JPH04187842A - Fuel injection quantity controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve the fuel injection control performance by compensating for a stationary deviation attributable to the flow delay of the exhaust gas and the detection delay of an air-fuel ratio sensor itself. CONSTITUTION:A flow delay correction means 106 corrects the relation between the fuel injection quantity determined by a fuel injection quantity calculation means 103 and the output of an air-fuel ratio sensor 100 in corresponding relation to the flow delay of an exhaust gas while a sensor detection delay correction means 107 corrects the relation between the fuel injection quantity determined by the means 103 and the output of the sensor 100 in corresponding relation to the detection delay of the sensor itself. A parameter estimation means 105 estimates the parameters of a simulation model in the fuel injection quantity calculation means 103, on the basis of that relation between the fuel injection quantity determined by this means 103 and the output of the sensor 100 which has been corrected by the correction means 106 and 107. By this, it is possible to estimate precisely the parameters of a dynamic characteristics model of fuel, thereby improving the fuel injection control performance.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a fuel injection amount control device for an internal combustion engine, and more particularly to a control device for controlling the 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 fuel behavior model representing.

[Prior Art] As a method for controlling the amount of fuel to be injected from an injector of an internal combustion engine, the applicant uses a precise simulation model representing the dynamic characteristics of fuel in the vicinity of the injector installed in the intake pipe of the internal combustion engine. proposed an injection fuel control device (Japanese Patent Application Laid-Open No. 2-193806).

In this method, the amount of fuel injected from the injector is determined based on a simulation model whose state variable is 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. The parameters of the simulation model are identified from the deviation between the amount of fuel actually flowing into the cylinder measured from the air-fuel ratio of exhaust gas and the amount of fuel flowing into the cylinder calculated by the simulation model. It becomes possible to maintain a predetermined air-fuel ratio.

[Problems to be Solved by the Invention] However, in reality, the air-fuel ratio sensor that detects the air-fuel ratio of exhaust gas not only has a unique detection time constant, but also the air-fuel ratio sensor attached to the exhaust valve has a The parameters of the fuel simulation model cannot be accurately identified due to the presence of a flow delay or due to steady state deviations due to changes in the characteristics of the air-fuel ratio sensor or actuator.

The present invention has been made in view of the above problems, and includes a data processing unit for compensating for the detection delay of the air-fuel ratio sensor and the flow delay of the exhaust gas when identifying the parameters of the simulation model, and/or the air-fuel ratio. It is an object of the present invention to provide a fuel injection amount control device including a data processing section for detecting changes in characteristics of a sensor or an actuator.

[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, the air-fuel ratio sensor 100 installed in the exhaust pipe of the internal combustion engine detects the air-fuel ratio of exhaust gas, the operating state detecting means 101 detecting operating state quantities of the internal combustion engine other than the air-fuel ratio, and the operating state detecting means 101 detects the air-fuel ratio. Intake air amount calculation means 10 that calculates the amount of intake air taken into each cylinder from the calculated operating state quantity.
2, and a fuel injection amount calculation means 103 that determines the amount of fuel to be injected using a simulation model representing the dynamic behavior of fuel in the vicinity of the injector of each cylinder based on the calculation result of the intake air amount calculation means 102; , flow delay correction means 104 for correcting the relationship between the fuel injection amount determined by the fuel injection amount calculation means 103 and the output of the air-fuel ratio sensor 100 by the amount of flow delay of exhaust gas; Fuel injection amount and air-fuel ratio sensor 10
Sensor detection delay correction means 105 corrects the relationship with the output of 0 by the detection delay of the air-fuel ratio sensor itself, and fuel injection amount calculation means corrected by the flow delay correction means (104) and the sensor detection delay correction means (106). Parameter estimating means 10 for estimating the parameters of the simulation model in the fuel injection amount calculation means 103 based on the relationship between the fuel injection amount determined by 103 and the output of the air-fuel ratio sensor 100
It consists of 6 and.

In the second invention, the sensor detection delay correction means 105
Instead, a steady deviation removing means 107 is provided to remove the steady deviation of the sensor and/or actuator.

[Function] In the fuel injection amount control device for an internal combustion engine configured as described above, there are problems caused by a delay in the flow of exhaust gas in the air-fuel ratio sensor and a detection delay in the air-fuel ratio sensor and changes in the characteristics of the sensor and/or actuator. By compensating for the steady-state deviation, it becomes possible to accurately estimate the parameters of the fuel dynamic characteristic model.

[Example] (1) Configuration of Example FIG. 2 is a diagram showing one example of the fuel injection amount control device for an internal combustion engine according to the present invention. In FIG. 2, an air flow meter 3 is installed in an intake passage 2 of an internal combustion engine 1. The air flow meter 3 is a device for measuring the amount of air taken into the internal combustion engine, and outputs an electrical signal proportional to the volumetric flow rate of the intake air.

