JP4985384B2 - Ignition timing control device for internal combustion engine - Google Patents

Description

  The present invention relates to an ignition timing control device for an internal combustion engine that includes model learning means for correcting (learning) an ignition timing model, and that controls the ignition timing using the corrected (learned) ignition timing model.

  Conventionally, a combustion ratio MFB (Mass Fraction Burned) is calculated based on the in-cylinder pressure (pressure in the combustion chamber) detected by the in-cylinder pressure detecting means, and a predetermined crank angle (for example, a crank angle 8 after compression top dead center) It is known that the torque generated by the internal combustion engine can be maximized by controlling the ignition timing so that the combustion rate MFB at (°) matches the target combustion rate (for example, 60%). By controlling the ignition timing in this way, even if there is an individual difference between the manufactured internal combustion engines of the same model, an appropriate ignition timing can be set for each engine. Therefore, the combustion efficiency is improved and the output torque of the engine can be increased.

  The combustion ratio MFB is a combustion state index value indicating the state of combustion occurring in the combustion chamber. The combustion ratio MFB is a value substantially equivalent to the ratio of the indicated heat quantity. 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”.

One of such ignition timing control devices acquires an actual combustion ratio at a predetermined crank angle and feedback-controls the ignition timing so that the difference between the acquired combustion ratio and the target combustion ratio becomes small. (For example, refer to Patent Document 1).
JP-A-9-317522

  By the way, instead of the method of determining the ignition timing using a map (look-up table) with the operating state quantities (for example, engine load and engine speed) representing the operating state of the internal combustion engine as arguments, an ignition timing model is used. Methods have been developed that use it to determine ignition timing. The ignition timing model is represented by a function (formula) having the operating state quantity of the internal combustion engine as a variable. This ignition timing model is preliminarily adapted so that the combustion rate at a predetermined crank angle matches the target combustion rate for various operating state quantities. More specifically, the function representing the ignition timing model is generally a function having a plurality of coefficients, and these coefficients are adapted as described above. In this specification, the ignition timing model represented by a function (function having a coefficient that has been adapted) in advance is referred to as an “initial ignition timing model” for convenience.

  On the other hand, there are individual differences between individual manufactured internal combustion engines. Furthermore, with the use of an internal combustion engine, the characteristics of the engine change over time. Therefore, the optimum ignition timing cannot always be determined by the initial ignition timing model. Therefore, the function that represents the ignition timing model is corrected by learning so that the actual combustion ratio at a predetermined crank angle matches the target combustion ratio (the actual combustion state index value matches the target combustion state index value). It is conceivable to execute learning control. That is, in the learning control, the coefficient is sequentially corrected by a known error reduction method such as a sequential least square method so that the difference between the actual combustion ratio and the target combustion ratio at a predetermined crank angle becomes zero. In this specification, the ignition timing model represented by the function learned in this way (function having a modified coefficient or the like) is referred to as a “post-learning ignition timing model” for convenience.

  However, as a result of further studies, the inventor has determined that the ignition timing calculated based on the post-learning ignition timing model in the operation region where learning is insufficient when learning is biased in a specific operation region (learning region). Has been found to be an inappropriate value, particularly when knocking occurs during transient operation such as during rapid acceleration, or when the combustion state becomes unstable and torque fluctuations occur. .

  Hereinafter, this point will be described in detail. FIG. 5 shows the ignition timing calculated by the ignition timing model when learning is performed without bias for all operation regions. That is, the ignition timing obtained by the ignition timing model shown in FIG. 5 is a substantially appropriate value. On the other hand, FIG. 6 shows the ignition timing calculated by the ignition timing model after learning is performed only in a specific operating region (for example, a region of medium and low load and medium speed rotation). From the comparison between FIG. 5 and FIG. 6, if learning is performed biased in the specific operation region, the ignition timing in the specific operation region becomes a value close to the appropriate value, but the ignition timing in other regions is in the specific operation region. It is understood that it is different from the appropriate value under the influence of learning. The learning of the ignition timing model is control for correcting the ignition timing model by feedback control based on the combustion state index value while leaving past information (information about the combustion state up to the previous time). Therefore, learning cannot correct the ignition timing model with sufficient responsiveness in a transient operation state in which the engine load changes rapidly, such as rapid acceleration.

  On the other hand, FIG. 7 is a graph showing the number of learning (learning frequency) for each driving region when the vehicle is driven to a certain point. From FIG. 7, it is understood that learning is often performed intensively in a specific driving region.

