JPH01267332A - Fuel injection quantity controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To make improvements in controllability by constituting a control law so as to compensate the variable portion of a model parameter attendant upon a driving variation in internal combustion engine with a multiplying result between a specified factor and a fuel injection quantity in the case where fuel injection of the internal combustion engine is controlled by the specified control low. CONSTITUTION:Engine speed of an internal combustion engine M2, evaporation per unit time of fuel sticking to a wall surface of an intake pipe M1, and air quantity flowing into a cylinder M3 are detected each by a means M5. In addition, the fuel evaporation is divided by engine speed with a means M6. On the other hand, a specified factor set according to a driving state of the engine M1 and a fuel injection quantity out of a fuel injection valve M4 are multiplied by a means M7. Furthermore, a fuel sticking quantity to a state variable and the evaporation are estimated each by a means M8 on the basis of at least the divided result and the fuel injection quantity. Then, on the basis of the product of division, multiplication and estimation results, the air quantity and a desired air-fuel ratio, a fuel quantity to be sprayed in the next time is calculated by a means M9.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is directed to an internal combustion engine that controls the amount of fuel injected from a fuel injection valve in accordance with a physical model representing the behavior of fuel flowing into a cylinder of an internal combustion engine. Set the fuel injection amount control fall device.

[Prior Art] Conventionally, as one of the fuel injection amount control devices that control the amount of fuel injection from a fuel injection valve so that the air-fuel ratio of the fuel mixture supplied to the internal combustion engine becomes a target air-fuel ratio, for example, As described in Japanese Unexamined Patent Publication No. 59-196930, a correction value for correcting the basic fuel injection amount determined from the rotational speed of the internal combustion engine and the intake air amount is manually controlled, and the air-fuel ratio is detected using an air-fuel ratio sensor. The actual measured value of the internal combustion engine is taken as the control output, and the identification is performed assuming that a linear approximation holds between the control human power and the control output, and a mathematical model that describes the dynamic behavior of the internal combustion engine is obtained, and the engine is designed based on this. A control 'a device based on so-called linear control theory, which controls the fuel injection amount using a control law, is known.

[Problem to be solved by the invention] However, the relationship between the control human power and the control output is inherently non-linear, and if a mathematical model is simply obtained by linear approximation as described above, the dynamic behavior of the internal combustion engine will be extremely narrow. It can only be described under operating conditions, and in order to perform good control, a mathematical model is required for each of multiple operating regions that can be considered to be linearly approximated, as described in Japanese Patent Laid-Open No. 59-7751. was set, and control laws had to be determined for each operating region based on this. For this reason, conventionally,
There is a problem in that the control law must be changed for each operating range of the internal combustion engine, making the control complicated. There is also the problem that control becomes unstable due to switching of control laws at the boundary points of each operating region.

Therefore, in Japanese Patent Application No. 62-189889, Japanese Patent Application No. 62-189891, etc., the applicant has determined the above-mentioned control law by determining a non-linearly compensated control law based on a physical model describing fuel behavior in an internal combustion engine. Fuel injection control i without switching the control law (i.e. with one control law)
We proposed a fuel injection amount control device that can perform wholesale.

However, even with the physical model described above, it is difficult to completely describe the fuel behavior of an internal combustion engine, and in reality, model parameters vary in accordance with operating fluctuations of the internal combustion engine. Controlled variable errors caused by such fluctuations can be compensated for by extending the control law to a well-known servo system and using integral action, but increasing the integral compensation ratio may result in poor response, which may result in poor controllability. For further improvement, it is desirable to determine the control amount in anticipation of variations in model parameters.

Therefore, the present invention provides an apparatus for controlling fuel injection of an internal combustion engine using a control law set based on a physical model that describes the fuel behavior of the internal combustion engine as described above. As illustrated in FIG. from the fuel injection valve M4 in accordance with a physical model that describes the behavior of fuel flowing into the cylinder M3 of the internal combustion engine M2 using the amount of fuel fw adhering to the wall surface of the pipe M1 and the evaporated fuel ifv in the intake pipe Ml as state variables. A fuel injection amount control device for an internal combustion engine that controls the fuel injection amount q of the internal combustion engine, the rotation speed ω of the internal combustion engine M2, the evaporation amount Vf per unit time of the fuel adhering to the wall surface of the intake pipe M1, and the an operating state detecting means M5 that detects the amount m of air flowing into the cylinder M3; a dividing means M6 that divides the evaporation amount Vf of the fuel adhering to the intake pipe wall surface detected by the operating state detecting means M5 by the rotational speed ω; Coefficient △ set according to the operating state of the internal combustion engine M2
α and the fuel injection amount q (n-1
) and a multiplier M7 that calculates the product Δα・q(n-1), and an arithmetic expression set based on the above physical model,
Estimating means M8 for estimating the state variables f- and fv based on at least the calculation result Vf/ω of the dividing means M6 and the fuel injection amount q (n-1) from the fuel injection valve M4;
And, using the calculation formula set based on the above physical model,
The calculation result Vf/ω of the division means M6 and multiplication means M7
, △α・q(n-1), the estimation result of the above estimation means M8?
L-? υ, and the amount of fuel q (n) to be injected next from the fuel injection valve M4 based on the air fAm detected by the operating state detection means M5 and the target fuel-air ratio m. The gist of the present invention is a fuel injection amount control device for an internal combustion engine, characterized by comprising: an injection amount calculation means M9;

