JP2705113B2 - Fuel injection amount control device for internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection amount control device for an internal combustion engine that controls a fuel injection amount in accordance with a physical model representing the behavior of fuel of the internal combustion engine.

[Prior Art] Conventionally, various techniques have been proposed as techniques for controlling a fuel injection amount so that an air-fuel ratio of a fuel mixture supplied to an internal combustion engine becomes a target air-fuel ratio. Japanese Patent Application Nos. 62-189889 and 62-189891, based on a physical model describing the fuel behavior in an internal combustion engine,
A fuel injection amount control device capable of executing fuel injection control without switching the control law (that is, with one control immediately) by determining the control law with nonlinear compensation has been proposed.

Further, in order to more completely describe the fuel behavior of the internal combustion engine based on the physical model, it is preferable to change the coefficient (model parameter) according to the operation fluctuation of the internal combustion engine. Technology for controlling the fuel injection amount by calculating it sequentially (on board) (Japanese Patent Application No. 63-63)
No. 24483).

[Problems to be Solved by the Invention] However, the calculation of the model parameters and the calculation of the fuel injection amount using the calculated model parameters require a great deal of calculation. The calculation must be performed quickly, and for example, a small computer mounted on an automobile imposes a heavy burden on the computer and causes a reduction in controllability.

As a measure to reduce the amount of such enormous calculations and to quickly calculate the fuel injection amount, the model parameters are fixed values, the amount of change in the model parameters is read from a predetermined map, and the fuel injection amount is read. Has been proposed, but it has not been possible to adequately cope with fluctuations in model parameters due to machine differences and changes over time.

Accordingly, the present invention provides an apparatus for performing fuel injection control of an internal combustion engine according to one control law set based on a physical model describing the fuel behavior of an internal combustion engine as described above. The purpose of the present invention is to provide a structure capable of accurately compensating for the fluctuation, and to further improve the controllability.

[Means for Solving the Problems] That is, a configuration of the present invention made to achieve the above object is, as illustrated in FIG. 1, an operating state detecting means M2 for detecting an operating state of an internal combustion engine M1.
The behavior of the fuel of the internal combustion engine M1 is described using the operating state, the state variable, and the fuel injection amount, and a coefficient predetermined as a value to be multiplied by each of the amounts and a variation amount of the coefficient. Injection amount control means M3 for sequentially calculating and controlling the fuel injection amount in accordance with the physical model, and set value storage means for storing a set value determined in advance according to the operation state as a variation amount of the coefficient of the physical model. M4 and a variation output means for outputting the set value stored by the set value storage means M4 as a variation of the coefficient in accordance with the operation state detected by the operation state detection means M2.
M5, a fuel injection amount control device for the internal combustion engine M1 comprising: an operation state detected by the operation state detection means M2, a state variable and a fuel injection amount used by the injection amount control means M3. Data storage means M6 for storing the data as time-series data, and coefficient identification means M7 for identifying the coefficients of the physical model based on the data stored by the data storage means M6.
And a difference between the coefficient identified by the coefficient identification means M7 and the predetermined coefficient to calculate a change amount of the coefficient, and a change amount calculation means M8 to obtain the change amount of the coefficient. A variation amount updating means M9 for updating the set value by using the variation amount of the coefficient, and an arithmetic processing device for performing an operation of the fuel injection amount control device, an identification operation process by the coefficient identification means M7 and the variation amount Time allowance determination means M1 for determining whether or not the coefficient by the calculation means M8 has a time allowance required for the calculation processing of the variation amount
When the time margin determination means M10 determines that there is a time margin necessary for the calculation, the coefficient identification means M7, the variation calculation means M8, and the variation update means M9 are provided.
The gist of the present invention is a fuel injection amount control device for an internal combustion engine M1 that performs the process of

[Operation] In the fuel injection amount control device for the internal combustion engine M1 of the present invention, the operating state is detected by the operating state detecting means M2 and the value stored in the set value storing means M4, that is, determined in advance according to the operating state. The set value of the variation amount of the coefficient of the physical model is output by the variation amount output means M5 according to the above-mentioned operation state.

Further, the injection amount control means M3 uses a predetermined coefficient and a variation amount of the coefficient, a state variable, and a fuel injection amount,
The fuel injection amount is sequentially calculated and controlled in accordance with the physical model.With the control, the operation state detected by the operation state detection unit M2 by the data storage unit M6 and the injection amount control unit M3 The used state variables and the fuel injection amount are temporarily stored as time-series data.

When the time margin determining means M10 determines that there is a time margin necessary for the calculation, the coefficient identifying means M6 performs the above-described physical model based on the temporarily stored data instead of the sequential calculation as described above. Identify the coefficient of
The variation amount calculating means M8 calculates the difference between the coefficient identified by the coefficient identifying means M7 and the predetermined coefficient to determine the variation amount of the coefficient. Next, the set value is updated by the variation updating means M9 using the variation of the coefficient.

That is, by expressing the physical model showing the fuel behavior using a predetermined coefficient and the variation of the coefficient, the fuel injection amount can be calculated quickly, and when there is a margin for the calculation, The controllability of the fuel injection amount is improved by identifying the above-mentioned coefficient using the data of the operating state and the like once stored, and appropriately updating the fluctuation amount of the above-mentioned coefficient.

That is, by expressing the physical model showing the fuel behavior using a predetermined coefficient and the variation of the coefficient, the fuel injection amount can be calculated quickly, and the data such as the operating state once stored is used to calculate the fuel injection amount. The controllability of the fuel injection amount is improved by identifying the coefficient and appropriately updating the fluctuation amount of the coefficient.

Example A first example of the present invention will be described below with reference to the drawings. FIG. 2 is a schematic configuration diagram showing the configuration of the internal combustion engine 2 to which the present invention is applied and its peripheral devices.

