predicted combustion state amount and the actual combustion state amount with respect to the previous combustion stroke is a model error amount that reflects the error itself based on the model error included in the combustion state model.

  The current predicted combustion state quantity acquisition means includes the same combustion state model as the combustion state model possessed by the previous predicted combustion state quantity acquisition means. Further, the current predicted combustion state quantity acquisition means applies the operation state quantity for the current combustion stroke acquired by the operation state quantity acquisition means to the combustion state model, so that the combustion state at the specific timing of the current combustion stroke Is obtained as the current predicted combustion state amount.

The model error compensating means obtains the corrected predicted combustion state quantity for the current combustion stroke by correcting the obtained current predicted combustion state quantity by the model error quantity obtained by the model error quantity obtaining means.
The ignition timing control means controls the ignition timing of the engine based on the corrected predicted combustion state quantity for the acquired current combustion stroke. In this case, for example, the ignition timing control means may feedback control the ignition timing of the engine so that the “corrected predicted combustion state quantity for the current combustion stroke” matches the “predetermined target combustion state quantity”. desirable.

  Thus, the difference between the actual combustion state amount and the previous predicted combustion state amount with respect to the previous combustion stroke is a value reflecting the error (model error amount) itself generated based on the model error. Therefore, the corrected predicted combustion state quantity for the current combustion stroke is accurately obtained by correcting the current predicted combustion state quantity with the model error amount. As a result, even in the transient operation state of the engine, the combustion state quantity for the current combustion stroke is accurately predicted, so the ignition timing determined based on the predicted combustion state quantity approaches the optimal ignition timing.

More specifically,
The previous predicted combustion state amount acquisition means applies the ignition timing for the previous combustion stroke and the operation state amount other than the ignition timing for the previous combustion stroke acquired by the operation state amount acquisition means to the combustion state model. Configured to obtain the previous predicted combustion state quantity by
The current predicted combustion state quantity acquisition means applies an ignition timing for the previous combustion stroke and an operating state quantity other than the ignition timing for the current combustion stroke acquired by the operating state quantity acquisition means to the combustion state model. By doing so, the present predicted combustion state quantity can be obtained.

  According to this, since the ignition timing and the operating state quantity that resulted in the actual combustion state quantity with respect to the previous combustion stroke coincide with the ignition timing and the operating state quantity that became the basis of the previous predicted combustion state quantity, The amount can be acquired with high accuracy.

As previously mentioned,
The combustion state detection sensor is an in-cylinder pressure sensor,
The actual combustion state quantity acquisition means includes the fuel burned in the combustion chamber up to the specific timing relative to the total amount of fuel that has contributed to work on the piston among all the fuel burned in the combustion chamber as the actual combustion state quantity. It is configured to obtain a combustion ratio that is a ratio of an accumulated amount of fuel that has contributed to work on the piston,
The combustion state model is preferably a model that describes a relationship between the operation state amount and a combustion ratio as a combustion state at a predetermined timing of the combustion stroke.

  According to this, a combustion ratio suitable for determining the ignition timing so as to improve the efficiency of the engine is accurately predicted. As a result, the fuel consumption of the engine can be improved and / or the torque of the engine can be increased.

Further, the combustion state model represents the combustion ratio MFBθ at the crank angle θ (predetermined timing of the combustion stroke) after compression top dead center,
MFBθ = 1−exp {−c · ((θ + αi) / αb) ^d }
Wiebe function approximated by
The parameters c and d are constant values, the parameter αi changes based on the ignition timing, and the parameter αb changes based on the overlap period in which the intake valve and the exhaust valve are simultaneously opened. It is desirable that

  The inventor has found that the combustion ratio MFBθ calculated when the parameter αi of the Wiebe function is changed and the actual combustion ratio MFBθ when the ignition timing is changed show very similar changes. More specifically, when the ignition timing is changed, the increase rate of the actual combustion rate MFBθ with respect to the crank angle θ hardly changes, but the crank angle θ at which the actual combustion rate MFBθ starts increasing changes. Similarly, when the parameter αi is changed, the increase speed of the calculated MFBθ with respect to the crank angle θ hardly changes, but the calculated crank angle θ at which the MFBθ starts to increase changes.

  Furthermore, the inventor has found that the combustion rate MFBθ calculated when the parameter αb of the Wiebe function is changed and the actual combustion rate MFBθ when the overlap period is changed show very similar changes. . More specifically, when the overlap period (for example, VVT advance amount) is changed, the crank angle θ at which the actual combustion rate MFBθ starts to increase hardly changes, but the crank angle θ of the actual combustion rate MFBθ. The rate of increase with respect to changes. Similarly, when the parameter αb is changed, the crank angle θ at which the calculated MFBθ starts increasing hardly changes, but the calculated increase rate of the MFBθ with respect to the crank angle θ changes.

  Therefore, by determining the parameter αi and the parameter αb as described above, it is possible to provide a combustion state model for obtaining the combustion ratio with higher accuracy.

  Hereinafter, an internal combustion engine control apparatus according to each embodiment of the present invention will be described with reference to the drawings. In this specification, the crank angle X ° after compression top dead center is expressed as “ATDC X ° or ATDCX”, and the crank angle Y ° before compression top dead center is expressed as “BTDC Y ° or BTDCY. ".

1. First embodiment (configuration)
FIG. 1 shows a schematic configuration of a system in which an ignition timing control device according to a first embodiment of the present invention is applied to a piston reciprocating spark ignition type multi-cylinder (four-cylinder) four-cycle internal combustion engine 10. Although FIG. 1 shows only a cross section of a specific cylinder, other cylinders have the same configuration.

  The internal combustion engine 10 includes a cylinder block portion 20 including a cylinder block, a cylinder block lower case, an oil pan, and the like, a cylinder head portion 30 fixed on the cylinder block portion 20, and a gasoline mixture to the cylinder block portion 20. An intake system 40 for supplying and an exhaust system 50 for releasing exhaust gas from the cylinder block 20 to the outside are included.

  The cylinder block unit 20 includes a cylinder 21, a piston 22, a connecting rod 23, and a crankshaft 24. The piston 22 reciprocates in the cylinder 21, and the reciprocating motion of the piston 22 is transmitted to the crankshaft 24 through the connecting rod 23, whereby the crankshaft 24 rotates. The heads of the cylinder 21 and the piston 22 form a combustion chamber 25 together with the cylinder head portion 30.

  The cylinder head unit 30 includes an intake port 31 that communicates with the combustion chamber 25, an intake valve 32 that opens and closes the intake port 31, an intake valve control device 33 that opens and closes the intake valve 32, an exhaust port 34 that communicates with the combustion chamber 25, an exhaust An exhaust valve 35 that opens and closes the port 34, an exhaust camshaft 36 that drives the exhaust valve 35, an ignition plug 37, an igniter 38 that includes an ignition coil that generates a high voltage applied to the ignition plug 37, and fuel are injected into the intake port 31. An injector (fuel injection means) 39 is provided.

  The intake valve control device 33 has a known configuration that adjusts and controls the relative rotation angle (phase angle) between an intake cam shaft and an intake cam (not shown) by hydraulic pressure, and opens the intake valve 32 (intake valve). The valve opening time) can be changed. In this example, the valve opening period (the valve opening crank angle width) of the intake valve is constant. Therefore, when the intake valve opening timing is advanced or retarded by a predetermined angle, the intake valve closing timing is also advanced or retarded by the predetermined angle. Further, the opening timing and closing timing of the exhaust valve 35 are constant. Accordingly, the overlap period changes as the intake valve opening timing is changed by the intake valve control device 33.

  The intake system 40 includes an intake manifold 41 including an intake manifold that communicates with the intake port 31 and forms an intake passage together with the intake port 31, an air filter 42 provided at an end of the intake pipe 41, and an intake pipe 41. A throttle valve 43 having a variable opening cross-sectional area of the passage and a throttle valve actuator 43a including a DC motor constituting throttle valve driving means are provided.

  The exhaust system 50 includes an exhaust manifold 51 communicating with the exhaust port 34, an exhaust pipe (exhaust pipe) 52 connected to the exhaust manifold 51, an upstream three-way catalyst 53 disposed in the exhaust pipe 52, and the catalyst 53. A downstream three-way catalyst 54 is provided in the downstream exhaust pipe 52. The exhaust port 34, the exhaust manifold 51, and the exhaust pipe 52 constitute an exhaust passage.

  On the other hand, this system includes a hot-wire air flow meter 61, a throttle position sensor 62, a cam position sensor 63, a crank position sensor 64, an in-cylinder pressure sensor 65 provided in each cylinder, a coolant temperature sensor 66, and an upstream of the first catalyst 53. An air-fuel ratio sensor 67 disposed in the exhaust passage, an air-fuel ratio sensor 68 and an accelerator opening sensor 69 disposed in the exhaust passage downstream of the first catalyst 53 and upstream of the second catalyst 54 are provided.

  The hot-wire air flow meter 61 detects the mass flow rate per unit time of the intake air flowing through the intake pipe 41 and outputs a signal representing the mass flow rate Ga. The throttle position sensor 62 detects the opening of the throttle valve 43 and outputs a signal representing the throttle valve opening TA. The cam position sensor 63 outputs one pulse every time the intake camshaft rotates 90 degrees, 90 degrees, and 180 degrees from a predetermined angle. This signal is also referred to as a G2 signal. The crank position sensor 64 outputs a pulse every time the crankshaft 24 rotates 10 degrees. The pulse output from the crank position sensor 64 is converted into a signal representing the engine rotational speed NE.