Here, the operating state detection means M5 is for detecting the rotational speed ω of the internal combustion engine M2, the evaporation amount Vf of fuel adhering to the intake pipe wall surface, and the amount m of air flowing into the cylinder M3. A known rotation speed sensor can be used to detect the rotation speed of M2.

Next, the amount of evaporation Vf of fuel from the wall surface of the intake pipe M1 can be determined as a function of the saturated vapor pressure Ps of the fuel in the intake pipe M1 and the pressure inside the intake pipe M1 (intake pipe pressure) P. . Although it is difficult to directly detect the saturated vapor pressure Ps with a sensor, the saturated vapor pressure PS is a function of the temperature T of the fuel adhering to the intake pipe wall surface, and the adhering fuel temperature T is the function of the adhering fuel temperature T.
This can be represented by the water jacket water temperature or the cylinder head temperature near the intake boat, so we can use an example in which the water jacket water temperature or cylinder head temperature is detected by a temperature sensor and the detection result T (°K '') is used as a parameter. The saturated vapor pressure Ps can be determined using an arithmetic expression as shown in the following equation (1).

Ps = β1-T2-β2-T+β3 ・(1)
(However, β1.β2.β3: Constant) Therefore, the detection of the amount of fuel evaporation Vf from the intake pipe wall is as follows:
The saturated steam pressure P is determined based on the detection signal from the temperature sensor that detects the water temperature of the outer jacket or the temperature of the cylinder.
In addition to finding s, the intake pipe pressure P may be detected using a well-known intake pressure sensor, and the evaporation amount Vf may be detected using a data map or an arithmetic expression using these values Ps and P as parameters. In addition, since the fuel evaporation amount Vf varies greatly depending on the saturated vapor pressure Ps, the following equation (1)' using the saturated vapor pressure PS as a parameter: Vf = β4 4 Ps = (1)
' (However, β4 is a constant).

Next, the amount of air m flowing into the cylinder M3 can be easily calculated using, for example, the following formula (2)% formula %(2) using the intake pipe pressure P, intake air temperature Ti, and rotational speed ω of the internal combustion engine M2 as parameters. can do. Therefore air mm
is detected by detecting the intake pipe pressure P and intake air temperature Ti using a well-known intake pressure sensor and intake air temperature sensor, and calculating them using the above equation (2) based on the detection results and the detection results from the rotational speed sensor. can do. The air amount m can also be detected by calculating the basic air amount m using a map using the intake pipe pressure P and the rotational speed ω as parameters, and correcting the calculation result using the intake air temperature Ti.

Alternatively, a well-known air flow meter may be provided upstream of the throttle valve to detect the amount of air flowing into the intake pipe MI, and based on the detection result, the amount m of air flowing into the cylinder M3 during the intake stroke may be estimated. .

Next, an example of a physical model that is the basis of the configuration of the present invention will be explained.

First, the amount of fuel f flowing into the cylinder M3 of the internal combustion engine M2
c is the fuel injection amount q from the fuel injection valve M4 and the intake pipe M
It can be expressed as in the following equation (3) using the amount fw of fuel adhering to one wall surface and the amount fv of evaporated fuel inside the intake pipe M1.

fc = αl conflict q+ α2◆fw+ α3◆fv
-(3) That is, the above fuel amount fc is determined by the direct inflow amount α1◆q of the injected fuel from the fuel injection valve M3 and its injection rJ'J
Indirect inflow amount α2・fw from the intake pipe M1 with fuel attached
Then, due to evaporation of the injected fuel or the fuel attached to the wall, the intake pipe M1
Since it is considered to be the sum of the inflow amount α3·fν of the vaporized fuel existing in the interior, the fuel amount fc flowing into the cylinder M3 can be described as in the above equation (3).

In the above equation (3), the fuel injection amount q is determined by the control amount of the fuel injection valve M4, so if the amount of fuel adhering to the wall of the intake pipe M1 f- and the amount of evaporated fuel fv within the intake pipe M1 are known, then , fuel IN f c can be predicted.