In the drawing, reference numeral 4 denotes an intake pipe for sucking air through an air cleaner 6. The intake pipe 4 includes a throttle valve 8 for controlling the amount of intake air, a surge tank 10 for suppressing pulsation of intake air, An intake pressure sensor 12 for detecting an internal pressure (intake pipe pressure) P and an intake temperature sensor 14 for detecting an intake temperature Ti are provided.

On the other hand, reference numeral 16 denotes an exhaust pipe provided with a three-way catalytic converter 18 for purifying exhaust gas.

In addition to the intake pressure sensor 12 and the intake air temperature sensor 14, the internal combustion engine 2 detects the operating state of the internal combustion engine 2 from the rotation of the distributor 20.
A rotation speed sensor 22 for detecting a rotation speed ω of the engine, and a crank angle sensor 2 for detecting a timing t of fuel injection from the rotation of the distributor 20 to the internal combustion engine 2.
4, and a water temperature sensor 26 that is attached to the water jacket of the internal combustion engine 2 and detects the cooling water temperature T. The distributor 20 is for applying a high voltage from the igniter 28 to the ignition plug 29 at a predetermined ignition timing.

A detection signal from each of the above sensors is output to an electronic control circuit 30 configured as a logical operation circuit centered on a microcomputer, and drives the fuel injection valve 32 to control the fuel injection amount from the fuel injection valve 32. Used to do.

That is, the electronic control circuit 30 performs an arithmetic process for controlling the fuel injection amount according to a preset control program.
CPU 40, a ROM 42 in which control programs and initial data necessary for executing arithmetic processing by the CPU 40 are recorded in advance,
A RAM 44 for temporarily reading and writing data used to execute arithmetic processing at 40, an input port 46 for inputting a detection signal from each of the above sensors, and a fuel injection valve 32 according to the arithmetic result at the CPU 40. And an output port 48 for outputting a drive signal to the cylinder 2a of the internal combustion engine 2.
The fuel injection amount q from the fuel injection valve 32 is controlled such that the fuel / air ratio λ of the fuel mixture flowing into the fuel tank reaches a preset target fuel / air ratio λr.

(I) Setting of Physical Model of First Embodiment Next, a physical model of the present embodiment that shows fuel behavior will be described. This physical model is based on any modern control theory using the amount of fuel fw adhering to the intake pipe wall surface 4a and the amount of fuel vapor fv inside the intake pipe 4b as state variables.

First, the fuel amount fc flowing into the cylinder 2a of the internal combustion engine 2
Is the fuel injection amount q from the fuel injection valve 32 and the intake pipe wall surface 4a
The following equation (1) can be described using the amount of fuel fw attached to the fuel tank and the amount of fuel vapor fv in the intake pipe interior 4b.

fc = α1 · q + α2 · fw + α3 · fv (1) That is, the fuel amount fc is the direct inflow amount α1 · q of the injected fuel from the fuel injection valve 32 and the indirect inflow from the intake pipe 4 to which the injected fuel is attached. Since it is considered that this is the sum of the amount α2 · fw and the inflow amount α3 · fv of the evaporated fuel present in the intake pipe interior 4b due to the evaporation of the injected fuel or the fuel deposited on the wall, the following equation (1) is used. The amount of fuel fc flowing into the cylinder 2a can be described.

In the above equation (1), since the fuel injection amount q is determined by the control amount of the fuel injection valve 32, if the amount of fuel fw adhering to the intake pipe wall surface 4a and the amount of evaporated fuel fv inside the intake pipe 4b can be known, The fuel amount fc can be predicted.

Therefore, the amount of deposited fuel fw and the amount of evaporated fuel fv will now be considered.

First, the amount of fuel fw adhering to the intake pipe wall surface 4a is reduced by a part of α2 in each intake cycle due to inflow into the cylinder 2a during the intake stroke, and is also reduced by evaporation to the intake pipe interior 4b. The amount increases due to the attachment of a part α4 of the fuel injection amount q injected from the fuel injection valve 32 in synchronization with the cycle. The amount of fuel evaporation for each intake stroke is α5 · Vf / ω
Can be expressed as Therefore, the amount of fuel fw adhering to the intake pipe wall surface 4a can be described as shown in the following equation (2).

fw (k + 1) = (1−α2) · fw (k) + α4 · q (k) −α5 · Vf (k) / ω (k) (2) (where k: intake cycle) On the other hand, inside the intake pipe 4b The fuel vapor amount fv at the time of the intake stroke is reduced by the inflow into the cylinder 2a, a part α3 of the fuel injection amount q is reduced in each intake cycle, and a part α6 of the fuel injection amount q is increased by evaporation. It increases due to the fuel evaporation of the attached fuel. For this reason, the amount of evaporated fuel inside the intake pipe 4b
fv can be described as shown in the following equation (3).

fv (k + 1) = (1−α3) · fv (k) + α6 · q (k) + α5 · Vf (k) / ω (k) (3) Next, the fuel sucked into the cylinder 2a of the internal combustion engine 2 Quantity fc
(K) can be described as the following equation (4) from the fuel-air ratio λ (k) detectable based on the oxygen concentration in the exhaust gas and the air amount m (k) flowing into the cylinder 2a.

fc (k) = λ (k) · m (k) (4) Therefore, if the parameters α2 to α6 in the above equations are determined by a known identification method, as shown in the following equations (5) and (6), The amount of fuel fw adhering to the intake pipe wall surface 4a expressed in a discrete system using the intake cycle of the internal combustion engine 2 as a sampling cycle.
A state equation (5) and an output equation (6) using と and the evaporated fuel amount fv as state variables can be obtained, whereby a physical model representing the fuel behavior in the internal combustion engine 2 is determined.