  From the above, one of the objects of the present invention is to provide an ignition timing control device equipped with model learning means for sequentially correcting the ignition timing model by learning. An object of the present invention is to provide an ignition timing control device for an internal combustion engine in which knocking or the like due to a great deviation from the timing does not occur.

  An ignition timing control device for an internal combustion engine according to the present invention that achieves the above object includes an initial ignition timing model. The initial ignition timing model is a model that is the original form (initial value) of the ignition timing model to be learned. The ignition timing model is represented by a function that calculates the ignition timing of the engine with the operating state quantity representing the operating state of the engine as a variable. In the initial ignition timing model, when ignition is performed at the ignition timing calculated by the initial ignition timing model, the combustion state index value indicating the combustion state of the engine matches the target combustion state index value indicating the predetermined target combustion state as much as possible. To be pre-adapted.

  The ignition timing control device further includes an operating state quantity acquisition means, an initial ignition timing calculation means, a combustion state index value acquisition means, a correction amount calculation means, a model learning means, a post-learning ignition timing calculation means, Is provided.

The operating state quantity acquisition means acquires “actual operating state quantity representing the operating state of the engine” as “actual operating state quantity”. The operating state quantity is, for example, an engine load and an engine speed.
The initial ignition timing calculation means calculates the initial ignition timing by applying the acquired actual operation state quantity to the initial ignition timing model.

The combustion state index value acquisition means acquires an actual combustion state index value for combustion based on the previous actual ignition as an actual combustion state index value. The combustion state index value is, for example, a combustion ratio at a predetermined crank angle, a ratio of indicated heat quantity at a predetermined crank angle, an in-cylinder pressure at a predetermined crank angle, and the like.
The correction amount calculation means is based on the difference between the acquired actual combustion state index value and the target combustion state index value so that the combustion state index value for the combustion based on the current ignition approaches the target combustion state index value. To calculate a correction amount for the previous ignition timing.

The model learning means sets the initial ignition timing model as an initial value of the ignition timing model so that the correction amount approaches 0 each time the correction amount is calculated. To obtain a post-learning ignition timing model. That is, each time the correction amount is obtained, the model learning means further modifies (performs learning) the post-learning ignition timing model at that time based on the correction amount, thereby updating the post-learning ignition timing model.
The after-learning ignition timing calculating means calculates the after-learning ignition timing by applying the acquired actual operating state quantity to the after-learning ignition timing model.

  In addition, the ignition timing control device includes transient operation state determination means, ignition timing control means, and ignition execution means.

  The transient operation state determination means determines whether or not the engine operation state is a transient operation state. For example, the transient operation state determination means acquires the load change speed of the engine, and the engine operation state is a transient operation state when the acquired load change speed is greater than a predetermined load change speed threshold. May be configured to determine.

The ignition timing control means is
(1) When it is determined that the operating state of the engine is a transient operating state, the feedback ignition timing determined by the previous actual ignition timing and the correction amount for the previous ignition timing is the initial ignition timing and the learning It is determined whether it is close to the post-ignition timing .

And the ignition timing control means
(1-1) If it is determined that the feedback ignition timing is closer to the initial ignition timing than the post-learning ignition timing, the initial ignition timing is set to the current final ignition timing;
(1-2) When it is determined that the feedback ignition timing is closer to the post-learning ignition timing than the initial ignition timing, the post- learning ignition timing is set to the current final ignition timing.

Furthermore, the ignition timing control means
(2) When it is determined that the operating state of the engine is not a transient operating state,
The post-learning ignition timing is set to the current final ignition timing.

  The ignition execution means executes actual ignition at the final ignition timing set by the ignition timing control means.

  According to this, as described in (2) above, when it is determined that the operating state of the engine is not a transient operating state, actual ignition is executed at the post-learning ignition timing. If the engine is not in the transient operation state, the change in the engine operation state is gentle, so that the learning of the ignition timing model is not greatly delayed with respect to the change in the operation state. Accordingly, the post-learning ignition timing becomes an ignition timing close to the appropriate ignition timing, and thus a state close to a desired combustion state can be obtained by performing actual ignition at the post-learning ignition timing.

On the other hand, as described in (1-1) above, when it is determined that the engine operating state is the transient operation state, the feedback ignition timing is more than the initial ignition timing than the after-learning ignition timing. When it is determined that the timing is close, ignition is performed at the initial ignition timing.

When the feedback ignition timing is closer to the initial ignition timing than the post-learning ignition timing , learning of the post-learning ignition timing model is not sufficient for the driving state at that time (the influence of learning in other driving regions is affected). Therefore, the initial ignition timing model that is preliminarily adapted is considered to be a more preferable model for the operating state at that time. Therefore, the occurrence of knocking or the like can be avoided by performing ignition at the initial ignition timing calculated based on the initial ignition timing model.

