JPH0656112B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control device for optimally setting a fuel injection amount during restart and transition of an internal combustion engine.

<Prior Art> Conventionally, in a fuel injection control device for an internal combustion engine equipped with an electronically controlled fuel injection device, in order to improve the startability of the engine and ensure stable rotation after the start, the fuel injection amount at and after the start Is corrected to increase the air-fuel ratio on the dark side.

Specifically, at the time of starting (cranking), an increase correction is performed according to the engine cooling water temperature, and correction control is performed immediately after the start to decrease the increase correction coefficient every predetermined rotation (for example, 5 rotations) of the engine. There is. In addition, the fuel amount is corrected to improve the response during acceleration (Japanese Patent Laid-Open No. 58-144).
632, JP-A-58-14463, etc.).

<Problems to be Solved by the Invention> However, in such a conventional fuel injection control device, fuel is injected from the fuel injection valve provided at the upstream position of the intake passage toward the intake manifold on the downstream side. In the case of a so-called single-point injection type fuel injection device that injects fuel, the amount of fuel adhering to and floating in the intake system (intake manifold and intake port) varies considerably depending on the operating state immediately before the engine is stopped. At the time of restarting after the engine has been stopped under almost no operating condition, the fuel adhering to and floating in the intake system is supplied to the engine combustion chamber together with the injected fuel that has been started and increased after the start of the engine. HC due to excessive supply,
There have been problems such as an increase in unburned emissions such as CO and smoldering of the spark plug, making restarting difficult.

Further, even in the case where a fuel injection valve is provided in the intake port of each cylinder, the above tendency is unavoidable because the fuel remains in the intake system due to the phenomenon of blowback of intake air.

Further, in the one disclosed in JP-A-56-154133, the cooling water temperature and the intake pipe wall temperature when the engine is restarted are detected,
When the cooling water temperature is low, it is assumed that the amount of fuel adhering to the intake pipe wall is large, and the startup increase correction is performed. When both the cooling water temperature and the intake pipe wall temperature are high, the fuel amount in the intake system is saturated. However, when the cooling state temperature is high and the intake pipe wall temperature is low, the fuel vaporized in the intake system is adsorbed by the canister, etc. As the number is large, the increase correction at starting is performed.

However, the above-mentioned one simply determines whether or not the amount of residual fuel at the time of starting is large or small according to the combination of the two types of temperature at the time of starting, and determines whether or not to increase the amount of starting fuel. The residual fuel amount at the time of starting is not accurately predicted while calculating the change in the residual fuel amount in the intake system when the engine is stopped and the change in the residual fuel amount after the engine is stopped. Therefore, the fuel increase correction amount at the time of starting cannot be set with high accuracy according to the residual fuel amount, and the restart performance cannot be sufficiently improved.

Also, the amount of fuel remaining in the intake system changes during acceleration and deceleration. Conventionally, there has been a method of correcting the fuel supply amount by estimating such a change in the fuel amount by a change in intake pipe pressure, etc. Since the change in the amount depends on the absolute value of the intake pipe pressure, the engine rotation speed, the engine temperature, etc., the conventional estimation has low accuracy,
The acceleration / deceleration performance could not be sufficiently improved because the fuel correction amount could not be set to a sufficiently appropriate value.

The present invention has been made in view of such conventional problems, and by constantly predicting and calculating the amount of fuel adhering to and floating in the intake system not only during engine operation but also after engine stop, it is A fuel for an internal combustion engine in which the fuel correction amount at the time of acceleration / deceleration is appropriately set and the air-fuel ratio is controlled to a good value to improve the starting performance and the acceleration / deceleration performance, and the emissions of HC, CO, etc. can be reduced. An object is to provide an injection control device.