Therefore, next, consider the amount of adhered fuel f- and the amount of evaporated fuel fv.

First, the amount of fuel f- adhering to the wall surface of the intake pipe M1 decreases by a part α2 in each intake cycle due to the inflow into the cylinder M3 during the intake stroke, and also decreases due to evaporation inside the intake pipe M1. Fuel injector M4 synchronizes with the intake cycle.
The amount α4 of the fuel injection amount q injected from q is increased by adhesion. Also, the amount of fuel evaporation per intake stroke is α5
- Can be expressed as Vf/ω. Therefore, the intake pipe M
The amount of fuel adhering to one wall f- can be described as shown in the following equation (4).

f w(k+1) = (1-α2)・f(I<)+
α4◆q(k)−α5◆Vf(k)/ω(k) =(
4) (where k: intake cycle) On the other hand, the amount of evaporated fuel fν inside the intake pipe M1 decreases by a part α3 in each intake cycle due to the inflow into the cylinder M3 during the intake stroke, and also due to the fuel injection The amount q increases as a portion α6 evaporates, and further increases as the adhering fuel evaporates. Therefore, the amount of evaporated fuel fυ in the intake pipe Ml can be expressed as shown in the following equation (5).

f v (k+1) = (1-α3)◆fν(1〈)+α
6・q(k)+α5・V f(k)/ω(k) ・・
・(5) Next, the amount of fuel fc(k) taken into cylinder M3 of internal combustion engine M1 is calculated based on the fuel-air ratio λ(k), which can be detected based on the oxygen moisture content in the exhaust gas, and the fuel air ratio in cylinder M3. From the amount of air m (k) that has flowed into , it can be written as shown in the following equation (6).

fc (k) = λ (k) m (k) - (6) Therefore, when the parameters α2 to α6 of each of the above equations are determined by the well-known identification method, the internal combustion It is possible to obtain the state equation (7) and output equation (8) whose state variables are the amount of fuel adhering to the intake pipe wall surface and the amount of evaporated fuel, which are expressed in a discrete system with the intake cycle of engine M2 as the sampling period ill. This establishes a physical model that describes the behavior of fuel in an internal combustion engine.

+ (1-α4-α6)q(k) ...(8) In such a physical model, nonlinear compensation is performed by the term Vf/ω, so by defining each model parameter α2 to α6, the fuel behavior can be adjusted. can be described almost accurately over the entire operating range of the internal combustion engine.

However, when attempting to describe the fuel behavior of an internal combustion engine with higher accuracy using the above physical model, each model parameter is set to a fixed value because it fluctuates due to a drop in engine temperature, fluctuations in intake pressure, etc. It becomes impossible to set.

Therefore, in the present invention, the parameters α4 and α6 related to the fuel injection amount q among the fluctuation amounts of the model parameters are
Considering the fluctuation amounts Δα4 and Δα6, for example, the following equation (7
)- and (8)' are set, and control laws are determined based on these.

"Mu αb" + (1-04-α6)・q (k) −(Δα4+Δα6)・q(k)...(8)' Furthermore, in the above equations (7) 7 and (8) 7, α4 Although the variation amounts Δα4 and Δα6 of α6 and α6 are included, it is possible to configure the present invention and improve control accuracy even if the physical model is set to include only the variation amount of either one. It is. The physical model in this case is the above equation (7) and (8).
The part Δα4 or Δα6 in Equation 7 becomes 0.

Next, the multiplication means M7 calculates the model parameters α4, α6
This is to compensate for the fluctuation error of the controlled variable due to the fluctuation of
The product of α and the fuel injection amount q(n-1) is calculated. Note that this coefficient Δα is based on the above model parameters α4 and/or α6.
This is the amount of variation in each parameter α4 and/or α6 that occurs during identification, and can be determined by storing the amount of variation in each parameter α4 and/or α6 corresponding to the operating state of the internal combustion engine and reading it out.

Next, the estimation means M8 calculates the state variables fw and fv mentioned above.
This is to estimate the In other words, the adhering fuel amount f- and the evaporated fuel amount fv cannot be directly detected using a sensor like the rotational speed ω, and are calculated using the sensor detection results as parameters like the fuel evaporation amount Vf and the air amount m. Since indirect detection using a formula or the like is not possible, the present invention uses this estimating means M8 to estimate. As this estimation means M8, the above (7) and (8) are used.
The observer may be configured as an observer based on the equation (7)' and (8)7, or may be configured to calculate the state variable using the above equation (7) or (7)7.

