JP2956340B2 - 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 an internal combustion engine, and more particularly to a fuel injection control device for an internal combustion engine which has a variable valve timing device and controls the fuel injection amount by predicting an intake air amount. .

[0002]

2. Description of the Related Art A method is generally known in which a sensor value detected by a sensor such as an intake pipe pressure sensor or an air flow meter is directly used as an intake air amount for determining a fuel injection amount of an internal combustion engine. . However, according to this method, for example, during transient operation such as when the throttle is suddenly depressed with the accelerator pedal depressed, the sensor value itself deviates from the actual value due to sensor detection delay, etc., so that the air-fuel ratio during transient operation is accurately controlled. It was difficult to do. Therefore, in order to solve the above problem, in recent years, the throttle opening TA
A technology for predicting the intake air amount from the engine speed NE and the engine speed NE has been developed and is well known. This predicted intake air amount GNF
The method of calculating WD will be described in detail later. GNTA (a steady-state intake air amount determined by TA and NE) is obtained from a two-dimensional map using the throttle opening TA and the engine speed NE as parameters. Is basically determined by performing a predetermined operation on GNFWD. According to GNFWD, the amount of intake air actually taken in is always accurately obtained without delay, so that the air-fuel ratio can be accurately controlled even during the transient operation.

[0003]

In an internal combustion engine provided with a variable valve timing device (hereinafter referred to as VVT) for changing the valve timing of an intake valve, the throttle opening degree TA and the engine speed NE are the same. However, the actual intake air amount changes due to a change in the valve timing of the intake valve. On the other hand, the predicted intake air amount G
Since NFWD is uniquely calculated from the values of TA and NE via GNTA as described above, only one predicted intake air amount GNFWD is calculated when TA and NE are the same. Therefore, in the case of the internal combustion engine with VVT, the predicted intake air amount GNFWD deviates from the actual intake air amount except for a specific valve timing.
Even when the estimated intake air amount GNFWD is employed, there has been a problem that the air-fuel ratio cannot be accurately controlled during the transient operation.

Accordingly, the present invention has been made in view of the above problems, and in an internal combustion engine with a VVT, an air-fuel ratio can be accurately controlled even during a transient operation by always obtaining an accurate intake air amount regardless of valve timing. It is an object of the present invention to provide a fuel injection control device for an internal combustion engine.

[0005]

FIG. 1 is a block diagram showing the principle of the present invention for achieving the above object. Claims as shown in the figure
The invention described in the first aspect is based on the valve of the intake valve 2 depending on the engine state.
Variable valve timing system
3 is provided in the internal combustion engine 1 having the
The fuel injection amount of the internal combustion engine 1 is controlled based on the amount of incoming air.
To a fuel injection control device for an internal combustion engine having control means 4
In this case, the control means 4 operates at different valve timings.
A plurality of rotations of the internal combustion engine 1
Suitable for the valve timing from the number and throttle opening
To determine the intake air volume suitable for the valve status
Step 5 and the current valve timing corresponding to the engine status
The actual advance angle value which is the advance angle value of
And the valve state conformity determined from the plurality of maps
Calculation for calculating the predicted intake air amount based on the intake air amount
This is a configuration in which means 6 are provided . According to a second aspect of the present invention, there is provided a fuel injection control device for an internal combustion engine according to the first aspect.
In addition, the calculating means 6 calculates an optimum value according to the current engine state.
While calculating the target advance value which is the valve timing,
Detecting the temperature of the hydraulic oil of the variable valve timing device
And based on the target advance value and the temperature of the hydraulic oil,
This is a configuration for calculating an actual advance angle value.

[0006]

According to the first aspect of the present invention, during a transition,
Assuming that the valve timing of the intake valve 2 has been changed
Also, the calculating means 6 calculates the plurality of maps obtained from the plurality of maps 5 respectively.
Number of valve status compatible intake air volume and current valve timing
Valve timing based on the actual advance value
Is calculated. That is, during the transition
Even if the variable valve timing device 3 is changed, the calculating means 6 predicts an accurate intake air amount corresponding to an actual intake air amount for an arbitrary valve timing of the intake valve 2. For this reason, the control means 4 controls the intake
For any valve timing of the internal combustion engine 1
Is controlled to an optimum value. Claim 2
According to the invention, the calculating means 6 calculates an actual advance value.
The temperature of the hydraulic oil of the variable valve timing device 3
Variable valve according to the viscosity of hydraulic oil.
In consideration of the response delay of the
More accurate actual advance angle corresponding to changes in lube timing
The value can be determined.