Further, as described in (1-2) above, when it is determined that the feedback ignition timing is closer to the post-learning ignition timing than the initial ignition timing , ignition is performed at the post-learning ignition timing.

When the feedback ignition timing is closer to the post-learning ignition timing than the initial ignition timing, the post-learning ignition timing model is considered to be a more preferable model for the operating state at that time than the initial ignition timing model. . Therefore, by performing ignition at the post-learning ignition timing calculated based on the post-learning ignition timing model, it is possible to execute ignition that can bring the combustion state index value closer to the target combustion state index value.

Hereinafter, an ignition timing control device for an internal combustion engine according to an embodiment of the present invention will be described with reference to the drawings.
(Constitution)
FIG. 1 shows a spark ignition type multi-cylinder (4-cylinder) four-cycle internal combustion engine in which an ignition timing control device according to an embodiment of the present invention (hereinafter sometimes simply referred to as “control device”) is a piston reciprocating type. 10 shows a schematic configuration of the system applied to FIG. 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, and a downstream three-way catalyst 54. The upstream three-way catalyst 53 is disposed in the exhaust pipe 52. The downstream three-way catalyst 54 is disposed in the exhaust pipe 52 downstream of the upstream three-way catalyst 53. 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 cooling water 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 speed NE. Further, the crank angle of the engine 10 is obtained based on signals from the cam position sensor 63 and the crank position sensor 64.

  The in-cylinder pressure sensor 65 detects the pressure in the combustion chamber 25 and outputs a signal representing the in-cylinder pressure Pc. One in-cylinder pressure sensor 65 is provided for each cylinder. The coolant temperature sensor 66 detects the coolant temperature of the engine 10 and outputs a signal representing the coolant temperature THW. 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.

(Outline of control)
Next, an outline of ignition timing control performed by the ignition timing control device for the internal combustion engine 10 configured as described above will be described.

<Estimation (acquisition) of combustion ratio MFB>
The combustion ratio MFB defined as described above is estimated (acquired) as a value representing the ratio Qsum / Qtotal of the indicated heat quantity defined as described above. The combustion ratio MFB and the ratio of the indicated heat quantity are both combustion state index values indicating the combustion state of the engine 10. 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.

  In this example, the combustion ratio MFB 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 (crank angle θ1 ° before compression top dead center). The fact that θ = θ2 ° (θ2> 0) indicates that the crank angle is ATDCθ2 (crank angle θ2 ° after compression top dead center).

The combustion ratio MFBθ at the crank angle θ is estimated by the following equation (1). In the equation (1), the crank angle θs (θs <0) is set so that both the intake valve 32 and the exhaust valve 35 are closed in the compression stroke toward the target combustion stroke (expansion stroke) and is higher than the ignition timing. It is a time when the angle is sufficiently advanced (for example, θs = −60 °, that is, BTDC 60 °). The crank angle θe (θe> 0) is a predetermined timing later than the latest timing at which combustion in the target combustion stroke is substantially ended and a timing advanced from the exhaust valve opening timing (for example, θe = 60). °, ie ATDC 60 °).

This equation (1) is based on the knowledge that the change pattern of the accumulated amount Q of heat contributed to the work for 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 denominator of equation (1) is a value corresponding to 100% of MFB.

<Basic contents of ignition timing control>
First, the basic contents of ignition timing control by this control device will be described.

  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. The 8 ° combustion rate MFB8 is the combustion rate MFB when the crank angle θ is 8 ° (= ATDC 8 °) after compression top dead center. 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 control device controls the ignition timing so that the 8 ° combustion ratio MFB8 becomes a predetermined target value MFB8tgt (for example, a value in the vicinity of 60%). The target value naturally varies depending on the type of engine. For example, the target combustion ratio MFB8tgt may be 50%. In an engine in which the generated torque TRQ becomes maximum when the 5 ° combustion ratio MFB5 is the target combustion ratio MFB5tgt (for example, 50%), the control device allows the 5 ° combustion ratio MFB5 to be the target value MFB5tgt (for example, The ignition timing is controlled so as to be a value in the vicinity of 50%.

  More specifically, the control device has each function achievement unit shown in FIG. 3 which is a functional block diagram. Hereinafter, the function of each block will be described in order. In this specification, the symbol (k) given after a variable indicates that the variable is a variable for a 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 end of the combustion, that is, the combustion stroke one time before (720 ° crank angle)) in the specific cylinder. It is. Further, the ignition timing SA (SA> 0) means that ignition is performed at BTDC SA ° (crank angle SA ° before compression top dead center).