In addition, when configuring the estimation means M8 as an observer,
By using various design methods explained in detail by Katsuhisa Furuta et al., ``Basic System Theory'' (1973) Corona Publishing, or ``Mechanical System Control Section'' (1987) by Katsuhisa Furuta et al., Ohm Publishing, etc. , small-dimensional observer (M
initial 0rder 0bserver), same dimension observer (Identity 0bserver)
), finitely settled observer (Dead Beat 0b
server), linear function observer (Linear
Various observers such as a Function 0bserver and an Adaptive 0bserver can be configured.

Next, the fuel injection amount calculating means M9 calculates the above equations (7)' and (8).
)', the calculation results Vf/ω, Δα・q(n-f) of the division means M6 and the multiplication means M7, and the estimation result 7u of the estimation means M8 are calculated based on the physical model described in ,? Based on the product rm of the air amount m detected by the operating state detection means M5 and the target fuel-air ratio λ, the fuel amount q (n) to be injected next time from the fuel injection valve M4 is calculated. The fuel injection amount calculation means M9 is divided by the division means M6.
and the calculation result of the multiplication means M7 Vf/ω, △α・q (n
-1), the amount of adhering fuel estimated by estimation means M8? 1Amount of evaporated fuel? (7)'
and (8)′, multiplied by a preset coefficient,
The value obtained by adding these multiplication values is the amount of fuel! Mffiq(n)
It is configured to calculate as follows.

[Function] As explained above, in the fuel injection amount control device of the present invention, the multiplier M6 converts the variation amount △α of the model parameter related to the fuel injection amount q of the physical model for determining the control law into that of the internal combustion engine M2. It is set based on the operating state and is multiplied by the amount of fuel q (n-1) injected from the fuel injection valve M4 to calculate the product Δα·q (n-1). Then, the fuel injection amount calculation means M9 calculates the product △ calculated by the multiplication means M6.
Using α·q(n-1) as one parameter, the next fuel injection amount q (n) from the fuel injection valve M4 is calculated.

For this reason, the difference in control amount due to operating fluctuations of the internal combustion engine is multiplied by △α
- It becomes possible to compensate by q(n-1), and it becomes possible to further improve fuel injection control accuracy.

[Example code] Embodiments of the present invention will be described below with reference to the drawings.

First, FIG. 2 is a schematic configuration diagram showing the configuration of an internal combustion engine 2 and its peripheral devices to which the present invention is applied.

In the figure, 4 represents an intake pipe that sucks air through an air cleaner 6, and this intake pipe 4 includes a throttle valve 8 for controlling the amount of intake air, a surge tank 10 for suppressing intake pulsation, An intake pressure sensor 12 that detects the internal pressure (intake pipe pressure) P, and an intake temperature sensor 14 that detects the intake air temperature Ti are provided.

On the other hand, 16 is an exhaust pipe, which is equipped with a three-way catalytic converter 18 for purifying exhaust gas.

In addition to the intake pressure sensor 12 and intake temperature sensor 14, the internal combustion engine 2 has sensors for detecting its operating state, as well as a rotational speed sensor for detecting the internal combustion engine 20 rotational speed ω from the rotation of the distributor 20. sensor 22
, Similarly, from the rotation of the distributor 20, the internal combustion engine 2
A crank angle sensor 24 for detecting fuel injection timing t to the internal combustion engine 2 and a water temperature sensor 26 attached to the water jacket of the internal combustion engine 2 for detecting the cooling water temperature T are provided. The distributor 20 is for applying the high voltage from the igniter 2 to the spark plug 29 at a predetermined ignition timing.

The detection signals from each of the above sensors are output to an electronic control circuit 30 configured as a logic operation circuit centered on a microcomputer, which drives the fuel injection valve 32 to control the amount of fuel injected from the fuel injection valve 32. used to do.

That is, the electronic control circuit 30 includes a CPU 40 that executes arithmetic processing for fuel injection amount control according to a preset control program, and a restriction program and period data necessary for the CPU 40 to perform arithmetic processing are recorded in advance. taR
OM42, same < RAM44 where data used to execute arithmetic processing on CPU40 is temporarily read and written.
, a human-powered boat 46 for manually inputting the detection signals from each of the sensors, and an output boat 46 for outputting a drive signal to the fuel injection valve 32 according to the calculation result of the CPU 40;
etc., and the fuel-air ratio λ of the fuel mixture flowing into the cylinder 2a of the internal combustion engine 2 is a preset target fuel-air ratio λ.
The fuel injection amount q from the fuel injection valve 32 is controlled so that

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

Note that FIG. 3 is a diagram showing a control law, and does not show a hardware configuration. Fuel injection control is realized by executing a series of programs shown in the flowchart of FIG. 4. In addition, the control law of this embodiment is based on the above-mentioned (7) and (8).
In the physical model shown in Eq., the model parameter α4
The following equation (7) is set including the amount of variation △α4.
, (8)'' is designed based on the physical model.