  The in-cylinder pressure sensor 65 detects the in-cylinder pressure that is the pressure in the combustion chamber 25 and outputs a signal representing the in-cylinder pressure Pc. That is, the in-cylinder pressure sensor 65 functions as a combustion state detection sensor that actually detects a physical quantity (in-cylinder pressure Pc) that changes in accordance with the combustion state of the air-fuel mixture in the combustion chamber 25.

  The upstream air-fuel ratio sensor 67 and the downstream air-fuel ratio sensor 68 detect the upstream and downstream air-fuel ratios of the catalyst 53 and output signals representing the upstream and downstream air-fuel ratios, respectively. The accelerator opening sensor 69 detects the operation amount of the accelerator pedal 81 operated by the driver, and outputs a signal representing the operation amount Accp of the accelerator pedal 81.

  The electric control device 70 includes a CPU 71 connected by a bus, a routine (program) executed by the CPU 71, a ROM 72 pre-stored with tables (look-up tables, maps), constants, and the like, and the CPU 71 temporarily stores data as necessary. The microcomputer 73 includes a RAM 73 that stores data, a backup RAM 74 that stores data while the power is on, and retains the stored data even when the power is shut off, and an interface 75 that includes an AD converter. The interface 75 is connected to the sensors 61 to 69 and supplies signals from the sensors 61 to 69 to the CPU 71. The interface 75 sends a drive signal to the intake valve control device 33, the injector 39, and the throttle valve actuator 43a in accordance with an instruction from the CPU 71, and sends an ignition signal to the igniter 38.

(control)
Next, various control contents performed by the ignition timing control device (hereinafter referred to as “first control device”) of the internal combustion engine 10 configured as described above will be described. In this example, the combustion ratio MFB as the combustion state quantity is obtained corresponding to the crank angle θ representing a predetermined timing. The combustion ratio MFB at the crank angle θ is expressed as MFBθ. This crank angle θ is 0 at the compression top dead center, takes a negative value that increases in absolute value as it advances from the compression top dead center toward the compression top dead center, and from the compression top dead center to the compression top dead center. It is defined to take a positive value, the absolute value of which increases as the angle is retarded later. For example, θ = −θ1 ° (θ1> 0) indicates that the crank angle is BTDCθ1.

<Overview of ignition timing control>
FIG. 2 is a graph showing the relationship between the ignition timing SA, the 8 ° combustion ratio MFB8, and the generated torque TRQ of the engine 10. In this specification, the ignition timing being SA means that the ignition timing is BTDC SA ° (SA> 0).

  As is apparent from FIG. 2, the 8 ° combustion ratio MFB8 at which the generated torque TRQ is maximum is about 60% (see region A in FIG. 2). Therefore, the first control apparatus sets the target value MFB8tgt (hereinafter referred to as “target combustion ratio MFB8tgt”) of the 8 ° combustion ratio MFB8 to 60% and estimates the 8 ° combustion ratio MFB8 in the current combustion stroke.

  Actually, the first control apparatus predicts the 8 ° combustion ratio MFB8 with respect to the current combustion stroke using the combustion state model at the time before the current combustion stroke, and corrects the predicted value with the correction value. To do. Further, the first control device feedback controls the ignition timing SA so that the corrected 8 ° combustion rate MFB8 matches the target combustion rate MFB8tgt. In addition, the first control unit obtains the previous combustion acquired based on the predicted and corrected 8 ° combustion ratio MFB8 and the detected in-cylinder pressure, which are the basis for determining the ignition timing with respect to the previous combustion stroke. The correction value is calculated based on the actual 8 ° combustion ratio MFB8 with respect to the stroke. As a result, an 8 ° combustion ratio MFB8 with respect to the current combustion stroke can be obtained with high precision even in a transient operation state such as during acceleration.

  Then, the first control device determines the ignition timing SA for the current combustion stroke so that the estimated and corrected 8 ° combustion ratio MFB8 for the current combustion stroke matches the target combustion ratio MFB8tgt. Therefore, the generated torque of the engine 10 is increased and the combustion efficiency is improved, so that the fuel consumption of the engine 10 can be improved. Moreover, it becomes possible to avoid the occurrence of knocking and the deterioration of emission, particularly in a transient operation state.

  In the present specification, the symbol (k) given after a variable indicates that the variable is a variable for the combustion stroke that occurs next in a specific cylinder (that is, the current combustion stroke). Therefore, the variable to which (k-1) is assigned is a variable for the previous combustion stroke (the combustion stroke immediately before the completion, that is, the previous combustion stroke) in the specific cylinder.

<Details of ignition timing control>
The first control device has each unit shown in FIG. 3 which is a functional block diagram of the first control device. Hereinafter, the function of each block will be described in order.

  The target value setting means A1 outputs a target combustion ratio MFB8tgt. The target combustion ratio MFB8tgt is a constant value (60%) in this example. The target value setting means A1 is configured to input an amount representing the engine operating state such as the load of the engine 10 and the engine speed NE, and to change the target combustion ratio MFB8tgt according to the amount representing the operating state. May be. The target combustion ratio MFB8tgt is set to such a value that the combustion efficiency of the engine is good, the emission amount of HC, CO, etc. is low, and torque fluctuation due to knocking or the like does not occur.

  The MFB calculation model A2 includes a combustion state model. This combustion state model will be described in detail later. The MFB calculation model A2 includes the ignition timing SA (k-1), the current engine load KL (k), the current engine speed NE (k) in the previous combustion stroke as the operating state quantities that affect the combustion state. The current VVT advance amount VVT (k) is input. The ignition timing SA (k-1) is acquired from the ignition timing data delay unit A3. The ignition timing data delay means A3 stores the ignition timing SA (k) for the current combustion stroke output from the feedback controller A6, which will be described later, in the RAM 73. From the stored data, the ignition timing SA ( k-1) is output.

  The MFB calculation model A2 applies the input operation state amount to the combustion state model at the calculation timing immediately before the start of the next combustion stroke (current combustion stroke), so that during the current combustion stroke The combustion ratio MFB8 (k) at ATDC 8 °, which is the specific timing, is predicted (calculated). The 8 ° combustion ratio MFB8 (k) predicted by the MFB calculation model A2 is referred to as “calculated combustion ratio MFB8cal (k)”.

  Since the calculation timing of the MFB calculation model A2 is immediately before the start of the current combustion stroke, the engine load KL is between that timing and the end of the current combustion stroke (or at least until ATDC 8 °). The engine speed NE and the VVT advance amount VVT can be regarded as not changing significantly. Accordingly, the current engine load KL (k), the current engine speed NE (k), and the current VVT advance amount VVT (k) are respectively the engine load KL (k) and the current VVT advance amount VVT (k). Are treated as the engine speed NE (k) in the combustion stroke and the VVT advance amount VVT (k) in the current combustion stroke. As described above, the operating state quantities of the ignition timing SA (k−1), the engine load KL (k), the engine speed NE (k), and the VVT advance amount VVT (k) are input to the MFB calculation model A2. Thus, the first control device is a physical quantity that is substantially different from the physical quantity (in-cylinder pressure) detected by the in-cylinder pressure sensor 65 and that represents the operating state of the engine 10. The operation state quantity acquisition means for acquiring the operation state quantity is provided.

  The load KL is a value (filling rate) proportional to the weight of the sucked cylinder air and is obtained from the mass flow rate Ga detected by the air flow meter 61 and the engine speed NE. The load KL may be acquired by a well-known air model describing the behavior of air. As described above, the VVT advance amount is determined based on the intake valve opening timing that is set to the most retarded angle when the opening timing and closing timing of the exhaust valve are constant. This is the advance amount of the valve opening timing. Further, the engine load KL (k), the engine speed NE (k), and the VVT advance amount VVT (k) are determined based on respective values at the present time and the like (for example, BTDC 5). It is also possible to predict and estimate each value of °).

  The calculated combustion ratio MFB8cal (k) acquired by the MFB calculation model A2 is an amount representing the combustion state at a predetermined timing of the combustion stroke. Therefore, it can be said that the combustion state model is a model that describes the relationship between the operation state amount and the amount representing the combustion state at a predetermined timing of the combustion stroke. Further, the MFB calculation model A2 applies the operation state quantity to the combustion state model, and obtains a quantity representing the combustion state at a specific timing of the combustion stroke (calculated combustion ratio MFB8cal (k)) as a predicted combustion state quantity. It can be said that it is a state quantity acquisition means.

  The predicted combustion state quantity correction means A4 obtains the corrected combustion ratio MFB8mfd (k), which is the corrected predicted combustion state quantity, by correcting the calculated combustion ratio MFB8cal (k), which is the predicted combustion state quantity, with the correction amount HMFB. It is supposed to be. More specifically, the predicted combustion state amount correction means A4 acquires the corrected combustion rate MFB8mfd (k) by adding the correction amount HMFB to the calculated combustion rate MFB8cal (k). The correction amount HMFB is output from a low-pass filter A10 described later.

  The feedback control deviation calculating means A5 calculates the feedback control deviation dMFB8 (= dMFB8 (k)) by subtracting the corrected combustion ratio MFB8mfd (k) from the target combustion ratio MFB8tgt.

