JPH01134040A - Fuel injection quantity controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To make high control accuracy demonstrable irrespective of a sudden change in a driving state by performing only the calculation of a stable variable of sticking fuel quantity and evaporation fuel quantity in an intake pipe at each fuel injection, and making other fuel injection quantity calculating processes so as to be repeatedly executed all the time. CONSTITUTION:In this controller, there is provided with a driving state detecting means M5 which detects engine speed omega of an internal combustion engine M2, evaporated quantity Vf of fuel stuck to an intake pipe wall surface and intake air quantity (m), and each value of Vf/omega is calculated by a dividing means M6. In addition, on the basis of the calculated result and a fuel injection quantity (q), state variables fw, fv of sticking fuel and evaporating fuel in an intake pipe M2 are estimated at each fuel injection by an estimating means M7. On the basis of these data Vf/omega, fw, fv and the product lambdarm of intake air quantity (m) and desired fuel-air ratio lambdar, the fuel injection quantity (q) is calculated by a calculating means M8. Then, at each specified fuel injection timing synchronized with engine speed, a fuel injection valve M4 is made so as to be driven according to the fuel injection quantity (q) calculated.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates 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 propellant flowing into a cylinder of an internal combustion engine. The present invention relates to a fuel injection amount control device.

[Prior Art] Conventionally, as one type of fuel injection amount control device that controls 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. 59-196930i, 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 physical model that describes the dynamic behavior of the internal combustion engine is obtained, and the engine is designed based on this. 2. Description of the Related Art A control device based on a so-called linear control theory, which is configured to control a fuel injection amount using a control law, is known.

[Problems to be solved by the invention] However, the relationship between the amount of control human power and the amount of control output is inherently nonlinear, and simply obtaining a physical model by linear approximation would result in an extremely narrow dynamic stability of the internal combustion engine. Since accurate description can only be made under operating conditions, conventional control devices of this type derive mathematical models for each of multiple operating regions that can be considered to hold linear approximation, and then calculate each operating region based on the mathematical model. A control law had to be designed.

Therefore, in this type of control device, the control law used for control has to be changed for each operating range of the internal combustion engine in accordance with the above-mentioned physical model, resulting in a problem that the control becomes complicated. There is also the problem that control becomes unstable due to switching between the five control laws at the boundary points of each operating region.

Therefore, the applicant of the present application has developed a fuel injection amount control device that can accurately control the fuel injection amount under a wide range of operating conditions of an internal combustion engine without changing the control law (i.e., with one instantaneous control) as described above. , patent application 18988-1988
No. 9, Japanese Patent Application No. 62-189891, etc., proposed a fuel injection amount control device whose control law is designed in accordance with a physical model representing the behavior of fuel flowing into the cylinder of an internal combustion engine.

However, the fuel injection amount control device proposed above is configured to execute a series of fuel injection amount calculation processes every time fuel is injected into the internal combustion engine. Like the injection quantity control device,
It was not possible to control the fuel injection amount based on the latest detection signals from various sensors that detect the operating state of the internal combustion engine.

In other words, the conventional fuel injection amount control device is configured to repeatedly calculate the fuel injection ITI amount based on detection signals from various sensors that detect the operating state of the internal combustion engine, and drive and control the amount at each fuel injection timing. Therefore, the fuel injection amount can be controlled at all times according to the latest operating conditions.However, in the device proposed above, the fuel injection amount is calculated for each fuel injection of the internal combustion engine, so the fuel injection amount calculation is not possible. If the operating condition of the rear internal combustion engine suddenly changes, there is a problem in that the operating condition of the internal combustion engine at the time of actual fuel injection and the fuel injection amount temporarily no longer correspond.

In addition, in the device proposed above, the fuel injection amount is calculated for each injection of sulfur because the control law uses the amount of fuel adhering to the wall of the intake pipe and the amount of evaporated fuel in the intake pipe as state variables. This is because the intake cycle of the internal combustion engine must be estimated as one cycle using an observer or the like in order to obtain the state variables.

Therefore, in the present invention, only the calculation of the state variable is executed for each fuel injection, and the other fuel injection amount calculation processes are constantly repeated as in the past, so that the fuel injection amount is always updated to the latest level of the internal combustion engine. This was done with the purpose of allowing settings to be made depending on the driving condition.

