JPH07111149B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control device for a fuel injection type internal combustion engine.

[0002]

2. Description of the Related Art As a conventional fuel injection control device for an internal combustion engine, for example, as disclosed in Japanese Patent Application Laid-Open No. 60-169647, the intake air amount or the intake pipe pressure is detected every time the engine rotates by a predetermined crank angle. Then, by using the detected value of this time and at least the detected value of the previous time, the intake air amount or the intake pipe internal pressure at the time when the fuel injected based on the calculated value of the fuel injection amount reaches the combustion chamber. Predict,
There is a device that calculates an injected fuel amount using the predicted value and performs actual fuel injection according to the calculated fuel amount.

[0003]

In such a conventional fuel injection control device for an internal combustion engine, the engine rotates at a predetermined crank angle (180 ° CA for a 4-cylinder engine, 120 ° CA for a 6-cylinder engine). At the time when the fuel injected based on this calculation arrives at the combustion chamber by the approximate expression (the following expression) from a polynomial such as Maclaurin expansion, using only the intake air amount or the information in the intake pipe pressure for each The intake air amount or the intake pipe internal pressure f (x + h) was predicted.

F (x + h) = 2.5f (x) -2f (x-h) + 0.5f (x-2h) ... In the above formula, f (x), f (x-h), f (x-2h) ) Is the intake air amount or the intake pipe internal pressure at the present time, the previous time, and the last time before, respectively. However, according to such a prediction calculation, since the prediction result matches the true value only under a certain specific condition, it is difficult to sufficiently correct it, resulting in deterioration of drivability and deterioration of emission. was there.

For example, when the throttle opening changes from TH0 to TH1 at a certain point as shown in FIG. 5 (a), the actual intake pipe internal pressure shows a delay system characteristic and is shown by a solid line in FIG. 5 (b). In contrast to the change as shown, the predicted value becomes as shown by the broken line, which is too small at the beginning and too large at point E. This is because the formula (prediction formula) is originally established when h is small, and h = 180 ° CA (or 120 ° CA) like the pressure in the intake pipe at the time of transition.
On the other hand, it is impossible to apply it to the one showing a fast response.

Therefore, the first and second fuel injection amounts greatly deviate from the required value, especially during acceleration, but during acceleration, the first and second fuel injection amounts are important, and particularly lean. Since it is necessary to prevent the engine from exceeding the misfire limit, such a conventional fuel injection control device could not handle it. The present invention aims to solve such conventional problems.

[0007]

Therefore, according to the present invention, in a fuel injection control device for an internal combustion engine, a predetermined delay occurs from the injection of fuel until the injected fuel reaches the combustion chamber of the engine. Alternatively, the first detecting means for detecting the pressure in the intake pipe, the second detecting means for detecting the throttle opening or the accelerator operation amount of the engine, and the intake air amount or the intake pipe pressure from the throttle opening or the accelerator operation amount. State quantity calculating means for calculating a state quantity representing the behavior of the intake air amount or the intake pipe pressure from the throttle opening or the accelerator operation amount and the detected value of the intake air amount or the intake pipe pressure based on the transfer characteristic, The state quantity and the transfer characteristic and the detected value of the throttle opening or the accelerator operation amount are used to determine when the injected fuel reaches the combustion chamber of the engine. Prediction value calculation means for calculating a prediction value of intake air amount or intake pipe pressure, injection fuel amount calculation means for calculating the injection fuel amount using the calculated prediction value, and the calculated injection fuel amount for the engine. And a fuel injection means for injecting into the intake pipe.

[0008]

In this fuel injection control device, the behavior of the intake air amount or the intake pipe pressure is determined by using the information of the throttle opening or the accelerator operation amount, which is a factor that causes the change of the intake air amount or the intake pipe pressure. The state quantity to represent is calculated. That is, the state quantity representing the behavior of the intake air amount or the intake pipe pressure is calculated based on the transfer characteristic from the throttle opening or the accelerator operation amount to the intake air amount or the intake pipe pressure.

Then, using the calculated state quantity, the transfer characteristic, and the throttle opening or accelerator operation quantity of the engine detected by the second detecting means, the intake fuel is sucked at the time when it reaches the combustion chamber of the engine. The predicted value of the air amount or the intake pipe pressure is calculated. Then, the injected fuel amount is calculated using the predicted value.