<Means for Solving Problems> Therefore, according to the present invention, as shown in FIG. 1, the operating state detecting means for detecting the operating state of the engine from parameters including at least the engine speed, the engine load and the engine temperature. a and
Basic injection amount calculation means b for calculating the basic injection amount (T _P ) of fuel based on the operating state of the engine, and adhesion of the intake system and equilibrium amount of floating fuel (based on engine speed, engine load and engine temperature) M0) for calculating the equilibrium amount calculation means c, the adhesion calculated by the equilibrium amount calculation means, the floating fuel equilibrium amount (M0) and the intake system adhesion at that time, and the difference value (M0) between the predicted variables of the floating fuel. -M) and a correction coefficient (DK) indicating how much the difference value (M0-M) calculated by the difference value calculation means is reflected in the correction of the fuel injection amount. A correction coefficient calculation means e that calculates based on speed, engine load and engine temperature, and a first correction that calculates a correction amount (DM) based on the difference value (M0-M) and the correction coefficient (DK). Amount calculation means f and the correction amount calculated by the first correction amount calculation means DM) and the attachment, the first predictor calculation means g predictors floating fuel and (M) are added in synchronism with the fuel injection, to update the predictors (M) with said added value,
Basic injection amount (T _P ) calculated by the basic injection amount calculation means
And the correction amount (DM) calculated by the first correction amount calculation means
On the basis of the fuel injection amount (T ₁ ) and outputs an injection signal, fuel injection amount calculation means h for supplying fuel to the engine based on the injection signal, and stopping the engine. The engine stop detection means j for detecting, and the second correction amount calculation means k for calculating the correction amount (DM) at the time of engine stop at predetermined time intervals based on the engine temperature after the engine stop is detected.
And the correction amount calculated by the second correction amount calculation means (D
M) and the predictive variable (M) of the adhered and floating fuel are added at predetermined time intervals, and the predictive variable (M) is updated with the added value. To do.

<Operation> In the steady operation state, the amount of fuel remaining in the intake system, that is, the predictive variable (M) is constant, and therefore coincides with the equilibrium amount calculated by the equilibrium amount calculation means, and the fuel injection amount is not corrected.

In the transient operation state, the equilibrium amount (M0) calculated by the equilibrium amount calculation changes due to the change of the operation state, and a difference is generated between the estimated variable (M) and the difference value (M0-M) is the difference value. It is calculated by the calculation means.

Next, a correction coefficient indicating how much the difference value (M0-M) is reflected in the correction of the fuel injection amount is calculated by the correction coefficient calculation means based on the engine speed, the engine load and the engine temperature, and the difference is calculated. Value (M0-M) and the correction coefficient (DK)
Based on the above, the first correction amount calculation means calculates the correction amount (DM) of the fuel injection amount during engine operation.

The prediction variable calculation means adds the correction amount (DM) calculated by the first correction amount calculation means and the current prediction variable (M) to change the prediction variable (M) during transient operation.
To correct.

On the other hand, since the correction amount (DM) is a value corresponding to the amount of change in the residual fuel amount in the intake system, the fuel injection amount calculation means corrects the fuel injection amount based on this value and the corrected fuel amount is corrected. An injection signal is output, and the corrected amount of fuel is supplied to the engine from the fuel supply means.

In this way, while the fuel amount remaining in the intake system during operation is sequentially predicted, the second correction amount calculation means predicts the change in the residual fuel amount according to the engine temperature even after the engine is stopped, and the correction amount is calculated. (DM) is calculated every predetermined time. In this case, since the engine speed and the engine load are both 0 when the engine is stopped, it is possible to approximately obtain the correction amount (DM) of adhered and floating fuel after the engine is stopped as a function of the engine temperature. .
When the predictive variable (M) immediately before the engine is stopped is used as an initial value and the predictive variable (M) is gradually changed by the correction amount (DM), it corresponds well to the actual amount of fuel remaining in the intake system. When the fuel remains at the time of restart after the time stop, the fuel correction increase at the time of start can be reduced.

<Example> An example of the present invention will be described below with reference to the drawings.