[0007]

An embodiment of the present invention will be described with reference to the drawings.

FIG. 2 shows an embodiment of an internal combustion engine (engine) to which the present invention is applied and peripheral devices thereof. This embodiment is an example in which the present invention is applied to a four-cylinder four-cycle spark ignition type internal combustion engine as the internal combustion engine 1, and FIG. 2 shows a structural sectional view of an arbitrary one cylinder. Each part of the internal combustion engine is controlled by a microcomputer described later.

In FIG. 2, reference numeral 10 denotes an engine body, in which an engine block 22 houses a piston 23 which reciprocates vertically in the drawing. A combustion chamber 24 formed above the piston 23 is connected to an intake manifold 25 via an intake valve 26 (corresponding to the intake valve 2).
While being connected to an exhaust manifold 28 via an exhaust valve 27. Further, the combustion chamber 24
A spark plug 29 is provided such that a plug gap protrudes from the plug.

The upstream side of the intake manifold 25 is connected to an intake pipe 31 via a surge tank 30 in common with the four cylinders. A throttle valve 3 is provided in the intake pipe 31.
3. A hot wire type air flow meter 32 is provided. The throttle valve 33 has a configuration in which the opening is adjusted in conjunction with the accelerator pedal, and the opening is detected by a throttle position sensor 34. The hot wire air flow meter 32 has a hot wire 32a
The current value required to maintain a constant temperature is used as a signal of the flow rate of the intake air, that is, the signal of the intake air amount. An intake air temperature sensor 35 for measuring the intake air temperature is provided downstream of the hot wire air flow meter 32.

A bypass passage 36 bypassing the throttle valve 33 and connecting the upstream side and the downstream side of the throttle valve 33 is provided.
Idle speed control valve (ISCV) 37 whose valve opening is controlled by a solenoid in the middle of
Is installed.

Reference numeral 38 denotes a fuel injection valve which injects fuel into an air flow passing through the intake manifold 25 in accordance with an instruction from a microcomputer 21 described later. The oxygen concentration detection sensor (O ₂ sensor) 39 is connected to the exhaust manifold 2.
8 is provided so as to protrude partially therethrough, and detects the oxygen concentration in the exhaust gas before entering the catalyst device. Reference numeral 40 denotes a water temperature sensor which is provided so as to penetrate the engine block 22 and partially project into the water jacket, and detects the temperature of the engine cooling water. An igniter 41 opens and closes a primary current of an ignition coil (not shown).
Reference numeral 42 denotes a distributor having a cylinder discrimination sensor 43 for generating a reference position detection signal of the engine crankshaft, and a rotation angle sensor 44 for generating an engine speed signal at every 30 ° C., for example.

Reference numeral 46 denotes a hydraulically driven valve operating mechanism for changing the valve timing of the intake valve 26 and the exhaust valve 27. The hydraulic operating mechanism controls the hydraulic pressure supplied to the valve operating mechanism 46 in response to a signal from the microcomputer 21. Together with a control solenoid valve (hereinafter simply referred to as a solenoid valve) 45, a variable valve timing device 47 (VVT) corresponding to the variable valve timing device 3 is configured. The lubricating oil of the engine 10 having a predetermined oil pressure is supplied to the solenoid valve 45 as hydraulic oil. Reference numeral 48 denotes an oil temperature sensor for detecting the temperature of the lubricating oil of the engine 10 as the hydraulic oil, and its output value is used in the control of the present invention as described later. VVT
47 is a well-known structure that changes the opening / closing timing of the intake valve 26 or the exhaust valve 27 according to the hydraulic pressure of the hydraulic oil.