  The operation state amount acquisition unit A1 acquires an amount (operation state amount) representing the operation state of the engine. In this example, the operating state quantities are the load KL and the engine speed NE of the engine 10. The load KL is a “filling rate” proportional to the in-cylinder air weight (in the case of a four-cylinder engine, KL = 4 · Mc / (ρ · L), Mc: weight of intake air into one cylinder, ρ: Air density, L: displacement). The load KL 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. The operating state quantity acquisition unit A1 is configured to acquire the operation amount Accp of the accelerator pedal 81, the throttle valve opening TA, the intake air amount Ga per engine rotation, and the like as the load of the engine 10 instead of the load KL. May be.

  The transient operation state determination unit A2 determines whether or not the operation state of the engine 10 is a transient operation state, and outputs the determination result. More specifically, the transient operation state determination unit A2 inputs the throttle valve opening TA from the throttle position sensor 62, and the amount of change per unit time of the throttle valve opening TA (that is, the load change of the engine 10). (Throttle valve opening changing speed) ΔTA as a speed. Further, the transient operation state determination unit A2 determines whether or not the throttle valve opening change rate ΔTA is greater than a predetermined throttle valve opening change rate threshold (load change rate threshold) ΔTAth, and the throttle valve opening change rate ΔTA. Is greater than a predetermined throttle valve opening change speed threshold value ΔTAth, a signal indicating that the engine operating state is a transient operating state is output.

  The ignition timing control unit A3 includes an initial ignition timing calculation unit A3a, a post-learning ignition timing calculation unit A3b, and a final ignition timing setting unit A3c.

The initial ignition timing calculation unit A3a applies the actual operation state quantity (NE (k), KL (k)) acquired by the operation state quantity acquisition unit A1 to the initial ignition timing model, thereby calculating the ignition timing for the current combustion. A certain “initial ignition timing SAin” is calculated. The initial ignition timing model and the after-learning ignition timing model to be described later are ignition timing models represented by a function of the following equation (2).

  The initial ignition timing model is a function having, as variables, operating state quantities (NE (k), KL (k)) representing the operating state of the internal combustion engine as shown in the above equation (2). It is an ignition timing model represented by a function for calculating (k). In the initial ignition timing model, coefficients (initial values, initial coefficients) θ0, θ1, θ2, and θ3 that are preliminarily adapted so that the 8 ° combustion ratio MFB8 accurately matches the target combustion ratio MFB8tgt in all operating regions. Have. The previously adapted coefficients (initial values, initial coefficients) θ0, θ1, θ2, and θ3 are stored in the ROM 72 and the backup RAM 74.

  Therefore, the actual operating state quantities (NE (k), KL (k)) are substituted into the function in which the coefficients θ0 to θ3 in the following equation (2) are returned to the previously adapted (initial value, initial coefficient). The ignition timing SA (k) obtained this time is “initial ignition timing SAin”.

  The target value setting unit A4 outputs “target combustion ratio MFB8tgt” which is a target value for the 8 ° combustion ratio MFB8. The target combustion ratio MFB8tgt is a constant value M0 (for example, 60%) in this example. The target value setting unit A4 may be configured to input an operating state quantity and change the target combustion ratio MFB8tgt according to the operating state quantity. For example, the target value setting unit A4 may be temporarily set to a value M1 smaller than the value M0 during a rapid acceleration operation in which the throttle valve opening change rate ΔTA is larger than a predetermined throttle valve opening change rate threshold ΔTAth. . Note that the target combustion ratio MFB8tgt is desirably set to a value such 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 actual combustion ratio MFB8 calculation unit A5 calculates the combustion ratio MFB8 (k−1) at ATDC 8 ° during the previous combustion stroke according to the above equation (1). That is, the actual combustion ratio MFB8 calculation unit A5 calculates the 8 ° combustion ratio MFB8 (k−1) based on the following equation (3). Each value on the right side in the equation (3) is a value obtained during the previous combustion stroke. Note that −60 ° means a crank angle of 60 ° before compression top dead center. Further, 8 ° and 60 ° mean crank angles 8 ° and 60 ° after compression top dead center, respectively.

The correction amount calculation unit A6 calculates the difference dMFB8 (k) between the target combustion rate MFB8tgt acquired from the target value setting unit A4 and the actual 8 ° combustion rate MFB8 (k-1) acquired from the actual combustion rate MFB8 calculation unit A5. −1), a correction amount (crank angle to advance) ΔSA (k−1) to be advanced with respect to the previous ignition timing SA (k−1) is calculated. That is, assuming that the ignition timing that is considered to be close to an appropriate value as the current ignition timing SA (k) is the feedback ignition timing SAfb, the feedback ignition timing SAfb is expressed by the following equation (4).