In such a physical model, the nonlinear behavior is compensated by the term of Vf / ω. Therefore, by determining the model parameters α2 to α6, the fuel behavior can be almost accurately described in the entire operation range of the internal combustion engine 2. However, when trying to describe the fuel behavior of the internal combustion engine 2 with higher accuracy using the physical model, each of the model parameters changes due to a decrease in the engine temperature, a change in the intake pipe pressure, and the like. It cannot be set to a value.

Therefore, in the present embodiment, the parameter (1) related to the state variable amounts fw and fv among the fluctuation amounts of the model parameters is described.
−α2) and (1−α3), the physical models such as the following equations (5) ′ and (6) ′ are set in consideration of △ (1−α2) and △ (1−α3), A control law is determined based on this.

In the above equations (5) ′ and (6) ′, the variation amount of two types of model parameters (1−α2) and (1−α3) △ (1−
α2) and △ (1-α3) are included, but even if the physical model is set to include only one of the fluctuation amounts,
By configuring this embodiment, controllability can be improved.

The evaporation amount Vf of the fuel from the intake pipe wall 4a used in the above physical model is obtained as a function of the saturated vapor pressure Ps of the fuel inside the intake pipe 4b and the pressure P (the intake pipe pressure) inside the intake pipe 4b. be able to. Although it is difficult to directly detect the saturated vapor pressure Ps by a sensor, the saturated vapor pressure Ps is related to the temperature T of the fuel adhering to the intake pipe wall surface 4a, and the temperature T of the adhering fuel is the water jacket water temperature of the internal combustion engine 2 or Since the temperature can be represented by the cylinder head temperature near the intake port, the water jacket sensor detects the water jacket water temperature or the cylinder head temperature.
The saturation vapor pressure Ps can be obtained by using, for example, an arithmetic expression such as the following expression (7) using

Ps = β1 · T ² −β2 · T + β3 (7) (where β1, β2, β3: constant) Therefore, the detection of the evaporation amount Vf of the fuel from the intake pipe wall surface 4a is based on the water jacket water temperature or the cylinder head temperature. The saturated vapor pressure Ps is obtained based on the detection signal from the water temperature sensor 26 that detects the intake air pressure, the intake pipe pressure P is detected by using the well-known intake pressure sensor 12, and a data map or a data map using these values Ps and P as parameters is provided. May be used to detect the evaporation amount Vf using an arithmetic expression. Further, since the fuel vaporization amount Vf changes greatly depending on the saturated vapor pressure Ps, the following equation (7) ′ Vf = β4 · Ps (7) ′ (where β4 is a constant) using the saturated vapor pressure Ps as a parameter is used. Approximately.

Next, the amount of air m flowing into the cylinder 2a is calculated by the following equation (8) using, for example, the intake pipe pressure P, the intake temperature Ti, and the rotation speed ω of the internal combustion engine as follows: m = ｛β × (ω) · P− βy (ω)｝ / Ti (8) It can be easily calculated. Therefore, the air volume m
Is a well-known intake pressure sensor that measures intake pipe pressure P and intake temperature Ti.
12 and the intake air temperature sensor 14, and can be detected by using the above expression (8) based on the detection result and the detection result by the rotation speed sensor 22. Further, the basic air amount m is obtained from a map using the intake pipe pressure P and the rotation speed ω as parameters, and the calculation result is calculated as the intake air temperature Ti.
Thus, the air amount m can be detected by performing the correction. A well-known air flow meter may be provided upstream of the throttle valve 8 to detect the amount of air flowing into the intake pipe 4, and based on the detection result, estimate the amount m of air flowing into the cylinder 2a during the intake stroke. .

In addition, the attached fuel amount fw and the evaporated fuel amount fv in the above state variables.
Cannot be detected directly using a sensor, such as the rotational speed ω, and indirectly detected using an arithmetic expression that uses the detection result of the sensor as a parameter, such as the fuel evaporation amount Vf or air amount m. (5) and (6)
The observer may be configured as an observer based on the equation or the equations (5) ′ and (6) ′, or may be configured to calculate using the above equation (5) or (5) ′.

The above-mentioned observer is described in detail in Katsuhisa Furuta et al., "Basic System Theory" (1973), Corona Corporation, or Katsuhisa Furuta et al., "Mechanical System Control" (1984), Ohmsha, etc. By using various design methods, the minimum order observer (Minimal Order Observe
r), various observers such as the same-dimensional observer (Identity Observer), a finite set observer (Dead Beat Observer), a linear function observer (Linear Function Observer), and an adaptive observer (Adaptive Observer) can be configured.

(II) Setting of Control Rule for Fuel Injection Next, a method of designing a control rule for fuel injection control shown in FIG. 3 will be described.

As a method of designing this kind of control law, for example, Katsuhisa Furuta, “Digital Control of Real System” System and Control, Vol.28, ωo.12 (1984) A brief explanation follows.

The control rule of this embodiment is based on the model parameters (1-α) in the physical model shown in the above-mentioned equations (5) ′ and (6) ′.
It is designed based on the physical model of the following equations (5) "and (6)" in which △ (1-α3) is set to 0, including the variation △ (1-α2) of 2).

Since this model is nonlinear, the above model is first linearly approximated in order to apply the linear control theory.

In the above equations (5) ″ and (6) ″, first, Vf (k) / ω (k) = Vfw (k) (9) Then, the above equations (5) ″ and (6) ″ are Can be represented by

here, When becomes steady, Then, the above equations (17) and (18) become the following equations (19) and (20)
It becomes as shown in.

From the above equations (17) to (20), It can be expressed as. Next, in the above equations (21) and (22), Then, the equations (21) and (22) are as shown in the following equations (26) and (27).