Therefore, it is possible to always accurately grasp the behavior of the intake air amount or the intake pipe pressure and appropriately calculate the intake air amount or the intake pipe pressure value when the fuel enters the combustion chamber. Therefore, the fuel injection is controlled so that the amount of fuel that makes the mixing ratio appropriate when the injected fuel enters the combustion chamber is calculated.

[0011]

Embodiments of the present invention will now be described in detail with reference to FIG. FIG. 2 schematically shows an electronically controlled fuel injection type internal combustion engine to which the present invention is applied. In the figure, 10 is an intake pipe, 12 is a pressure sensor that detects the pressure in the intake pipe, 14 is a distributor that has a built-in angle sensor that detects crank angles of 2 ° and 180 °, and 16a.
16d is an injector for injecting fuel, 18 is an electronic control unit incorporating a microcomputer, 20 is an igniter for generating a high voltage for ignition, 22 is an intake air temperature sensor, 24 is a throttle valve, 26 is the opening of the throttle valve. A throttle sensor for detection, 28 is a water temperature sensor, and 30 is an oxygen concentration sensor.

The electronic control unit 18 receives the detection signals from the above-mentioned sensors and also receives a starter signal (S
TART), air conditioner signal (A / C), vehicle speed signal (VS)
P), the battery voltage (VB), etc. are also input, and the signal PM from the intake pipe pressure sensor 12 and 2 ° and 180 ° from the angle sensor in the distributor 14 are input.
The fuel injection pulse width is calculated using the crank angle signal of °, and the drive signal FI having a pulse width corresponding to the pulse width is individually output to the injectors 16a to 16d.

The microcomputer of the electronic control unit 18 includes an A / D converter 18a for converting an analog input signal into a binary signal, an input / output port (I / O) 18b,
It has a CPU 18c, a RAM 18d, a ROM 18e, a backup RAM 18f for holding information even after the ignition switch is turned off, and the like, which are connected by a bus 18g.

Further, the rotational speed NE is calculated from the crank angle 2 ° or 180 ° signal from the angle sensor in the distributor 14 and stored in the RAM 18d. In addition,
1 for performing the fuel injection control according to the present invention, that is, the state quantity calculating means for calculating the state quantity representing the behavior of the intake air amount or the intake pipe pressure described above,
The predictive value calculating means for calculating the predictive value of the intake air amount or the intake pipe internal pressure at the time when the injected fuel reaches the combustion chamber of the engine and the injected fuel amount calculating means for calculating the injected fuel amount (including various corrections) are Is also executed by the microcomputer in the electronic control unit 18.

Next, the operation of the microcomputer for executing each means according to the present invention will be described with reference to the flow charts of FIGS. 3 and 4. 3 and 4 are flowcharts showing different embodiments, both of which are 180 ° CA interrupt routines (a) performed at every crank angle of 180 °, and are fast enough to show the behavior of the intake pipe internal pressure. , For example, a constant time interrupt routine (b) which is performed at every small predetermined time such as several ms. In the following description, the calculation cycle of this constant time interrupt routine is ts
Show as.

First, in the 180 ° CA interrupt routine of FIG. 3A, a predicted value PMPR, which will be described later, is read in step 1, and the basic pulse width TP is known from the predicted value PMPR and the engine speed NE in step 2. Method, eg T
P = g (NE, PMPR) table is used to obtain the value, and in step 3, the detection signals from the cooling water temperature sensor 28, the intake air temperature sensor 22, the oxygen concentration sensor 30 and the like and the correction using the battery voltage VB are performed to finally obtain Then, the drive signal FI is individually output to the injectors 16a to 16d through the I / O 18b.
This corresponds to the injected fuel amount calculation means.

Further, in the constant time interrupt routine of FIG. 3B, the signals from the throttle opening sensor 26 and the pressure sensor 12 are A / D converted in step 4, and the throttle opening T
H and the intake pipe pressure PM are read, differences ΔTH and ΔPM between preset reference values THi and PMi are calculated, and these values TH, PM, ΔTH and ΔPM are stored in RAM1.
Store in 8d.