  The feedback controller A6 determines the ignition timing SA (k) so that the feedback control deviation dMFB8 becomes zero. In other words, the feedback control deviation calculating means A5 and the feedback controller A6 perform the corrected combustion ratio MFB8mfd (k) that is the corrected predicted combustion state quantity for the current combustion stroke and the target combustion ratio MFB8tgt that is the predetermined target combustion state quantity. The ignition timing control means for performing feedback control (proportional / integral control) of the ignition timing SA (k) of the engine 10 is configured so that.

（１）式のＫｐは比例定数であり、Ｋｉは積分定数である。ＳｄＭＦＢ８（ｋ）はフィードバック制御用偏差ｄＭＦＢ８（ｋ）の積分値であり、下記（２）式に基いて求められる。

More specifically, the feedback controller A6 determines the ignition timing SA (k) for the current combustion stroke based on the following equation (1), and executes ignition at the determined ignition timing SA (k). Thus, an ignition instruction signal is sent to the igniter 38.

In the equation (1), Kp is a proportional constant, and Ki is an integral constant. SdMFB8 (k) is an integral value of the feedback control deviation dMFB8 (k), and is obtained based on the following equation (2).

  The actual MFB calculation means A7 is based on at least the in-cylinder pressure Pc (θ) = PC (8 °) detected by the in-cylinder pressure sensor 65 at the combustion rate MFB8 (k−1) at ATDC 8 ° during the previous combustion stroke. It comes to calculate. The 8 ° combustion ratio MFB8 (k−1) calculated by the actual MFB calculation means A7 is referred to as “actual combustion ratio MFB8act (k−1)”. The actual combustion ratio MFB8act (k-1) is an amount representing the actual combustion state at the specific timing of the previous combustion stroke (ie, the actual combustion state amount).

  By the way, as described above, the combustion ratio MFB is acquired as a value representing the ratio Qsum / Qtotal of the indicated heat quantity. Details of the method for obtaining the combustion ratio MFB from the in-cylinder pressure Pc detected by the in-cylinder pressure sensor 65 are disclosed in, for example, Japanese Patent Application Laid-Open No. 2006-144645, and the outline thereof will be described below.

The combustion ratio MFBθ at the crank angle θ is estimated by the following equation (3). In the equation (3), the crank angle θs (θs <0) is set so that both the intake valve 32 and the exhaust valve 35 are closed in the process toward the target combustion stroke (expansion stroke) and is sufficiently greater than the ignition timing. Is advanced (for example, θs = −60 °, ie, BTDC 60 °), and the crank angle θe (θe> 0) is later than the latest time when the combustion in the target combustion stroke is substantially ended. Is a predetermined time later than the exhaust valve opening timing (for example, θe = 60 °, ie, ATDC 60 °).

This equation (3) is based on the knowledge that the change pattern of the accumulated amount Q of heat that contributes to the work on the piston among the generated heat is substantially coincident with the change pattern of Pc (θ) V (θ) ^κ . Pc (θ) is the in-cylinder pressure at the crank angle θ, V (θ) is the volume of the combustion chamber 25 at the crank angle θ, and κ is the specific heat ratio (for example, 1.32) of the mixed gas.

  The actual MFB calculating means A7 obtains an actual combustion ratio MFB8act (k-1) with respect to the previous combustion stroke by substituting 8 ° into θ in the above equation (3).

  The combustion rate data delay means A8 stores the corrected combustion rate MFB8mfd (k) in the RAM 73 every time the corrected combustion rate MFB8mfd (k) is calculated, and corrects the previous combustion stroke from the stored data. The post-combustion ratio MFB8mfd (k-1) is output.

  The corrected basic amount calculation means A9 calculates the corrected basic amount eMDL by subtracting the corrected combustion rate MFB8mfd (k-1) from the actual combustion rate MFB8act (k-1). In other words, the corrected basic amount calculation means A9 is the corrected predicted combustion state quantity acquired for the previous combustion stroke by the MFB calculation model A2 as the predicted combustion state quantity acquisition means and the predicted combustion state quantity correction means A4. And the actual combustion ratio MFB8act (k−) as the actual combustion state quantity acquired for the previous combustion stroke by the actual MFB calculation means A7 as the actual combustion state quantity acquisition means. The difference (correction basic amount eMDL) from 1) is acquired.

  The low-pass filter A10 calculates the aforementioned correction amount HMFB by performing a known low-pass filter process on the correction basic amount eMDL acquired by the correction basic amount calculation means A9. This low-pass filter process is substantially the same as the process of time-integrating the correction basic quantity eMDL.

  As described above, the combustion rate data delay unit A8, the corrected basic amount calculation unit A9, and the low-pass filter A10 perform the corrected combustion rate MFB8mfd (k-1) acquired for the previous combustion stroke and the previous combustion stroke. On the other hand, a correction amount calculating means for calculating the correction amount HMFB based on the difference from the actual combustion ratio MFB8act (k−1) acquired for the above-described configuration is provided.

<Combustion state model>
Next, a combustion state model included in the MFB calculation model A2 will be described. This combustion state model is a model for obtaining a combustion rate MFB called a Wiebe function, and is represented by the following equation (4).

In the present embodiment, the variable (parameter) αi and the variable αb in the above equation (4) are obtained according to the following equations (5) and (6). In the MFB calculation model A2, SA (k-1) is substituted into the ignition timing SA of the equation (5), and the load KL, the engine speed NE, and the VVT advance amount VVT of the equations (5) and (6) are substituted. , KL (k), NE (k), and VVT (k) are respectively substituted to obtain the variable αi and the variable αb. In the MFB calculation model A2, the calculated combustion for the current combustion stroke is performed by substituting the variable αi and the variable αb obtained in the equation (4) and by substituting 8 ° for θ in the equation (4). The ratio MFB8cal (k) is calculated. Therefore, the combustion state model is a calculated combustion ratio that is an amount representing the combustion state at a predetermined timing of the operation state (SA (k−1), KL (k), NE (k), VVT (k)) and the combustion stroke. It can be said that this is a model describing the relationship with MFB8cal (k). Note that k1 to k7 are fitness constants.

  The above-mentioned Wiebe function is generally expressed by the following equation (7). The Wiebe function itself is known as an approximate function model that simulates how the combustion ratio changes. In this function, the parameters c and d interfere with the parameters αi and αb. Therefore, it is recommended that the parameters c and d be fixed values. Therefore, the inventor set the parameter c and the parameter d to “5” and “4”, respectively, as described above.

However, the approximation accuracy cannot be improved unless the parameters αi and αb are set appropriately. Therefore, the inventor conducted the following studies. As a result, the inventor has found that it is preferable to set the parameter αi and the parameter αb according to the above equations (5) and (6).

  First, the inventor measured the change of the actual combustion ratio MFB with respect to the crank angle θ when the ignition timing SA was set to 22 ° BTDC, 28 ° BTDC, and 32 ° BTDC. FIG. 4 is a graph showing the results. On the other hand, FIG. 5 is a graph showing the change of y with respect to the variable x when the parameter αi in the equation (7) is changed and the other parameters c, d, and αb are set to constant values.

  The inventor has compared the ignition timing SA with the parameter αi by comparing FIG. 4 and FIG. 5 (that is, the actual change in the combustion ratio MFB when the ignition timing SA is changed, and the parameter It was found that the change in the calculated value y when αi is changed is similar. More specifically, as shown in FIG. 4, when the ignition timing SA is changed, the rate of increase of the actual combustion rate MFB with respect to the crank angle θ hardly changes, but the actual combustion rate MFB starts to increase. The crank angle θ changes. Similarly, as shown in FIG. 5, when the parameter αi is changed, the slope (increase speed) of the calculated value y with respect to x hardly changes, but the value of x at which the calculated value y starts to increase changes.

  Next, the inventor measured the change of the actual combustion rate MFB with respect to the crank angle θ when the VVT advance amount VVT was set to 0 °, 20 °, and 40 °. FIG. 6 is a graph showing the results. On the other hand, FIG. 7 is a graph showing the change of y with respect to the variable x when the parameter αb in the above equation (7) is changed and the other parameters c, d, and αi are constant values.

  The inventor found that the VVT advance amount VVT (that is, the overlap period) and the parameter αb are very correlated by comparing FIG. 6 and FIG. In other words, it has been found that the actual change in the combustion ratio MFB when the VVT advance amount VVT is changed is similar to the change in the calculated value y when the parameter αb is changed. More specifically, as shown in FIG. 6, when the VVT advance amount VVT is changed, the crank angle θ at which the actual combustion rate MFB starts increasing hardly changes, but the actual combustion rate MFB increases. The speed changes. Similarly, as shown in FIG. 7, when the parameter αb is changed, the value of x at which the calculated value y starts to increase hardly changes, but the slope (increase rate) of the calculated value y with respect to x changes.

  From the above, the inventor determines that it is preferable that the parameter αi is expressed by a linear expression of the ignition timing SA (at least, the parameter αi is expressed by a function having the ignition timing SA as a variable). The parameter αb is expressed by a linear expression of the VVT advance amount VVT (at least, the parameter αb is expressed by a function having the VVT advance amount VVT as a variable). It was judged that it was suitable (see the above formula (6)). Further, as the load KL increases and the NE decreases, the combustion speed with respect to the crank angle θ (the rate of increase of the combustion ratio with respect to the crank angle θ) increases, so the parameter KL / NE was introduced. That is, it is determined that the parameter αb is preferably expressed by a linear expression of the variable KL / NE. Then, as an adjustment to the introduction of the variable KL / NE into the parameter αb, the variable KL / NE and the variable NE were introduced into the parameter αi (see the above formula (5)).

