JPH01305142A - Fuel injection controller of internal combustion engine - Google Patents

Abstract

PURPOSE:To make adequate control of a state of engine operation by calculating a stabilized temperature and a temperature delay time constant on a fuel sticking area inside an air intake pipe based upon the running condition of an engine and also predicting the temperature on the fuel sticking area on the basis of those data so as to calculate a transient corrective amount of a fuel injection quantity. CONSTITUTION:The running condition of an engine is detected by a means (a). Then, a stabilized temperature on a fuel sticking area inside an intake pipe is calculated by a means (b) and similary the delay time constant on the fuel sticking area is calculated by a means (c). Further, the temperature on the fuel sticking area is predicted by a means (d) on the basis of the outputs from respective means (b) and (c). Furthermore, when the engine is in the state of its prescribed temperature, a transient corrective quantity of the quantity of fuel injection is calculated by a means (e) according to the output of the means (d). On the other hand, as well as the quantity of fuel injection is calculated by a means (f) on the basis of the detected result of the means (a), the quantity of fuel injection is corrected on the basis of transient corrective quantity similary by a means (f). Thereafter, fuel is injected by a means (g) in response to the output of means (f).

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a fuel injection control device for internal combustion engines such as automobiles, and in particular to a fuel injection control device that predicts the temperature of a fuel adhesion part and uses the result to obtain a transient correction amount. Regarding a control device.

(Prior art) When the required output for the engine of a vehicle such as an automobile changes, it is necessary to control the fuel injection amount with good responsiveness according to the degree of the request. This affects driving performance such as drive feeling and exhaust composition.

Generally, the deviation of the air-fuel ratio from the target air-fuel ratio during engine acceleration/deceleration is due to changes in the amount of adhering fuel and floating fuel adhering to the intake manifold and intake boat of the intake system. The amount of fuel varies greatly depending on the operating state of the engine.

Against this background, as a conventional fuel injection control device for an internal combustion engine, there is one described, for example, in Japanese Patent Application Laid-open No. 18758/1983. In this device, the required load per unit rotation of the engine is determined from the output of an air flow meter provided upstream of the throttle valve, and the fuel injection amount is calculated from this. In addition, during a transient period, the fuel injection amount is corrected using a transient correction amount to take into account so-called wall flow. It should be noted that the transient correction amount is a wall flow correction bone, and is not necessarily used during acceleration/deceleration, but is also used, for example, immediately after starting, when the influence of wall flow is large, or immediately after gluing from a trundle cut.

(Problem to be Solved by the Invention) However, in such a conventional fuel injection control device for an internal combustion engine, since the wall flow bone corresponding to the transient correction amount is determined from the cooling water temperature, it is not possible to There was a problem in that it was not possible to perform accurate transient correction.

That is, in the evaporation of a wall flow, the wall temperature of the adhering part is an important parameter, but the adhering part temperature varies greatly depending on the operating conditions as shown in FIG. 7, and has a lag as shown in FIG. 8. In other words, the tendency for the temperature of the deposited portion to rise differs depending on the operating conditions, and this appears as a difference in the delay time constant. Therefore, the adhering part temperature varies depending on the operating conditions before acceleration etc., and the air-fuel ratio during transients such as acceleration and deceleration becomes inappropriate, resulting in poor drivability.

In particular, in multi-point injection type engines, the cylinder head 3
1, when injector A injects fuel directly toward the intake valve 32 and when injector B injects fuel toward the wall of the intake boat, the air-fuel ratio after startup differs as shown in FIG. The change in the intake valve 32 is different between the two.
The change in air-fuel ratio is more significant when the fuel is injected. In other words, the error due to the temperature of the intake valve 32 is large (such a phenomenon tends to occur not only immediately after starting, but also under operating conditions where the temperature rise is different from normal, for example, immediately after fuel cant recovery. Therefore, during acceleration Hesitation is likely to occur, and variations in the air-fuel ratio cause a deviation from the three-way point in the three-way catalyst, resulting in a decrease in exhaust purification performance.

Although it is conceivable to provide a wall temperature sensor, for example, to detect the temperature of the adhesion part, this is not preferable because it not only increases cost but also reduces the productivity of installation.