In these (26) and (27), if X (k) → 0, then Y (k) = 0, and Becomes

Therefore, the optimum regulator of the above equation (26) may be designed. That is, by prescribing the discrete Riccati equation, the optimal control is obtained as in the following equation (28).

The equation (28) becomes the following equation (29) from the equations (23) and (24).

Therefore, in the above equations (19) and (20), But Equation (29) is determined if Can be asked for.

In the case of the present embodiment, the above equation (30) is equivalent to the above equations (10) to (16).
From the equation, the following equation (31) is obtained. (That is, fwr, fvr, qr) are obtained as in the following equations (32) to (34), respectively.

fwr = β11 · Vfw (k) + β12 · {λr · m (k) − (1−α4−α6) q (k) + △ (1−α2) · fw (k)} (32) fvr = β21 · Vfw (k) + β22 · {λr · m (k) − (1−α4−α6) q (k) + △ (1−α2) · fw (k)} (33) qr = β21 · Vfw (k) + Β23 · {λr · m (k) − (1−α4−α6) q (k) + {(1−α2) · fw (k)} (where β11 to β23 are constants) By substituting equations (32), (33), and (34) into equation (29), the control input That is, an arithmetic expression for obtaining q (k) is obtained as in the following expression (35).

q (k) = f1 · fw (k) + f2 · fv (k) + f3 · m (k) λr + f4 · Vf (k) / ω (k) + f5 · {(1−α2) · fw (k)} (35) The estimating device for estimating the state variable amount in the above equation (35), that is, the adhering fuel amount fw and the evaporated fuel amount fv, is usually designed as an observer by a Gopinas design method or the like. Since no air-fuel ratio sensor for measuring the air-fuel ratio λ of the fuel mixture actually supplied to the internal combustion engine 2 is provided, a normal observer cannot be designed. However, the fuel behavior in the internal combustion engine 2 can be described almost exactly by the above-mentioned equation (5). Therefore, in this embodiment,
The state variable quantities fw and fv are obtained using the equation (5) as it is.

That is, first, in equation (5), q (k) is the fuel injection valve.
Since it is the fuel injection amount from 32, it can be known on the electronic control circuit 30 side, and Vf (k) / ω (k) can be obtained based on the detection signal from each sensor.
The term and the third term can be calculated. Then, δw (k) = fw (k) −w (k) (36) δv (k) = fv (k) −v (k) (37) Becomes In the above equation (38), 1−α2 <1, 1−α3 <
(38) is stable because it is 1, δw (k), δv (k)
→ 0, ie, w (k) → fw (k), v (k) → fv
(K). Therefore, if appropriate initial values are given as fw (k) and fv (k), fw (k) and fv (k) can be estimated by the above equation (5).

Next, the control law designed as described above will be described based on the block diagram shown in FIG.
FIG. 3 is a diagram showing a control law and does not show a hardware configuration, and the fuel injection control is realized by executing a series of programs shown in the flowchart of FIG.

As shown in FIG. 3, in the present embodiment, first, the intake pipe pressure P detected by the intake pressure sensor 12 and the cooling water temperature T detected by the water temperature sensor 26 are input to the first calculation unit P1. Then, in the first arithmetic unit P1, the input cooling water temperature T is converted into the saturated vapor pressure Ps of the fuel in the intake pipe 4 by using the arithmetic expression such as the above-mentioned expression (7), and further converted. Saturated vapor pressure
From Ps and the intake pipe pressure P, the evaporation amount Vf of the fuel attached to the wall surface of the intake pipe 4 is calculated. Also, the converted evaporation amount Vf
Is input to the division unit P2, and is divided by the rotation speed ω of the internal combustion engine 2 detected using the rotation speed sensor 22. Then, the division result Vf / ω is input to the coefficient f4 multiplication unit P3, and is multiplied by a preset coefficient f4.

Next, the intake pipe pressure P and the rotation speed ω are also input to the second arithmetic unit P4 together with the intake air temperature Ti detected by the intake air temperature sensor 14. The second calculating unit P4 calculates the amount m of air flowing into the cylinder 2a from the input rotation speed ω, the intake pipe pressure P, and the intake air temperature Ti using an arithmetic expression such as the expression (8). The result of the calculation is the first multiplication unit
Output to P5. Then, in the multiplication unit P5, the calculated air amount m is multiplied by a preset target fuel-air ratio λr,
Thereby, the fuel amount (target fuel amount) λrm that should flow into the cylinder 2a is calculated. Then, the target fuel amount λrm is input to a coefficient f3 multiplication unit P6, and is multiplied by a preset coefficient f3.

On the other hand, the division result Vf / ω of the division unit P2 is
7 is also entered. The state variable estimating unit P7 is inputted with the division result Vf / ω of the dividing unit P2 and the primary delay unit P8 by using a preset arithmetic expression (Equation (5) in the present embodiment). Fuel quantity q (k-1) injected from fuel injection valve 32
From the state variable amounts w (k−1) and v (k−1) estimated last time by the state variable estimating unit P7, the fuel injection valve 32
, The state variable amount for calculating the next fuel injection amount q (k) from the above, that is, the attached fuel amount fw and the evaporated fuel amount fv are estimated.
The estimation results w and v are added to the coefficient f1 multiplication unit P9.
And the coefficient f2 are multiplied by coefficients f1 and f2, respectively.