In addition, there is a pressure detector 1 in the intake pipe to measure the intake pressure.
7 is attached and outputs an electrical signal proportional to the intake pressure.

These electrical signals are sent to the A/D converter 1 of the control circuit 10.
001.

The distributor 4 is attached with a crank angle sensor 5 that outputs a pulse signal every 720 degrees in terms of crank angle, and a crank angle sensor 6 that outputs a pulse signal every 30 degrees in terms of crank angle. The pulse output of the crank angle sensor is supplied to the input/output interface 1002 of the control circuit 10.

Further, an air-fuel ratio sensor 14 is installed in the exhaust pipe 13 downstream of the exhaust manifold 11, and outputs a voltage according to the oxygen concentration in the exhaust gas, which 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,
It includes a RAM 1005, an integrated RAM 1006, a clock generation circuit 1007, and the like.

Further, the throttle valve 15 installed in the intake passage 2 is provided with an idle switch 16 for detecting whether the throttle valve 15 is fully open or not, and the output of this switch is input to the control device 10 via the input/output interface 1002. Ru.

Further, in the control circuit 10, a down counter 1008,
Flip-flop 1009 and drive circuit 1010 are for controlling injector 7. That is, when the fuel injection amount is calculated, the calculation result is stored in the down counter 1.
008, and at the same time, the flip-flop 1009 is also set.

As a result, drive circuit 1010 energizes injector 7.

Down counter 1008 receives clock pulses (not shown)
starts counting, and when the value of the down counter 1008 reaches 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 only for the period calculated by the fuel injection amount control means, and fuel according to the calculation result is supplied to the internal combustion engine 1.
is supplied to each cylinder.

(2) Design of fuel injection amount control device The following points should be considered in order to configure a fuel injection amount control device that has high control accuracy and can perform stable control.

That is, not all of the fuel injected from the injector 7 is injected into the cylinder, but a portion of it adheres to the wall surface 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 will be a predetermined value, the predetermined air-fuel ratio will not be achieved.

Taking this point into account, the fuel injection amount is determined by taking into account the dynamic characteristics of the fuel near the intake valve, but pre-processing to determine the parameters of this dynamic characteristic model is to consider the flow delay of exhaust gas and/or The control device is configured to correct the detection delay inherent in the fuel ratio sensor.

1) Construction of fuel dynamic characteristic model In order to obtain the mass balance of fuel near the injector, consider a virtual control volume C■ near the injector as shown in FIG. 3.

Let the index representing a predetermined crank angle (cycle) be the fuel flow rate flowing into C at a predetermined crank angle (cycle) k.F i (k) is the fuel adhering to the wall surface at a predetermined crank angle (cycle) k. The amount is fw(k) The fuel flow rate flowing out from C■ at a given crank angle (cycle) k is fc(k) The proportion of the inflowing fuel flow rate f i (k) that adheres to the wall surface is R The amount of fuel adhering to the wall surface fw( If the proportion of k) that remains on the wall surface is P, the following equation holds true.

f w (k+1) −P −f w (k) 10R−f
i (k) (1) f c (k)
-(1-P) -fw (k)+ (1-R)
・fi (k') (2) 2] Parameter estimation of fuel dynamic characteristic model When the amount of fuel adhering to the wall fw is eliminated from equations (1) and (2), f c (k) - f i (k) -P-(f c (k-1) -f i (k-1)
)−R・(f i (k) −f i (k−
1)) (3) where y (k) −f c (k) −f i
(k) u (k) −f i (k−1)
−f i (k) (4), then (3)
The formula is y(k) -P-Y(k-1) 1R-u(k), and if y(k), y(k-1), and u(k) are obtained, the parameters P and R are It can be estimated by the well-known method of least squares or the like.

3) Determination of cylinder-wise intake air amount The air flow rate mc (k) taken into each cylinder can be determined by one of the following methods.

(a) Calculated using equation (6) below.

mc (k)= (βl・Ne−Pm−β2・Ne)/Ti where Ne=
Internal combustion engine rotational speed Pm - intake pressure Ti = intake air temperature β1, β2 constant number (b) The basic intake air amount is determined from a map using the intake pressure Pm and internal combustion engine rotational speed Ne as parameters, and it is corrected with the intake air temperature Ti and mc Find (k).

(c) Estimated from the detected value of air flow make 3.

That is, the intake air amount calculation means 102 calculates the above (a), (b), and (c).
) is calculated using one of the following methods.

4) Determining the target in-cylinder fuel amount If the target air-fuel ratio is λr, the fuel amount fcr that should be injected into the cylinder to obtain the target air-fuel ratio is f cr'=mc (k) /λr (7
) is calculated.