(Objective of the Invention) Therefore, the present invention aims to improve the operating performance and exhaust purification performance without increasing costs by appropriately predicting the adhesion part temperature from various operating conditions and making the amount of transient correction appropriate. The purpose is

(Means for Solving the Problems) In order to achieve the above object, the fuel injection control device for an internal combustion engine according to the present invention has an operating state detection means for detecting the operating state of the engine, as a basic conceptual diagram thereof is shown in FIG. a, an equilibrium temperature calculation means for calculating the equilibrium state temperature of the fuel adhesion part in the intake pipe based on the operating state of the engine; a delay calculating means C; a predicting means d for predicting the temperature of the fuel adhesion part in the intake pipe based on the outputs of the equilibrium temperature calculating means and the delay calculating means C; and at least the predicting means when the engine is in a predetermined temperature state. correction amount calculation means e for calculating a transient correction amount for correcting the fuel injection amount using the output of d; injection amount calculation means f for correcting the fuel injection amount according to;
The fuel injection device g injects fuel based on the output of the injection amount calculation device f.

(Operation) In the present invention, the equilibrium state temperature of the fuel adhesion part in the intake pipe and the delay time constant of the adhesion part temperature are determined based on the operating state of the engine, and the adhesion part temperature is predicted from this. When calculating the transient correction amount, at least the predicted value of the adhesion part temperature is added to one of the calculation parameters.

Therefore, the amount of transient correction becomes appropriate without increasing costs, and driving performance and exhaust gas purification performance are improved.

(Example) Hereinafter, the present invention will be explained based on the drawings.

2 to 10 are diagrams showing an embodiment of a fuel injection control device for an internal combustion engine according to the present invention.

First, the configuration will be explained. FIG. 2 is a diagram showing the overall configuration of this device. In Fig. 2, 1 is an engine;
Intake air passes through an intake pipe 3 from an air cleaner 2, and fuel is injected into an injector (fuel injection means) 4 based on an injection signal St.
is sprayed from. Then, the exhaust gas combusted in the cylinder is introduced into the catalytic converter 6 through the exhaust pipe 5, where the harmful components (COlHC, NOx) in the exhaust gas are purified by a three-way catalyst and then discharged.

The intake air flow IQa is detected by an air flow meter 7 in the hot wire 2 and controlled by a throttle valve 8 in the intake pipe 3. The types of air flow meter 7 are as follows:
A hot film type may be used, as long as it measures the flow rate of intake air.

The opening TVO of the throttle valve 8 is detected by a throttle valve opening sensor 9, and the rotation speed N of the engine 1 is detected by a crank angle sensor 10. Further, the temperature Tw of the cooling water flowing through the water jacket is detected by a water temperature sensor 11, and the oxygen concentration in the exhaust gas is detected by an oxygen sensor 12. The oxygen sensor 12 used has a characteristic of detecting a wide range of air-fuel ratios from rich to lean. Furthermore, the operation of the starter motor is detected by the start switch 13.

The air flow meter 7, throttle valve opening sensor 9, crank angle sensor 10, water temperature sensor 11, oxygen sensor 12, and start switch 13 constitute an operating state detecting means 14, and the output from the operating state detecting means 14 is controlled. input to unit 20.

The control unit 20 has functions as an equilibrium temperature calculation means, a delay calculation means, a prediction means, a correction amount calculation means, and an injection amount calculation means, and includes a CPU 21, a ROM 22, an RA
It is composed of M23 and I10 boats 24. C.P.
The U21 takes in necessary external data from the I10 boat 24 according to the program written in the ROM 22, and performs arithmetic processing on processing values necessary for fuel injection control while exchanging data with the RAM 23. The processed data is output to the I10 boat 24 as necessary.

A signal from the operating state detection means 14 is input to the I10 boat 24, and an injection signal Si is output from the I10 port 24. The ROM 22 stores calculation programs for the CPU 21, and the RAM 23 stores data used in calculations in the form of a map or the like.

Next, the effect will be explained.

Figure 3 shows the temperature of fuel adhesion inside the intake pipe 3 (hereinafter referred to as
This is a flowchart showing a program for calculating Th (simply referred to as adhesion temperature) and a delay time constant 5PTF, and this program is executed in synchronization with a timer, for example, once every 1 sec.

First, P determines whether or not the start switch 13 is ON, and when the start switch 13 is ON, it is determined that cranking is in progress, and P determines the adhesion temperature Th at the cooling water temperature at that time. Assuming that it is equal to Tw, proceed to P.

On the other hand, when the start switch 13 is not ON, it is determined that cranking has already been completed, and the equilibrium adhesion temperature ThO of the fuel adhesion portion is determined at P2. Equilibrium adhesion temperature Tho is determined from the map shown in Fig. 7 based on the operating conditions using the intake air 1 tQcyl at that time (the same map characteristics are obtained even if the intake negative pressure is replaced with the intake air amount) and the engine speed N as parameters. Lookup and calculate. In addition, Qc
yl is the amount of air sucked into the cylinder,
It corresponds to the engine load. The map shown in Figure 7 was created in advance through experiments, etc., and the actual equilibrium adhesion temperature Tho
It matches with good accuracy.