[Means for solving the problems] That is, the configuration of the present invention made to achieve the above object is as follows:
As illustrated in FIG. 1, the behavior of the fuel flowing into the cylinder M3 of the internal combustion engine M2 is described using the amount fw of fuel adhering to the wall surface of the intake pipe M1 and the amount fv of evaporated fuel within the intake pipe M1 as state variables. A fuel injection amount control device for an internal combustion engine that controls a fuel injection amount q from a fuel injection valve M4 in accordance with a physical model, the fuel injection amount control device being at least attached to a wall surface of the intake pipe M1 at a rotational speed of the internal combustion engine M2. an operating state detecting means M5 for detecting the evaporated amount f of the fuel that has been evaporated and the amount m of air flowing into the cylinder M3; A division means M6 that divides by the rotational speed, and the physical model or an arithmetic expression set based on the physical model are used to calculate at least the calculation result of the division means M6 and the fuel injection amount from the fuel injection valve M6. Using an estimation means M7 that estimates the condition parameters fw and fv based on the above, and an arithmetic expression set based on the physical model,
At least the calculation result Vf/ω of the dividing means M6 and the estimation result of the estimating means M7? W.

? Fuel injection amount calculation that calculates the fuel injection amount q from the fuel injection valve M4 based on the product of the air amount m detected by the operating state detection means M5 and the target fuel-air ratio λr. means M8; and at every predetermined fuel injection timing in relation to the rotation of the internal combustion engine M2, the fuel injection valve M4 is driven according to the fuel injection ff1q calculated by the fuel injection amount calculation means M8 to execute fuel injection. and a fuel injection execution means M9, wherein the estimation means M7 executes the fuel injection execution means M9.
The state variables fW and fv are calculated each time the fuel injection is executed, and the fuel injection amount calculating means M8 calculates the variable Vf/u detected or calculated by each of the parts.

? L-? Using the latest values of V, λ'm, the fuel injection amount q
The gist of this invention is a fuel injection amount control device for an internal combustion engine, characterized in that it is configured to repeatedly calculate . .

Here, the operating state detection means M5 is for detecting at least the rotational speed of the internal combustion engine M2, the amount of evaporation of fuel adhering to the wall surface of the intake pipe V', and the amount of air flowing into the cylinder M3. A well-known rotation speed sensor can be used to detect the rotation speed of the internal combustion engine 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 within the intake pipe M1 and the pressure (intake pipe pressure) P inside the intake pipe M1.

Although it is difficult to directly detect the saturated 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 temperature T of the adhering fuel is a function of the temperature T of the fuel adhering to the inner combustion engine M2's outer jacket water temperature or Since it can be represented by the cylinder head temperature near the intake boat, the overjacket water temperature or cylinder head temperature is detected by a temperature sensor, and the detection result is expressed as the following equation (1) using T(g()) as a parameter. The saturated vapor pressure Ps can be determined using the following arithmetic expression.

Ps = β1◆T2-β2-T+β3 ・(1)
(However, f31.β2.β3: Constant) Therefore, the detection of fuel vaporization ff1Vf from the intake pipe wall is based on the detection signal from the temperature sensor that detects the water jacket water temperature or cylinder head temperature. At the same time, 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 meter or an arithmetic expression using these parts Ps and P as parameters.

Furthermore, since the fuel evaporation amount Vf changes greatly depending on the saturated thermal pressure Ps, the following equation (1)' with the saturated vapor pressure Ps as a parameter: Vf = β4 ◆Ps , -(1)' (However, β4
: constant) may be used to approximate it.

Next, the amount of air m flowing into the cylinder M3 can be easily calculated using, for example, the following formula (2), which uses the intake pipe pressure P, the intake air temperature Ti, and the rotational speed of the internal combustion engine M2 as parameters. can do. Therefore, the amount of air m
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 based on the intake air temperature. In addition, a well-known air flow meter is installed upstream of the throttle valve to detect the amount of air flowing into the intake pipe M1, 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 above configuration will be explained.

~ First, the fuel amount fc flowing into the cylinder M3 of the internal combustion engine M2 is determined by the fuel injection amount q from the fuel injection valve M4, the fuel adhering to the wall of the intake pipe M1, and the evaporated fuel inside the intake pipe M1. It can be written as in the following equation (3) using the quantity fv.

fc = αiq + 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, the indirect inflow amount α2・fw from the intake pipe M1 to which the injected fuel adheres, and the amount of injected fuel attached to the wall surface. Since it is considered to be the sum of the inflow amount α3·fv of evaporated fuel existing inside the intake pipe M1 due to fuel evaporation, the fuel amount fc flowing into the cylinder M3 is described as in the above equation (3). It is possible.

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 surface of the intake pipe M1 fw and the amount of evaporated fuel fv within the intake pipe Ml can be known, The fuel amount fc can be predicted.