  Specifically, the correction amount calculation unit A6 includes a table (or function) that predefines the relationship between the difference dMFB8 (k-1) and the correction amount ΔSA (k-1). The correction amount calculation unit A6 calculates the actual correction amount ΔSA (k−1) by applying the difference dMFB8 (k−1) actually obtained to the table.

  As described above, the correction amount calculation unit A6 performs the difference so that the 8 ° combustion ratio MFB8 (k) that is the combustion state index value for the combustion based on the current ignition timing SA (k) approaches the target combustion state index value MFB8tgt. Based on dMFB8 (k−1), a correction amount ΔSA (k−1) with respect to the previous ignition timing SA (k−1) is calculated. That is, if the feedback ignition timing SAfb obtained by adding the correction amount ΔSA (k−1) to the previous ignition timing SA (k−1) is the current ignition timing, 8 obtained by combustion based on the current ignition. The difference dMFB8 (k) between the combustion ratio MFB8 (k) and the target combustion state index value MFB8tgt is smaller than the difference dMFB8 (k-1) in the previous combustion.

The correction amount calculation unit A6 performs the PI (proportional / integral) process on the difference dMFB8 (k-1) as shown in the following equation (5) to obtain the correction amount ΔSA (k-1). You may ask for it. In the equation (5), Kp is a proportionality constant, and Ki is an integral constant. SdMFB8 (k−1) is an integral value of the difference dMFB8, and is obtained based on the following equation (6).

  The delay unit A7 holds the operating state quantities (NE (k), KL (k)) for the current combustion stroke acquired by the operating state quantity acquiring unit A1, and determines the ignition timing for the previous combustion stroke. The “operation state quantity (NE (k−1), KL (k−1)) with respect to the previous combustion stroke” is used.

  The model learning unit A8 includes the correction amount ΔSA (k−1) obtained from the correction amount calculation unit A6 and the previous operation state amount (NE (k−1), KL (k−1)) obtained from the delay unit A7. Based on the above, the ignition timing model is learned. More specifically, the model learning unit A8 calculates the ignition timing obtained by applying the previous operation state amount to the post-learning ignition timing model so that the correction amount ΔSA (k−1) becomes the minimum value. Is approximated (matched) with the feedback ignition timing SAfb), the coefficients θ0 to θ3 of the function representing the ignition timing model described above are calculated based on the well-known “Sequential Least-Squares (RLS)”. Calculate / update.

  A post-learning ignition timing calculation unit A3b included in the ignition timing control unit A3 is a table that substitutes coefficients (post-learning coefficients) θ0 to θ3 corrected / updated (learned) by the model learning unit A8 into the above equation (2). This function is held as a “learning ignition timing model”. The post-learning coefficient is also stored in the backup RAM 74 like the initial coefficient. The post-learning ignition timing calculation unit A3b applies the actual operation state quantity (NE (k), KL (k)) acquired by the operation state quantity acquisition unit A1 to the post-learning ignition timing model, thereby igniting the current combustion. The “post-learning ignition timing SAgk”, which is the timing, is calculated.

  The final ignition timing setting unit A3c of the ignition timing control unit A3 is calculated by the initial ignition timing SAin that is the current ignition timing candidate calculated by the initial ignition timing calculation unit A3a and the after-learning ignition timing calculation unit A3b. One of “candidate ignition timing SAgk”, which is another candidate for this ignition timing, is selected, and the selected ignition timing is output as “current final ignition timing SA (k)”. It has become.

Specifically, the final ignition timing setting unit A3c is a model that is more preferable with respect to the operation state at that time when the operation state of the engine 10 is determined to be a transient operation state by the transient operation state determination unit A2. There whether it is a to whether the initial ignition timing model learning ignition timing model, "at least correction amounts ΔSA (k-1) (in fact, the previous ignition timing SA (k-1), the correction amount [Delta] SA (k- 1), current initial ignition timing SAin and current post-learning ignition timing SAgk) ”.

  More specifically, the final ignition timing setting unit A3c determines the absolute value Zin (Zin = | SAin−SAfb |) of the difference between the current initial ignition timing SAin and the feedback ignition timing SAfb obtained based on the above equation (4). ) Is smaller than the absolute value Zgk (Zgk = | SAgk−SAfb |) of the difference between the current post-learning ignition timing SAgk and the feedback ignition timing SAfb.