Next, in P3, it is determined whether or not phenyl cutting is in progress, and if the phenyl cutting is in progress, the process branches to P, and if the phenyl cutting is not in progress, the process proceeds to P4.

In P4, the adhesion temperature Th is calculated according to the following equation (2).

Th=Tho-(80-Tw)XCI-(25-Ta)XC2-... ■However, C1, C
By calculating l constant TW: cooling water temperature Ta: intake air temperature, the adhesion temperature Th corresponding to the operating conditions at that time can be accurately determined based on the equilibrium adhesion temperature Tho. Next, the delay time constant 5PTF for Pb is determined by look-amplification based on the operating conditions Qcy1 and N from the map shown in FIG. The delay time constant 5PTF corresponds to the rate of change of the deposition temperature Th, and this is expressed in [%] in FIG.

FIG. 4 is a flowchart showing a program for calculating a predicted temperature value (hereinafter referred to as a predicted deposition temperature value) Tf of the temperature of the fuel adhesion part, and this program is also executed in synchronization with a timer, for example, once every 1 sec.

For pH and pHZ, input the adhesion temperature Th and delay time constant 5PTF, which were respectively obtained in the subroutine of Fig. 3 above, and
At I3, a predicted adhesion temperature value Tf is calculated according to the following equation (2).

Tf=ThxSPTF+Tf-.

x (l-3PTF) ・・・・・・■However, Tf-
, :Previous value (2) By calculating the equation, the predicted adhesion temperature value Tf is obtained as a first-order lag of the adhesion temperature Th.

FIG. 5 is a flowchart showing a program for calculating the transient correction amount Kathos.
Executed once per ec. First, the equilibrium adhesion amount Mfh of fuel wall flow bones in the intake pipe 3 is determined using pz+. For example, this can be expressed as AvTpXMfhtvo −−・−・・■,
Furthermore, the calculation is performed by adding a correction based on the predicted adhesion temperature value Tf. In formula 0, Avtp is the smooth injection amount, and in order to accurately determine the amount of air flowing through the injector 4, the output of the air flow meter 7 is smoothed with a first-order lag, and the fuel injection amount is calculated based on the smoothed air amount. It is calculated as follows.

Therefore, Avtp is the cylinder air amount equivalent pulse width (
m s ). Note that the method for calculating Avtp has already been disclosed by the present applicant in another application approximately at the same time as the present application. On the other hand, Mfhtvo is the adhesion magnification [unit: times], and is determined from the load and rotation speed for each cooling water temperature TW. In such processing, when calculating Mfh, the predicted adhesion temperature value Tf is required, unlike the conventional method.
The accuracy of the equilibrium adhesion amount Mfh becomes high.

Next, the quantity ratio Kmf (%) is determined in P2□.

This is calculated, for example, by adding a correction based on the predicted adhesion temperature value Tf to the equation KmfatxKmfn. In formula 0, Kmfat is the basic amount ratio [%
] is obtained from a predetermined map using the α-N flow rate Qho and the cooling water temperature Tw with interpolation calculation. Note that the α-N flow rate is the air flow rate determined from the throttle valve opening TVO and the rotational speed N, and is already known. Also, Kmfn [times]
is the quantity ratio rotation correction rate, which is obtained from a predetermined table with interpolation calculation from the rotation speed N. Unlike the conventional method, the deposition temperature predicted value Tf is used when calculating the quantity ratio Kmf, so that the calculation accuracy is high. Then, P
At X3, the adhesion speed Vmf (ms) is calculated according to the following equation (2).

Vmf= (Mf h−Mf) ×Kmf・・−・−0
In the formula 0, Mf is the adhesion amount (m s ), for example, Mf
= (Mf-1ref)+Vmf-...-■. (Mf-1ref) is the adhesion amount (at the time of the previous injection, which is one revolution before). Adhesion speed Vmf
is the flow rate of fuel taken up by the wall flow, and is determined as the flow rate per rotation.

Next, the correction factor Ghf (%) is determined using pza according to the following formula.

Ghf=Ghfgen
When mf≧0), Gh f gen=Q is used; otherwise, the larger value of the correction factor load terms Ghfg and Ghfdn is used. Here, Ghfg is determined by looking up a table without interpolation based on the equilibrium injection amount Avtp. Further, KtgKL is a transient learning low frequency coefficient, and uses a value after 1°0@, for example. Next, at P□, the transient correction amount Kathos is determined according to the following formula 〇.

After calculating Kathos by the above process, the actual injection amount Ti
is calculated according to the following equation in step P31 of the program shown in FIG.