  FIG. 8 is calculated by the ignition timing SA during acceleration, the load KL, the VVT advance amount VVT, the actual 8 ° combustion ratio MFB8 (actually measured value), and the combustion state model expressed by the above equations (4) to (6). It is the graph which showed the mode of the change of the calculated 8 degree combustion ratio MFB8 (model value). As is apparent from this figure, although there is an error Δ due to a model error between the actual measurement value and the model value, it is understood that the timing of the actual value change and the timing of the model value change are very close. Further, the error Δ can be reduced by strictly adapting the adaptation constants k1 to k7 in the above equations (5) and (6). That is, if the parameter αi and the parameter αb are determined as in the above equations (5) and (6), the 8 ° combustion ratio MFB8 can be accurately estimated using the combustion state model.

  The parameter αi may be represented by a function that monotonously increases with respect to the ignition timing SA (the advance angle of the ignition timing before top dead center is positive), and the parameter αb may be represented by a function that monotonously increases with respect to the VVT advance amount VVT. .

  As described above, the first controller predicts the 8 ° combustion ratio MFB8 with respect to the current combustion stroke (explosion stroke, expansion stroke) using the combustion state model. Even in the state, the ignition timing can be accurately controlled. Furthermore, the calculated combustion rate predicted for the current combustion stroke based on the difference between the corrected combustion rate MFB8mfd (k-1) and the actual combustion rate MFB8act (k-1), both of which are values relative to the previous combustion stroke. By correcting MFB8cal (k), the corrected combustion rate MFB8mfd (k) used for ignition timing control is obtained, and thus the corrected combustion rate MFB8mfd (k) can be obtained with high accuracy. As a result, even if a model error is included in the combustion state model, the ignition timing approaches the optimum value, so that the torque and fuel consumption of the engine 10 can be improved.

  FIG. 9 is a graph showing the behavior of each value in the conventional control device and the first control device when the VVT advance amount is suddenly changed. In FIG. 9, the thin broken line C1 indicates the actual 8 ° combustion ratio when the ignition timing is not changed, and the thick broken line C2 indicates the conventional actual combustion ratio MFB8act (k−1) for controlling the ignition timing for the current combustion stroke. The behavior of the actual 8 ° combustion rate when used is shown. On the other hand, the thin solid line C3 shows the corrected combustion rate MFB8mfd (k) when the ignition timing is not changed, and the thick solid line C4 shows the case where the corrected combustion rate MFB8mfd (k) is used for controlling the ignition timing for the current combustion stroke. Shows the behavior of the actual 8 ° combustion rate.

  As understood from this figure, when the conventional actual combustion rate MFB8act (k-1) is used for controlling the ignition timing, when the VVT advance amount suddenly changes, the 8 ° combustion rate associated with the VVT advance amount The gap is corrected one cycle later. For this reason, the difference between the 8 ° combustion ratio and the target value becomes large, and it takes a long time for the 8 ° combustion ratio to converge to the target value (see curve C2). On the other hand, when the corrected combustion rate MFB8mfd (k) is used to control the ignition timing as in the first control device, a sudden change in the 8 ° combustion rate accompanying a sudden change in the VVT advance amount is predicted. The ignition timing is controlled so as to suppress a sudden change in the 8 ° combustion ratio. As a result, the amount of deviation from the target value of the 8 ° combustion ratio accompanying the VVT advance amount can be quickly reduced (see curve C4). In FIG. 9, “err” represents an error due to the combustion state model. However, according to the first control device, this error can be reduced by the correction value HMFB, so that the ignition timing is made closer to an appropriate value. be able to.

(Actual operation)
Next, the actual operation of the first control device will be described. The routine described below is a routine executed by the CPU 71 of the electric control device 70 for a specific cylinder. The CPU 71 executes the same routine for the other cylinders.

  The CPU 71 executes an in-cylinder pressure acquisition routine (not shown) every time a predetermined minute crank angle elapses, and the crank angle θ and the in-cylinder pressure Pc (θ) at the time when the routine is executed are stored in the RAM 73.

  Further, the CPU 71 repeatedly executes the routine shown in FIG. 10 every time the crank angle matches the “predetermined crank angle (for example, ATDC 160 °) after the combustion stroke is substantially finished”. Therefore, when the predetermined timing is reached, the CPU 71 starts the processing of the routine of FIG. 10 from step 1000, performs the following processing from step 1010 to step 1060, proceeds to step 1095, and once ends this routine.

  Step 1010: The CPU 71 substitutes the in-cylinder pressure Pc (θ) for each crank angle θ acquired by the in-cylinder pressure acquisition routine and the combustion chamber volume V (θ) corresponding to the crank angle θ into the above equation (3). Then, the combustion ratio MFBθ for each crank angle θ is calculated. Each combustion ratio MFBθ calculated here is an actual combustion ratio MFBθact (k−1) in the previous combustion stroke. The calculated actual combustion ratio MFBθact (k−1) includes the actual combustion ratio MFB8act (k−1) at ATDC 8 °.

  Step 1020: The CPU 71 uses the actual combustion ratio MFBθact (k−1) calculated in Step 1010 to change the amount ΔMFB of the actual combustion ratio MFBθact (k−1) in the N ° (here, crank angle 15 °) width. Is calculated for each predetermined minute crank angle. That is, the amount of change ΔMFB is calculated according to ΔMFB = MFBθact (k−1) −MFBθbact (k−1) (where θb = θ−N).

  Step 1030: The CPU 71 obtains a maximum value (combustion rate maximum change rate) ΔMFBmax from the plurality of combustion rate change amounts ΔMFB calculated in Step 1020 (see FIG. 11). Further, the CPU 71 acquires the crank angle θ with respect to the maximum combustion rate change rate ΔMFBmax as the crank angle CAmax, and acquires the actual combustion rate MFBθact (k−1) at the crank angle CAmax as MFBcamax.

Step 1040: The CPU 71 applies the ignition timing SA (= SA (k−1)) for each combustion value obtained in step 1030 and the immediately preceding combustion stroke to the following equation (8) to obtain all the values shown in FIG. The combustion corresponding period CP is estimated (calculated). The total combustion correspondence period CP is represented by a crank angle width (crank angle magnitude, unit (°)).

  The total combustion correspondence period CP obtained by the above equation (8) is a period from the ignition timing SA (k−1) to the combustion end timing CAe. The combustion end timing CAe is a timing at which the combustion of the mixed gas in the combustion chamber substantially ends. Since the combustion end timing CAe is obtained by the following method, the above equation (8) is obtained.

  (1) As shown in FIG. 11, a straight line (extrapolated line) Lext that approximates a change in the actual combustion ratio MFBθact (k−1) is drawn. The straight line Lext is a point Pmax determined by the crank angle CAmax corresponding to the maximum value ΔMFBmax (the maximum combustion rate change rate) of the combustion rate change amount ΔMFB obtained in step 1030 and the actual combustion rate MFBcamax at the crank angle CAmax. Pass through. The slope of the straight line Lext is ΔMFBmax / N.

  (2) The crank angle CAe corresponding to the point Pe at which the straight line Lext reaches the combustion rate of 100% is obtained as the combustion end timing CAe. The combustion rate of 100% corresponds to the total amount of fuel that contributed to the work for the piston among all the fuel burned in the combustion chamber from the crank angle θs (BTDC 60 °) to the crank angle θe (ATDC 60 °). Value, which corresponds to the denominator of equation (3).

  Step 1050: The CPU 71 calculates the corrected basic amount eMDL by subtracting the corrected combustion rate MFB8mfd (k−1) from the actual combustion rate MFB8act (k−1) at ATDC 8 °. The corrected combustion ratio MFB8mfd (k−1) is obtained in step 1570 of the routine shown in FIG.

Step 1060: The CPU 71 calculates the above-described correction amount HMFB by performing low-pass filter processing on the correction basic amount eMDL acquired in step 1050. This low-pass filter process is simply performed based on the following equation (9), for example. The value n in the equation (9) is a predetermined constant greater than 0 and less than 1.

  In addition, the CPU 71 performs a routine for controlling the VVT advance amount shown in FIG. 12 according to a predetermined crank angle (for example, BTDC 180 ° after the combustion stroke is substantially finished). Therefore, at a predetermined timing, the CPU 71 starts the routine of FIG.12 from step 1200, proceeds to step 1210, and obtains it in step 1040 described above. It is determined whether or not the total combustion correspondence period CP is longer than the target total combustion correspondence period CPtgt.

  The target total combustion correspondence period CPtgt is set to the total combustion correspondence period CP corresponding to the longest overlap period (the most advanced VVT advance amount) within a range in which the HC and CO emissions do not increase. It is predetermined. When the overlap period becomes longer, the amount of burned gas (also referred to as “internal EGR gas” or “self EGR gas”) that is discharged from the combustion chamber to the intake port and then sucked back into the combustion chamber. Will increase. As a result, the combustion speed becomes smaller, so that the total combustion correspondence period CP becomes longer. Conversely, when the overlap period is shortened, the amount of internal EGR gas decreases. As a result, the combustion speed increases, so the total combustion response period CP is shortened.