+ (1-α4-α6)・q(k) −Δα4◆q (k) ...(8)'' As shown in FIG. The pipe pressure P and the cooling water temperature T detected by the water temperature sensor 26 are manually input to the first calculation unit Pl.Then, the first calculation unit P1 calculates the manually input cooling water temperature T as shown in equation (1) above. The saturated vapor pressure Ps of the fuel in the intake pipe 4 is converted using the formula, and the evaporation amount Vf of the fuel adhering to the wall of the intake pipe 4 is calculated from the converted saturated vapor pressure Ps and the intake pipe pressure P. The converted evaporation amount Vf is manually input to the dividing section P2 and divided by the rotational speed ω of the internal combustion engine 2 detected using the rotational speed sensor 22.Then, the division result Vf/ω is the coefficient f4
The multiplier P3 is manually operated and multiplied by a preset coefficient f4.

Next, the intake pipe pressure P and rotation speed are calculated by the second calculation unit P4 together with the intake temperature Ti detected by the intake temperature sensor 14.
It is also man-powered. The second calculation unit P4 calculates the amount of air m flowing into the cylinder 2a from the manually input rotational speed ω, the intake pipe pressure P, and the intake air temperature Ti using a calculation formula such as the above-mentioned formula (2). The calculation result is output to the multiplier P5. Then, the multiplier P5 multiplies the calculated air amount m by the preset target fuel-air ratio input, thereby calculating the fuel amount (target fuel amount) input rm that should flow into the cylinder 2a. .

This target fuel waste amount "m" is input manually to the coefficient f3 multiplier P6 and multiplied by a preset coefficient f3.

On the other hand, the division result Vf/ω of the division section P2 is also input manually to the state variable estimation section P7. The state variable estimation unit P7 calculates the division result Vf/ω of the division unit P2 and the −th order delay unit P using a preset arithmetic expression (in this embodiment, the above-mentioned equation (7)).
8, the amount of fuel q (1<-1) injected from the fuel injection valve 32 that is manually operated via the state variable estimation HBP 7, the state variable amount rQ (k-1) estimated last time using the state variable estimation HBP7, and the state variable amount rQ (k-1) and ? ν(k-1)
From this, the next fuel injection amount q from the fuel injection valve 32 (
The state variables for calculating k), an adhering fuel amount fw and evaporated fuel amount fv, are estimated. And the estimated results? W and? V is multiplied by coefficients f1 and f2 in a coefficient f1 multiplier P9 and a coefficient f2 multiplier P10, respectively.

Next, the intake pipe pressure P9 rotational speed ω and the cooling water temperature T are also input manually to the third calculation unit pH. The third calculation unit pH is calculated according to the operating state of the internal combustion engine 2 which is manually operated.
)", the amount of variation in model parameter α4 is expressed as coefficient Δα
Calculated as 4. In addition, for this calculation, a map is used that is set by associating the amount of variation Δα4 with respect to the model parameter α4 obtained when determining the model parameters in (7) and (8) above with each of the above operating conditions. .

Then, the coefficient Δα4 calculated by the third calculation unit pH is multiplied by the coefficient f5 in the coefficient f5 multiplication unit P12, and is further inputted from the manually operated fuel injection valve 32 via the primary delay unit P8 in the second multiplication unit P13. It is multiplied by the injected fuel amount q (k-1).

The multiplication result by this second multiplier P13 is then applied to another multiplier P3. P6. P9. It is added together with the multiplication result in PIO in adders P14 to P17, and thereby the next fuel injection amount q (k) from the fuel injection valve 32 is determined.

Next, a method of designing the control law shown in FIG. 3 will be explained.

As a method for designing this type of control law, for example, see "Digital Control of Actual Systems" by Katsuhisa Furuta.
J], Vo 1. 2B, (AJo, 12
(1984), the Society of Instrument and Control Engineers, etc., so I will briefly explain it here.

As described, the above control law is designed based on the physical model shown in equations (7)'' and (8).Since this model is nonlinear, in order to apply the linear control theory, first the above model is Approximate linearly.

In the above equations (7)" and (8)", x(k)=
[f w(k) f v(k)] ' −
(10)...(13) y(k)=in(k)m(k) -(1-a4- Q!6
) q(k)+Δα4・q(k)...(14
)u(k)=q(k)
...(15) C=[α2 α3
...(16), equations (7) and (8) are x(k+1)=A-x(k)+B-111(k)+vy
(k) =-(17)y (k)= C-x(k)
...(18) can be expressed.