Then, the final ignition timing setting unit A3c the direction of the absolute value Zin may be determined to be smaller than the absolute value Zgk, selects the current initial ignition timing SAin as This time the final ignition timing SA (k).

In contrast, the final ignition timing setting unit A3c, when the direction of the absolute value Zgk is determined to be smaller than the absolute value Zin, select the current learning ignition timing SAgk as This time the final ignition timing SA (k) To do.

  Further, the final ignition timing setting unit A3c determines the current final ignition timing SA (k) as the current post-learning ignition timing when the transient operation state determination unit A2 determines that the operation state of the engine 10 is not the transient operation state. Select SAgk.

  Then, the ignition timing control unit A3 sends an ignition signal (ignition instruction signal) to the igniter 38 so that ignition is performed at the ignition timing selected as the final ignition timing SA (k).

<Action>
Next, the operation of this control device (electric control device 70) will be described.
The CPU 71 executes an in-cylinder pressure acquisition routine (not shown) to output Pc (−60 °), Pc (8 °), and Pc (60 °) of each cylinder from the in-cylinder pressure sensor 65 disposed in each cylinder. Is obtained based on the data and stored in the RAM 73 for each cylinder. Further, the CPU 71 performs the ignition timing control routine shown by the flowchart in FIG. 4 with a predetermined crank angle immediately before the start of the combustion stroke when the crank angle of the specific cylinder (for example, crank angle 90 ° before compression top dead center of the specific cylinder = BTDC 90 It is repeatedly executed every time it matches (°). The CPU 71 executes the same routine for other cylinders at the same timing.

  When the crank angle of the specific cylinder matches the predetermined crank angle, the CPU 71 starts the processing of the routine of FIG. 4 from step 400, and performs the following processing in steps 405 to 435.

  Step 405: The CPU 71 calculates the actual 8 ° combustion ratio MFB8 (k−1) in the previous combustion stroke of the specific cylinder based on the above equation (3). At this time, the CPU 71 applies Pc (−60 °), Pc (8 °), and Pc (60 °) of the specific cylinder stored in the RAM 73 to the equation (3). The CPU 71 assigns values stored in the ROM 72 in advance to the combustion chamber volumes V (−60 °), V (8 °), and V (60 °) of the equation (3).

  Step 410: The CPU 71 obtains the engine speed NE (k−1) and the load KL (k−1) (used when determining the previous ignition timing of the specific cylinder) for the previous combustion stroke of the specific cylinder. . At the same time, the CPU 71 obtains the engine speed NE (k) and the load KL (k) for the current combustion stroke of the specific cylinder (used when determining the current ignition timing of the specific cylinder). The engine speed NE (k) and the load KL (k) are equal to the engine speed NE and the load KL at the current time, respectively.

Step 415: The CPU 71 calculates a difference dMFB8 (k−1) between a predetermined target combustion ratio MFB8tgt and the actual 8 ° combustion ratio MFB8 (k−1) acquired in Step 405 from the target combustion ratio MFB8tgt to 8 ° Calculated by subtracting the combustion rate MFB8 (k-1).
Step 420: The CPU 71 calculates the correction amount ΔSA (k−1) by applying the difference dMFB8 (k−1) to the lookup table f (function f). In this example, the lookup table is defined to multiply the difference dMFB8 (k−1) by a constant k.

  Step 425: The CPU 71 executes learning of the ignition timing model. Specifically, the CPU 71 calculates (determines) the coefficients θ0, θ1, θ2, and θ3 that minimize the correction amount ΔSA (k−1) based on the sequential least square method. At this time, the CPU 71 uses the engine speed NE (k−1) and the load KL (k−1) for calculation. The calculated new coefficients θ0, θ1, θ2, and θ3 are stored in the backup RAM 74 as post-learning coefficients.

  Step 430: The CPU 71 sets the coefficients θ0 to θ3 in the above equation (2) to the coefficients θ0 to θ3 updated (learned) in step 425, and the engine speed NE (k) in the equation (2). Then, by substituting the load KL (k), the ignition timing SAgk corresponding to the current ignition timing (ignition timing for the next combustion stroke) is calculated. As described above, the ignition timing obtained by the ignition timing model (post-learning ignition timing model) in which the coefficients θ0 to θ3 are set to learned values (post-learning coefficient) is referred to as “post-learning ignition timing SAgk”. .

  Step 435: The CPU 71 sets the coefficients θ0 to θ3 in the above equation (2) to initial values (initial coefficients), and substitutes the engine speed NE (k) and the load KL (k) into the equation (2). Thus, the ignition timing SAin corresponding to the current ignition timing is calculated. As described above, the ignition timing obtained by the ignition timing model (initial ignition timing model) in which the coefficients θ0 to θ3 are returned to the initial values is referred to as “initial ignition timing SAin”.

