JP2830461B2 - Fuel injection amount control device for internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a fuel injection amount of an internal combustion engine, and more particularly, to a dynamic behavior of fuel near an injector attached to an intake pipe of an internal combustion engine. The present invention relates to a control device that determines a fuel injection amount based on a represented fuel behavior model.

2. Description of the Related Art As a method of controlling the amount of fuel to be injected from an injector of an internal combustion engine, the present applicant has developed a precise simulation model representing the dynamic behavior of fuel near an injector installed in an intake pipe of an internal combustion engine. (Japanese Patent Laid-Open No. 1-200040).

In this method, the amount of fuel fw adhering to the inner wall surface of the intake pipe in a virtual closed space (control volume) near the injector and the amount of fuel fv evaporated in this closed space
Is constructed as a state variable, and the amount of fuel actually flowing into the cylinder is detected from the output of the air-fuel ratio sensor provided in the exhaust passage, and the above-described state variable is set to the above-mentioned state variable so that the value matches the target value. Since the fuel injection amount from the injector is feedback-controlled based on this, a predetermined air-fuel ratio can be maintained with high accuracy. However, this method is a so-called feedback control, that is, a control in which the fuel injection amount can be corrected only when the exhaust air-fuel ratio of the internal combustion engine is detected. In such a case, there is a disadvantage that the control accuracy is reduced.

In order to solve this drawback, the present applicant uses a control device that executes a control operation that has a relationship opposite to the dynamic characteristic of the internal combustion engine from a target in-cylinder fuel flow predetermined according to the operating state of the internal combustion engine. A system for controlling the engine is proposed (Japanese Patent Application No. 2-193806).

[Problems to be Solved by the Invention] However, in a control device using an inverse model, it is necessary to accurately describe a model in which the parameters of the control device have a relationship between the dynamic characteristic of the internal combustion engine and the inverse characteristic. It is difficult to know accurate parameters due to variations in the manufacturing process of the engine and changes over time, and errors in these parameters may cause unstable control.

The present invention has been made in view of the above problems, and determines an appropriate amount of fuel injection in response to the operating state of the internal combustion engine promptly, and adjusts the fuel injection amount in accordance with the temporal change of the internal combustion engine. It is an object of the present invention to provide a fuel injection control device for an internal combustion engine, which corrects the above.

[Means for Solving the Problems] The basic configuration of such a fuel injection amount control device for an internal combustion engine is shown in FIG. 1 and is configured as follows.

That is, an air-fuel ratio sensor 100 installed in the exhaust pipe of the internal combustion engine to detect the air-fuel ratio of the exhaust gas, operating state detecting means 101 to detect an operating state of the internal combustion engine other than the air-fuel ratio, Reference target in-cylinder fuel amount calculating means 102 for calculating the amount of fuel to be injected into each cylinder to obtain a predetermined exhaust gas property from the operating state amount detected by the state detecting means 101; A fuel injection amount calculation unit 103 that determines a fuel amount to be injected from the injector using an inverse model of a simulation model representing a dynamic behavior of fuel in the vicinity of the injector of each cylinder based on a calculation result of the amount calculation unit 102; An injector 104 for injecting fuel into the intake pipe flow near the intake valve based on the calculation result of the fuel injection amount calculating means 103, and a simulation showing the dynamic behavior of the fuel near the injector of each cylinder. Fuel behavior simulation means 105 for calculating an estimated in-cylinder fuel amount that would have been injected into each cylinder based on the simulation model; specific state detection means 107 for detecting that the operating state of the internal combustion engine is in a specific operating state; The parameter identification means 108 for identifying parameters included in the fuel behavior simulation means 105 when the specific state detection means detects that the internal combustion engine is in the specific state, and the internal combustion engine is not in the specific state by the specific state detection means 107 Fuel injection amount calculating means based on the output of the air-heat ratio sensor 100 and the predicted in-cylinder fuel amount calculated by the fuel behavior simulation means 105 using the parameters identified by the parameter identifying means 108 And a fuel injection amount correcting means 106 for correcting the fuel amount determined by 103.