Here, when it becomes stationary at y(k) = y r (target value), if u(k) = ur and x(k) = xr, then the above equations (17) and (18) can be changed to the following equation (19 ), (20).

x r =A-x r +IB-ur + VW(k)
−(19)y r = Cφx r
−(20) From the above equations (17) to (20), x(k+1) −x r =A (x(k) −x r
)+13(u(k)-ur)-(21)y(k)
−y r =C(x(k)−x r ) −(2
2) Next, in the above equations (21) and (22), X (k
) = x(k) −x r −(
23) U (k) = u (k) − u r
−(24)Y(k)=y(k)−y r
−(25), then (2
1) and (22) become as shown in the following equation (26×27).

X (k+1)= A X (k) + IB U (
k) −(26)Y(k)=CX(k)
...(27) In these (26) and (27), if X (k) → 0, then Y(k)
= 0, and if u(k)-+ur, then y(k)-+
It becomes yr. Therefore, it is sufficient to design an optimal regulator according to the above formula (26). That is, by explaining the discrete Rica-Nchi equation, optimal control can be found as shown in the following equation (28).

U(k)=Fx(k)
- (28) Also, this equation (28) becomes the following equation (29) from the above equations (23) and (24).

u(k)=F*x(k)−F−xr+u
r −=(29) Therefore, the above (19) and (2
0), if is solved for xr and ur, the above equation (
29) is established, and u (k) can now be found.

In the case of this example, the above equation (30) is replaced by the above-mentioned (10) to (1
From equation 6), the following equation (31) is obtained, and...(31)

fwr=βl 1◆V f(k)/ta(k)+β
12◆(λr◆m(k)-(1-α4-α6) q (
k)+△α4・q (k))...(32)fvr=
β21 ・V f(k)/ (1) (k) +β22
・(λ r −m(k)−(1−α4−α6)q(k
)+△α4・q (k))...(33)qr=β21
- V f(k)/ (,) (k)+β23・(λ"
・m(k)-(1-α4-α6) q(k)+△α4
・q (k))...(34) (However, β11 to β23
is a constant) Therefore, by substituting these equations (32), (33), and (34) into the above equation (29), the control unit human power u(k) can be calculated.

That is, the arithmetic expression for determining q (k) is determined as shown in the following equation (35).

Q (k)=r 1φf w(k)+ r2◆f v(
k) + r 3◆m(k) entered "+ γ4 order V f(k)
/ω(k) ...(35) However, when calculated in this way, the above equations (32) to (34) include Δα4・q
Since there is a term (k), it is necessary to change the coefficients γ1 to γ4 in the above equation (35) according to the variation of the model parameter α4. Therefore, in this embodiment, since the fuel injection amount does not vary greatly during one cycle of the internal combustion engine 2, the term Δα4・q(k) is replaced by Δα4・q(k
-1), and the calculation formula for determining q (k) is set as shown in the following formula (36) using the same method as above.

q (k) = fl conflict fw (k) + f2・fv (k
) + f3・m(k) in “+f4・V f(k)/ω
(k) + f 5・Δα4◆q (k-1)...(3
6) The above equation (36) is calculated using the above-mentioned fuel injection amount calculation means M9.
This corresponds to the arithmetic expression used in , and describes the control law shown in FIG.

Next, the state variable estimation unit P7 calculates the state variable quantity in the above equation (36), ! This is for estimating the amount of adhering fuel f− and the amount of evaporated fuel fv. This type of estimation device is normally designed as an observer using Gopinath's design method, etc., but in this embodiment, an air-fuel ratio sensor is provided to measure the air-fuel ratio λ of the fuel mixture actually supplied to the internal combustion engine 2. Therefore, it is not possible to design a normal observer. However, the fuel behavior in the internal combustion engine 2 can be almost accurately described by the above-mentioned equation (7). Therefore, in this example, (
7) Each state variable fft f W and fV are determined using the formula as is.

In other words, first, in equation (7), q(k) is the amount of fuel injected from the fuel injection valve 32, so it can be known on the electronic control circuit 30 side, and V f (k)/ω(k) can be determined based on the detection signals from each sensor, so the second and third terms on the right side can be calculated.

So, 8w(k)=f w(k) −? w(k)
=-(37) δv(k)= f v(k) −
? If we set v(k) - (3B), then it becomes. In the above formula (39), 1-α2<1.1-α3
Since (39) is stable, 8w(k), δV(
I<)-+0, i.e.? w(k)−+f w(k),
Y v(k)→? v(k).

Therefore, if appropriate period values are given for the above fw(k) and fv(k), fw(k) and fv(k) can be calculated by the above equation (7
), it becomes possible to determine li.

