JPS63302158A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To restrain the fluctuation of an air-fuel ratio by operating a fuel injection amount through the correction of a basic fuel injection amount via a deceleration correction amount when an engine is in an deceleration condition, and limiting the fuel injection amount when the amount is equal to or less than the predetermined value and the basic fuel injection amount is equal to or larger than the predetermined value. CONSTITUTION:An operation condition detecting means (a) detects an engine operation condition and a basic fuel injection amount is operated by a basic injection amount operation means (c) on the basis of a detected value. On the other hand, a deceleration condition detecting means (b) detects an engine deceleration condition and on the basis of a detected value, a deceleration correction amount operation means (d) corrects the basic fuel injection amount. Also, a fuel injection amount operation means (e) operates a fuel injection amount on the basis of a correction amount via the means (d). Furthermore, a control means (f) limits the fuel injection amount to the predetermined value so that the amount will not be equal to or less than the predetermined value, when the amount is equal to or less than the predetermined value and a reference injection amount is equal to or over the predetermined value. And a control means (g) outputs an injection signal corresponding to the predetermined value limited with the means (f), and a fuel injection means (h) injects fuel corresponding to the injection signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fuel injection control device for an internal combustion engine such as an automobile, and particularly to a device that determines an optimal fuel injection amount by correcting a basic injection amount during deceleration.

(Prior art) In general, the deviation of the air-fuel ratio from the target air-fuel ratio during engine acceleration/deceleration is mostly due to quantitative changes in adhering fuel and floating fuel adhering to the intake manifold and intake ports of the intake system. The amount of adhering and floating fuel varies greatly depending on the operating condition of the engine. Furthermore, the amount of adhering and floating fuel changes with a certain delay in response to changes in operating conditions, and the time constant of this delay is also not constant. Further, changes in the amount of adhering and floating fuel vary not only depending on changes in operating conditions but also depending on the magnitude of the difference between the amount at that point in time and the amount in equilibrium state a (steady state a).

Therefore, as a conventional example, changes in adhesion and floating fuel are approximately determined from changes in intake pipe pressure and accelerator opening during a transient period, and the amount of fuel injection is increased during acceleration and decreased during deceleration, and when the engine is warmed up. In JP-A-58-144632 and JP-A-58-144634, the correction coefficients for acceleration increase and deceleration decrease are further corrected using a correction factor according to the cooling water temperature.
No. 5B-144636, No. 58-144637, and No. 5B-150033, each publication).

By the way, the present applicant has developed a system that can be accurately controlled under all acceleration/deceleration conditions, including transient conditions as described above, and can reduce matching time by minimizing complex corrections such as further corrections of various correction coefficients. A device that can be used has already been applied for (patent application
No. 0-243605). In this prior application, the transient correction amount DM required when calculating the actual injection amount (final injection amount) Ti is determined by adjusting the equilibrium IMφ corresponding to the equilibrium amount of adhesion and floating fuel in the intake system and the current fuel injection amount. The calculation is based on the correction coefficient DK which indicates the ratio of compensation.

The reason why such transient correction is necessary is that adhered fuel or floating fuel that adheres to the intake manifold or intake port of the intake system affects the air-fuel ratio and engine performance during transient periods.For example, when the throttle valve is fully open, If the throttle valve is rapidly decelerated, there may already be a large amount of wall flow when the throttle valve is fully open, causing the air-fuel ratio to become rich transiently, resulting in engine misfires, etc. This may lead to a decrease in performance, an increase in CO emissions, and a worsening of fuel efficiency. In particular, S P I (Single Po1n
Since there is a considerable distance between a single injector and each cylinder in an engine of the t injection type, the engine is greatly affected by such adhering and floating fuel.

(Problems to be Solved by the Invention) However, in such a conventional fuel injection control device for an internal combustion engine, the accuracy of the injector (especially linearity) deteriorates when performing weight reduction correction during deceleration operation. In some cases, the reduction correction during deceleration is performed even in a region where the injection pulse width is small, which causes a problem in that the air-fuel ratio becomes significantly leaner or richer due to deterioration of the accuracy of the injector. In other words, areas where injector accuracy deteriorates (injector NG)
zone), the air-fuel ratio may become significantly leaner or richer, as shown by the broken line in Figure 6(C), and the significantly leaner ratio may cause engine stalling, as shown by the broken line in Figure 6(d). or, conversely, due to excessive enrichment
o. Problems such as an increase in the amount of HC discharged occur. In addition, as shown in Figure 7, the injector flow characteristics show that in the region where the injection pulse width Ti is small (and therefore the injector flow rate is also small) (see the dashed line in the figure), the air-fuel ratio fluctuates, causing deceleration. The feel may not be smooth, resulting in an unsafe condition.