In step 5, the state quantity representing the behavior of the pressure in the intake pipe is calculated. That is, the state quantity Φ calculated and stored in the previous routine and the current step 4
Based on the transfer characteristics from the throttle opening to the intake pipe internal pressure, using the values of the changes ΔTH and ΔPM from the reference values of the throttle opening and the intake pipe internal pressure calculated and stored in
The state quantity Φ after ts time from the present time is calculated, and after the calculation, the calculated Φ is used as the state quantity to be used next time in the RAM1.
Store in 8d. As described above, in step 5, the state quantity after ts time (after one calculation cycle of the routine) is calculated, so the state quantity calculated in the previous routine becomes a value corresponding to the intake pipe internal pressure at the present time. . This corresponds to the state quantity calculating means.

Then, in step 6, the time tl from the injection of fuel to the entry into the combustion chamber and the current state quantity Φ
And a predicted value of the intake pipe pressure PMPR at the time when fuel enters the fuel chamber, that is, at a time point tl ahead of the present time, from the amount of change ΔTH from the reference value of the throttle opening calculated and stored in step 4. RAM18 the value
Store in d. This corresponds to a part of the predicted value calculation means.

Next, the state quantity calculating means and the predicted value calculating means will be described. First, the transfer characteristic from the throttle opening to the intake pipe internal pressure, which represents the behavior of the intake pipe internal pressure when the throttle valve 24 moves, is expressed by the linear ARMA model of the following equation.

[0021]

[Equation 1]

Here, A, B and C are constant matrices that can be predetermined according to the characteristics of the engine, ω is an internal state variable, and k is a value at time k, (k + 1).
Indicates that it is the value at the next time of k. Also ΔT
H and ΔPM represent changes in the throttle opening and the intake pipe internal pressure from a preset reference value as described above.

At this time, the above-mentioned internal state ω is calculated by the following equation.
The state quantity Φ (k + 1), which is the calculated value of Φ (k + 1) = (A−F · C) · Φ (k) + B · ΔTH (k) + F · ΔPM (k) ... where Φ (k) is the current state quantity, and Φ (k +
1) is the state quantity after ts time. Further, F is a constant matrix indicating the estimated gain, and is defined so that the eigenvalue of (A−F · C) is inside the unit circle (stable).

In particular, when F is selected so that the eigenvalue of (A-F-C) becomes completely zero, the estimation is quickly settled and the estimation performance is improved. Even if the initial value of Φ is different from the initial value of the actual internal state ω, Φ approaches ω because the function of correcting the actual intake pipe internal pressure value works by the estimated Gail matrix F, and The value of can be estimated.

The above-mentioned ω and Φ are vectors having the minimum number of elements required to represent the transfer characteristic from the throttle opening to the pressure in the intake pipe. That is, according to the above equation, the state quantity Φ
Obtaining (k + 1) corresponds to the state quantity calculating means according to the present invention. Next, using the current state quantity Φ,
A method for predicting the pressure in the intake pipe when fuel enters the combustion chamber will be described.

When the time from injection of fuel to the time of entering the combustion chamber is tl, this tl is generally expressed by a predetermined crank angle width, and therefore expressed by a function of the engine speed NE. Further, the calculation cycle in which the constant time interrupt routine of FIG. 3B is performed is indicated by ts as described above. Then, the intake pipe pressure PMPR at the time when the fuel enters the combustion chamber is predicted and calculated by the following equation.

M = [tl / ts + 0.5], v (1) = Φ (k) v (i + 1) = A · v (i) + B · ΔTH (k) (i = 1, 2 ... m) PMPR (K) = C · v (m + 1) + PMi ... Here, [tl / ts + 0.5] is tl / ts + 0.5.
Represents an integer not exceeding.

Therefore, m indicates the number of times when the time tl to be predicted is divided by the calculation cycle ts. PMi represents the reference value of the intake pipe internal pressure used in the equation. The prediction by this formula is that the intake pipe pressure tl of the characteristic shown by the formula is tl.
The latter value is approximated by PMPR (k) which is the value after mts. In the method of the present invention, since the state quantity Φ, which is the value calculated by the formula, is used, the past intake pipe internal pressure value is indirectly used by using the current intake pipe internal pressure value to determine the intake pipe internal pressure value. The predicted value PMPR is accurate because the state quantity representing the behavior can be accurately estimated.

Next, a flow chart according to another embodiment, which is executed by the microcomputer for the fuel injection control, will be described. In the flow charts of FIGS. 4 (a) and 4 (b), the calculation of the predicted value PMPR is actually required 18
The 0 ° CA interrupt routine is used. That is, in the constant time interrupt routine of FIG.
The throttle opening TH and the intake pipe pressure PM are read in step 5, and the differences ΔTH and ΔPM from the respective reference values are obtained and stored. In step 16, the state quantity Φ is calculated and the RAM 18d is calculated.
Remember.