In the case of this embodiment, the control law is as described in (7)" and (8) above.
In order to correspond to this, the state variable estimator P7 may be designed to estimate the state variables fw and fν using equation (7). in this case,(
7)" includes the variation amount Δα4 of the model parameter α4, so it is necessary to manually input Δα4 obtained by the third calculation unit pH to the state variable estimation unit P7. Also, the above-mentioned (7)
′ may be used to estimate the state variable quantity.

Next, the fuel injection control executed by the electronic control circuit 30 is
This will be explained based on the flowchart shown in the figure. In the following explanation, the amount handled in the current process is expressed as the subscript (k
), and the previous time (i.e.

The value obtained in the process (one cycle before internal combustion engine 2) is subscripted (
k-1).

The fuel injection control is started with the start of the internal combustion engine 2,
It is repeatedly executed while the internal combustion engine 2 is operating.

When the process starts, first step 100 is executed,
Amount of fuel attached? w(k-1), amount of evaporated fuel? v(k-1
), the fuel injection amount q(k-1) is set for the first time, and the process proceeds to step 110, where the intake pipe pressure P(k), intake air temperature Ti(k'), The internal combustion engine 20 rotational speed ω(k) and cooling water temperature T(k) are determined.

Next, in step 120, the intake pipe pressure P (k) obtained in step 110 and the rotational speed of the internal combustion engine 2 (, J
(k), the target fuel air ratio input according to the load of the internal combustion engine 2 is calculated.In this step 120, normally,
The target fuel-air ratio input r is set so that the excess air ratio of the fuel mixture becomes 1 (that is, the stoichiometric air-fuel ratio), and when the internal combustion engine 2 is operating under high load, the amount of fuel is increased compared to normal to reduce the output of the internal combustion engine. In order to increase fuel efficiency, the target fuel-air ratio λ is set to the rich side, and when the internal combustion engine 2 is operating with a light load, the target fuel-air ratio λ is set to the lean side in order to reduce fuel consumption compared to normal and improve fuel efficiency. set on the side.

When the target fuel/air ratio input (k) is set in step 120, the process moves to step 130, and the step 120
The above-mentioned (
2) A process as the second calculation unit P4 is executed to calculate the air ffim(k) flowing into the cylinder 2a using the calculation formula or data map as shown in the equation.

In the subsequent step 140, the amount of evaporation Vf of the fuel adhering to the wall surface of the intake pipe 2a is determined based on the cooling water temperature T (k) and the intake pipe pressure P (k) determined in the above step 110, and the value is calculated as divided by the rotational speed ω(k), and the amount of fuel evaporated from the wall of the intake pipe 4 from the previous intake stroke to the next intake stroke Vfw(k) (that is, Vf(k)/ω(
k))), the first calculation unit P1 and division unit P2 execute processing.

The following step 150 calculates the fuel evaporation amount Vfw(k) from the intake pipe wall surface obtained in step 140, the previous fuel injection amount q (k-1), and the previously obtained adhering fuel amount? w(
k-1) and amount of evaporated fuel? v(k-1), the amount of adhering fuel? w(k) and amount of evaporated fuel? It executes processing as a state variable estimation unit P7 that estimates v(k).

Next, in step 160, the target fuel air ratio input (k) set in step 120 is multiplied by the air mm(k) obtained in step 130 to determine the target amount of fuel flowing into the cylinder 2a. The first multiplication unit P5 calculates rm(k).

Then, in the subsequent chip 170, the model parameter α4 is varied using a preset map based on the cooling water temperature T (k), the intake pipe pressure P (k), and the rotational speed ω (k) obtained in step 110. The third step to calculate the amount △α4
Processing is performed as a calculation unit pH, and the process moves to step 180.

In step 180, the steps 140 to 1 described above are performed.
Is the fuel evaporation amount Vfw(k) obtained in step 70 a state variable quantity?
w(k), amount of evaporated fuel? v(k), target fuel amount λrm(
k), the coefficient △α4, and the previously determined fuel injection amount q (
k-1), the next fuel injection amount q (k) is calculated using the above-mentioned equation (36), and the process moves to step 190.

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

In this step 190, fuel injection is performed, and the internal combustion engine 2
Once the fuel supply to is completed, the process moves to step 200, and the state variable quantity ? w(k) and? v(k)
and the fuel injection amount q(k), respectively, for the next processing as 7w(k-1), ? v(k-1), q(k-1
), and the process returns to step 110.