The microcomputer 21 for controlling the operation of each unit having such a configuration has a hardware configuration as shown in FIG. 2, the same components as those in FIG. 2 are denoted by the same reference numerals, and the description thereof will be omitted. In FIG. 3, a microcomputer 21 includes a central processing unit (CPU) 5.
0, a read-only memory (ROM) 51 storing a processing program, and a random access memory used as a work area.
An access memory (RAM) 52, a backup RAM 53 for retaining data even after the engine is stopped, an input interface circuit 54, an A / D converter 56 with a multiplexer, an input / output interface circuit 55, and the like are provided. Connected to each other.

The A / D converter 56 detects an intake air amount detection signal from the hot wire type air flow meter 32 and the intake air temperature sensor 3
5, a throttle opening detection signal from the throttle position sensor 34, a water temperature detection signal from the water temperature sensor 40, an oxygen concentration detection signal from the O ₂ sensor 39, and an oil temperature detection signal from the oil temperature sensor 48. The signals are sequentially switched and input through the input interface circuit 54,
It is converted from analog to digital and transmitted to the bus 57 sequentially.

The input / output interface circuit 55 receives a detection signal from the throttle position sensor 34 and a rotation speed signal corresponding to the engine rotation speed (NE) from the rotation angle sensor 44, and the like.
Input to 50.

The CPU 50 is connected to the input / output interface circuit 55 and the A / D converter 56 via a bus 57.
Various types of arithmetic processing are executed based on the data input through the ISCV 37 and the fuel injection valve 3 through the bus 57 and the input / output interface circuit 55.
8, by appropriately selecting and outputting to the igniter 41 and the hydraulic control solenoid valve 45, controlling the opening degree of the ISCV 37 to control the idle speed to the target speed, and the fuel injection time by the fuel injection valve 38, that is, the fuel injection time per unit time. The fuel injection amount and the injection timing are controlled, the ignition timing is controlled by the igniter 41, and the solenoid valve 4 is controlled.
5, the valve timing is controlled by the valve mechanism 46.

Next, the valve timing control by the VVT 47 will be described.

FIGS. 4A and 4B show an intake valve 26, respectively.
4 is a timing chart showing the valve timing of the most advanced angle (x = 60 ° CA) and the most retarded angle (x = 0 ° CA). 4 (A) and 4 (B), the intake valve 26 is closed at the VVT most retarded position (I.
C) The timing is such that the valve is closed at the most advanced VVT (I.
C) It is later than the timing (β ′> β). Generally, in the high engine speed region, the flow rate of the intake air flowing into the cylinder is high. Therefore, by delaying the closing of the intake valve 26, an inertia supercharging effect due to the inertial force of the intake air can be expected, thereby increasing the charging efficiency. Thus, the output torque can be increased. On the other hand, in the low rotation region, since the flow rate of the intake air is slow and the inertia force of the intake air is small, the closing of the intake valve 26 is advanced so that
It is possible to prevent the intake air in the cylinder from being pushed back into the intake port with the rise of the piston. As described above, the valve timing of the intake valve 26 is basically set such that the closing of the intake valve is delayed (retard side) as the engine speed is high, and the valve closing is advanced as the engine speed is low (advance angle). Side), the valve timing is controlled to the optimum valve timing between the most advanced angle and the most retarded angle.

FIG. 5 is a diagram showing the pressure change in the intake port during the intake stroke under both the conditions of the most advanced VVT and the most retarded VVT. In the drawing, the pressure change at the most advanced angle indicated by the solid line becomes a large positive pressure near the intake TDC, then becomes a large negative pressure in accordance with the downward movement of the piston 23, and after passing the BDC, the intake valve 26 closes. Is ventured. In addition, the pressure change at the most retarded time indicated by the dotted line is a temporary positive pressure at the intake TDC at which the intake valve 26 is opened, a large negative pressure thereafter, and the upward movement of the piston 23 after passing the BDC. And the pressure becomes positive again, and the intake valve 26 is closed. In FIG. 5, if the positive pressure in the intake TDC portion is not considered because it is an effect of the residual pressure of the exhaust gas. In the case of the most retarded angle, the most advanced angle corresponds to the amount that the intake air is pushed back by the positive pressure after BDC. The amount of intake air decreases as compared with the case of. However, in the high rotation region, the intake air having the inertia as described above is supplied into the cylinder even at the positive pressure after the BDC, so that the intake air amount is larger on the retard side. As described above, although it depends on the engine speed, it is clear from the figure that changing the valve timing of the intake valve 26 changes the pressure in the intake port during the intake stroke, thereby changing the amount of intake air. .