Further, the intake pipe pressure P, the rotation speed ω, and the cooling water temperature T are also input to the third calculation unit P11. The third calculation unit P11 calculates the amount of change of the model parameter (1-α2) as a coefficient △ (1-α2) according to the input operating state of the internal combustion engine 2. In this calculation, the above (5) ″ and (6) ″
Of the model parameter (1-α2) generated when each of the model parameters is determined by system identification △
A map in which (1−α2) is associated with each of the above operating states is used. Then, the coefficient １− (1−α2) calculated by the third arithmetic unit P11 is multiplied by the coefficient f5 by the coefficient f5 multiplying unit P12, and the adhesion estimated by the state variable estimating unit P7 by the second multiplying unit P13. The fuel amount w is multiplied.

The multiplication result by the second multiplication unit P13 is added by the addition units P14 to P17 together with the multiplication results by the other multiplication units P3, P6, P9, and 10, whereby the next fuel injection amount from the fuel injection valve 32 is q (k) is determined.

In the case of the present embodiment, the regulation rule is set to the aforementioned (5) ″,
Since the state variable estimating unit P7 is designed using the equation (6), the state variable estimating unit P7 may be configured to estimate the state variable quantities fw, fv using the equation (5). . In this case, since the equation (5) ″ includes the variation of the model parameter (1-α2) △ (1−α2), the variation △ (1−α2) obtained by the third arithmetic unit P11 is used as the state variable. It is necessary to input to the estimating unit P7, and the state variable amount may be estimated using the above (5) '.

Next, a configuration for updating the value of the map used when setting the variation amount to △ (1−α2) will be described.

First, the fuel vapor amount v output from the state variable estimating unit P7 is input to the coefficient α3 multiplying unit P18, multiplied by the coefficient α3, and then input to the data storage unit P19. Addition unit P
The fuel injection amount q output from 17 is input to a coefficient multiplying unit P20, multiplied by a coefficient (1−α4−α6), and then input to a data storage unit P19. Further, the target fuel amount λrm output from the first multiplier P5 is also input to the data storage P19.

The data input to the data storage unit P19 is calculated by the coefficient identification unit Is calculated. Next, the identification method will be described. The method of parameter identification performed here is described in detail in Takayoshi Nakamizo's "Identification Method of Linear Discrete-Time System-I" System and Control Vol.25 No.8 P476-489 1981. I do.

First, based on the output equation of the above equation (5), the error e
(K) is calculated by the following equation (39) using the measured value λM (k) mM (k) of the inflow fuel amount, the fuel injection amount q (k), the state variables w (k), v (k) and the like. Describe.

Here, w (k) and v (k) are the calculated values of the observer, and q (k) is the manipulated variable, so that {e (k)} ² is minimized using α3, α4, α6 as known quantities. Is calculated by the least squares algorithm. Can be requested. That is, Y (k) = λM (k) mM (k) − (α3v (k) + (1−α4−α6q (k))) (40) X (k) = w (k) (41) Then By transforming this equation into the following equation suitable for sequential calculation, The above formula (43) can be expressed by a general recursive least squares calculation formula of the following formula (44).

Coefficient calculated by identification in this way Whether the value input to the verification unit P22 is physically significant, for example, It is verified whether or not the coefficient α is already significant.
2 and the following equation (47), the variation △ (1−α2) is calculated.

The fluctuation amount △ (1−α2) calculated in this manner is input to the third calculation unit P11, and the value of the map used in the third calculation unit P11 is updated.

(III) Flowchart of Injection Amount Control Next, the process of calculating the fuel injection amount q and performing the fuel injection executed by the electronic control circuit 30 will be described with reference to the flowchart shown in FIG.

The fuel injection control is started when the internal combustion engine 2 is started, and is repeatedly executed while the internal combustion engine 2 is operating.

When the process is started, first execute step 100,
The attached fuel amount w (k-1) and the evaporated fuel amount v (k-
1) Initializing the fuel injection amount q (k-1), and proceeding to step 110, based on the output signals from the sensors, the intake pipe pressure P (k), the intake temperature Ti (k), The rotation speed ω (k) of the internal combustion engine 2 and the cooling water temperature T (k) are obtained.

Next, at step 120, a target fuel-air ratio λr corresponding to the load on the internal combustion engine 2 is calculated based on the intake pipe pressure P (k) obtained at step 110 and the rotational speed ω (k) of the internal combustion engine 2. I do. In this step 120, normally, the target fuel-air ratio λr is set so that the excess air ratio of the fuel mixture becomes 1 (that is, the stoichiometric air-fuel ratio). The target fuel / air ratio λr is set to a rich side to increase the output of the internal combustion engine by increasing the amount of fuel. The ratio λr is set to the lean side.

When the target fuel-air ratio λr (k) is set in step 120, the process proceeds to step 130, in which the intake pipe pressure P (k) and intake temperature Ti (k) obtained in step 120 and the internal combustion engine 2 Based on the rotation speed ω (k), the cylinder 2a is calculated using an arithmetic expression or a data map as shown in the above expression (8).
The processing as the second calculating unit P4 for calculating the amount of air m (k) flowing into the inside is executed.

In the following step 140, the evaporation amount Vf of the fuel adhering to the intake pipe wall surface 4a is determined on the basis of the cooling water temperature T (k) and the intake pipe pressure P (k) determined in step 110, and the internal combustion engine 2 Of the fuel from the intake pipe wall 4a during the period from the previous intake stroke to the next intake stroke (ie, Vf (k) / ω (k)). ) Is calculated. The processing as the first operation unit P1 and the division unit P2 is executed.

In the following step 150, the fuel evaporation amount Vfw (k) from the intake pipe wall surface 4a obtained in step 140, the previous fuel injection amount q (k-1), and the previously obtained attached fuel amount w (k-
The following equation (48) set based on the above equation (5), based on 1) and the evaporated fuel amount v (k-1) Is used to determine the amount of deposited fuel w (k) and the amount of evaporated fuel v
The processing as the state variable estimating unit P7 for estimating (k) is executed.