As explained above, in the fuel injection control device of this embodiment,
Since the control law is set based on a physical model that describes the behavior of fuel in the internal combustion engine 2, the behavior of the fuel that changes depending on the intake pipe temperature of the internal combustion engine 2, that is, the warm-up state of the internal combustion engine 2, is expressed as Vfw (1!II). Vf/ω), and the fuel injection amount can be controlled using a single control law. In addition, as shown in equation (36), the control law includes a term Δα4・q(k−1) for compensating for the variation amount Δα4 of the model parameter α4. When an operational fluctuation such as a fluctuation occurs, the control amount error accompanying this operational fluctuation can be compensated, and control accuracy can be improved.

Here, in the above embodiment, the control laws are (7)", (8)
``Setting based on the physical model described in Equation (7)' and (8)' above prevents control errors due to fluctuations in model parameters α4 and α6. m control accuracy can be further improved.In this case, the control law can be designed using the same method as in the above embodiment, and becomes as shown in the following equation (41).

q(k) = f 1 conflict f w(k) + f 2・f
v(k)+f 3・m(k) in r+f 4・V
f(k)/ω(k)+f 5-△a4・q(k-1
)+f6・Δαθφq (k-1) ・・
- (41) Furthermore, in the models of (7)' and (8)', control accuracy can be improved even if Δα4 is set to 0 and the control amount is compensated for fluctuations in model parameter α6. is possible. In this case, the control law is the following equation (
42).

q(1<)=f L ・fw(k)+ f2 ・
fv(k)+ f3 ・m(k) in "+ f 4-V
f(k)/ω(k)+ f 6◆△a 6◆q (k-
1)-(4NAlso, in the above embodiment, the fuel injection amount control device that can control the air-fuel ratio to the target air-fuel ratio without using an air-fuel ratio sensor was explained as an example. Control accuracy can be further improved if the air-fuel ratio is feedback-controlled.In this case, the control law is based on the actual air-fuel ratio of the internal combustion engine 2 detected by the air-fuel ratio sensor. It can be designed as a well-known servo system that determines the fuel injection amount using the deviation from the target air-fuel ratio as one parameter.Also, in this case, since the actual air-fuel ratio of the internal combustion engine can be detected, the state variable quantity can be estimated. An observer can be used to

[Effects of the Invention] As explained above, according to the fuel injection amount control device for an internal combustion engine of the present invention, the control law is designed based on a physical model that describes the fuel behavior of the internal combustion engine. Fuel injection control can be executed without changing the control law depending on the state. In addition, when operating fluctuations occur in the internal combustion engine, such as fluctuations in the model parameters related to the fuel injection amount of the physical model, the control amount error due to the operating fluctuations can be compensated for by the calculation result of the multiplier, improving control accuracy. It becomes possible to do so.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a schematic configuration diagram showing an internal combustion engine and its peripheral equipment according to an embodiment, and FIG.
The figure is a block diagram showing a control law for fuel injection control by the electronic control circuit, and FIG. 4 is a flowchart showing the fuel injection control processing executed by the electronic control circuit. Ml, 4...Intake pipe M2.2...Internal combustion engine M
3.2a...Cylinder Ml, 32...Fuel injection valve M5...Operating state detection means M6...Dividing means M
7... Multiplying means M8... Estimating means M9... Fuel injection amount calculating means 12... Intake pressure sensor 14...
Intake temperature sensor 20...Rotational speed sensor 26...
Water temperature sensor 30...Electronic control circuit representative Patent attorney Tsutomu Sadate (and 2 others) Figure III4

Claims (1)

[Scope of Claims] From the fuel injection valve according to a physical model that describes the behavior of fuel flowing into the cylinder of an internal combustion engine using the amount of fuel adhering to the intake pipe wall surface and the amount of evaporated fuel in the intake pipe as state variables. A fuel injection amount control device for an internal combustion engine that controls the fuel injection amount of the internal combustion engine, the rotational speed of the internal combustion engine, the amount of evaporation per unit time of the fuel adhering to the wall surface of the intake pipe, and the air flowing into the cylinder. an operating state detecting means for detecting the amount of fuel adhering to the intake pipe wall; a dividing means for dividing the evaporated amount of the fuel adhering to the intake pipe wall surface detected by the operating state detecting means by the rotational speed; and a coefficient set according to the operating state of the internal combustion engine. and the amount of fuel injected from the fuel injection valve, and an arithmetic expression set based on the physical model.
estimating means for estimating the state variable based on at least the calculation result of the division means and the fuel injection amount from the fuel injection valve; and using the calculation formula set based on the physical model,
Fuel to be injected next from the fuel injection valve based on the calculation results of the division means and the multiplication means, the estimation results of the estimation means, and the product of the air amount detected by the operating state detection means and the target fuel-air ratio. A fuel injection amount control device for an internal combustion engine, comprising: a fuel injection amount calculation means for calculating the amount of fuel injection.