  Next, the CPU 71 proceeds to step 440 to determine whether or not the throttle valve opening change rate ΔTA is smaller than a predetermined throttle valve opening change rate threshold ΔTAth. The throttle valve opening TA is controlled by the CPU 71 and the throttle valve actuator 43a so as to increase as the operation amount Accp of the accelerator pedal 81 increases. In addition, the amount of change per unit time of the throttle valve opening TA is a routine executed every time a predetermined time Δt (not shown) is executed, and the throttle valve opening TA at the time of executing the routine and the previous execution of the routine are executed. It is obtained by obtaining the difference (ΔTA = TA−TAold) between the throttle valve opening TA (= TAold = throttle valve opening before Δt) at the time point. This step 440 is a step for determining whether or not the operating state of the engine 10 is a transient operating state (in this example, a rapid acceleration state).

  Now, it is assumed that the operation state of the engine 10 is not a transient operation state (in this example, a rapid acceleration state). At this time, the CPU 71 makes a “Yes” determination at step 440 and proceeds to step 445 to set the post-learning ignition timing SAgk obtained at step 430 to the final ignition timing (ignition timing for the current combustion stroke) SA (k). Set.

  Next, the CPU 71 proceeds to step 450 and sends an ignition signal to the igniter 38 so that ignition is performed at the final ignition timing SA (k) set in step 445 (that is, the post-learning ignition timing SAgk). . Then, the CPU 71 proceeds to step 495 and once ends this routine. This step corresponds to ignition execution means.

  On the other hand, it is assumed that the operation state of the engine 10 is a transient operation state (in this example, a rapid acceleration state). At this time, the CPU 71 makes a “No” determination at step 440 to proceed to step 455 to calculate the feedback ignition timing SAfb based on the above equation (4). Next, the CPU 71 proceeds to step 460, where the absolute value Zin (Zin = | SAin−SAfb |) of the difference between the current initial ignition timing SAin and the feedback ignition timing SAfb obtained based on the above equation (4) is It is determined whether or not the difference between the after-learning ignition timing SAgk and the feedback ignition timing SAfb is smaller than the absolute value Zgk (Zgk = | SAgk−SAfb |).

At this time, if the absolute value Zin is smaller than the absolute value Zgk, it is determined that a more preferable model for the operating state at that time is the initial ignition timing model . Therefore, in this case, the CPU 71 determines “Yes” at step 460 and proceeds to step 465 to set the initial ignition timing SAin obtained at step 435 as the current final ignition timing SA (k). Next, the CPU 71 proceeds to step 450, and sends an ignition signal to the igniter 38 so that ignition is performed at the final ignition timing SA (k) set in step 465 (that is, the initial ignition timing SAin). Then, the CPU 71 proceeds to step 495 and once ends this routine.

On the other hand, if the absolute value Zin is larger than the absolute value Zgk (the absolute value Zin is greater than or equal to the absolute value Zgk), the more preferable model for the operating state at that time is the post-learning ignition timing model. To be judged. Therefore, in this case, the CPU 71 makes a “No” determination at step 460 to proceed to step 445 to set the post-learning ignition timing SAgk obtained at step 430 as the current final ignition timing SA (k). Next, the CPU 71 proceeds to step 450 and sends an ignition signal to the igniter 38 so that ignition is performed at the final ignition timing SA (k) set in step 445 (that is, the post-learning ignition timing SAgk). . Then, the CPU 71 proceeds to step 495 and once ends this routine.

As described above, according to the embodiment of the ignition timing control device of the present invention, when the engine operating state becomes a transient operation state (rapid acceleration operation state), it is more preferable for the operation state at that time. Whether the model is a post-learning ignition timing model or an initial ignition timing model is determined based on at least the correction amount ΔSA (k−1), and the feedback ignition timing is more than the initial ignition timing than the post-learning ignition timing. Is determined to be close to the initial ignition timing SAin. When the feedback ignition timing is determined to be closer to the post-learning ignition timing than the initial ignition timing, the post- learning ignition timing SAgk is set. And ignite. As a result, since the inappropriate post-learning ignition timing SAgk is not used as the ignition timing at the time of transient operation, it is possible to avoid the occurrence of knocking and unstable combustion state.