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

First, the amount of fuel fw adhering to the wall surface of the intake pipe M1 is partially reduced by 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 in synchronization with the 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 adhering fuel mfw to one wall surface can be described as shown in the following equation (4).

fv(k+1) = (1-02)・fw(k)+α4
・q(k)−α5・V f(k)/ω(k)...
(4) (where k: intake cycle) On the other hand, the amount of evaporated fuel fv 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. The injection amount q increases as a part α6 evaporates, and further increases as the adhering fuel evaporates. Therefore, the amount of evaporated fuel fv in the intake pipe M1 can be expressed as shown in the following equation (5).

f v(k+1.) = (1-α3)・fv(k)+
α6・q (k)+α5・V f(k)/ω(k)
...(5) Next, the amount of fuel f c (k) sucked into the cylinder M3 of the internal combustion engine M2 is determined by the fuel-air ratio input (k) of the fuel mixture supplied to the internal combustion engine M2 and the inside of the cylinder M3. From the amount of air flowing into m (k), it can be written as shown in the following equation (6).

fc (k) = input (k) m (k) - (6) Therefore, when the coefficients α1 to α6 of each of the above equations are determined by the system 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 and the amount of evaporated fuel, which are expressed in a discrete system with the intake cycle of engine M2 as the sampling period. , this establishes a physical model that represents the behavior of fuel in an internal combustion engine.

+(1-α4-α6)q(k)...-(8) The estimation means M7 uses the above physical model (specifically, the state equation of equation (7)) or an arithmetic expression set based on the physical model. is used to estimate the state variables fw and fV. That is, the amount of adhering fuel fW and the amount of evaporated fuel fv cannot be directly detected using a sensor like the rotational speed ω, and the amount of adhering fuel fW and the amount of evaporated fuel fv cannot be directly detected using a sensor, and like the amount of evaporated fuel Vf and the amount of air m, they are calculated using calculation formulas that use the detection results by the sensor as parameters. Since it is not possible to detect it indirectly using, etc., the estimation means M7 is used for estimation.

Note that this estimating means M7 may be, for example, a minimal dimension observer (Minimal 0rder 0bserver).
), same dimension observer (Identity 0bse
rver), finitely settled observer (Dead Beat
0bserver), linear function observer ([,1n
ear Function 0bserver) or adaptive observer (Adaptive 0bserver)
), by Katsuhisa Furuta et al., ``Fundamental System Theory'' (1978), Corona Publishing, or Katsuhisa Furuta et al., ``Mechanical System Control'' (1987), Ohm Publishing, etc., using well-known design methods. It may be configured as an observer, or it may be configured to calculate the state variable using the above equation (7) as it is.

Next, the fuel injection amount calculation means M8 uses an arithmetic expression preset based on the physical model to calculate at least the calculation result Vf/ω of the division means M6 and the estimation result of the estimation means M7? L-? V, and the product of the air amount m detected by the operating state detection means M5 and the target fuel/air ratio input (i.e., the target fuel amount to flow into the cylinder M3) input rm.
Calculate the fuel injection amount q from 4.

That is, the fuel injection amount calculation means M8 calculates the state variable amount (adhered fuel amount? W and the amount of evaporated fuel (v) and the target fuel type (m) to be flowed into the cylinder M3 are each multiplied by a preset coefficient based on the above physical model, and the control tH
In order to nonlinearly compensate the system, the calculation result Vf/ω(k) by the dividing means M6 is multiplied by a coefficient set in advance based on the above physical model, and the sum of these multiplication values is calculated as a controlled variable. , is configured as a non-linearly compensated control amount calculation means.

The control amount calculation means M8 detects the amount of fuel flowing into the cylinders of the internal combustion engine M2 so that the fuel-air ratio does not deviate greatly from the target fuel-air ratio due to disturbance, and compares the detection result with the above-mentioned target. Sequentially adding the field difference with the fuel type input rm, and adding the value obtained by multiplying the detection result by a coefficient to the calculation result of the fuel injection amount q to obtain the fuel injection amount q used for control,
It may be configured as a control amount calculation means expanded to a so-called servo system. In this case, it is necessary to detect the amount of fuel that has flowed into the cylinder of the internal combustion engine M2, and for this purpose, a well-known air-fuel ratio sensor is used to detect the fuel-air ratio λ of the fuel mixture supplied to the internal combustion engine M2. death,
The fuel λm may be determined by multiplying this detection result by the air amount m detected by the operating state detection means M5.