5) Determining the amount of fuel in the cylinder If the air-fuel ratio measured by the air-fuel ratio sensor 14 is λ(k), there is a flow delay before the exhaust gas reaches the position where the air-fuel sensor is installed. Therefore, since the output of the air-fuel ratio sensor 14 at time k is the fuel amount and air intake amount at time (k-d), the in-cylinder fuel amount fc(
k) is expressed by the following formula.

f c (k-d) −mc (k-d) /λ (
k) However, d is the flow delay of the exhaust gas when expressed in a discrete system.

That is, equation (8) is used as the flow delay compensating means 106.

6) Compensation for detection delay of air-fuel ratio sensor Although it is possible to compensate for the flow delay of exhaust gas by using equation (8), it is not possible to compensate for the detection delay of the air-fuel ratio sensor 14 itself. .

In order to solve this problem, the fuel injection amount control device according to the present invention uses, as the fuel injection amount, a fuel injection fi (kd) that has compensated for the flow delay, and whose time constant is equal to the detection delay time constant of the air-fuel ratio sensor 14. It is assumed that a filtered compensation fuel injection amount fi(k-d) which is approximately equal to τ is used.

That is, as the sensor detection delay compensating means 107, fi(k-
d) "-τ・fi(k-dl)"+ (1-τ
)・f i (k−d−1) (9) is used.

FIG. 4 is an explanatory diagram of the above-mentioned compensation method, where the joint axis represents the fuel amount and the horizontal axis represents the sampling time.

a is the actual fuel injection amount f i (k), b is the in-cylinder fuel amount fc (k) determined based on the output of the air-fuel ratio sensor, and C is the in-cylinder fuel amount fc (k-d) which compensated for the flow delay. ), d is the true in-cylinder fuel amount fc.

According to FIG. 4, the amount of fuel fc flowing into the cylinder due to the fuel injection amount a at time point is detected by the air-fuel ratio sensor at time +4 due to the flow delay of the exhaust gas. Therefore, by calculating the in-cylinder fuel amount fc at time (k-d) [d-4 in Figure 4] from the output of the air-fuel ratio sensor at time using equation (8) above, the flow delay of exhaust gas can be calculated. It can be compensated.

Furthermore, due to the detection delay inherent in the air-fuel ratio sensor, the in-cylinder fuel MC that compensates for the exhaust gas flow delay has a delay with respect to the true in-cylinder fuel amount d, as shown in FIG.

In this embodiment, the current fuel injection amount f i (k) is passed through a filter with a time constant τ, that is, the detection delay compensation fuel injection amount fi (k)' which compensates for the sensor detection delay is calculated. Therefore, the detection delay compensation fuel injection amount f i
The relationship between (k)' and the in-cylinder fuel amount fcck-d) that compensates for the exhaust gas flow delay is a relationship that does not include errors due to the exhaust gas flow delay and sensor detection delay.

7) Compensation for steady-state deviations of air-fuel ratio sensors and/or actuators Equations (5) are used to estimate the parameters P and R, but sensors such as air-fuel ratio sensors or air flow meters and/or actuators such as injectors When the characteristics of change, fc(k)≠f i (k) (10
), and y (k)≠O(11) However, since the fuel injection amount maintains a constant value, u (
k) =0.

Therefore, in Equation (5), P=1 (12), which means that correct parameters cannot be estimated.

Therefore, y (k) = f c (k) − f i (k
) Apply a filter with time constant T to (13) and let the calculation result be y(k)', then y (k+1)' = T-y (k)'+(1-T)
・y(k) (14) and Δy(k)=y(k)−y(k)' (15), and equation (5) is changed to Δy(k)=P・Δy(k−1) +R− u(k)
By doing so, it becomes possible to eliminate steady-state deviations caused by changes in the characteristics of the air-fuel ratio sensor and/or actuator.

Note that in order to further improve the accuracy of parameter estimation, compensation for flow delay and detection delay and compensation for characteristic fluctuations of the air-fuel ratio sensor and/or actuator may be performed at the same time.

(3) Execution of Control FIG. 5 shows a functional diagram of a control device configured to perform two types of compensation simultaneously.

That is, in 501, (a), (b), and (C) described in 3)
The intake air i1mc(k) of each cylinder is calculated based on the internal combustion engine rotational speed Ne and the intake pipe pressure Pm by one of the following methods.

At 502, mc(k) is compensated for the flow delay of exhaust gas, and mc(k-d) is calculated.

At 503, the in-cylinder fuel amount fc(k-d) is calculated using the detected value λ(k) of the air-fuel ratio sensor 14.

In 504, the flow delay of exhaust gas is compensated for the fuel injection 11fi, and fi(kd) is calculated.