In FIG. 2 showing the overall configuration of one embodiment, a microcomputer 1 for performing various arithmetic controls described later is C
PU1A, ROM1B, RAM1C, I / O port 1D
It is composed of The I / O port 1D has an intake air flow rate signal Qa from an air flow meter 3 installed upstream of an intake passage 2 of the engine as a detection signal of an engine operating state, and a throttle sensor 5 installed on a spindle of a throttle valve 4. Throttle position (throttle valve opening) signal θ and throttle speed (opening / closing speed) signal V _θ , engine rotation speed signal N from a crank angle sensor 6 provided near the crankshaft, and water temperature provided in the water jacket 7. The cooling water temperature signal Tw from the sensor 8, the intake passage wall temperature signal Ti from the temperature sensor 9 mounted on the wall of the intake manifold 9, the air-fuel ratio signal from the air-fuel ratio sensor 11 provided in the exhaust manifold 10, etc. are input. It It should be noted that these various sensors form an operating state detecting means. A fuel injection valve 12 as a fuel supply means is mounted in the vicinity of the upstream side of the throttle valve 4, a fuel injection signal T ₁ is output from the I / O port 1D to the fuel injection valve 12, and the amount calculated by the CPU 1A. Fuel is injected and supplied in synchronization with the engine rotation. In addition, the intake manifold 2
A is provided with an intake heating water jacket 13 for circulating engine cooling water, and the fuel injected from the fuel injection valve 12 passes through the intake manifold 2A to form a combustion chamber 14A.
Is heated until it flows in to accelerate atomization. An exhaust gas purification catalyst 15 is provided in the exhaust manifold 10.

Next, the air-fuel ratio (fuel injection amount) control by the microcomputer 1 is calculated according to the flowcharts shown in FIGS.

FIG. 3 shows the basic injection amount TP, the equilibrium amount M0 for correcting the basic injection amount TP, the correction coefficient DK, and the first correction amount DM.
A routine for calculating is shown.

First, in step 1 (denoted as S1 in the figure, the same applies hereinafter),
Intake air flow rate Qa read from the air flow meter 3,
Engine rotation speed N detected by the crank angle sensor 6
Based on and, the basic fuel injection amount TP is calculated by the following equation. The function of step 1 constitutes the basic injection amount calculation means.

TP = Qa / N × K (where K is a constant) Next, in step 2, the representative temperature T of the engine is calculated.

This is calculated by the following equation based on the cooling water temperature Tw detected by the water temperature sensor 8 and the intake passage wall temperature Ti detected by the temperature sensor 9.

T = Tw × K1 + Ti (1-K1) (K1 is a constant, K1 <1) In step 3, the intake manifold 2A downstream of the fuel injection valve 12 when the operating state is set to a steady state according to the engine operating state, A fuel amount (hereinafter referred to as an equilibrium amount) M0 that adheres to and floats in the intake port 2B (hereinafter referred to as an intake system) is calculated. That is, the function of step 3 corresponds to the equilibrium amount calculation means.

The calculation of the equilibrium amount M0 is performed, for example, according to the flowchart shown in FIG.

Here, the ROM 1B of the micro computer 1 stores a two-dimensional table of the equilibrium amounts M01 to M04 obtained by experiments for the representative temperatures T0 to T4 of different engines (see FIG. 7).

Then, in Steps 11, 15, and 19, it is determined which of the four areas the representative temperature T determined in Step 2 belongs to is divided into T0 to T4, and two representative temperatures of large and small that partition the belonging area. The equilibrium amount corresponding to the engine rotation speed N and the basic injection amount TP is retrieved from the table corresponding to, and the linear approximation interpolation calculation is performed from the actual representative temperature T and the corresponding representative temperatures of the two retrieved tables to achieve equilibrium. Calculate the quantity M0.

For example, if the representative temperature T is equal to or higher than T ₁ , first, the table (M00) corresponding to T0 is searched for M00 corresponding to N, TP, and then the table (M01) corresponding to T ₁ is searched for N, T.
The value M01 corresponding to P is searched. Next, the equilibrium amount M0 is interpolated by the following equation.

The same is true for other representative temperature ranges. When the calculation of M0 is completed in this way, the process proceeds to step 4 in FIG. 3 to calculate the correction coefficient DK. The calculation of the correction coefficient DK is performed according to the flowchart shown in FIG. The routine shown in FIG. 5 constitutes a correction coefficient calculating means.