Therefore, as described above, the conventional problem arises that the predicted intake air amount uniquely obtained from the engine speed and the throttle opening deviates from the actual intake air amount that changes according to the valve timing. . Therefore, in the present embodiment, it is an object to accurately obtain the intake air amount at an arbitrary valve timing of the intake valve 26, and thereby to accurately control the air-fuel ratio.

For this reason, the microcomputer 21 in the present embodiment executes the processing of the flowchart described below in accordance with the program stored in the ROM 51,
The control means 4 (including the map 5 and the calculation means 6) according to the present invention is realized by software processing. Next, VVT control / prediction is performed as a control program constituting a main part of an embodiment of the present invention apparatus. A routine for calculating the intake air amount GNFWD will be described. FIG. 6 shows a flowchart of the above-described VVT control / predicted intake air amount GNFWD calculation routine. This routine is a subroutine started every time the main routine goes around. When the VVT control / predicted intake air amount GNFWD calculation routine is started, first, at step 102, the engine speed NE and the throttle opening at the present time are obtained from the detection signal from the rotation angle sensor 44 and the detection signal from the throttle position sensor 34. T
The data of A is read. Each of the read data is NE
₁ , TA ₁ . In the next step 104, various data of the engine at the present time are read from the detection signals of the above-mentioned sensors, and the VVT target advance value d, that is, the current engine operating state, together with NE ₁ and TA ₁ obtained in the step 102 The optimum valve timing of the intake valve 26 according to the above is calculated. In the next step 106,
The microcomputer 21 outputs a control output to the VVT 47 so that the valve timing of the intake valve 26 becomes the VVT target advance value d calculated in step 104. In the VVT 47, a hydraulic pressure corresponding to the VVT target advance value d is generated by the solenoid valve 45 based on a signal from the microcomputer 21, and this hydraulic pressure acts on the intake valve 26 side of the valve operating mechanism 46. The timing changes to the target advance value d.

Here, at a low temperature where the viscosity of the hydraulic oil is high,
Since the movement of the VVT 47 becomes slow, a time difference occurs between when the microcomputer 21 outputs the control output to the VVT 47 as described above and when the valve timing of the intake valve 26 actually reaches the target advance value d. That is, VV
A response delay occurs at T47. Then, the change in the actual intake air amount when the valve timing changes also gradually changes over a certain period of time in accordance with the response delay. Steps 108 and 110 described below are processes for making the predicted intake air amount when the valve timing changes close to the above-described actual intake air amount change. In step 108, the smoothing coefficient n is calculated from the map of the smoothing coefficient n shown in FIG. And step 1
In step 10, the VVT actual advance angle value c is calculated in consideration of the response delay of the VVT 47 by the following equation.

C (i) = c (i−1) + {d−c (i−1)} / n (1) From the above equation (1), the actual VVT advance value c at the time of passing the current routine (I) is obtained by dividing the difference between the target advance value d and the actual advance value c (i-1) at the time of passing the previous routine by the smoothing coefficient n into the actual advance value c (i-1). It is obtained by adding.
According to the above equation (1), by repeating the routine, the actual VVT advance value c gradually approaches the target advance value d over time from the advance value before the start of the change. Also,
The smoothing coefficient n is, as shown in FIG.
, The speed until the VVT actual advance value c reaches the target advance value d decreases as THO decreases (the smoothing coefficient n increases). The larger the THO, the faster the speed (the smaller the smoothing coefficient n). N = 1.0 next in the oil temperature THO ₁ in the steady warm-up is finished completely, the actual advance value c in this case becomes a target advance value d immediately. That is, in the steady state, VV
This means that there is almost no response delay at T47.