  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 embodiments described above, learning of the ignition timing model is performed by the sequential least square method, but learning may be performed using other methods. The learning of the ignition timing model has been performed by correcting all the coefficients θ0 to θ3. However, the learning may be executed so as to correct only some of the coefficients θ0 to θ3. . In addition, when the ignition timing model has adaptation parameters other than coefficients θ0 to θ3, the initial ignition timing model is a model to which such an adaptation parameter is adapted, and the post-learning ignition timing model has such an adaptation parameter. It may be corrected by learning.

In the above-described embodiment, the combustion rate MFB, which is the combustion state index value, is acquired based on the in-cylinder pressure. However, the combustion rate MFB is a combustion model called a Wiebe function (see, for example, JP-A-2006-9720). .)). This Wiebe function gives the combustion rate MFBθ at ATDC θ °,
MFBθ = 1−exp {−e · ((θ + αi) / αb) ^f }
Is a function approximated by Here, the parameter e and the parameter f are constant values, the parameter αi changes based on the ignition timing, and the parameter αb is based on an overlap period (VVT (k)) in which the intake valve and the exhaust valve are simultaneously opened. It is good to be comprised so that it may change. Further, the combustion state index value may be an in-cylinder pressure at a predetermined crank angle and / or a change speed of the in-cylinder pressure.

1 is a schematic view of an internal combustion engine to which an ignition timing control device according to an 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 flowchart which showed the routine which CPU shown in FIG. 1 performs. It is the figure which showed the ignition timing calculated by the ignition timing model when learning is performed with no bias over all the operation regions. It is the figure which showed the ignition timing calculated by the ignition timing model after learning was performed only in a certain specific operation area | region. It is the graph showing the frequency according to the driving | operation area | region of learning of the ignition timing model after performing a predetermined driving | operation.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 25 ... Combustion chamber, 37 ... Spark plug, 38 ... Igniter, 39 ... Injector, 61 ... Hot-wire air flow meter, 62 ... Throttle position sensor, 63 ... Cam position sensor, 64 ... Crank position sensor, 65 ... In-cylinder pressure sensor, 70 ... electric control device, 71 ... CPU.

Claims (3)

An ignition timing model represented by a function for calculating the ignition timing of the engine with the operating state quantity representing the operating state of the internal combustion engine as a variable, wherein the combustion state index value indicating the combustion state of the engine has a predetermined target combustion state An ignition timing control device for an internal combustion engine having an initial ignition timing model that is preliminarily adapted to match the target combustion state index value shown
Driving state quantity acquisition means for acquiring the actual driving state quantity as an actual driving state quantity;
Initial ignition timing calculation means for calculating an initial ignition timing by applying the acquired actual operating state quantity to the initial ignition timing model;
Combustion state index value acquisition means for acquiring an actual combustion state index value for combustion based on the previous actual ignition as an actual combustion state index value;
Based on the difference between the acquired actual combustion state index value and the target combustion state index value so that the combustion state index value for the combustion based on the current ignition approaches the target combustion state index value, Correction amount calculating means for calculating a correction amount;
Each time the correction amount is calculated, post-learning ignition is performed by performing learning to sequentially correct a function representing the ignition timing model with the initial ignition timing model as an initial value of the ignition timing model so that the correction amount approaches zero. A model learning means for obtaining a time model;
A post-learning ignition timing calculating means for calculating a post-learning ignition timing by applying the acquired actual operating state quantity to the post-learning ignition timing model;
Transient operation state determining means for determining whether or not the operation state of the engine is a transient operation state;
When it is determined that the engine operating state is a transient operation state, the feedback ignition timing determined by the previous actual ignition timing and the correction amount for the previous ignition timing is the initial ignition timing and the post-learning ignition timing. determining either the or near the said if feedback spark timing is determined to be close to the initial ignition timing than ignition timing the learning set the initial ignition timing to the current final ignition timing, the If it is determined that the feedback ignition timing is closer to the post-learning ignition timing than the initial ignition timing, the post- learning ignition timing is set to the current final ignition timing, and the engine operating state is not a transient operating state. If determined, ignition timing control means for setting the post-learning ignition timing to the final ignition timing of this time;
Ignition execution means for executing actual ignition at the set final ignition timing;
Ignition timing control device. The ignition timing control device for an internal combustion engine according to claim 1,
The transient operation state determination means includes
An ignition timing configured to acquire a change rate of the load of the engine and determine that the operation state of the engine is a transient operation state when the acquired change rate of the load is greater than a predetermined load change rate threshold. Control device. In the ignition timing control device for an internal combustion engine according to claim 1 or 2,
The combustion state index value is an actual combustion ratio when the crank angle of the engine is a predetermined crank angle, and the target combustion state index value is a combustion when the crank angle of the engine is the predetermined crank angle. Ignition timing control device that is the target value of the ratio.