[Function] In the fuel injection amount control device of the present invention configured as described above, the estimating means M7 calculates the calculation result Vf/ω of the dividing means M6 and the fuel injection amount every time the fuel injection execution means M9 executes the fuel injection. Based on the fuel injection amount q from valve M4, state variables 7W and ? V is estimated, and the fuel injection amount calculation means M8 calculates the calculation result Vf/ω of the division means M6 and the estimation result of the estimation means M7? Enemy.

? V, and the air amount m detected by the operating state detection means M5
The fuel injection amount q from the fuel injection valve M4 is repeatedly calculated based on the latest value of the product "m" of the target fuel-air ratio λr and the target fuel-air ratio λr.

Therefore, the fuel injection amount q injected from the fuel injection valve M4 by the operation of the fuel injection execution means M9 has a value that corresponds to the latest operating state of the internal combustion engine M2, and even if the operating state of the internal combustion engine M2 suddenly changes, it will not change. It becomes possible to control the fuel injection amount accordingly.

[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 a four-cylinder vehicle 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 the pulsation of intake air, and a An intake pressure sensor 12 that detects pressure (intake pipe pressure) P, and an intake temperature sensor 14 that detects intake air temperature Ti are provided. On the other hand, 16 is an exhaust pipe, which is equipped with a three-way catalytic converter 1B 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 rotation sensor for detecting the rotational speed of the internal combustion engine 2 from the rotation of the distributor 20. Speed 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 into each cylinder, and a water temperature sensor 26 attached to the water jacket of the internal combustion engine 2 for detecting a cooling water temperature T are provided.

The distributor 20 is for distributing the high voltage generated by the igniter 2 to the spark plugs 29 of each cylinder.

The detection signals from each of the sensors are output to an electronic control circuit 30 configured as a logical operation circuit, which drives the fuel injection valves 32 provided in each cylinder of the internal combustion engine 2 to control the fuel injection amount. It is used to execute fuel injection control and ignition time control that controls the timing at which high voltage is generated from the igniter (i.e., ignition timing).

That is, the electronic control circuit 30 includes a CPU 40 that executes arithmetic processing for the fuel injection control unit and ignition time control according to a preset control program, and a control program and initial data necessary for the CPU 40 to perform arithmetic processing. A recorded ROM 42, a RAM 44 where data used to execute arithmetic processing by the same CPU 40 is temporarily read and written, a human power port 46 for manually inputting detection signals from each of the above sensors, and arithmetic results by the CPU 40. The control program includes an output boat for outputting a drive signal to the fuel injection valve 32 of each cylinder according to the operation state of the internal combustion engine 2, and injects fuel according to the operating state of the internal combustion engine 2 according to a control program stored in advance in the ROM 42. The amount and ignition timing are optimally controlled.

In the electronic control circuit 30 of this embodiment configured as described above, the fuel-air ratio of the fuel mixture flowing into each cylinder of the internal combustion engine 2 is set according to the operating state of the internal combustion engine 2. The fuel injection valve 3 of each cylinder is adjusted so that the fuel-air ratio is λr.
The fuel injection amounts from 2 are independently controlled.

The control system for this fuel injection control will be explained below based on the block diagram shown in FIG.

Note that FIG. 3 is a diagram showing the fuel injection control system for one cylinder, and does not show the hardware configuration.In fact, each cylinder is It is realized every time. Further, the control system of this embodiment is designed based on the physical model shown in the above-mentioned equations (7) and (8).

As shown in FIG. 3, 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 manually input to the first calculation section P1. Then, in the first calculation section P1, the manually calculated cooling water temperature T is converted into the saturated vapor pressure Ps of the fuel in the intake pipe 4 using a calculation formula such as the above-mentioned formula (1), and further the converted temperature is The evaporation amount Vf of the fuel adhering to the wall surface of the intake pipe 4 is calculated from the saturated vapor pressure Ps and the intake pipe pressure P. Also, 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. The division result Vf/ω is then manually input to the coefficient f4 multiplier P3, and multiplied by a preset coefficient f4.

On the other hand, the intake pipe pressure P detected by the intake pressure sensor 12 and the rotation speed ω detected by the rotation speed sensor 22 are:
The intake temperature Ti detected by the intake temperature sensor 14 is also manually input to the second calculation unit P4. The second calculation unit P4 calculates the amount of air flowing into the cylinder m from the rotational speed ω of the internal combustion engine 2, 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, in the multiplier P5, the air amount m calculated in the second calculation giPJP4 is multiplied by the preset target fuel air ratio input, thereby determining the fuel amount (target fuel amount) input that should flow into the cylinder. "m" is calculated.The target fuel amount λ"m calculated by the multiplication section P5 is manually inputted to the coefficient f3 multiplication section P6, and multiplied by a preset coefficient f3.