(Objective of the Invention) Therefore, the present invention calculates the fuel injection amount by correcting the basic injection amount by the deceleration correction amount when the engine is in a predetermined deceleration state, and also calculates the fuel injection amount when the fuel injection amount is equal to or less than the predetermined value and the basic injection amount By limiting the fuel injection amount to the predetermined value so that the fuel injection amount does not reach the predetermined value when The purpose is to suppress fluctuations in the air-fuel ratio, prevent engine stalling, and improve exhaust emission characteristics and driving sensation.

(Means for Solving the Problems) In order to achieve the above object, the fuel injection control device for an internal combustion engine according to the present invention has an operating state detection system that detects the operating state of the engine, as shown in FIG. Means a, deceleration state detection means for detecting that the engine has transitioned to a predetermined deceleration state; basic injection amount calculation means C for calculating a basic injection amount based on the operating state of the engine; deceleration correction amount calculating means d for calculating a deceleration correction amount for correcting the basic fuel injection amount based on the deceleration correction amount; and a fuel injection amount that corrects the basic fuel injection amount by the deceleration correction amount when the engine is in a predetermined deceleration state. a fuel injection amount calculation means e for calculating the fuel injection amount; a limiting means f for limiting the fuel injection amount to a predetermined value; and a control means g for outputting an injection signal corresponding to the fuel injection amount and outputting an injection signal corresponding to the predetermined value when the fuel injection amount is limited to the predetermined value. ,
a fuel injection means for supplying fuel based on the injection signal;
It is equipped with

(Function) In the present invention, a deceleration correction amount that corrects the basic injection amount of fuel is calculated based on the deceleration state of the engine, and when the engine is in a predetermined deceleration state, the basic injection amount is corrected by the deceleration correction amount and the fuel The injection amount is calculated. Then, when the fuel injection amount is less than a predetermined value and the basic injection amount is greater than or equal to the predetermined value, the fuel injection amount is limited to the predetermined value so that the fuel injection amount does not reach the predetermined value. Therefore, injection below a predetermined pulse width, which deteriorates the accuracy of the injector, is avoided,
Fluctuations in the air-fuel ratio are suppressed, preventing engine stalling and improving exhaust emission characteristics and driving sensation.

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

2 to 7 are diagrams showing one embodiment of the present invention, and are examples in which the present invention is applied to an SPi type engine.

First, the configuration will be explained. In Fig. 1, 1 is an engine, and intake air passes from an air cleaner 2 to a throttle chamber 3, and then is turned 0N10FF by a heater control signal S.
After being heated by the PTC heater 4, the fuel is supplied to each cylinder from each branch of the intake manifold 5, and the fuel is supplied to a single injector (fuel injection means) 7 provided upstream of the throttle valve 6 based on the injection signal St+. is injected by.

An ignition plug 8 is attached to each cylinder, and a high-pressure pulse PULSE is supplied to the ignition plug 8 from an ignition coil IO via a distributor 9.

The air-fuel mixture in the cylinder is ignited and exploded by the discharge of the spark plug 8 by the high-pressure pulse PULSE, and becomes exhaust gas.
Co, HC, NOx) are purified by a three-way catalyst and discharged from the muffler 13.

Here, the flow of intake air is controlled by a throttle valve 6 in the throttle chamber 3 that is linked to the accelerator pedal, and the throttle valve 6 is almost closed during idling. The air flow during idling passes through the bypass passage 14, and the opening signal 5I
The flow rate control valve 15 operated based on SC ensures the appropriate amount of air.

Further, a swirl control valve 16 is disposed near the intake boat of each cylinder.
6 is connected to a servo diaphragm 18 via a rod 17. A predetermined control negative pressure is applied to the servo diaphragm 18 from a solenoid valve 19, and the solenoid valve 19 converts the negative pressure supplied from the intake manifold 5 to the atmosphere based on the swirl control signal sscv having a duty value Dscw. By leaking, the controlled negative pressure introduced into the servo diaphragm 18 is continuously varied. The servo diaphragm 18 responds to the control negative pressure and adjusts the opening degree of the swirl control valve 16 via the rod 17.

The opening degree α of the throttle valve 6 is detected by the throttle valve opening sensor 21,
The temperature Tw of the cooling water is detected by the water temperature sensor 22.