[Operation] In the fuel injection amount control device for an internal combustion engine configured as described above, an appropriate fuel injection amount for controlling the air-fuel ratio of the exhaust gas to a predetermined value is determined by an inverse model of the fuel dynamic characteristic. In addition, the fuel injection amount is corrected in accordance with the change in the characteristics of the internal combustion engine, and the control is stably maintained.

Embodiment (1) Configuration of Embodiment FIG. 2 is a diagram showing an embodiment of a fuel injection amount control device for an internal combustion engine according to the present invention. In FIG. 2, an air flow meter 3 is provided in an intake passage 2 of the internal combustion engine 1. The air flow meter 3 is a device for measuring the amount of air taken in by the internal combustion engine, and outputs an electric signal proportional to the volume flow rate of the intake air. This electric signal is transmitted to the control circuit 10
Is supplied to the A / D converter 1001.

The distributor 4 is provided with, for example, a crank angle sensor 5 that outputs a pulse signal every 720 ° converted to a crank angle and a crank angle sensor 6 that outputs a pulse every 30 ° converted to a crank angle.
The pulse output of the crank angle sensor is supplied to the input / output interface 1002 of the control circuit 10.

An air-fuel ratio sensor 14 is provided in the exhaust pipe 13 downstream of the exhaust manifold 11, outputs a voltage corresponding to the oxygen concentration in the exhaust gas, and is supplied to the A / D converter 1001.

The control circuit 10 is composed of, for example, a microcomputer system, and includes an A / D converter 1001, an input / output interface 1002, a CPU 1003, a ROM 1004, a RAM 1005, and a backup RAM.
1006, a clock generation circuit 1007, and the like.

The throttle valve 15 installed in the intake passage 2 is provided with an idle switch 16 for detecting whether or not the throttle valve 15 is fully opened. This output is input to the control circuit 10 via the input / output interface 1002. You.

In the control circuit 10, the down counter 1008, the flip-flop 1009 and the driving circuit 1010 are connected to the injector 7
Is to control the That is, when the fuel injection amount is calculated, the calculation result is set in the down counter 1008, and at the same time, the flip-flop 1009 is also set.

 As a result, the drive circuit 1010 energizes the injector 7.

The down counter 1008 starts counting clock pulses (not shown). When the value of the down counter 1008 becomes zero, the flip-flop 1009 is reset, and the drive circuit 1010 stops energizing the fuel injection valve.

That is, the injector 7 is energized for a period calculated by the fuel injection amount control means, and fuel according to the calculation result is supplied to each cylinder of the internal combustion engine 1.

(2) Design of Fuel Injection Amount Control Apparatus Points to be considered for configuring a control apparatus having high control accuracy and capable of performing stable control are as follows.

That is, all the fuel injected from the injector 7 is not injected into the cylinder but partially adheres to the wall of the intake pipe.

For this reason, even if the injection amount from the injector 7 is determined so that the air-fuel ratio of the exhaust gas becomes a predetermined value, the air-fuel ratio does not become the predetermined air-fuel ratio.

The dynamic characteristics of the internal combustion engine change over time or due to changes in fuel properties.

The control device is configured to determine the fuel injection amount in consideration of the dynamic characteristics of the fuel near the intake valve in consideration of the above points, and to detect a change in the dynamic characteristics to correct the fuel injection amount.

1) Construction of fuel dynamic characteristic model (internal model) To obtain the fuel mass balance near the injector,
Consider a virtual control volume CV near the injector as shown in the figure.

The index representing the predetermined crank angle (cycle) is k. The fuel flow rate flowing into the CV at the predetermined crank angle (cycle) k is fi (k) The fuel amount adhering to the wall surface at the predetermined crank angle (cycle) k fw (k) The fuel flow rate of the CV flowing out of the CV at a predetermined crank angle (cycle) k is fc (k) The ratio of the inflowing fuel flow rate fi (k) that adheres to the wall surface is R of the fuel amount fw (k) adhering to the wall surface. The following equation is established if the ratio remaining on the wall surface is P and the error associated with the modeling is δf.

fw (k + 1) = P · fw (k) + R · fi (k) −δf (1) fc (k) = (1−P) · fw (k) + (1−R) · fi (k) + δf ( 2) Expression (2) constitutes the fuel behavior simulation means 105 of FIG.