  If the total combustion corresponding period CP is larger than the target total combustion corresponding period CPtgt at the time of determination in step 1210, it means that the combustion speed is too low (the amount of burned gas is excessive). Accordingly, the CPU 71 proceeds to step 1220 to retard the intake valve opening timing IO by a predetermined angle ΔIO so that the overlap period is shortened and the combustion speed is increased. That is, the VVT advance amount is decreased. On the other hand, if the total combustion correspondence period CP is smaller than the target total combustion correspondence period CPtgt, it means that the combustion speed is too high (the amount of burned gas is too small). Accordingly, the CPU 71 proceeds to step 1230 to advance the intake valve opening timing IO by a predetermined angle ΔIO so that the overlap period is lengthened and the combustion speed is decreased. That is, the VVT advance amount is increased.

  In this example, the intake valve opening timing IO takes a positive value that increases in absolute value as it advances from the intake top dead center (exhaust top dead center) toward the intake top dead center. It is represented by a crank angle that takes a negative value, the absolute value of which increases as the angle is retarded from the dead center toward the intake top dead center.

  Thereafter, the CPU 71 proceeds to step 1240, and sets the intake valve opening timing IO so that the intake valve 32 opens at the intake valve opening timing IO determined in step 1220 or step 1230. As a result, the intake valve control device 33 opens the intake valve 32 at the set intake valve opening timing IO. The intake valve control device 33 closes the intake valve 32 so that a timing obtained by adding a constant intake valve opening angle IOθ to the intake valve disclosure valve timing IO becomes the intake valve closing timing IC.

  Next, the CPU 71 proceeds to step 1250 and stores the value obtained by subtracting the intake valve opening reference timing IOint from the intake valve opening timing IO as the VVT advance amount VVT (k) for the current combustion stroke. The intake valve opening reference timing IOint is the intake valve opening timing IO when it is set to the most retarded side within a range in which the intake valve opening timing can be changed. Thereafter, the CPU 71 proceeds to step 1295 to end the present routine tentatively.

By the way, FIG. 13 represents the measurement results on how the CO ₂ and HC emissions and the total combustion response period CP change with respect to the VVT advance amount. In this measurement, the ignition timing SA was changed so that the 8 ° combustion ratio MFB8 was 20, 30, 40, and 50%.

As understood from FIG. 13, even if the ignition timing SA varies, the VVT advance amount and the total combustion correspondence period CP maintain a substantially 1: 1 relationship. In other words, if the VVT advance amount (overlap period, burned gas amount) is a certain value, even if the ignition timing SA changes, the total combustion correspondence period CP hardly changes. Therefore, as shown by the region A, the VVT advance amount is increased as much as possible in a range where the CO and HC emission amounts do not increase (the CO ₂ emission amount does not decrease and the HC emission amount does not increase). In order to control the VVT advance amount so that the overlap period is the longest and the burnt gas amount is the maximum, the total combustion correspondence period CP is the total combustion correspondence period CP in the region A (example in FIG. 13). Then, the VVT advance amount may be controlled so as to coincide with CP = 70 °.

  Therefore, the first control device controls the VVT advance amount so that the total combustion correspondence period CP coincides with a predetermined target total combustion correspondence period CPtgt. The target total combustion correspondence period CPtgt is set to a period in which the overlap period is as long as possible within a range where the CO and HC emission amounts do not increase. Therefore, the first control device can reduce the NOx emission amount without increasing the HC and CO emission amounts and reduce the pumping loss. As a result, an internal combustion engine having a small exhaust gas emission amount and excellent fuel efficiency is provided.

FIG. 13 also shows the relationship between the substantial combustion period CPa and the CO ₂ and HC emissions with respect to the VVT advance amount. The substantial combustion period CPa is a crank angle width until the combustion ratio approximated by the straight line Lext reaches 0 to 100% as shown in FIG. As shown in the region B with respect to the region A in FIG. 13, the substantial combustion period CPa corresponding to the VVT advance amount at which the CO and HC emission starts to increase varies as the ignition timing SA changes. Therefore, it is understood that it is preferable to use the above-described total combustion correspondence period CP for feedback control of the VVT advance amount rather than the substantial combustion period CPa.

  FIG. 14 is a graph showing the results of measuring the relationship between the substantial combustion period CPa and the HC emission amount and the relationship between the total combustion response period CP and the HC emission amount for another engine 10. In this measurement, the ignition timing SA was changed so that the 8 ° combustion ratio MFB8 was 20, 30, 40, and 50%.

  According to FIG. 14A, when the 8 ° combustion ratio MFB8 is 20, 30, 40, and 50%, the optimum value of the substantial combustion period CPa in a range where the HC emission amount does not increase is the straight line L1, As indicated by L2, L3, and L4, it varies depending on the ignition timing SA and exists so as to have a certain width W. In other words, when the ignition timing changes even if the VVT advance amount is feedback controlled so that the actual combustion period CPa matches the optimum target combustion period in a state where ignition is performed at a certain ignition timing. Since the VVT advance amount is excessively large or small, the HC and CO emissions may be increased, or the NOx emissions may be increased and the pumping loss reduction width may be decreased.

  According to FIG. 14B, even if the ignition timing SA is changed so that the 8 ° combustion ratio MFB8 matches 20, 30, 40, and 50%, the HC emission amount starts to increase. The period CP is only one point indicated by the straight line Lopt. Accordingly, the total combustion corresponding period CP indicated by the straight line Lopt is set to the target total combustion corresponding period CPtgt, and the VVT advance amount is set so that the actually estimated total combustion corresponding period CP coincides with the target total combustion corresponding period CPtgt. , The overlap period can be set as long as possible (the amount of burned gas as much as possible) within a range in which the HC emission amount (and hence the CO emission amount) does not increase regardless of the ignition timing SA. Thus, the NOx emission amount can be reduced and the pumping loss can be reduced.

  As can be understood from the above description, the first control device controls the VVT advance amount by using the total combustion correspondence period CP, so that the overlap amount becomes appropriate and the burned gas amount becomes an appropriate amount. . As a result, the first control device can reduce the NOx emission amount and the pumping loss without increasing the HC and CO emission amounts.

  On the other hand, the CPU 71 repeatedly executes the routine shown in FIG. 15 every time the crank angle coincides with a predetermined crank angle (for example, BTDC 90 °) immediately before the start of the combustion stroke. Accordingly, when the predetermined timing comes, the CPU 71 starts the processing of the routine of FIG. 15 from step 1500, performs the following processing in steps 1510 to 1560, then proceeds to step 1595 to end the present routine tentatively.

  Step 1510: The CPU 71 sets the current engine rotational speed NE (k), the current engine load KL (k), the current VVT advance amount VVT (k), and the previous operating state quantities that affect the combustion state. Ignition timing SA (k-1) in the combustion stroke is input and stored as engine speed NE, load KL, VVT advance amount VVT, and ignition timing SA.

  Step 1520: The CPU 71 applies the operating state quantities (NE, KL, VVT and SA) stored in Step 1510 to the combustion state model (Wiebe function) expressed by the above equations (4) to (6). The calculated combustion ratio MFB8cal (k) is calculated by substituting 8 ° into the crank angle θ in the equation (4).

  Step 1530: The CPU 71 stores a value obtained by adding the correction value HMFB to the calculated combustion ratio MFB8cal (k) obtained in Step 1520 as a corrected combustion ratio MFB8mfd (k). The correction value HMFB is obtained in step 1060 of FIG.

  Step 1540: The CPU 71 determines an 8 ° target combustion ratio MFB8tgt. Here, the target combustion ratio MFB8tgt is a constant value. Note that the 8 ° target combustion ratio MFB8tgt may be changed based on a parameter representing the operating state of the engine 10 for determining the target combustion ratio. The parameters representing the operation state for determining the target combustion ratio are the load KL and the engine speed NE. Other parameters such as the cooling water temperature THW may be added as parameters representing this operating state.

Step 1550: The CPU 71 calculates a feedback control deviation dMFB8 (k) by subtracting the corrected combustion ratio MFB8mfd (k) from the target combustion ratio MFB8tgt.
Step 1560: The CPU 71 performs feedback control (proportional / integral control) of the ignition timing so that the value of the feedback control deviation dMFB8 (k) becomes “0”.
Step 1570: The CPU 71 stores the corrected combustion rate MFB8mfd (k) calculated in step 1530 in the corrected combustion rate MFB8mfd (k-1) used in step 1050 of FIG.

  As described above, according to the ignition timing control apparatus according to the first embodiment, the correction basics are obtained by subtracting the corrected combustion rate MFB8mfd (k-1) from the actual combustion rate MFB8act (k-1) at ATDC 8 °. An amount eMDL is calculated (step 1050 in FIG. 10), and a correction amount HMFB obtained by low-pass filtering the correction basic amount eMDL is calculated (step 1060). The ignition timing control device obtains a value obtained by adding the correction value HMFB to the calculated combustion rate MFB8cal (k) as a corrected combustion rate MFB8mfd (k) (step 1530 in FIG. 15), and the corrected combustion rate MFB8mfd ( This ignition timing SA is determined so that k) coincides with the target combustion ratio MFB8tgt (steps 1540 to 1560).

  Therefore, since the corrected combustion ratio MFB8mfd (k) is accurately obtained before the start of the combustion stroke (before the ignition timing is calculated), the ignition timing can be accurately controlled even in a transient operation state such as during acceleration. In addition, since the VVT advance amount increases in a range where the HC and CO emission amounts do not increase (the overlap period becomes longer), the torque and fuel consumption of the engine 10 can be improved. Note that the ignition timing control device according to the first embodiment can also be said to be a device that obtains the corrected combustion rate MFB8mfd (k) by the “disturbance observer” method.