First, in step 31, using the representative temperature T obtained in step 2 of the flowchart shown in FIG. 3 and the DM obtained in step 5 of the previous flow, the DK · T table (FIG. 8) stored in the ROM 1B is used. The first correction coefficient DK · T is obtained from Next, at step 32, the second correction coefficient DKN (see FIG. 9) is obtained from the table also stored in the ROM by using the engine rotation speed N and the basic injection amount TP, and at step 33, the final correction coefficient is obtained. Then, the correction coefficient DK is calculated by the following equation.

DK = DK.multidot.T.times.DK.N. After obtaining the correction coefficient DK in this way, the routine proceeds to step 5 in FIG. 3 to obtain the first correction amount (hereinafter simply referred to as correction amount) DM by the following equation.

DM = DK (M0-M) The functions of steps 4 and 5 correspond to the first correction amount calculation means. In step 5, a difference value (M0-
Since M) is calculated at the same time, it also corresponds to difference value calculation means.

Here, the M indicates the residual fuel amount (hereinafter referred to as a prediction variable) predicted to be presently attached to and floating in the intake system.
This predictor variable M is M = M in step 44 of FIG.
It is sequentially updated with the arithmetic expression of old M + DM. As is clear from this equation, M matches M0 in the steady state, but changes in response to changes in M0 during transient operation such as acceleration / deceleration.

Next, the fuel injection pulse width T that is performed in synchronization with the engine rotation
The I operation routine will be described with reference to the flowchart shown in FIG.

In step 41, the corrected basic injection pulse width TPF is calculated by adding the correction amount DM found in step 5 to the basic injection amount TP found in step 1 of FIG.

Next, at step 42, the feedback correction coefficient α obtained by increasing or decreasing based on the actual air-fuel ratio detected by the air-fuel ratio sensor 11 and the sum of the correction coefficients obtained according to various operating conditions such as cooling water temperature are calculated. Various correction factors C
The final fuel injection pulse width TI output to the fuel injection valve 12 is determined by the OEF and the invalid pulse width Ts required for rising and falling of the fuel injection valve according to the battery voltage.
Is calculated by the following equation.

TI = TP.alpha..COEF + Ts or more The functions from step 41 to step 42 constitute the fuel injection amount calculation means.

In step 43, the TI obtained as described above is I
It is stored in the output register of the / O port 1D, and the start of injection is commanded. As a result, the fuel injection valve 12 injects an amount of fuel corresponding to the calculated value.

Next, at step 44, the M value is updated by adding the correction amount DM to the previous M value (old M). The function of this step 44 constitutes the first predictive variable calculation means.

With this configuration, during acceleration / deceleration, the amount of fuel remaining in the intake system is predicted according to the change in the operating state, and the fuel injection amount is corrected according to the change. For example, at the time of acceleration, M0 searched in step 3 first increases due to a change in operating conditions, and accordingly, a positive difference value ΔM with respect to the prediction variable M before acceleration is generated, and the correction coefficient DK is added to this. The correction amount DM obtained by multiplying by is increased in proportion to the increase in the residual fuel amount. As a result, it is possible to prevent the amount of fuel supplied to the combustion chamber 14 from becoming insufficient due to an increase in the residual fuel amount, prevent the air-fuel ratio from becoming lean, and improve the acceleration response.

At the time of deceleration, M0 similarly decreases, a negative deviation is generated between M and M, and the fuel injection amount is corrected to be decreased. In this case as well, the fuel corresponding to the decrease in the residual fuel amount flows into the combustion chamber, so by correcting the amount of fuel corresponding to this when reducing, the deceleration response is improved and the air-fuel ratio is enriched. It is possible to prevent misfire and increase unburned emissions such as CO and HC.

Further, during gear change of the transmission, acceleration is performed after deceleration, so the fuel reduction correction during deceleration and the fuel increase correction during acceleration are continuously performed, and the torque change of the transmission can be reduced and smoothed. Gear shifting is performed.

Each state quantity during acceleration, deceleration, and gear change is the 10th
Change as shown in the figure.

Next, the control performed for restarting while the engine is stopped
A description will be given according to the flowchart shown in the figure.

First, the current is continuously supplied to the microcomputer 1 for a while after the engine is stopped. This routine is started by turning off the engine key switch, is repeated at regular time intervals by the internal timer of the microcomputer 1, and ends within the set time. Therefore, the engine key switch constitutes the engine stopping means.