As described above, according to the map shown in FIG. 7 and the above equation (1), the response delay of the VVT 47 due to the viscosity of the hydraulic oil is taken into account, and the actual VVT advance angle value c corresponding to the actual change in the valve timing is taken into account. Can be requested. In the present embodiment, the smoothing coefficient n is obtained from the oil temperature THO by the oil temperature sensor 48, but the cooling water temperature THW by the water temperature sensor 40 also changes in the same manner as the oil temperature THO, and the VVT 47 similarly to the oil temperature THO. Can be a value representative of the viscosity of the hydraulic oil in the above, the same effect as described above can be obtained by obtaining the smoothing coefficient n from the cooling water temperature THW as shown in FIG. The provision of the temperature sensor 48 can be omitted.

In the next step 112, the above step 1
02, the value of the engine speed NE ₁ and the throttle opening TA ₁ at the present time, and the VV shown in FIG.
GNTA map 1 for T most advanced angle (corresponding to map 5 above)
From the time of most advanced GNTA (valve state adapted intake air amount)
Is calculated. Then, the calculated data is set to a. The next step 114, the NE _1, TA ₁ values and FIG. 8 (B) in GNTA map 2 for VVT most retarded shown (the map 5 in equivalent) from the time the most retarded GNTA (bulb-shaped
Calculated intake air volume) . Then, the calculated data is set to b. Here, GNTA is a steady-state intake air amount determined by the engine speed NE and the throttle opening TA.
However, in the internal combustion engine with VVT, the intake air amount changes depending on the valve timing of the intake valve as described above. For this reason, in the present embodiment, V shown in FIG.
The intake air amount when NE and TA are changed at the valve timing at the time of the most advanced VT is measured in advance, and G shown in FIG.
An NTA map 1 is created, and the VV map shown in FIG.
As shown in FIG. 8, the intake air amount is measured in advance when NE and TA are changed in the same manner as above at the valve timing at the T most retarded angle.
A GNTA map 2 shown in (B) is created. As described above, in this embodiment, the two GNs at the time of the most advanced VVT and the most retarded VVT are used.
A TA map is provided.

Next, the routine proceeds to step 116, where GNT is a GNTA value corresponding to the VVT actual advance angle value c according to the following equation.
Af is calculated.

GNTAf = (ab) × c / 60 + b (2) As shown in FIG. 9, the GNTA value corresponding to the VVT actual advance angle value c is changed to the most advanced value as shown in FIG. It is obtained by interpolating from a which is the GNTA at the time of the angle and b which is the GNTA at the most retarded time. VV with a valve timing displacement angle of about 60 ° CA
In the case of T, since the intake air amount changes almost linearly in accordance with the displacement of VVT, the G corresponding to the actual advance value c does not generate a large error in the primary interpolation as in the above equation (2).
NTAf can be determined.

Since the calculation of GNTAf is performed every time the routine is passed, it corresponds to the change of the valve timing caused by NE, TA and VVT 47 every moment.

In the next steps 118 to 122, a predetermined calculation is performed on the GNTAf corresponding to the VVT actual advance value c obtained in step 116, and the predicted suction corresponding to the VVT actual advance value c is performed. This is a process for calculating the air amount GNFWD. Accordingly, steps 112 to 12
The calculation means 6 described above is realized by the processing contents up to 2. Then, the control means 4 is realized together with the two GNTA maps shown in FIG.

Next, step 1 of the routine shown in FIG.
A method of calculating the predicted intake air amount GNFWD from GNTAf will be described. still,
In the following description, the above-mentioned GNTAf will be simply referred to as GNTA for convenience of explanation.

This embodiment is applied to an internal combustion engine in which the fuel injection amount is controlled based on the intake air amount and the engine speed. However, since the intake pipe pressure per revolution corresponds to the intake air amount, It is well known that the fuel injection amount may be controlled based on the intake pipe pressure per rotation and the engine speed. In the latter device, a diaphragm type pressure sensor is attached to the surge tank on the downstream side of the throttle valve, and an intake pipe pressure is detected by this pressure sensor, though not described with reference to the drawings.