2. Second Embodiment Next, an ignition timing control device (hereinafter referred to as “second control device”) according to a second embodiment of the present invention will be described. The second control device is different from the first control device only in the function (operation) of the electric control device 70. Accordingly, differences from the first control device will be described below.

<Overview of ignition timing control>
Similar to the first control device, the second control device predicts the 8 ° combustion ratio MFB8 with respect to the current combustion stroke using the combustion state model at the time before the current combustion stroke, and corrects the predicted value. Correct by value. Then, the ignition timing SA is feedback-controlled so that the corrected 8 ° combustion ratio matches the target combustion ratio MFB8tgt. However, the second control device corrects the 8 ° combustion ratio MFB8 for the current combustion stroke estimated in the same manner as the first control device by a method different from that of the first control device.

  In the first control device, the corrected combustion ratio MFB8mfd (k) is determined based on the ignition timing SA (k-1) in the previous combustion stroke. Therefore, the corrected combustion rate MFB8mfd (k-1) compared with the actual combustion rate MFB8act (k-1) for the purpose of compensating for the error of the combustion state model is the ignition timing SA two times before (two times before). It is determined based on (k-2). On the other hand, the actual combustion ratio MFB8act (k-1) is a value obtained as a result of ignition and combustion performed at the previous (one time before) ignition timing SA (k-1). That is, the basic ignition timing SA is different between the actual combustion ratio MFB8act (k-1) and the corrected combustion ratio MFB8mfd (k-1). For this reason, the corrected basic quantity eMDL, which is the difference between the actual combustion rate MFB8act (k-1) and the corrected combustion rate MFB8mfd (k-1), does not represent the error itself of the combustion state model. It is necessary to perform a filter process to obtain the correction value HMFB, and correction may be delayed.

<Details of ignition timing control>
The second control device is a device that pays attention to the problems of the first control device described above, and includes each unit illustrated in FIG. 16 that is a functional block diagram thereof. Hereinafter, the function of each block will be described in order.

  The target value setting means B1 is the same means as the target value setting means A1. That is, the target value setting means B1 outputs the target combustion ratio MFB8tgt.

  The first MFB calculation model B2 is the same means as the MFB calculation model A2. That is, the first MFB calculation model B2 includes the combustion state model (that is, the Wiebe function expressed by the above expressions (4) to (6)) included in the MFB calculation model A2. The first MFB calculation model B2 includes, as the operating state quantity that affects the combustion state, the ignition timing SA (k-1) in the previous combustion stroke, the (current) engine load KL (k) for the current combustion stroke, and the current time The engine rotational speed NE (k) for the current combustion stroke and the VVT advance amount VVT (k) for the current combustion stroke are input. The ignition timing SA (k-1) is acquired from the ignition timing data delay means B3 which is the same means as the ignition timing data delay means A3.

  In the first MFB calculation model B2, the input operation state quantities (SA (k-1), KL (k), KL, k) are calculated at a calculation timing immediately before the next combustion stroke (current combustion stroke) is about to start. By applying NE (k) and VVT (k)) to the combustion state model, the combustion rate MFB8 (k) at ATDC 8 ° which is a predetermined timing during the current combustion stroke (that is, the calculated combustion rate MFB8cal (k) )) Is predicted (calculated).

  The predicted combustion state quantity correction means B4 corrects the calculated combustion ratio MFB8cal (k), which is the predicted combustion state quantity, with the model error amount GosaMDL (correction quantity), thereby correcting the corrected combustion ratio MFB8mfd, which is the corrected predicted combustion state quantity. k). More specifically, the predicted combustion state amount correction means B4 acquires the corrected combustion rate MFB8mfd (k) by adding the model error amount GosaMDL to the calculated combustion rate MFB8cal (k). The model error amount GosaMDL is output from model error amount calculation means B10 described later.

  The feedback control deviation calculating means B5 is the same means as the feedback control deviation calculating means A5. That is, the feedback control deviation calculating means B5 calculates the feedback control deviation dMFB8 (= dMFB8 (k)) by subtracting the corrected combustion ratio MFB8mfd (k) from the target combustion ratio MFB8tgt.

  The feedback controller B6 is the same means as the feedback controller A6. That is, the feedback controller B6 determines the ignition timing SA (k) so that the feedback control deviation dMFB8 (k) becomes zero. In other words, the feedback control deviation calculating means B5 and the feedback controller B6 perform the corrected combustion ratio MFB8mfd (k) that is the corrected predicted combustion state quantity for the current combustion stroke and the target combustion ratio MFB8tgt that is the predetermined target combustion state quantity. The ignition timing control means for performing feedback control (proportional / integral control) of the ignition timing SA (k) of the engine 10 is configured so that.

  The real MFB calculation means B7 is the same means as the real MFB calculation means A7. That is, the actual MFB calculating means B7 sets “actual combustion ratio MFB8act (k−1)”, which is the combustion ratio MFB8 (k−1) at ATDC 8 ° during the previous combustion stroke, to θ in the above equation (3). It is calculated by substituting 8 °.

  The operating state amount delay means B8 is the engine load KL (k) for the current combustion stroke, which is the operating state amount that affects the combustion state, the engine speed NE (k) for the current combustion stroke, and the current combustion stroke. The VVT advance amount VVT (k) is input. The operating state quantity delay means B8 stores these data in the RAM 73, and among the stored data, the engine load KL (k-1) for the previous combustion stroke, the engine speed NE (k for the previous combustion stroke). -1) and the VVT advance amount VVT (k-1) with respect to the previous combustion stroke are output.

  The second MFB calculation model B9 is the same combustion state model as the combustion state model included in the MFB calculation model A2 and the first MFB calculation model B2 (that is, the Wiebe function expressed by the equations (4) to (6)). It has. The second MFB calculation model B9 receives the ignition timing SA (k-1) output from the ignition timing data delay means B3 and the operating state quantity (load KL (k-1) output from the operating state quantity delay means B8. ), NE (k-1) and VVT (k-1)).

  Further, the second MFB calculation model B9 uses the input operation state quantities (SA (k-1), KL (k-1), NE (k-1), and VVT (k-1)) as the combustion state model. By applying, the combustion ratio MFB8 (k-1) (that is, the calculated combustion ratio MFB8cal (k-1)) at ATDC 8 ° which is a predetermined timing during the previous combustion stroke is predicted (calculated). Yes.

  The model error amount calculation means B10 calculates the model error amount GosaMDL by subtracting the calculated combustion rate MFB8cal (k-1) from the actual combustion rate MFB8act (k-1).

  By each means described above, the second control apparatus acquires the model error amount GosaMDL by subtracting the calculated combustion ratio MFB8cal (k-1) from the actual combustion ratio MFB8act (k-1). The actual combustion ratio MFB8act (k-1) and the calculated combustion ratio MFB8cal (k-1) are equal to each other in the ignition timing SA (k-1) and the operating state quantities (KL (k-1), NE (k-1). ) And VVT (k-1)). Moreover, the calculated combustion ratio MFB8cal (k-1) is a value obtained by adding no correction to the value calculated based on the combustion state model.

  Accordingly, the model error amount GosaMDL is a value that directly reflects the model error of the combustion state model, and thus the calculated combustion ratio MFB8cal (k) predicted for the current combustion stroke is corrected by the model error amount GosaMDL. The second control device can compensate the model error of the combustion state model more directly. As a result, the corrected combustion ratio MFB8mfd (k) used for the ignition timing control is estimated quickly and more accurately, so that the ignition timing of the engine can be made closer to an appropriate value including the transient operation state.

  FIG. 17 is a time chart showing the results of measuring changes in each value when the load KL and the VVT advance amount VVT change. In FIG. 17, the solid line Da represents the ignition timing in the second control device, and the broken line Db represents the ignition timing in the conventional device. The solid line Ea indicates the 8 ° combustion rate MFB8 in the second control device, and the broken line Eb indicates the 8 ° combustion rate MFB8 in the conventional device (device that determines the ignition timing by the actual combustion rate MFB8act (k−1)). In this example, the target combustion ratio MFB8tgt is 60%.

  As is apparent from FIG. 17, the 8 ° combustion rate MFB8 according to the conventional apparatus requires a long time Tb from the change of the load KL and the VVT advance amount VVT until it converges, and the 8 ° combustion rate MFB8 The fluctuation range is as large as Wb. On the other hand, the 8 ° combustion rate MFB8 by the second control device converges in a short time Ta after the load KL and the VVT advance amount VVT change, and the fluctuation range of the 8 ° combustion rate MFB8 is as small as Wa. It has become. Therefore, according to the second control device, it is confirmed that the ignition timing SA is appropriately controlled even in the transient operation state, and as a result, the 8 ° combustion ratio MFB8 does not deviate significantly from the target combustion ratio MFB8tgt. .

(Actual operation)
Next, the actual operation of the second control device will be described. The routine described below is a routine executed by the CPU 71 of the electric control device 70 for a specific cylinder. The CPU 71 executes the same routine for the other cylinders.

  As in the first embodiment, the CPU 71 executes an in-cylinder pressure acquisition routine (not shown) every time a minute crank angle elapses, and stores the crank angle θ and the in-cylinder pressure Pc (θ) at the time when the routine is executed in the RAM 73. Storing.