On the other hand, the division result Vf/ω of the division section P2 is also output to the state variable estimation section P7. The state variable estimating unit P7 calculates the division result Vf/(a) of the dividing unit P2 and the fuel injection from the fuel injection valve 32 using a preset arithmetic expression (in this embodiment, the above-mentioned equation (7)). Quantity q and intake pipe 4 estimated last time
Amount of fuel attached to the wall? Amount of evaporated fuel in W and intake pipe 4? From V, the state variables of the physical model shown in equations (7) and (8) above, that is, the amount of adhering fuel fw and the amount of evaporated fuel f
It is for estimating v, and the estimation result? Blasphemy?
V is multiplied by coefficients f1 and f2 in a coefficient f1 multiplier P8 and a coefficient f2 multiplier P9, respectively.

The multiplication results from these multiplication units P8 and P9 are added together with the multiplication results from other multiplication units P3 and P6.
0 to P12 are added, and thereby the fuel injection failure q from the fuel injection valve 32 is determined.

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

As a design method for this type of control system, for example: i, “Digital Control of Actual Systems” by Katsuhisa Furuta
Wholesale, Vo1.2B, ωo, 12 (1984) Society of Instrument and Control Engineers, etc. is very detailed, so I will briefly explain it here.

As mentioned above, the control system of this embodiment has the above-mentioned (7) and (
8) It is designed based on the physical model shown in Eq. Since this physical model is nonlinear, first, the physical model is linearly approximated.

In the above equation (7), (R), x(k) = [f s di(k) f v(k)]
■ ... (10) vV(k) = [
V f(k)/ (1) (k)] −(1
4) y(k) = [in(k) ・m(k)]
−・−(15) u, (k) = [q(k)]
...(16)△=[1-α4-
α6] ... (17) e= [α2
α3] ... (18), then
Equations (7) and (8) are x(k+l)=1d)・x(k)+f・u(k)+
E −tw(k)...(19) y(k)=e−x(k)+△・u(k)=
−(20).

Here, y(k) = y r (When stationary at the target (1M), if u(k) = u r, x(k) = x r, the above equations (19) and (20) become as follows. Formula (19)',
(20) It becomes as shown in '.

xr=◇・xr+F・ur+EW(k) −(19
)'y r = e meeting x r + A◆u r
-(20)' Above formulas (19), (19)' and (20)
, (20) ', x(k+1) −x r =
@ (x(k) −x r )+f (u(k) − u
r) = (21)y(k)-y r =(9(x(
k)-x r )+A(u(k)-ur) = (22
) Next, in the above equations (21) and (22), X (k)
= x(k) −x r −(2
3) U, (k) - u (k) - u r
---(24) Y(k)=y(k)-y r-
By setting A (u(k) −ur ) −(25), equations (21) and (22) become as shown in the following equation (26X27).

X (k+1)= oX (k)+ F U (k)
−(26)Y(k)=θX(k)
...(27) This (26) and (
27), if X(k)→0, then Y(k)=O
If u(k) → ur, then y(k) → y''. Therefore, it is good to design the optimal regulator of the above formula (26). In other words, by explaining the distance-type Rikkatsu-cho formula, , the 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-x r +u r
= (29) Therefore, (19)' and (20)' above
In the equation, if is solved for xr and ur, the above equation (29
) is determined, and TLI (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 8), the following equation (31) is obtained, and xr and ur (ie, fwr, fvr, qr) are determined as shown in the following equations (32) to (34), respectively.

fwr= β11 conflict V f(k)/ω(k)+β12
◆ (λ r φm(k)−(1−α4−α6)u(
k)) −(32) fvr=β21・V j(k)/
ω(k) 1β22・(λr−m(k)−(1−α4−
α6)u(k)) −(33)qr= β21 ◆V
f(k)/(J(k)+β23・(λ r
−m(k)−(1−α4−α6)u(k))−(3
4) (However, β11 to β23 are constants) Therefore, from the above formula (29), with f1 to f4 as constants,
u(k)= f i f w(k)+ f 2◆f v
(k) + f 3・m(k) included “+f4・V f(k)
/ω(k) (35), and the control system shown in FIG. 3 above can be designed.

The above equation (35) is an arithmetic expression used by the above-mentioned fuel injection amount calculation means M8 for determining the fuel injection amount.