2) Construction of control system using internal model and inverse model FIG. 4 shows a basic configuration of an adaptive control system configured using an internal model and a control device.

The equivalent transfer function of the controller is G. The equivalent transfer function of the internal model is H. The equivalent transfer function of the actual internal combustion engine is P. The reference target in-cylinder fuel amount is fcro. The target in-cylinder fuel amount is fcr. Is the difference between the actual in-cylinder fuel amount fc and the in-cylinder fuel amount calculated from the internal model as δf Holds. Therefore, from equation (3), if HG = 1 (5), that is, if the control device is an inverse model of the internal model, then fcro = fc (6), and the in-cylinder fuel amount is independent of the dynamic characteristics of the internal combustion engine. fc becomes equal to the reference target in-cylinder fuel amount fcro.

From the equation (4), it can be seen that if an error occurs between fc and fcro when HG = 1, the value of δf becomes infinite and the control becomes unstable as described above.

That is, if the control system shown in FIG. 4 is configured, the air-fuel ratio λ of the exhaust gas can be controlled to the target air-fuel ratio λr.

3) Calculation of reference target in-cylinder fuel amount fcro The reference target in-cylinder fuel amount fcro to be injected into each cylinder is determined by the following equation, where λr is a predetermined exhaust gas air-fuel ratio and mc (k) is an intake air amount. Can be.

fcro = λr · mc (k) (7) Here, the air flow rate mc (k) flowing into each cylinder can be obtained by any of the following methods.

(A) It is calculated by the following equation (8).

mc (k) = (β1 · Ne · Pm−β2 · Ne) / Ti (8) where Ne = internal combustion engine speed Pm = intake pipe pressure Ti = intake temperature β, α = constant (b) intake pressure Pm and internal combustion The basic intake air amount is determined from a map using the engine speed Ne as a parameter, and corrected using the intake air temperature Ti to determine mc (k).

(C) Estimate from the detected value of the air flow meter 3.

That is, either equation (7) or any of the above (a), (b) and (c) constitutes a part of the reference target in-cylinder fuel amount calculation means (102) in FIG.

(4) Construction of feedforward control system In the control system shown in FIG. 4, the corrected fuel amount is as follows: δf = fc (k) −fcm (k) (9) where fcm = model cylinder fuel amount calculated from the internal model However, since the in-cylinder fuel amount fc (k) cannot be directly measured, the output λ of the air-fuel ratio sensor 14 and the intake air amount
It is determined by calculation from mc (k).

However, the measurement of the air-fuel ratio λ includes the delay of exhaust gas flow and the detection delay inherent in the sensor.
As is clear from equation (4), equation (9) becomes unstable.

In order to eliminate this problem, the present applicant has proposed a control device that determines a correction fuel amount to be subjected to feedforward control from an operation state amount of an internal combustion engine (Japanese Patent Application No. 1-5442).
0).

Therefore, in the present invention, for example, δf = δo · fw (k) ｛Pm (k) −Pm (k−1)｝ where, δo = proportional coefficient (10), and the correction fuel amount to be fed forward is determined. .

That is, the remaining part of the reference target in-cylinder fuel amount calculating means (102) in FIG. 1 is constituted by the equation (10).

 Therefore, the target in-cylinder fuel amount fcr is calculated by fcr = fcro + δf (11).

5) Determination of fuel injection amount If fw (k) determined from the equation (1) is used, the basic fuel flow rate fio (k) to be injected from the injector 7 can be calculated from the equation (2) as fio (k) =） fcr− (1−P) · fw (k)｝ / (1−R) (12)

That is, equation (12) is used to calculate the fuel injection amount calculating means 103 in FIG.
Is configured.

6) Correction of Fuel Injection Quantity If fi = fio + Δf (13), the fuel quantity actually injected into the cylinder is given by the following equation.