  Further, the CPU 71 repeatedly executes the routine shown in FIG. 18 every time the crank angle matches the “predetermined crank angle (for example, ATDC 160 °) after the combustion stroke is substantially finished”. Therefore, when the predetermined timing is reached, the CPU 71 starts the processing of the routine of FIG. 18 from step 1800, and performs the following processing in steps 1810 to 1840.

Step 1810: The CPU 71 calculates the actual combustion ratio MFBθact (k−1) with respect to each crank angle θ using the above equation (3), similarly to step 1010. The calculated actual combustion ratio MFBθact (k−1) includes the actual combustion ratio MFB8act (k−1).
Step 1820: As in step 1020, the CPU 71 calculates a change amount ΔMFB of the actual combustion ratio MFBθact (k−1) in the width of N ° (here, the crank angle is 15 °) for each predetermined minute crank angle.

  Step 1830: The CPU 71 obtains the maximum value (combustion rate maximum change rate) ΔMFBmax from the combustion rate change amount ΔMFB calculated in step 1820, similarly to step 1030. Further, the CPU 71 acquires the crank angle θ with respect to the maximum combustion rate change rate ΔMFBmax as the crank angle CAmax, and acquires the actual combustion rate MFBθact (k−1) at the crank angle CAmax as MFBcamax.

  Step 1840: Similar to step 1040, the CPU 71 applies the ignition timing SA (k-1) for the previous combustion and the ignition timing SA (k-1) for the previous combustion to the above equation (8) to set the total combustion correspondence period CP. Estimate (calculate).

  Next, the CPU 71 executes the processes of steps 1210 to 1240 described above. Thereby, the VVT advance amount is controlled so that the total combustion correspondence period CP matches the target total combustion correspondence period CPtgt. Next, the CPU 71 proceeds to step 1850, and stores the value stored as the VVT advance amount VVT (k) for the current combustion stroke at this time as the VVT advance amount VVT (k-1) for the previous combustion stroke. .

  Next, the CPU 71 proceeds to step 1250 and stores the value obtained by subtracting the intake valve opening reference timing IOint from the intake valve opening timing IO as the VVT advance amount VVT (k) for the current combustion stroke. The intake valve opening reference timing IOint is the intake valve opening timing IO when it is set to the most retarded side within a range in which the intake valve opening timing can be changed. Thereafter, the CPU 71 proceeds to step 1895 to end the present routine tentatively.

  On the other hand, the CPU 71 repeatedly executes the routine shown in FIG. 19 every time the crank angle matches a predetermined crank angle (for example, BTDC 90 °). Accordingly, when the predetermined timing is reached, the CPU 71 starts the processing of the routine of FIG. 19 from step 1900, performs the processing described below in steps 1910 to 1990, and then proceeds to step 1995 to end this routine once.

  Step 1910: The CPU 71 sets the operating state quantity for the previous combustion stroke as the operating state quantity that affects the combustion state, that is, the engine speed NE (k-1) for the previous combustion stroke, and the engine speed for the previous combustion stroke. The load KL (k-1), the VVT advance amount VVT (k-1) with respect to the previous combustion stroke, and the ignition timing SA (k-1) with respect to the previous combustion stroke are input, and these are input to the engine speed NE and the load KL. , VVT advance amount VVT and ignition timing SA are stored.

  Step 1920: The CPU 71 applies the operation state quantities (NE, KL, VVT and SA) stored in Step 1910 to the combustion state model (Wiebe function) expressed by the above equations (4) to (6). The calculated combustion ratio MFB8cal (k−1) is calculated by substituting 8 ° into the crank angle θ in the equation (4). The calculated combustion ratio MFB8cal (k-1) is a predicted amount of combustion state at the specific timing of the previous combustion stroke (previous predicted combustion state amount).

  Step 1930: The CPU 71 subtracts the calculated combustion ratio MFB8cal (k-1) obtained in Step 1920 of FIG. 19 from the actual combustion ratio MFB8act (k-1) obtained in Step 1810 of FIG. A model error amount GosaMDL (correction value) is calculated.

  Step 1940: The CPU 71 sets (current) engine rotational speed NE (k) for the current combustion stroke, and (current) engine load KL (k) for the current combustion stroke as operating state quantities that affect the combustion state. The (current) VVT advance amount VVT (k) for the current combustion stroke and the ignition timing SA (k-1) in the previous combustion stroke are input, and these are input to the engine speed NE, load KL, and VVT advance amount. Stored as VVT and ignition timing SA.

  Step 1950: The CPU 71 applies the operation state quantities (NE, KL, VVT and SA) stored in Step 1940 to the combustion state model (Wiebe function) represented by the above equations (4) to (6). The calculated combustion ratio MFB8cal (k) is calculated by substituting 8 ° into the crank angle θ in the equation (4). The calculated combustion ratio MFB8cal (k) is a current predicted combustion state amount that represents the combustion state at the specific timing of the current combustion stroke.

  Step 1960: The CPU 71 stores a value obtained by adding the model error amount GosaMDL obtained in Step 1930 to the calculated combustion rate MFB8cal (k) obtained in Step 1950 as a corrected combustion rate MFB8mfd (k).

Step 1970: The CPU 71 determines the target combustion ratio MFB8tgt, similarly to step 1540. Here, the target combustion ratio MFB8tgt is a constant value.
Step 1980: The CPU 71 calculates a feedback control deviation dMFB8 (= dMFB8 (k)) by subtracting the corrected combustion ratio MFB8mfd (k) from the target combustion ratio MFB8tgt.
Step 1990: The CPU 71 performs feedback control (proportional / integral control) of the ignition timing so that the value of the feedback control deviation dMFB8 (k) becomes “0”.

  As described above, according to the second control device, the model error amount GosaMDL that directly reflects the model error of the combustion state model is obtained, and the model error amount GosaMDL is used to predict the current combustion stroke. The calculated calculated combustion ratio MFB8cal (k) is corrected. As a result, the corrected combustion rate MFB8mfd (k) used for the ignition timing control is estimated with higher accuracy without delay, so that the ignition timing of the engine is brought closer to an appropriate value including the transient operation state. Can do.

  In the second device, the in-cylinder pressure sensor 65 corresponds to a combustion state detection sensor that actually detects a physical quantity that changes in accordance with the combustion state of the air-fuel mixture in the combustion chamber. The actual MFB calculation means B7 acquires, as an actual combustion state quantity (actual combustion ratio MFB8act (k-1)), an amount representing the combustion state at a specific timing of the combustion stroke based on the physical quantity detected by the combustion state detection sensor. It corresponds to actual combustion state quantity acquisition means.

  The second MFB calculation model B9 includes a combustion state model that describes the relationship between the operation state amount and the amount that represents the combustion state at a predetermined timing of the combustion stroke, and applies the operation state amount for the previous combustion stroke to the combustion state model. This corresponds to the previous predicted combustion state quantity acquisition means for acquiring the quantity representing the combustion state at the specific timing of the previous combustion stroke as the previous predicted combustion state quantity (calculated combustion ratio MFB8cal (k-1)).

The model error amount calculation means B10 is the actual predicted combustion state quantity (calculated combustion ratio MFB8cal (k-1)) obtained and the actual combustion state quantity for the previous combustion stroke obtained by the actual combustion state quantity obtaining means. This corresponds to model error amount acquisition means for acquiring the difference between (actual combustion ratio MFB8act (k-1)) as the model error amount (GosaMDL).
The first MFB calculation model B2 includes a combustion state model, and applies an operation state amount corresponding to the current combustion stroke to the combustion state model to thereby calculate a quantity representing the combustion state at the specific timing of the current combustion stroke. This corresponds to the current predicted combustion state quantity acquisition means which is acquired as a quantity (calculated combustion ratio MFB8cal (k)).

  The predicted combustion state quantity correction means B4 corrects the acquired current predicted combustion state quantity (calculated combustion ratio MFB8cal (k)) with the model error amount (GosaMDL) acquired by the model error amount acquisition means. This corresponds to the model error compensation means for obtaining the corrected predicted combustion state quantity (corrected combustion ratio MFB8mfd (k)) for the combustion stroke of the engine. Note that the ignition timing control device according to the second embodiment can also be said to be a device that obtains the corrected combustion rate MFB8mfd (k) by the “Smith predictor”.

  The embodiments of the ignition timing control device according to the present invention have been described above. The present invention is not limited to the above embodiment, and various modifications can be employed within the scope of the present invention. For example, in each of the above-described embodiments, the intake valve control device 33 is configured to adjust only the opening timing and closing timing of the intake valve 32, but further, the maximum lift amount during the opening period of the intake valve 32 You may be comprised so that can be adjusted. Further, the intake valve control device 33 may be configured to be able to adjust the valve opening timing and the valve closing timing of the intake valve 32 independently of each other. Furthermore, in the above embodiment, in addition to the intake valve control device 33, an exhaust valve control device that independently adjusts the valve closing timing, the valve opening timing, the lift amount during the valve opening period of the exhaust valve 35, and the like may be provided. Good.

In the above embodiment, the fuel injection amount TAU, the cooling water temperature THW, and the air-fuel ratio A / F are adopted as parameters that affect the combustion speed, and all of them are based on the following formulas (10) to (13). The VVT advancement amount (intake valve opening timing IO) may be controlled by correcting the combustion correspondence period CP and using the obtained correction value CPmfd instead of the total combustion correspondence period. Of course, the total combustion correspondence period CP may be modified by any one of these or a combination of any two of them.