505, the detection time constant τ specific to the air-fuel ratio sensor 14
Compensated fuel injection amount fi through a filter with a time constant equal to
Find (k-d)'.

At 506, the in-cylinder fuel amount fc(
k-d) and the fuel injection amount fi(k-d)' calculated in step 505 for which the flow delay and detection delay time have been compensated for.

At 507, a filter with a time constant T is used to compensate for steady-state deviations of the air-fuel ratio sensor and/or actuator, and only the changes that are useful for parameter estimation are extracted.

At 508, parameters of the dynamic characteristic model are estimated using equation (16).

On the other hand, in 509, mc (k) and target air-fuel ratio λr
The target in-cylinder fuel 1ifcr(k) is calculated from .

Then, in step 510, a fuel injection amount fi(k) is determined from the fuel dynamic characteristic model using the estimated parameters.

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, detected values necessary for executing this routine, ie, internal combustion engine rotational speed Ne, intake pipe pressure Pm, and exhaust gas air-fuel ratio λ are read.

In step 602, the flow delay of the exhaust gas is corrected by calculating the intake air amount mc (k) and reading the value before the time step d corresponding to the flow delay.

Then, in step 603, a target in-cylinder fuel amount is calculated, a fuel injection amount is determined by equations (1) and (2), and fuel injection is executed in step 604.

In step 605, it is determined whether the engine is in a steady state such as idling, and if the engine is in a steady state, the process proceeds to step 606 to estimate parameters, and if not in a steady state, this routine is ended.

In step 606, a value d steps before is read in order to compensate for the flow delay of exhaust gas with respect to the fuel injection amount.

In step 607, the detection delay inherent in the air-fuel ratio sensor is compensated for.

In step 608, steady-state deviations due to changes in air-fuel ratio sensor and/or actuator characteristics are compensated.

In step 609, the parameters of the fuel dynamic characteristic model are estimated using equation (16), the parameters are updated, and this routine ends.

[Effects of the Invention] According to the fuel injection control device for an internal combustion engine according to the present invention, when identifying the parameters of a simulation model, the exhaust gas flow delay included in the detected value of the air-fuel ratio sensor and the detection delay specific to the air-fuel ratio sensor are eliminated. is compensated for, and furthermore, by removing steady-state deviations due to changes in the characteristics of the air-fuel ratio sensor and/or actuator, it becomes possible to accurately estimate the parameters of the fuel dynamic characteristic model,
Improves fuel injection control performance.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the basic configuration of a fuel injection amount control device according to the present invention, Fig. 2 is a diagram showing the configuration of an embodiment of the present invention, and Fig. 3 is a schematic diagram for explaining a fuel behavior simulation model. 4 is an explanatory diagram of a delay compensation method, FIG. 5 is a functional diagram of a fuel injection control device according to the present invention, and FIG. 6 is a flowchart for executing fuel injection amount control according to the present invention. . 100... Air-fuel ratio sensor, 101... Operating state detection means, 102... Intake air amount calculation means, 103... Fuel injection amount calculation means, 104... Injector, 105... Parameter estimation means , 106...Flow delay compensation means, 107...Sensor detection delay compensation means.

Claims (1)

[Claims] 1. An air-fuel ratio sensor (100) installed in the exhaust pipe of an internal combustion engine to detect the air-fuel ratio of exhaust gas, and an operating state detection means (100) for detecting operating state quantities of the internal combustion engine other than the air-fuel ratio. 101)
and an intake air amount calculation means (102) that calculates the amount of intake air taken into each cylinder from the operating state quantity detected by the operation state detection means (101); and the intake air amount calculation means (102). a fuel injection amount calculation means (103) that determines the amount of fuel to be injected using a simulation model representing the dynamic behavior of fuel in the vicinity of the injector of each cylinder based on the calculation result; Flow delay correction means (103) corrects the relationship between the fuel injection amount determined by the air-fuel ratio sensor (100) and the output of the air-fuel ratio sensor (100) by the flow delay of exhaust gas.
04), and sensor detection delay correction for correcting the relationship between the fuel injection amount determined by the fuel injection amount calculation means (103) and the output of the air-fuel ratio sensor (100) by the detection delay of the air-fuel ratio sensor itself. means (105), the fuel injection amount determined by the fuel injection amount calculation means (103) corrected by the flow delay correction means (104) and the sensor detection delay correction means (105) and the air-fuel ratio sensor ( A fuel injection amount control device comprising: parameter estimating means (106) for estimating parameters of a simulation model in the fuel injection amount calculating means (103) based on a relationship with the output of the fuel injection amount calculating means (100). 2. The fuel injection amount control device according to claim 1, further comprising steady-state deviation removing means (107) for removing a steady-state deviation of the sensor and/or actuator in place of the sensor detection delay correcting means (105).