Next, at step 160, the target fuel-air ratio λr (k) set at step 120 is multiplied by the air amount m (k) obtained at step 130 to obtain the target fuel amount λrm flowing into the cylinder 2a. A process as the first multiplication unit P5 for calculating (k) is executed.

Then, at step 170, the cooling water temperature T (k), the intake pipe pressure P (k), and the rotation speed
Based on (k), a process is performed as a third calculation unit P11 for calculating a variation amount △ (1−α2) of the model parameter (1−α2) using a preset map.
Move to 80. The set value stored in the map for calculating the variation △ (1−α2) is updated to an appropriate value adapted to the driving variation by a process described later.

In step 180, the fuel evaporation amount Vfw (k) of one cycle obtained in steps 140 to 170, the attached fuel amount w (k) as the state variable amount, and the evaporated fuel amount v
(K), target fuel amount λrm (k), and fluctuation amount △ (1-α
From 2), the next fuel injection amount q is obtained by using the aforementioned equation (35).
(K) is calculated, and the routine proceeds to step 190.

In step 190, the fuel injection timing t determined based on the detection signal from the crank angle sensor 24
Then, the fuel injection valve 32 is opened according to the injection amount q (k) obtained in step 180, and the fuel injection is executed.

In step 190, fuel injection is performed and the internal combustion engine 2
Once the fuel supply to is completed, the process proceeds to step 200, in which the state variable amounts w (k) and v (k) obtained this time are calculated.
Then, the fuel injection amount q (k) is replaced with w (k-1), v (k-1), q (k-1) for the next processing, respectively, and the process returns to step 110 again.

Next, the variation amount of the model parameter △ (1−α2)
The process of updating the value of the map used to set the value will be described with reference to the flowchart of FIG.

To update the value of this map, it is necessary to identify the coefficient α2. However, since identification of the coefficient α2 requires a lot of calculations, the identification of the coefficient α2 and the The update of the map based on the identified values is not performed on-board, but is performed by temporarily storing data such as various operating states and the fuel injection amount q necessary for identifying the coefficient α2,
This is performed when the CPU 40 has sufficient computing power.

First, in step 300, data of the operating state such as the intake pipe pressure P, the rotational speed ω, the cooling water temperature T from the various sensors, and the state variables w, already calculated using those data,
The data such as v and the fuel injection amount q are read.

In the following step 310, it is determined whether or not the CPU 40 has a margin for processing a large amount of operations at present. If a negative determination is made here, the process proceeds to step 320.

In step 320, the above various data is stored as time-series data, and at this time, old data is sequentially deleted. Then, the process returns to step 300 again.

On the other hand, if it is determined in step 320 that the CPU 40 has sufficient calculation capability, the process proceeds to step 330, and the equations (44) to (4) are calculated based on the least squares algorithm described above.
6) Using the coefficient Is calculated.

In the following step 340, the coefficient Is a physically significant value It is determined whether or not the value is within the range. If the determination is affirmative, the process proceeds to step 350.

In step 350, the coefficient α2 already set and the coefficient calculated in step 330 are calculated based on the above equation (47). And the variation amount of the model parameter △ (1−α2)
Ask for.

In the next step 360. Using the variation △ (1−α2), the value of the map set according to the operating state is updated, and the routine proceeds to step 370.

On the other hand, in step 340 above, the calculated coefficient If it is determined that the value of
In step 37, a warning is issued to notify that there is something wrong, and step 37
Go to 0.

In the following step 370, the above coefficient The various types of data used for the calculation are deleted, and the process proceeds to step 300.

That is, through the processing of steps 300 to 380, the set value of the map can be updated using the appropriate variation amount 変 動 (1−α2) according to the operation variation.

As described above, in the fuel injection control device of the present embodiment, since the control law is set based on the physical model describing the behavior of the fuel in the internal combustion engine 2, the behavior of the fuel that changes according to the warm-up state of the internal combustion engine 2 Can be nonlinearly compensated by Vfw (that is, Vf / ω), and the fuel injection amount can be controlled by a single control law. Also, as shown in equation (35), １− (1−α2) · for compensating a control amount error due to a change in the model parameter (1−α2) in the control law.
Since the term w is provided, even if an operation fluctuation occurs in the internal combustion engine 2 such that the model parameter (1−α2) fluctuates, a control amount error accompanying the operation fluctuation can be compensated, and the control can be performed. Performance can be improved.

Further, the coefficient α2 of the model parameter (1−α2)
Is obtained by performing an identification calculation at a time when the CPU 40 has a margin, a variation amount of the model parameter △ (1−α2) is calculated, and a map is obtained by using the calculated variation amount △ (1−α2). Since the set value of is updated, it is possible to perform control that appropriately responds to the operation fluctuation.

That is, △ (1−α2) · for compensating the control amount error.
By adopting the physical model using the term of w,
The fuel injection amount q can be quickly controlled, and the value of the map for obtaining the fluctuation amount △ (1−α2) can be appropriately adjusted, so that accurate fuel injection control can be performed. Can be.