Ti= (TpXαm+Kathos)Xcr+'l'
s...■ However, Tp: Basic injection amount α is a λ control correction factor for the air-fuel ratio based on the output of the oxygen sensor 12, and αm is a mixture ratio learning control correction factor. T
S is the invalid pulse width.

The actual operation by executing each of the above programs is shown in the timing chart of FIG. FIG. 9 shows an example in which the engine 1 is accelerated about 4 minutes after starting. Since the adhesion temperature Th of the wall flow is a value in equilibrium in a steady state, as shown in the figure, it increases in a stepwise manner at the same time as the engine starts, and also increases in a stepwise manner during acceleration. However, such a step change does not match the actual deposition temperature.

On the other hand, in this embodiment, the predicted deposition temperature value Tf is used, which matches the actual deposition temperature with extremely high accuracy. Here, in particular, A in Figure 9
The change in air-fuel ratio when the vehicle is accelerated at the time shown in FIG. 10 is as shown in FIG. In the conventional example, since the adhesion temperature is determined from the cooling water temperature TV, the transient correction amount KathosO value becomes inappropriate and the air-fuel ratio fluctuates greatly during acceleration. On the other hand, in this example, unlike the case where the time constant is extremely large and equilibrium is achieved in a steady state, such as the cooling water temperature Tw, the predicted adhesion temperature value Tf is used, so the wall flow is appropriately corrected and the transient The amount of correction corresponds to the actual situation with high accuracy. Therefore, changes in the air-fuel ratio can be suppressed to a small level. From the above, the following effects can be obtained.

(1) Regardless of the driving conditions before acceleration, drivability is improved by appropriate acceleration correction. Furthermore, since the deviation of the air-fuel ratio from the ternary point is reduced, there are fewer emissions gaps and the exhaust gas purification performance is improved.

(II) In particular, since the drivability and emission characteristics immediately after starting are improved, it is possible to prevent power steering stall at the time of starting, and also to reduce emissions and improve fuel efficiency due to constant lean.

(II [) The same effect as described above can be obtained immediately after the twerking force is applied, and it is possible to prevent hesitation and reduce NOx.

(rV) The flatness of the transient air-fuel ratio is further improved.

(V) Expensive items such as wall temperature sensors are not used, and this can be solved by improving the software in the control unit 20 or improving the map data, and does not increase costs.

(Effects) According to the present invention, since the adhering part temperature is predicted from various operating conditions, it is possible to suppress fluctuations in the air-fuel ratio without increasing costs by setting an appropriate amount of transient correction. Performance and exhaust purification performance can be significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a basic conceptual diagram of the present invention, FIGS. 2 to 10 are diagrams showing an embodiment of a fuel injection control device for an internal combustion engine according to the present invention, FIG. 2 is an overall configuration diagram thereof, and FIG. is a flowchart showing a program for calculating the adhesion temperature and delay time constant, FIG. 4 is a flowchart showing a program for calculating the predicted adhesion temperature value, FIG. Figure 6 is a flowchart showing the program that calculates the fuel injection amount, Figure 7 is a diagram showing the characteristics of the adhesion part temperature, Figure 8 is a diagram showing the characteristics of the delay time constant, and Figure 9 is at the time of starting. Fig. 10 is a timing chart showing the fluctuation of the air-fuel ratio during acceleration.
．． FIG. 12 is a diagram showing a conventional fuel injection control device for an internal combustion engine, FIG. 11 is a schematic diagram showing its injection position, and FIG.
The figure is a timing chart showing fluctuations in the air-fuel ratio during acceleration. ■...Engine, 4...Injector (fuel injection means), 7...
... Air flow meter, 9 ... Throttle valve opening sensor, IO ... Crank angle sensor, 11 ... Water temperature sensor, 12 ... Oxygen sensor , 14... Operating state detection means, 20... Control unit (equilibrium temperature calculation means, delay calculation means, prediction means, correction amount calculation means, injection amount calculation means).

Claims (1)

[Scope of Claims] a) Operating state detection means for detecting the operating state of the engine; b) Equilibrium temperature calculation means for calculating the equilibrium state temperature of the fuel adhering portion in the intake pipe based on the operating state of the engine; c) d) delay calculation means for calculating a delay time constant of the temperature of the fuel adhesion part in the intake pipe based on the operating state of the engine; e) correction amount calculation means for calculating a transient correction amount for correcting the fuel injection amount using at least the output of the prediction means when the engine is in a predetermined temperature state; and f) operation of the engine. g) injection amount calculation means that calculates the fuel injection amount based on the state and corrects the fuel injection amount according to the transient correction amount when the transition to the transient state; g) fuel injection amount calculation means that calculates the fuel injection amount based on the output of the injection amount calculation means; A fuel injection control device for an internal combustion engine, comprising: a fuel injection means for injecting fuel;