Next, the state variable estimating unit P7 is used to estimate the amount of fuel adhering to the wall surface of the intake pipe 4 and the amount of evaporated fuel fv within the intake pipe 4 in the above equation (35) because it cannot be directly measured. It is. This type of estimation device is normally configured as an observer designed by Gopinath's design method, etc., but in this embodiment, since the air-fuel ratio λ of the fuel mixture actually supplied to the internal combustion engine 2 cannot be measured, It is not possible to use normal observers. However, since the fuel behavior in internal combustion engine 2 can be described by the above equation (7), (7
) can be used as is to determine the fuel amount fw adhering to the wall surface of the intake pipe 4 and the amount of evaporated fuel fV in the intake air v4.

That is, first, in equation (7), q (k) can be known as a controlled variable on the electronic control circuit 30 side, and Vf (
k) is obtained by determining the saturated vapor pressure Ps from the cooling water temperature T detected by the water temperature sensor 26, and can be detected from this value and the intake pipe pressure P detected by the intake pressure sensor 12,
Further, since ω(k) can be detected by the rotational speed sensor 22, the second and third terms on the right side can be calculated.

Therefore, 8w(k)=f w(k) −? w(k)
−(36) δv(k)=f v(
k) -? v(k) −(
37), we get . In the above formula (38), 1-α2<1.1-α3
〈1, so (38) is stable, and δ−(k), δv(
k) → 0, i.e.? w(k)−f w(k),? v(
k)→? v(k).

Therefore, if appropriate initial values are given for f w (k) and f v (k) above, f w (k) and f v (k) can be calculated using the above formula (
7) allows estimation.

Therefore, in this embodiment, the state variable estimation unit P7 is configured to estimate the amount of fuel adhering to the wall surface of the intake pipe 4 fw and the amount of evaporated fuel fv within the intake pipe 4 using the above equation (7). ing. Furthermore, due to disturbance, f w(k)≠? blasphemy, f
v(k)≠? Even if it becomes V, 7w(k),? v(k
) follows f w(k) and f v(k), so by equation (35) above, u(k)([mouth fuel injection m q
(k)) can be calculated without any problem.

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 and FIG. In the following explanation, the amount set for each cylinder will be explained with a subscript (i) representing cylinder number 1 (=1 to 4).

First, FIG. 4 is a flowchart showing a fuel injection amount calculation process that is started when the internal combustion engine 2 starts operating and is executed as one of the main routines that are repeatedly executed while the internal combustion engine 2 is running.

As shown in the figure, when the process starts, first step 100
Execute and set the amount of attached fuel for each cylinder? w(i
), amount of evaporated fuel? v(i) and fuel injection amount q(1) are all initialized. In the subsequent step 110, the intake pipe pressure P, intake air temperature Ti, rotational speed ω of the internal combustion engine 2, and cooling water temperature T are determined based on the output signals from each of the above-mentioned sensors.
The process moves to step 120.

In step 120, based on the intake pipe pressure P obtained in step 110 and the rotational speed ω of the internal combustion engine 2, a target fuel-air ratio input according to the load of the internal combustion engine 2 is calculated. Normally, the target fuel-air ratio input is set so that the excess air ratio of the fuel mixture is 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 internal combustion. In order to increase the engine output, the target fuel-air ratio input is set to the rich side, and when the internal combustion engine 2 is operating under a light load, the target fuel-air ratio ``is set to the lean side.

Once the target fuel-air ratio λ' is set in step 120, the process moves to step 130, where the above-mentioned The calculation section P4 calculates the air mm flowing into the cylinder 2a using the calculation formula or data map shown in equation (2).

In the subsequent step 140, the amount of evaporation Vf of fuel adhering to the wall surface of the intake pipe 2a is determined based on the cooling water temperature T and the intake pipe pressure P determined in step 110, and the value is divided by the rotational speed ω of the internal combustion engine 2. Intake pipe 4 in one intake cycle
Processing is executed as a calculation unit P1 and a division unit P2 to calculate the amount of evaporation of fuel from the wall surface Vfw (ie, Vf /ω).

Then, in the subsequent step 150, the target fuel air ratio input set in the step 120 is multiplied by the air amount m obtained in the step 130 to calculate the target fuel amount m flowing into the cylinder 2a. After executing the processing as the multiplication unit P5, the process moves to step 160.

In step 160, the amount of adhering fuel calculated for each cylinder after fuel injection is determined by an interrupt process to be described later. w(i) and amount of evaporated fuel?
v(i) and the target fuel amount λ ``m
From the fuel evaporation amount Vfh obtained in step 140,
The fuel injection amount q(1) of the next cylinder to be injected is calculated using the above-mentioned equation (35), and the process returns to step 110.

Next, FIG. 5 shows the fuel injection timing for each cylinder of the internal combustion engine 2 (
In this embodiment, since an independent injection method is adopted in which fuel is injected independently for each cylinder, the injection rate is at every 180°C. )
12 is a flowchart representing a fuel injection execution process that is executed to open the fuel injection valve 32 and inject fuel into the cylinder immediately before entering the intake stroke.