Here, in the above embodiment, the control rules are (5) ″, (6) ″
Although the setting is performed based on the physical model described by the equation, if the setting is performed based on the physical model described in the above (5) ′ and (6) ′, the amount of deposited fuel fw accompanying the operation fluctuation of the internal combustion engine 2 will be described.
In addition, the estimation error of the fuel vapor amount fv can be compensated for, and the control accuracy can be further improved. In this case, the control law can be designed in the same manner as in the above embodiment, and is expressed by the following equation (49).

q (k) = f1 · fw (k) + f2 · fv (k) + f3 · m (k) λr + f4 · Vf (k) / ω (k) + f5 · △ (1−α2) · w
(k) + f6 △ (1−α3) ・ v (k) (49) In the models of (5) ′ and (6) ′, △ (1-
Even if α2) is set to 0 and the configuration is made to compensate for the estimation error of the evaporated fuel amount fv with respect to the fluctuation of the model parameter (1−α3), the control accuracy can be improved. In this case, the control law is obtained as in the following equation (50).

q (k) = f1 · fw (k) + f2 · fv (k) + f3 · m (k) λr + f4 · Vf (k) / ω (k) + f6 · △ (1−α3) · v
(k) (50) In the above embodiment, the fuel injection amount control device capable of controlling the air-fuel ratio to the target air-fuel ratio without using the air-fuel ratio sensor has been described as an example. If a sensor is provided to perform feedback control of the air-fuel ratio, control accuracy can be further improved. In this case, the control law may be designed as a well-known servo system that determines the fuel injection amount using the deviation between the actual air-fuel ratio of the internal combustion engine 2 detected by the air-fuel ratio sensor and the target air-fuel ratio as one parameter. . In this case, since the actual air-fuel ratio of the internal combustion engine can be detected, an observer can be used to estimate the state variable amounts fw and fv.

(IV) Second Embodiment Next, a fuel injection amount control device according to a second embodiment will be described.

The difference between this embodiment and the first embodiment is that the value multiplied by the variation of the model parameter is not a state variable,
That is, the fuel injection amount q.

Therefore, in the present embodiment, among the fluctuation amounts of the model parameters of the physical model used in the first embodiment, the fluctuation amounts △ α4 and △ α6 of the model parameters α4 and α6 related to the fuel injection amount q are considered, and the (5) ) And (6), a physical model such as the following equation (51) and (52) is set,
A control law is determined based on this.

Note that the equations (51) and (52) include the fluctuation amounts αα4 and △ α6 of α4 and α6, however, the physical model is set so as to include only one of the fluctuation amounts. Even
By configuring this embodiment, controllability can be improved. Therefore, in the following description, the variation Δα6 in the above equations (51) and (52) is set to 0.

(V) Setting of Control Rule for Fuel Injection of Second Embodiment First, a method of designing the control rule of FIG. 6 will be described.

The design method of this embodiment is almost the same as that of the first embodiment, and its control rule is the variation amount of the model parameter α4 in the physical model shown in the above-mentioned equations (51) and (52).
It is designed based on the physical models shown in the following equations (51) 'and (52)', which are set to △ α6 and 0, including α4.

Since this model is nonlinear, the above model is first linearly approximated in order to apply the linear control theory.

In the above equations (51) 'and (52)', Then, the following equation (59) is derived in the same manner as in the first embodiment.

Further, fwr, fvr, and qr are obtained as in the following equations (60) to (62).

fwr = β11 · Vf (k) / ω (k) + β12 · {λr · m (k) − (1-α4-α6) q (k) + {α4 · q (k)} (60) fvr = β21 Vf (k) / ω (k) + β22 · {λr · m (k) − (1-α4-α6) q (k) + {α4 · q (k)} (61) qr = β21 · Vf ( k) / ω (k) + β23 · {λr · m (k) − (1-α4-α6) q (k) + {α4 · q (k)} (62) (where β11 to β23 are constants) Therefore, by substituting these equations (60), (61), and (62) into equation (71), the control input That is, an arithmetic expression for obtaining q (k) is obtained as in the following expression (63).

q (k) = γ1 · fw (k) + γ2 · fv (k) + γ3 · m (k) λ
r + γ4 · Vf (k) / ω (k) (63) However, in this case, in the above equations (60) to (62), there is a term of △ α4 · q (k). In accordance with the variation of the parameter α4, the coefficient γ1
~ Γ4 needs to be changed. Therefore, in the present embodiment, since the fuel injection amount does not fluctuate greatly during one cycle of the internal combustion engine 2, the term of 項 α4 · q (k) is set to △ α4 · q (k-1). In the same manner as above, q
An arithmetic expression for obtaining (k) is set as in the following expression (64).

q (k) = f1 · fw (k) + f2 · fv (k) + f3 · m (k) λr + f4 · Vf (k) / ω (k) + f5 · △ α4 · q (k−1) (64) Note that the state variable amount in the above equation (64), that is, the amount of deposited fuel
The fw and the fuel vapor amount fv are estimated in the same manner as in the first embodiment.

Next, a control law for this fuel injection control will be described based on a block diagram shown in FIG.

As shown in FIG. 6, each of the operation units Q1 to Q23 of this embodiment
Are substantially the same as the operation units P1 to P23 in the above embodiment. The difference is that the value output from the third calculation unit Q11 is not the variation value △ (1−α2) but the variation value of the model parameter α4 △ α4, and the value input to the second multiplication unit Q13 is the state variable estimation unit. The point is that the fuel injection amount is q (k-1) before being output from the primary delay unit Q8, not from Q7. Further, in the present embodiment, the amount of deposited fuel w output from the state variable estimating unit Q7 is input to the coefficient α2 multiplying unit Q24, multiplied by the coefficient α2, and the calculation result is input to the data storage unit Q19. I have.

In the case of the present embodiment, the control law is defined by the aforementioned (51) ′, (5)
2) ', the state variable estimating unit Q7 may be adapted to estimate the state variable quantities fw, fv using the equation (51)'. In this case, (5
Since 1) ′ includes the variation 変 動 α4 of the model parameter α4, it is necessary to input △ α4 obtained by the third arithmetic unit Q11 to the state variable estimation unit Q7. Alternatively, the state variable amount may be estimated using (51) described above.