In step 51, the representative temperature T of the engine is calculated.

In step 53, based on the representative temperature T obtained in step 51, the correction amount DM is retrieved from the ROM 1B storing the characteristics shown in FIG. The function of this step 53 is the second
Of the correction amount calculation means. Here, the equilibrium value of adhesion and floating fuel when the engine is stopped is 0, and this DM is set to a negative value because M0-M becomes a negative value.
Also, experimental values are used to improve accuracy. When the experimental value is not used, the correction coefficient DK when the engine is stopped is set based on the engine stop condition (the engine speed N and the basic injection amount T _P are 0) and the representative temperature T. It may be calculated from the above-described equation for obtaining DM with the equilibrium amount M0 of 0 as 0.

In step 54, the predictive variable M is obtained by the equation M = old M + DM and stored in the RAM (with backup function). This function corresponds to the second predictive variable calculation means when the engine is stopped.

In step 55, it is determined whether or not the value of M obtained in step 54 has become 0. If YES, the process proceeds to step 56 to stop the internal timer and at the same time terminate the calculation.

FIG. 13 shows changes in the prediction variable M and the correction amount DM during the calculation. The calculation cycle t is set to about 1 to 5 minutes in consideration of the current consumption of the microcomputer.

In such control, the predictive variable M gradually approaches 0 every t hours. If the engine is restarted before the predictive variable M becomes 0, that is, while fuel remains in the intake system, M0 is set based on the value of M0 set based on the state before starting and the value of M immediately before starting. Is corrected and updated, and changes as shown by the dotted line in FIG.

On the other hand, when the engine is stopped for a long time and the engine is started after M = 0, it changes as shown by the alternate long and short dash line.

It is possible to save fuel consumption as much as the amount of fuel remaining in the intake system, that is, the portion indicated by the diagonal lines inserted between the dotted line and the chain line, that is, the large amount.

FIG. 14 shows various waveforms at the time of starting. When the engine is stopped for a short time and restarted while M> 0 (shown by a chain line),
Compared to the case of starting with M = 0 (shown by the dotted line), the difference from M0 is small, so DM is small and the correction increase before starting is small, so fuel can be saved and startability is poor due to excessive supply of fuel. It is possible to reduce the amount of unburned exhaust such as HC, CO and the like.

A flowchart of FIG. 15 shows a control operation of an embodiment in which the fuel correction control according to the present invention is applied to a fuel cut (supply stop) under a predetermined deceleration condition and then the fuel supply is restarted.

The difference from the one shown in FIG. 3 is that in step 62 it is judged whether the fuel is being cut or not, and when it is being cut, step 63
The point is that the equilibrium amount M0 is held at a constant value MFC so as to be prepared when the fuel supply is restarted. Otherwise, in step 64, M0 is calculated in the same manner as in FIG.

Here, the value of the MFC is selected to be 0 or a value much smaller than the normal value of M0.

The operation of this one will be described. When the fuel supply is restarted after the normal fuel cut, the air-fuel ratio has an error in the lean direction. This is because the fuel remaining in the intake system flows into the combustion chamber of the engine during the fuel cut, and therefore the amount of residual fuel that adheres to the intake system again or floats in the fuel injection amount with respect to the intake air flow rate Qa when the fuel supply is restarted. This is because the fuel supply amount becomes insufficient and the air-fuel ratio becomes lean.

By setting M0 to 0 during fuel cut, M gradually decreases and approaches M0, that is, 0. As a result, when M0 increases at the time of restarting the fuel supply, M0-M increases, and the amount increase correction is performed so that the fuel remains in the supply system.

This is not a special example because the residual fuel amount is naturally 0 in view of the steady state of fuel cut, and the predictive variable M is also a value that well predicts the actual residual amount that gradually decreases after the fuel cut. Therefore, when the fuel cut time is short and the difference from M0 is still large, the correction amount DM also becomes small, and good control can be performed even in this case.

In the first embodiment shown in FIG. 3, the ROM 1B
The data of M0 corresponding to TP = (fuel cut) may be set to 0 or a value close to 0 in the map of M0 stored in.