As shown in the figure, when this process starts, first step 2
00 is executed to read the fuel injection amount q(i) calculated in the above fuel injection amount calculation process, and the process proceeds to step 210. In step 210, a valve opening signal is output to the fuel injection valve 32 of the cylinder (1) that is currently subject to fuel injection control, and the valve closing time is illustrated according to the fuel injection amount q(1) read above. The timer is set to "no", and the process moves to step 220. Note that the timer whose valve closing time has been set by the processing in step 210 stops outputting the valve opening signal to the fuel injection valve 32 when the valve closing time has elapsed, closes the fuel injection valve 32, and starts fuel injection. Terminate it.

Next, in step 220, the fuel evaporation amount Vfw from the intake pipe wall surface calculated in the fuel injection R calculation process and the step 2
The fuel injection amount q(i) read in 00 and the amount of attached fuel?
w(i) and amount of evaporated fuel? v(i), the next fuel injection amount q(
The amount of attached fuel used to calculate i)? w(i) and amount of evaporated fuel? , v(i), state variable estimation unit P7
Execute processing as .

The process then proceeds to step 230, where the cylinder number that enters the intake stroke next to the cylinder in which fuel injection is currently performed is set as the cylinder number subject to fuel injection control, and the process is temporarily terminated.

In the fuel injection amount control device of this embodiment in which the fuel injection control is executed as described above, as shown in FIG. amount? w(i) and amount of evaporated fuel? v(1) is estimated,
The fuel injection @q(i) of each cylinder is performed after the fuel injection of the cylinder immediately before in the fuel injection order is performed until the fuel injection for that cylinder is performed. The amount of adhering fuel calculated when injecting? w(i) and amount of evaporated fuel? It is repeatedly calculated using v(i).

For this reason, the fuel injection of this example! According to the iJ firefly control device,
A control law is set based on a physical model that describes the behavior of fuel in the internal combustion engine 2, and 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 determined by Vfw (i.e., Vf/ω). Not only can the fuel injection amount be controlled by a single control law, but also the various parameters necessary to calculate the fuel injection amount q(1), i.e., the intake pipe pressure P, the intake air It is now possible to use the latest values detected by each sensor for the temperature Ti, the rotational speed of the internal combustion engine 2, and the cooling water temperature T, and the fuel injection amount q(i) can be adjusted using the latest value of the internal combustion engine 2. It becomes possible to further improve control accuracy by setting according to the operating state.

Here, in the above embodiment, explanation was given by taking as an example a device that performs fuel injection control using an independent injection method for each cylinder. However, for example, in a device that performs fuel injection control using a group injection method, as shown in FIG. The cylinders in each group (
Intake air for g) - Amount of fuel adhering to the wall? w (g) and amount of evaporated fuel? What is necessary is to estimate v(g) and repeatedly calculate the fuel injection amount q(g) for the cylinder (g) of the next group to be injected between group injections and group injection amounts. In this case, the fuel injection amount q(
g) Amount of attached fuel? w(g) and amount of evaporated fuel? ! (g
) can be calculated for each group, so the amount of fuel attached to the rotation of the internal combustion engine? w (g) and amount of evaporated fuel?
The number of times v(g) is calculated can be reduced, and the time required for the calculation can be shortened.

In addition, when fuel injection is controlled using the double injection method, the amount of fuel q to be supplied to each cylinder is normally divided into two parts per revolution of the internal combustion engine and supplied from the fuel injection valve. As shown in Figure 8, the amount of fuel deposited on the wall of the intake pipe in the gold cylinder each time fuel is injected? W and amount of evaporated fuel? V is estimated, and during the next fuel injection amount after fuel injection is executed, the fuel amount q to be supplied to each cylinder during the intake stroke is repeatedly calculated, and when fuel injection is executed, half of the fuel amount q / 2 is injected. What is necessary is just to configure so that it may be injected from a valve.

Furthermore, in the above embodiment, the control system was designed based on the physical model of equations (7) and (8), which were obtained assuming that all the fuel evaporated from the wall surface of the intake pipe becomes evaporated fuel. Sometimes the intake pipe wall.