However, as described above, during the transient operation, the change in the detected intake pipe pressure is delayed due to the response delay of the pressure sensor with respect to the actual change in the intake pipe pressure. Therefore, the present applicant calculates the intake pipe pressure in the steady state from the throttle opening and the engine speed without time delay, and performs a first-order delay processing on the calculated intake pipe pressure in the steady state so that there is no time delay. While calculating the intake pipe pressure at the present time, predicting the intake pipe pressure at the time of closing the intake valve at which the intake air amount to the engine combustion chamber is determined, further calculating the difference between both the calculated intake pipe pressure at the present time and the predicted time, An intake air amount estimating apparatus has been proposed in which this difference is added to the current measured intake pipe pressure to calculate an estimated value PMFWD (JP-A-2-42160).

That is, according to the proposed apparatus, first, the intake pipe pressure PMTA during steady running determined by the throttle opening TA and the engine speed NE is calculated. Accordingly, the intake pipe pressure PMTA changes as shown in FIG. 10 during acceleration in response to a change in the throttle opening without a time delay. on the other hand,
Since the actual intake pipe pressure changes through a first-order lag system of the intake pipe pressure PMTA during steady running with respect to a change in throttle opening, PMTA is calculated as shown in FIG. .

Subsequently, the PMCRT is once again subjected to the first-order lag processing as a value having the same response as the pressure sensor value PM, and FIG.
The smoothed value indicated by PMCRT4 at 0 is calculated in a half cycle of the calculation cycle of PMCRT. Assuming that the amount of air leaked from the throttle valve, the opening of the idle speed control valve, and the atmospheric pressure have not changed, the smoothed value PMCRT4 and the sensor value PM are the same.

Now, assuming that the time from the present time to the time when the intake valve is closed is T, T is calculated as a calculated value PM of the intake pipe pressure.
The equation of tA _i = tA _i-1 + TIM × (PMTA-tA _i-1 ) is repeatedly calculated by the number of times divided by the calculation cycle Δt of the CRT, and finally the predicted value tPMVLV
Is calculated. However, the initial value tA ₀ is PMCRT.

If PM and PMCRT4 are equal, tPM
VLV may be used as the predicted value, but there is actually a deviation, so the difference (tpMVL) between the calculated intake pipe pressure tPMVLV at the time of prediction and the current calculated intake pipe pressure PMCRT4 at the present time.
V-PMCRT4) is added to the current sensor-measured intake pipe pressure PM to obtain a predicted intake pipe pressure PMFWD when the intake valve is closed.

In the internal combustion engine which controls the fuel injection amount based on the intake air amount and the engine speed as in the present embodiment, the air flow meter 32 is located upstream of the throttle valve 33, so that the pressure sensor Is a value advanced in phase with respect to the measured value (intake pipe pressure) PM. Therefore, by delaying the measured intake air amount GN of the air flow meter 32 per rotation to produce a value GNSM corresponding to the measured intake pipe pressure value PM, the above-described logic is applied to the present embodiment, and the predicted intake air The quantity GNFWD can be obtained.

FIG. 11 shows the predicted intake air amount GNFWD.
2 is a flowchart of an embodiment of the main part of the present invention for calculating the following. The GNFWD calculation routine is started by the microcomputer 21, for example, every 8 msec. When this routine is started, first in step 202,
From the intake air amount Q measured by the air flow meter 32 and the engine speed NE measured by the rotation angle sensor 44, an intake air amount GN per one engine revolution is calculated.

Next, at step 204, VV shown in FIG.
G corresponding to the VVT actual advance angle value c obtained in step 116 of the T control / predicted intake air amount GNFWD calculation routine
Read NTA.

In the next steps 206 to 220,
First-order lag processing is performed on the intake air amount GNTA during the steady running. That is, in step 206, the engine speed N
E and a map of the time constant TIMCA of the first-order lag determined based on the intake air amount GNTA during steady running are stored in the ROM 51.
To calculate the first-order lag time constant TIMCA. Next, at step 208, a first-order lag processing value GNCRT corresponding to the first-order lag processing value PMCRT is calculated based on the following equation.

GNCRT _i = GNCRT _i−1 + (GNTA−GNCRT _i−1 ) × TIMCA (3) In the above equation (3), GNCRT _i−1 is the first-order lag processing value of the previous intake air amount. It is. In the next step 210, GN is set as a value having the same response as the smoothed value GNSM of the detected intake air amount of the air flow meter 32 during the transient operation.
The CRT is further subjected to a first-order lag processing by the following equation to obtain an average value GN
Calculate CRT4.