The present invention can also be applied to a multi-injection type in which a fuel injection valve is attached to the intake port of each cylinder. Further, it is needless to say that the present invention can be applied to the one in which the basic injection amount is set based on the intake pressure, the throttle valve opening and the engine rotation speed.

<Object of the Invention> As described above, according to the present invention, the fuel amount remaining in the intake system is predicted during engine operation and after the engine is stopped, and the air-fuel ratio is corrected according to the residual fuel amount. It is possible to prevent excessive supply of fuel at the time of restart and obtain good starting performance, save fuel consumption, and reduce emissions of unburned emissions such as CO and HC.

Further, during acceleration / deceleration, the air-fuel ratio is corrected according to the change in the residual fuel amount, and the acceleration / deceleration performance is improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of the present invention, FIG. 2 is a configuration diagram showing a configuration of an embodiment of the present invention, and FIG. 3 is a flowchart showing a basic injection amount calculation routine in air-fuel ratio control of the same embodiment. FIG. 4 is a flow chart showing a balance calculation routine, FIG. 5 is a flow chart showing a correction ratio calculation routine, FIG. 6 is a flow chart showing a fuel injection pulse width calculation routine, and FIG. FIG. 8 is a diagram showing an example of a balance amount table map, FIG. 8 is a diagram showing a first correction ratio table map, FIG. 9 is a diagram showing a second correction ratio table map, and FIG. An example of a time chart showing changes in various state quantities at the time of acceleration, deceleration, and gear change, FIG. 11 is a flow chart showing control when the engine is stopped in the same embodiment, and FIG. Fig. 13 is a diagram showing correction amount characteristics to be used, Fig. 13 is a diagram showing steady-state fuel residual amount during control and changes in predictive variables, and Fig. 14 is a diagram showing changes in various state variables during control. FIG. 15 is a flow chart showing the control of the second embodiment of the present invention, and FIG. 16 is a diagram showing changes in various state quantities during the control. 1 ... Microcomputer, 2 ... Intake passage 3 ... Air flow meter, 6 ... Crank angle sensor 8 ... Water temperature sensor, 9 ... Temperature sensor, 11 ... Air-fuel ratio sensor, 12 ... Fuel injection valve

Claims (1)

[Claims] 1. A) operating state detecting means for detecting an operating state of an engine from parameters including at least engine speed, engine load and engine temperature; and b) basic injection amount of fuel based on the operating state of the engine ( A basic injection amount calculation means for calculating T _P ), c) a balance amount calculation means for calculating adhesion of the intake system and a balance amount (M0) of floating fuel based on the engine speed, engine load and engine temperature; ) A difference value for calculating a difference value (M0-M) between the adhesion amount calculated by the equilibrium amount calculation means, the equilibrium amount of the floating fuel (M0) and the adhesion of the intake system at that time, and the prediction variable (M) of the floating fuel. And a correction coefficient (D) indicating how much the difference value (M0-M) calculated by the difference value calculation means is reflected in the correction of the fuel injection amount.
Correction coefficient calculating means for calculating K) based on the engine speed, engine load and engine temperature; and f) correction amount (DM) based on the difference value (M0-M) and the correction coefficient (DK). And a correction amount (D) calculated by the first correction amount calculation unit.
M) and the predictive variable (M) of the adhered and floating fuel, which are added in synchronism with fuel injection, and the predictive variable (M) is updated with the added value, and h) the basic The basic injection amount (T
_P ) and the correction amount calculated by the first correction amount calculation means (D
M) to calculate a fuel injection amount (T _I ) and output an injection signal, i) fuel supply amount supply means for supplying fuel to the engine based on the injection signal, j) Engine stop detection means for detecting engine stop, and k) Second correction amount for calculating engine correction amount (DM) at predetermined time intervals based on engine temperature after engine stop is detected. And a correction amount (D) calculated by the second correction amount calculation unit.
M) and the predictive variable (M) of the adhered and floating fuel are added at predetermined time intervals, and the predictive variable (M) is updated with the added value. And a fuel injection control device for an internal combustion engine.