(In the case of a 4-cycle internal combustion engine, 1/4 of the amount of fuel evaporation from the intake stroke to the intake stroke α5・Vf/ω
It is also possible that the evaporated fuel does not stay inside the intake pipe but flows directly into the cylinder of the internal combustion engine, so the above equations (5) and (6) can be transformed into the following equations (4
0) and (7!1), as f v (k+1)
= (1-a3) f v (k) + α6・q (k) +
3・α5・V f(k)/ 4・ω(k) ...(4
0) fc(k)=λ(k)m(k) 10 α5・V f(k)/ 4・ω(k) ・・・(4
1) Obtain the physical model as shown in the following equations (42) and (43), +(1-α4-α6)◆q(k) +α8・V f(k)◆ω(k) ...(4
3) (However, α7: α5・3/4, α8: α5/
4) The control system may be designed based on this.

Next, in the above embodiment, the state variable estimator P7 is configured to be able to execute fuel injection control without measuring the actual fuel-air ratio input by using equation (7) as is, but it is configured as a well-known observer. However, the state variable may be estimated by J when the fuel-air ratio input is controlled to the target fuel-air ratio λr.

In other words, when the minimum dimension observer is designed from the above equation (7), it becomes as follows.This observer cannot be used directly in a device that does not detect the fuel-air ratio input, but when the fuel-air ratio λ is changed to the target fuel-air ratio input by the fuel injection control system. ``Assuming that it is controlled by
The second term may be set as nλrm(k) to estimate the adhering fuel amount fw and the evaporated fuel amount fv.

In addition, a well-known air-fuel ratio sensor is used to
The fuel-air ratio input of the fuel mixture supplied to the internal combustion engine from the preparation may be measured, and the adhering fuel amount fw and the evaporated fuel amount fv may be estimated using the above equation (44).

[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 state variables fw and fv are adjusted every time fuel injection is performed.
is estimated, and the fuel injection amount is determined by this estimated state variable f
It is repeatedly calculated based on w and fv, the amount of fuel evaporation per intake cycle Vf /ω calculated based on the operating state of the internal combustion engine, and the target fuel supply power to the internal combustion engine m. Not only is it possible to precisely control the fuel injection amount under a wide range of internal combustion engine operating conditions based on the immediate control, improving control accuracy, but also the fuel injection amount can be adjusted based on the latest operating conditions of the internal combustion engine immediately before fuel injection. Therefore, even if the operating condition of the internal combustion engine suddenly changes, the fuel injection amount can be controlled accordingly.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a block diagram showing the configuration of the present invention, Fig. 2 shows the internal combustion engine of the embodiment and its peripheral equipment (Table 1 (simplified configuration diagram), Fig. 3 shows the internal combustion engine FIG. 4 is a block diagram showing the control system set for each time, and FIG. 4 is a flowchart showing the fuel injection amount calculation process repeatedly executed by the electronic control circuit.
FIG. 5 is a flowchart showing a fuel injection execution process executed at each fuel injection timing by the electronic control circuit,
Fig. 6 is an operation explanatory diagram explaining the operation, Fig. 7 is an operation explanatory diagram explaining the operation when executing fuel injection control by group injection, and Fig. 8 is an operation explanatory diagram explaining the operation when fuel injection control is executed by group injection. An operation explanatory diagram explaining the operation when executing
It is.

Claims (1)

[Scope of Claims] A fuel injection valve is constructed based on 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 within the intake pipe as state variables. A fuel injection amount control device for an internal combustion engine that controls the amount of fuel injected from the internal combustion engine, at least the rotational speed of the internal combustion engine, the amount of evaporation of fuel adhering to the wall surface of the intake pipe, and the amount of air flowing into the cylinder. , an operating state detecting means for detecting the operating state detecting means, a dividing means for dividing the evaporation amount of the fuel adhering to the intake pipe wall surface detected by the operating state detecting means by the rotational speed, and the above physical model or an operation set based on the physical model. estimating means for estimating the state variable based on at least the calculation result of the dividing means and the amount of fuel injected from the fuel injection valve using a formula; and an arithmetic formula set based on the physical model. , the amount of fuel injected from the fuel injector is determined based on at least the calculation result of the dividing means, the estimation result of the estimating means, and the product of the air amount detected by the operating state detecting means and the target fuel-air ratio. a fuel injection amount calculation means to calculate the fuel injection amount, and a fuel injection valve is driven according to the fuel injection amount calculated by the fuel injection amount calculation means at each predetermined fuel injection timing synchronized with the rotation of the internal combustion engine to perform fuel injection. and a fuel injection execution means for executing the fuel injection, wherein the estimation means calculates the state variable each time the fuel injection execution means executes the fuel injection, and the fuel injection amount calculation means calculates the state variable of the variable detected or calculated by each of the parts. A fuel injection amount control device for an internal combustion engine, characterized in that the fuel injection amount is configured to repeatedly calculate the fuel injection amount using the latest value.