  Further, the VVT advance amount may be controlled so that the change amount of the combustion ratio MFBact (k−1) from the compression top dead center to ATDC 15 ° becomes a constant target change amount. Further, the “amount representing the combustion state at the specific timing of the combustion stroke” in each of the above embodiments is not limited to the 8 ° combustion rate MFB8, and is, for example, 7 ° combustion rate MFB7 or 9 ° combustion rate MFB9. May be. Furthermore, the present invention can also be applied to an internal combustion engine that does not include an intake valve control device. In this case, the VVT advance amount VVT used when obtaining the 8 ° combustion ratio MFB8 may be replaced with a constant value.

1 is a schematic view of an internal combustion engine to which an ignition timing control device according to a first embodiment of the present invention is applied. It is the graph which showed the relationship between ignition timing, an 8 degree combustion ratio, and the generated torque of an engine. FIG. 2 is a functional block diagram of the electric control device (ignition timing control device) shown in FIG. 1. It is the graph which showed the change with respect to the crank angle of the actual combustion rate at the time of changing ignition timing. It is the graph which showed the change of y with respect to the variable x when changing parameter (alpha) i in a Wiebe function and making other parameters c, d, and (alpha) b into a constant value. It is the graph which showed the change with respect to the crank angle of the actual combustion ratio at the time of changing VVT advance amount. It is the graph which showed the change of y with respect to the variable x when changing parameter (alpha) b in a Wiebe function and making other parameters c, d, and (alpha) i into a constant value. It is the graph which showed the mode of change of the ignition timing at the time of acceleration, load, VVT advance amount, actual 8 degree combustion rate, and calculation 8 degree combustion rate MFB8 calculated by the improved combustion state model. It is the graph showing the behavior of each value in the conventional control apparatus and the ignition timing control apparatus shown in FIG. It is the flowchart which showed the routine which CPU of the electric control apparatus shown in FIG. 1 performs. It is the graph which showed the mode of the change with respect to the crank angle of the combustion ratio in an expansion stroke (combustion stroke). It is the flowchart which showed the routine which CPU of the electric control apparatus shown in FIG. 1 performs. In the case of changing the ignition timing, CO ₂ emissions, HC emissions, is a graph showing how changes to the VVT advancement amount of real combustion period and the full combustion correspondence period. 14A is a graph showing the HC emission amount for each ignition timing with respect to the substantial combustion period, and FIG. 14B is a graph showing the HC emission amount for each ignition timing for each ignition timing. . It is the flowchart which showed the routine which CPU of the electric control apparatus shown in FIG. 1 performs. It is a functional block diagram of the electric control device (ignition timing control device) concerning a 2nd embodiment of the present invention. It is a time chart which showed change of each value when load and VVT advance amount change. It is the flowchart which showed the routine which CPU of the electric control apparatus which concerns on 2nd Embodiment of this invention performs. It is the flowchart which showed the routine which CPU of the electric control apparatus which concerns on 2nd Embodiment of this invention performs.

Explanation of symbols

  25 ... Combustion chamber, 37 ... Spark plug, 38 ... Igniter, 39 ... Injector, 65 ... In-cylinder pressure sensor, 70 ... Electric controller, A1 ... Target value setting means, A2 ... MFB calculation model, A3 ... Ignition timing data delay means A4: Predicted combustion state quantity correction means, A5: Feedback control deviation calculation means, A6: Feedback controller, A7: Actual MFB calculation means, A9: Correction basic quantity calculation means, A10: Low pass filter, B1: Target value setting means B2 ... First MFB calculation model, B3 ... Ignition timing data delay means, B4 ... Predicted combustion state quantity correction means, B5 ... Feedback control deviation calculation means, B6 ... Feedback controller, B7 ... Actual MFB calculation means, B8 ... Operating state Amount delay means, B9... Second MFB calculation model, B10... Model error amount calculation means.

Claims (6)

An ignition timing control device for an internal combustion engine,
A combustion state detection sensor that actually detects a physical quantity that changes according to the combustion state of the air-fuel mixture in the combustion chamber of the engine;
An actual combustion state quantity acquisition means for acquiring, as an actual combustion state quantity, an amount representing a combustion state at a specific timing of a combustion stroke based on a physical quantity detected by the combustion state detection sensor;
An operating state quantity acquisition unit that acquires an operating state quantity that is a physical quantity that is different from a physical quantity detected by the combustion state detection sensor and represents an operating state of the engine;
Including a combustion state model describing a relationship between the operating state quantity and a quantity representing a combustion state at a predetermined timing of the combustion stroke, and applying the operating state quantity acquired by the operating state quantity acquiring means to the combustion state model Predicted combustion state quantity acquisition means for acquiring, as a predicted combustion state quantity, an amount representing a combustion state at a specific timing of the combustion stroke,
A predicted combustion state amount correcting means for acquiring a corrected predicted combustion state amount by correcting the predicted combustion state amount by a correction amount;
The corrected predicted combustion state quantity acquired for the previous combustion stroke by the predicted combustion state quantity acquisition means and the predicted combustion state quantity correction means, and the previous combustion stroke by the actual combustion state quantity acquisition means. A correction amount calculating means for calculating the correction amount based on the difference between the actual combustion state amount acquired in the step;
The predicted combustion state quantity correction means is obtained by correcting the predicted combustion state quantity for the current combustion stroke obtained by the predicted combustion state quantity acquisition means with the correction amount calculated by the correction quantity calculation means. Ignition timing control means for controlling the ignition timing of the engine based on the corrected predicted combustion state quantity for the current combustion stroke;
Ignition timing control device. The ignition timing control device for an internal combustion engine according to claim 1,
The predicted combustion state quantity acquisition means applies an ignition timing for the previous combustion stroke and an operation state quantity other than the ignition timing for the current combustion stroke acquired by the operation state quantity acquisition means to the combustion state model. Thus, an ignition timing control device configured to acquire a predicted combustion state quantity for the current combustion stroke. An ignition timing control device for an internal combustion engine,
A combustion state detection sensor that actually detects a physical quantity that changes according to the combustion state of the air-fuel mixture in the combustion chamber of the engine;
Actual combustion state quantity acquisition means for acquiring, as an actual combustion state quantity, an amount representing a combustion state at a specific timing of a combustion stroke based on a physical quantity detected by the combustion state detection sensor;
An operating state quantity acquisition unit that acquires an operating state quantity that is a physical quantity that is different from a physical quantity detected by the combustion state detection sensor and represents an operating state of the engine;
A combustion state model that describes the relationship between the operating state quantity and the quantity that represents the combustion state at a predetermined timing of the combustion stroke is included, and the operating state quantity for the previous combustion stroke acquired by the operating state quantity acquisition means is the same combustion state. A previous predicted combustion state quantity acquisition means for acquiring a quantity representing a combustion state at the specific timing of the previous combustion stroke as a previous predicted combustion state quantity by applying to a model;
Model error amount acquisition means for acquiring a difference between the acquired previous predicted combustion state amount and the actual combustion state amount for the previous combustion stroke acquired by the actual combustion state amount acquisition means as a model error amount;
An amount representing the combustion state at the specific timing of the current combustion stroke by applying the operation state amount for the current combustion stroke acquired by the operating state amount acquisition means to the combustion state model, including the combustion state model. The current predicted combustion state quantity acquisition means for acquiring the current predicted combustion state quantity;
Model error compensation means for correcting the obtained current predicted combustion state quantity by the model error quantity obtained by the model error quantity obtaining means to obtain a corrected predicted combustion state quantity for the current combustion stroke;
Ignition timing control means for controlling the ignition timing of the engine based on the corrected predicted combustion state quantity for the acquired current combustion stroke;
Ignition timing control device. In the internal combustion engine ignition timing control device according to claim 3,
The previous predicted combustion state amount acquisition means applies the ignition timing for the previous combustion stroke and the operation state amount other than the ignition timing for the previous combustion stroke acquired by the operation state amount acquisition means to the combustion state model. Configured to obtain the previous predicted combustion state quantity by
The current predicted combustion state quantity acquisition means applies an ignition timing for the previous combustion stroke and an operating state quantity other than the ignition timing for the current combustion stroke acquired by the operating state quantity acquisition means to the combustion state model. An ignition timing control device configured to acquire the current predicted combustion state quantity by doing. The ignition timing control device for an internal combustion engine according to any one of claims 1 to 4,
The combustion state detection sensor is an in-cylinder pressure sensor that detects an in-cylinder pressure that is a pressure in the combustion chamber as a physical quantity that changes according to a combustion state of the air-fuel mixture,
The actual combustion state quantity acquisition means includes the fuel burned in the combustion chamber up to the specific timing relative to the total amount of fuel that has contributed to work on the piston among all the fuel burned in the combustion chamber as the actual combustion state quantity. It is configured to obtain a combustion ratio that is a ratio of an accumulated amount of fuel that has contributed to work on the piston,
The combustion state model is an ignition timing control device that describes a relationship between the operation state quantity and a combustion ratio as a quantity representing a combustion state at a predetermined timing of the combustion stroke. In the internal combustion engine ignition timing control device according to claim 5,
In the combustion state model, the combustion ratio MFBθ at the crank angle θ after compression top dead center is expressed as follows:
MFBθ = 1−exp {−c · ((θ + αi) / αb) ^d }
Wiebe function approximated by
The parameters c and d are constant values, the parameter αi changes based on the ignition timing, and the parameter αb changes based on the overlap period in which the intake valve and the exhaust valve are simultaneously opened. Is an ignition timing control device.

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