On the other hand, in the 180 ° CA interrupt routine of FIG. 4A, the state quantity Φ is read in step 11, and the PMPR prediction calculation is performed in step 12. Step 1
Steps 3 and 14 are the same as steps 2 and 3 in FIG.
With such a flow, the constant time interrupt routine can be shortened, so that the CPU usage time can be shortened.

Here, the effect of doing so will be described with reference to FIG. In response to a change in throttle opening as shown in FIG. 5 (a) during acceleration, the response of the actual intake pipe internal pressure as shown by the solid line in FIG. 5 (b) is transferred from the throttle opening to the intake pipe internal pressure. Since it can be grasped by calculating by, the response obtained by advancing the actual value by the time tl can be predicted as shown by the dashed line in the figure.

That is, for example, it becomes possible to accurately predict the pressure in the intake pipe at the point B at the point D, which is a time tl before the injection of fuel into the combustion chamber. Note that this time tl changes depending on the engine speed even if the fuel injection time is constant, but it can be set to the minimum necessary time by changing the fuel injection timing. Since it becomes easier, the prediction accuracy becomes higher.

[0033]

As described above, the fuel injection control device for an internal combustion engine according to the present invention uses information on the throttle opening or the accelerator operation amount, which is a factor causing a change in the intake air amount or the intake pipe pressure. , A state quantity that represents the behavior of the intake air amount or the intake pipe pressure is calculated, and the calculated state amount is used to predict the intake air amount or the intake pipe pressure when the injected fuel reaches the combustion chamber. Since the fuel injection amount is calculated using the predicted value, the intake air amount or the intake air amount at the time when the fuel enters the combustion chamber is constantly grasped by accurately grasping the behavior of the intake air amount or the pressure in the intake pipe. The value of the intake pipe pressure can be accurately predicted.

Therefore, the first and second fuel injection amounts at the time of acceleration, which greatly contributes to the stability at the time of acceleration, etc., match the required values, and the transient performance of the engine can be improved. There is an effect that.

[Brief description of drawings]

FIG. 1 is a diagram showing the correspondence of claims to a fuel injection control device for an internal combustion engine according to the present invention.

FIG. 2 is a system configuration diagram schematically showing an electronically controlled fuel injection type internal combustion engine to which the present invention is applied.

3 is a flowchart for explaining the control contents of the present invention executed by a microcomputer in the electronic control unit 18 of FIG.

4 is a flowchart for explaining the control contents of a different example of the present invention executed by a microcomputer in the electronic control unit 18 of FIG.

FIG. 5 is a diagram showing the effects of the present invention and a conventional example in comparison.

[Explanation of symbols]

10 Intake Pipe 12 Pressure Sensor 14 Distributor 16a to 16d Injector 18 Electronic Control Unit with Built-in Microcomputer 20 Igniter 22 Intake Air Temperature Sensor 24 Throttle Valve 26 Throttle Sensor 28 Water Temperature Sensor 30 Oxygen Sensor

Claims (1)

[Claims] 1. A fuel injection control device for an internal combustion engine, wherein a predetermined delay occurs from the injection of fuel to the arrival of injected fuel in a combustion chamber of the engine, the first detecting the intake air amount of the engine or the intake pipe internal pressure.
And a second detecting means for detecting the throttle opening degree or accelerator operation amount of the engine, and the throttle opening degree based on the transfer characteristic from the throttle opening degree or accelerator operation amount to the intake air amount or the intake pipe pressure. Alternatively, a state quantity calculating means for calculating a state quantity representing the behavior of the intake air quantity or the intake pipe pressure from the accelerator operation amount and the detected value of the intake air amount or the intake pipe pressure, and the calculated state quantity and the transfer characteristic and throttle. Using the detected value of the opening degree or accelerator operation amount, the predicted value calculation means for calculating the predicted value of the intake air amount or the intake pipe internal pressure at the time when the injected fuel reaches the combustion chamber of the engine, and the calculated predicted value. An injection fuel amount calculation means for calculating the injection fuel amount using the fuel injection means, and a fuel injection means for injecting the calculated injection fuel amount into the intake pipe of the engine, The fuel injection control device for an internal combustion engine, characterized in that it comprises.