 Δfc (k) = P · Δfc (k−1) + (1−R) · Δfi (k−d + 1) + (RP) · Δfi (k−d) (14) where y (k) = Δfc (K) u (k) = Δfi (k−d) x (k) = y (k) − (1−R) · u (k) P = Po + ΔPR R = Ro + ΔR Po, Ro is a steady value of each parameter and Then, the following equation is obtained.

 x (k + 1) = Po.x (k) + Ro. (1-Po) .u (k) + w1 (15) y (k) = x (k) + (1-Ro) .u (k) + w2 (16) Here, w1 and w2 are functions of ΔP and ΔR, and xs and us satisfy the following equations.

 xs = Po xs + Ro x (1-Po) us + w1 (17) ys = xs + (1-Ro) us + w2 (18) Further, variables are converted as in the following equation.

x (k) ′ = x (k) −xs y (k) ′ = y (k) −ys u (k) ′ = u (k) −us Δx (k) ′ = x (k) ′ − x ( k-1) '. DELTA.x (k)' = u (k) '-u (k-1)' (19) As a result, Equations (17) and (18) can be expressed as state variables as follows.

When the optimal regulator shown in pages 114 to 127 of the basic system theory (by Katsuhisa Furuta et al., Published by Corona) is designed for the system represented by the equation (20), the following equation is obtained.

 Δu (k) ′ = − f1 · Δx (k) ′ − f2 · y (k−1) ′ (21) Here, f1 and f2 are optimal gains.

 If we put the variables back, we get:

Here, wPR is a parameter correction term. Since equation (22) includes a future value of Δfc, it is replaced using equation (14).

That is, from equation (14) By sequentially substituting the above equations, it becomes possible to calculate a future value for Δfc from a known value.
The equations (22) and (23) correspond to the fuel injection amount correcting means shown in FIG.
Make up 106.

7) Identification of Parameters In the above description, the parameters in the model representing the dynamic characteristics of the fuel have been assumed to be known. However, since the parameters actually vary depending on the operating state of the internal combustion engine, the parameters are identified sequentially.

As the parameter identification method, for example, a method proposed by the present applicant (Japanese Patent Application No. 2-193806) can be used.

That is, the fuel injection amount is perturbed by a known ratio, and from the detected air-fuel ratio at that time, ε (k) = fcr (k) −fc (k) (24) so that the following evaluation function takes the minimum value. , Using the well-known least squares method.

Here, h = the number of time steps used for identification. Equations (24) and (25) constitute the parameter identification means 108 in FIG.

(3) Execution of Control FIG. 5 shows a functional diagram of the control device configured according to the above description.

That is, at 501, the reference target in-cylinder fuel amount is calculated based on the internal combustion engine speed Ne and the intake pipe pressure Pm by any of the methods (a), (b) and (c) described in the equations (7) and (3).
fcro is calculated.

At the same time, at 502, a corrected fuel amount δf is calculated based on the internal combustion engine speed Ne and the intake pipe pressure Pm according to equation (11).

The calculation results in 501 and 502 are added and the inverse model 50
Guided to 3.

In 503, the injector 7 is determined based on the expression (12).
The reference fuel injection amount fio to be injected is determined.

Based on the reference fuel injection amount fio, the model in-cylinder fuel amount fcm is calculated from the fuel dynamic characteristic model at step 504 using the equation (2).

Actual in-cylinder fuel amount fc of the internal combustion engine and model in-cylinder fuel amount fc
At step 505, the fuel injection amount correction amount Δfi is calculated based on m using the equations (21) and (22).

The fuel injection amount correction amount Δfi and the reference fuel injection amount fio calculated by 503 are added to obtain the fuel injection amount fi actually supplied to the internal combustion engine.

Further, based on the fuel injection amount fi and the in-cylinder fuel amount fc of the internal combustion engine, at 505, the parameters of the fuel dynamic characteristic model are identified using equations (24) and (25).

FIG. 6 shows a routine for executing the control according to the present invention, which is executed, for example, for each stroke.

That is, in step 601, the detected values necessary for executing this routine, that is, the internal combustion engine speed Ne, the intake pipe pressure Pm, and the air-fuel ratio λ of the exhaust gas are read.

In step 602, a reference target in-cylinder fuel amount fcro and a corrected fuel amount δf are calculated.

Then, in step 603, it is determined whether or not the internal combustion engine is in an idling state.