GNCRT4 _i = GNCRT4 _i−1 + (GNCRT−GNCRT4 _i−1 ) × K (4) In the above equation (4), GNCRT4 _i−1 is the previous smoothed value GNCRT4, and K is a constant, which is a coefficient for correcting a response delay amount by which the air flow meter 32 is on the upstream side of the throttle valve 33.

Subsequently, at step 212, the engine speed N
After searching the one-dimensional map in the ROM 51 according to E to calculate the time constant TIMC, in step 214, the smoothed intake air amount value GNSM corresponding to the measured intake pipe pressure PM is calculated by the following equation.

GNSM _i = GNSM _i−1 + (GN−GNSM _i−1 ) × TIMC (5) In the above equation (5), the smoothed intake air amount GNSM _i is determined by the time constant TIMC according to the engine speed NE. It has been corrected so that it has responsiveness. GNSM _i-1 is the previous average value GNSM.

Next, at step 216, the time T from the current time to the predicted intake air amount (that is, the closing time of the intake valve 26 at which the intake air amount to the engine combustion chamber is determined) is calculated. Thereafter, in step 218, this GNF
The execution cycle of the WD calculation routine is Δt (here, 8 _msec )
Then, the calculation of the following equation is repeatedly executed for the number of calculations represented by T / Δt.

TA _i = tA _i−1 + TIMCA × (GNTA−tA _i−1 ) (6) In the above equation (6), tA _i−1 is the previous smoothing value tA.
It is. The initial value tA ₀ is GNCRT. In step 220, the predicted intake air amount GNFWD at the time of closing the intake valve 26 is calculated by the following equation using the smoothed value tA _i calculated T / Δt times in the above step 218. After that, this routine ends.

GNFWD = GNSM + (tA _i −GNCRT4) (7) The predicted intake air amount GNFWD is equal to the predicted intake pipe pressure P.
With the same predicted value as MFWD, the intake air amount G during steady running is
This is a value obtained by performing first-order delay processing on NTA.

In the GNFWD calculation routine shown in FIG. 11, GNFWD is obtained using the GNTA corresponding to the actual VVT advance value c obtained in the routine shown in FIG. 6, so that the finally obtained GNFWD is When the valve timing is changed by the VVT 47, the change in the actual intake air amount, which changes every moment according to the change in the valve timing, is accurately represented without delay.

In this embodiment, the fuel injection amount TAU is calculated by multiplying the value of GNFWD by the fuel injection amount conversion coefficient tKINJ and multiplying or adding various correction values. For this reason, the calculated fuel injection amount TAU always becomes a stoichiometric air-fuel ratio without causing a response delay with respect to the actual intake air amount obtained as the predicted intake air amount GNFWD as described above. Therefore, according to the fuel injection control device of the present embodiment, even in the internal combustion engine provided with the VVT 47, the predicted intake air amount GNFWD matches the actual intake air amount for any valve timing of the intake valve 26 to be controlled. Since the intake air amount is indicated, the air-fuel ratio can be accurately controlled even during transient operation such as acceleration. As a result, in the VVT-equipped internal combustion engine, it is possible to improve exhaust emission, fuel efficiency, and drivability.

The present invention is not limited to the above embodiment, but includes an on / off type VVT that selectively uses either the advance side or the retard side as the valve timing of the intake valve. It is also applicable to internal combustion engines. In this case, in the flowchart shown in FIG. 6, the part where the VVT target advance value d switches to either the most advanced angle (x = 60 ° CA) or the most retarded angle (x = 0 ° CA) is described above. Although different from the embodiment, the other parts are completely the same as the above embodiment. Also in this case, the oil temperature TH
If O is low, the valve timing is switched, and the change in the intake air amount corresponding to this is accompanied by the above-described response delay. Therefore, GNTAf in step 116 and GN
By finding GNFWD by TAf every time the routine is passed, GNFWD can accurately adapt to the actual change in the intake air amount at the time of switching the valve timing.