As described above, in the fuel injection control device according to the present embodiment, the control law is set based on the physical model describing the behavior of the fuel in the internal combustion engine 2 as in the above-described embodiment. Compensation can be made, and the fuel injection amount can be controlled by a single control law.
Further, as shown in equation (64), the model parameter α
△ α4 · q (k−
Since the term (1) is provided, when an operation fluctuation occurs in the internal combustion engine 2 such that the model parameter α4 fluctuates, a control amount error caused by the operation fluctuation can be compensated, and the controllability is improved. Can be improved.

Further, the model parameter α4 is obtained by performing an identification calculation at a time when the CPU 40 has a margin, the variation Δα4 is calculated, and the value of the map used for obtaining the variation Δα4 is updated. It is possible to perform control appropriately corresponding to the operation fluctuation.

That is, △ α4 · q (k−
The fuel injection amount can be quickly controlled by the physical model which is easy to calculate using the term 1), and the value of the map used for the control can be optimized, so that the fuel injection can be accurately performed. Control can be performed.

Here, in the present embodiment, the control rule is set based on the physical model described by the equations (51) ′ and (52) ′, but the control rule is set based on the physical model described in the above (51) and (52). Then, a control error due to a change in the model parameters α4 and α6 can be prevented, and control accuracy can be further improved. In this case, the control law can be designed in the same manner as in the above embodiment, and is expressed by the following equation (65).

q (k) = f1 · fw (k) + f2 · fv (k) + f3 · m (k) λr + f4 · Vf (k) / ω (k) + f5 · △ α4 · q (k−1) + f6 · △ α6 Q (k-1) (65) In the models of (51) and (52), △ α4 is set to 0
Even if the control amount is compensated for the variation of the model parameter α6, the controllability can be improved. In this case, the control law is obtained as in the following equation (66).

q (k) = f1 · fw (k) + f2 · fv (k) + f3 · m (k) λr + f4 · Vf (k) / ω (k) + f6 · △ α6 · q (k−1) (66) In the above embodiment, the air-fuel ratio sensor is not used,
Although the fuel injection amount control device capable of controlling the air-fuel ratio to the target air-fuel ratio has been described as an example, if an air-fuel ratio sensor is provided in the exhaust system to perform the air-fuel ratio feedback control,
Control accuracy can be further improved. In this case, the control law may be designed as a well-known servo system that determines the fuel injection amount using the deviation between the actual air-fuel ratio of the internal combustion engine 2 detected by the air-fuel ratio sensor and the target air-fuel ratio as one parameter. . In this case, since the actual air-fuel ratio can be detected, an observer can be used to estimate the state variable amount.

[Effects of the Invention] As described above, according to the fuel injection amount control device for an internal combustion engine of the present invention, when an operation fluctuation occurs in which a model parameter of a physical model describing the fuel behavior of the internal combustion engine fluctuates, Since the correction is performed using the fluctuation amount of the model parameter, the control amount error due to the operation fluctuation can be quickly compensated. Further, since the value used for setting the above-mentioned fluctuation amount is updated by identifying the model parameter, it is possible to control the fuel injection amount accurately and appropriately corresponding to the operation fluctuation. In addition, since the process of identifying the coefficient and updating the variation is performed based on the data once stored when there is room in the arithmetic processing, control corresponding to the operation variation can be quickly performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of the present invention, FIG. 2 is a schematic configuration diagram showing an internal combustion engine and peripheral devices of the embodiment, FIG.
FIG. 4 is a block diagram showing a control law for fuel injection control, FIG. 4 is a flowchart showing a fuel injection control process, and FIG. 5 shows a process for updating a set value of a map used for obtaining a coefficient variation. Flowchart, 6th
The figure is a block diagram showing a control law for fuel injection control according to another embodiment. M1, 2 ... internal combustion engine, M2 operating state detection means M3 ... injection amount control means, M4 ... set value storage means M5 ... fluctuation amount output means, M6 ... data storage means M7 ... coefficient identification means, M8 … Fluctuation amount multiplying means M9… fluctuation amount updating means, M10… time margin judgment means, 2a
... cylinder 4 ... intake pipe, 12 ... intake pressure sensor 14 ... intake temperature sensor, 20 ... rotational speed sensor 26 ... water temperature sensor, 30 ... electronic control circuit

Claims (1)

(57) [Claims] 1. An operating state detecting means for detecting an operating state of an internal combustion engine, wherein the behavior of the fuel of the internal combustion engine is determined in advance as the operating state, state variables and fuel injection amount, and values multiplied by the respective amounts. Injection amount control means for sequentially calculating and controlling the fuel injection amount in accordance with the physical model described using the determined coefficient and the variation amount of the coefficient, and operating in advance as the variation amount of the coefficient of the physical model. Setting value storage means for storing a set value determined according to the state; and setting values stored by the set value storage means in accordance with the operating state detected by the operating state detecting means.
A fluctuation amount output means for outputting as a fluctuation amount of the coefficient, a fuel injection amount control device for an internal combustion engine comprising: an operation state detected by the operation state detection means;
Data storage means for storing the state variables and the fuel injection amount used by the injection quantity control means as time-series data; and identifying the coefficients of the physical model based on the data stored by the data storage means. Coefficient identification means, a difference between the coefficient identified by the coefficient identification means and the predetermined coefficient, and a fluctuation amount calculation means for obtaining a fluctuation amount of the coefficient; Using the variation of the coefficient,
A change amount updating means for updating the set value; and an arithmetic processing unit for performing the calculation of the fuel injection amount control device, an identification calculation processing by the coefficient identification means and a coefficient calculation processing of the coefficient by the change amount calculation means. Time margin determining means for determining whether or not there is a necessary time margin, and when the time margin determining means determines that there is a time margin necessary for the calculation, the coefficient identifying means; A fuel injection amount control device for an internal combustion engine, wherein the control unit executes processing by the fluctuation amount calculating unit and the fluctuation amount updating unit.