Whether the vehicle is idling can be detected by, for example, whether the idle switch 16 is on. Step 603 constitutes the characteristic state detecting means 107 shown in FIG.

When the vehicle is in the normal operation state, a negative determination is made in step 603, and the process proceeds to step 604.

In step 604, a reference fuel injection amount is calculated using an inverse model.

In step 605, the fuel injection correction amount is calculated, and in step 606, it is added to the reference fuel injection amount.

Then, in step 607, the injector 7 is opened for a time during which the fuel amount determined in step 606 is injected.

Step when the internal combustion engine is idling
If the determination is affirmative in 603, the process proceeds to step 608 to identify the parameters of the fuel dynamic characteristic model.

In step 608, the fuel injection amount is perturbed at a fixed rate, and in step 609, fuel is injected from the injector 7.

In step 610, the parameters P and R of the dynamic characteristic model
Are identified, and a parameter update is performed in step 611.

[Effect of the Invention] According to the fuel injection control device for an internal combustion engine according to the present invention,
By combining the inverse model of the fuel dynamics and the fuel dynamics model, not only can fuel injection control with excellent responsiveness be realized, but also control stability by correcting the fuel injection amount according to the fluctuations in the characteristics of the internal combustion engine. Can be increased.

[Brief description of the drawings]

1 is a diagram showing a basic configuration of a fuel injection amount control device according to the present invention, FIG. 2 is a diagram showing a configuration of one embodiment of the present invention, and FIG. 3 is a schematic diagram for explaining a fuel behavior simulation model. Fig. 4, Fig. 4 is a basic configuration diagram of a control system combining an inverse model and an internal model, Fig. 5 is a functional diagram of a fuel injection control device according to the present invention, and Fig. 6 is a fuel injection amount control according to the present invention. It is a flowchart of a routine. 100 air-fuel ratio sensor 101 operating state detecting means 102 reference target in-cylinder fuel amount calculating means 103 correction fuel amount calculating means 104 fuel injection amount calculating means 105 injector 106: fuel behavior simulation means, 107: fuel injection amount correction means.

Continuation of the front page (56) References JP-A-1-200040 (JP, A) JP-A-1-211648 (JP, A) JP-A-2-157453 (JP, A) JP-A-63-9644 (JP) , A) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02D 41/14 F02D 41/04 F02D 45/00

Claims (1)

(57) [Claims] An air-fuel ratio sensor (100) installed in an exhaust pipe of an internal combustion engine for detecting an air-fuel ratio of exhaust gas, an operating state detecting means (101) for detecting an operating state of the internal combustion engine other than the air-fuel ratio, A reference for calculating an amount of fuel to be injected into each cylinder in order to obtain a predetermined exhaust gas property from the output of the air-fuel ratio sensor (100) and the operation state amount detected by the operation state detection means (101). Based on the calculation results of the target in-cylinder fuel amount calculation means (102) and the reference target in-cylinder fuel amount calculation means (102), an inverse model of a simulation model representing the dynamic behavior of fuel in the vicinity of the injector of each cylinder is obtained. Fuel injection amount calculating means (103) for determining the amount of fuel to be injected from the injector, and injecting fuel into the intake pipe flow near the intake valve based on the calculation result of the fuel injection amount calculating means (103) Injector (10
4) The fuel injection control device configured to calculate the expected in-cylinder fuel amount that would have been injected into each cylinder based on a simulation model representing the dynamic behavior of fuel near the injector of each cylinder. Fuel behavior simulation means (105); specific state detection means (107) for detecting that the operating state of the internal combustion engine is in a specific operating state; detecting that the internal combustion engine is in a specific state by the specific state detecting means A parameter identification unit (108) for identifying a parameter included in the fuel behavior simulation unit (105) when the internal combustion engine is not in a specific state by the specific state detection unit (107). Fuel behavior simulation using the output of the air-heat ratio sensor (100) and the parameters identified by the parameter identification means (108) A fuel injection amount correcting means (106) for correcting the fuel amount determined by the fuel injection amount calculating means (103) based on the predicted in-cylinder fuel amount calculated by the stage (105). Fuel injection control device.