In the above-described embodiment, the actual VVT advance value accompanied by a response delay is estimated in the processing of steps 108 and 110 in the flowchart shown in FIG. 6. However, this sensor is provided separately from the VVT advance value sensor. The actual VVT advance angle value may be obtained from the value. In this case, the value of GNFWD becomes closer to the actual intake air amount, so that the above effect can be made more effective.

[0053]

According to the present invention as described above, the following various effects can be realized. Claim 1
According to Ming, variable valve timing device during transient
Even if 3 is changed, the calculating means 6 predicts an accurate intake air amount corresponding to an actual intake air amount for an arbitrary valve timing of the intake valve 2. For this reason, the control means 4
Arbitrary valve timing of intake valve 2 during transition
In response, the fuel injection amount of the internal combustion engine 1 is controlled to an optimum value. Therefore, in the internal combustion engine provided with the variable valve timing device, it is possible to improve the exhaust emission, the fuel efficiency, and the drivability. Further, according to the second aspect,
According to the description, when the calculating means calculates the actual advance value, the variable
Configuration that reflects the temperature of the hydraulic oil in the lube timing device
Variable valve timing based on the viscosity of hydraulic oil
Actual valve timing, taking into account the response delay of the
A more accurate actual advance angle value corresponding to the change in
Can be.

[Brief description of the drawings]

FIG. 1 is a principle configuration diagram of the present invention.

FIG. 2 is a system configuration diagram illustrating an embodiment of an internal combustion engine and peripheral devices to which the present invention is applied.

FIG. 3 is a hardware configuration diagram of the microcomputer in FIG. 2;

FIG. 4 is a timing chart showing a case where the valve timing of the intake valve is the most advanced angle and a case where the valve timing is the most retarded angle.

FIG. 5 is a graph showing a change in pressure in an intake port during an intake stroke by V;
FIG. 5 is a diagram illustrating both conditions at the time of a VT most advanced angle and a VVT most retarded angle.

FIG. 6 is a flowchart of a VVT control / predicted intake air amount GNFWD calculation routine according to one embodiment of the present invention.

FIG. 7 is an explanatory diagram of a map of an average coefficient n used in the flowchart of FIG. 6;

8 is a GNTA used in the flowchart of FIG.
FIG.

FIG. 9 is a diagram illustrating a method of calculating GNTAf in the flowchart of FIG. 6;

FIG. 10 is a diagram illustrating the principle of a method for calculating a predicted intake pipe pressure proposed by the present applicant.

FIG. 11 is a flowchart illustrating a GNFWD calculation routine according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2, 26 Intake valve 3, 47 Variable valve timing device (VVT) 4 Control means 5 Map 6 Calculation means 10 Engine main body 21 Microcomputer 25 Intake manifold 28 Exhaust manifold 30 Surge tank 32 Hot-wire type air flow meter 33 Throttle valve 34 Throttle position sensor 39 Oxygen concentration (O ₂ ) sensor 40 Water temperature sensor 42 Distributor 44 Rotation angle sensor 45 Hydraulic control solenoid valve 46 Valve train 50 Central processing unit (CPU)

Claims (2)

(57) [Claims] An intake valve valve according to an engine state.
Equipped with a variable valve timing device that changes the imaging
The fuel of the internal combustion engine is provided on the
In a fuel injection control device for an internal combustion engine including a control means for controlling an injection amount , a plurality of the control means are provided corresponding to different valve timings.
From the rotational speed of the internal combustion engine and the throttle opening.
Valve status compatible intake air volume suitable for valve timing
And the advance value of the current valve timing corresponding to the engine state.
Calculating an actual advance value, and calculating the actual advance value and the plurality of actual advance values;
Of the intake air suitable for the valve condition obtained from the map
Calculation means for calculating the predicted intake air amount based on
The fuel injection control device for an internal combustion engine, which is a only formed by configuration. 2. The fuel injection control of an internal combustion engine according to claim 1.
In the apparatus, the calculation means may be an optimal valve timing according to a current engine state.
Calculate the advance angle value and adjust the variable valve timing.
The temperature of the hydraulic oil of the device is detected, and the target advance value and the
And calculating the actual advance angle value based on the temperature of the hydraulic oil.
Fuel injection control device for an internal combustion engine
Place.