Further, the intake air temperature TA is detected by an intake air temperature sensor 23 in the throttle chamber 3, and the engine crank angle Ca is detected by a crank angle sensor 24 built into the distributor 9. Note that the engine rotation speed N can be determined by counting pulses representing the crank angle Ca. An oxygen sensor 25 is attached to the exhaust pipe 11, and the oxygen sensor 25 is connected to the air-fuel ratio detection circuit 2.
Connected to 6. The air-fuel ratio detection circuit 26 is an oxygen sensor 25
A pump current is supplied to the exhaust gas, and the oxygen concentration in the exhaust gas is detected over a wide range from rich to lean based on the value of this pump current. The operating position of the transmission is detected by a position sensor 27, and the speed svsp of the vehicle is detected by a vehicle speed sensor 28. Furthermore, the operation of the air conditioner is detected by the air conditioner switch 29, and the operation of the power steering is detected by the power steering detection switch 30. Furthermore, the operation of the rear defogger etc. is detected by the electric load detection switch 31, and the battery voltage Vs is detected by the voltage sensor 3.
Detected by 2.

Each of the above sensors 21.22.23.24.25.27.2
The signals from 8.29.30.31.32 are input to the control unit 41, and the control unit 41 performs engine combustion control (ignition timing control, fuel injection control, etc.) based on these sensor information. That is, the control unit 41 has functions as a basic injection amount calculation means, a deceleration correction amount calculation means, a fuel injection amount calculation means, a restriction means, and a control means, and has the functions of a CPU 42, a ROM 4
3, RAM 44 and I10 port 45. The CPtJ42 imports necessary external data from the I10 boat 45 according to the program written in the ROM43, and while exchanging data with the RAM44, generates processing values necessary for fuel supply control and idle speed control. Calculate and process data as necessary! 10 output to port 45. Each of the above sensors 21.22.23.24.25.27.2 is installed on the I10 boat 45.
8.29.30.31 The signals from 32 are input, and each previous signal 5t=s S is input from the I10 boat 45.
+s I S IGN% S sew, S, is output.

The ROM 43 stores calculation programs for the CPU 42, and the RAM 44 stores data used in calculations in the form of a map or the like.

Note that a part of the RAM 44 is made up of a nonvolatile memory, and its stored contents are retained even after the engine 1 is stopped.

Next, the effect will be explained.

FIG. 3 is a flowchart showing a fuel injection control program, and this program is executed once every predetermined period. First, P calculates the basic injection 1tTp according to the following formula (■), and P2 calculates the transient correction amount K based on the engine operating condition.
Calculate ATHO3 (see Figure 4 (a) to (c). However, the solid line indicates when the degree of deceleration is relatively small, and the broken line indicates when the degree of deceleration is relatively large. (d), ( e
), where this transient correction amount KATHO3 is a delay correction amount corresponding to a delay in fuel flowing into the cylinder due to the influence of fuel adhesion to the intake system, floating fuel, etc. Note that the calculation of the transient correction amount KATHOS will be explained in detail in the program shown in FIG. 5, which will be described later.

However, K: constant Qa: intake air amount N: engine rotational speed Then, P, the transient correction amount KATH is added to the basic injection amount 'rp.
Injector NG whose value including O3 is as shown in Figure 7
Is it greater than the level LINJNG (Tp+KATHO3
>L INJNG) or not. Tp+KATH
Judging that the pulse width of O3>LINJNG is not a relatively small pulse width that would deteriorate the accuracy (linearity) of the injector, the fuel injection amount TpF is calculated according to the following formula in P4, and the amount is increased during normal acceleration or during deceleration. Perform weight loss correction.

TpF=Tp+KATHO3・・・・・・■Tp+KA
When THO35L INJNG, it is determined that there is a possibility of reducing the amount during deceleration in a region where the accuracy of the injector deteriorates, and the basic injection amount Tp is set to the injector NG level L at P.
It is determined whether Tp is larger than INJNG (Tp>LINJNG). When Tp > LINJNG, to prevent the air-fuel ratio from fluctuating due to deterioration of injector accuracy, the fuel injection amount T is set at P, as shown by the solid line in Fig. 4(a).
Limit pF to injector NG level LINJNG (T
pF=LINJNG). On the other hand, TpfaLINJ
I' when it's NG? , the transient correction amount KATHO3 is positive (K
ATHO3≧O) or negative, and KAT
When HO3 is positive, it is determined that the amount is increased during acceleration and the normal correction is made at P4, and when it is negative, even if it is decreased during deceleration, TpF = TpF = As Tp, no correction is applied. Next, the injection pulse width (final injection amount) Ti is calculated according to the following equation (2) using P, and the current process ends.

Ti=TpFXαXC0EFXTs ・−・−・−■
However, α: Air-fuel ratio feedback correction coefficient C0EF:
Various correction coefficients TS: Invalid pulse width Here, each of the air-fuel ratio feedbank correction coefficients α, various correction coefficients C0EF, and voltage correction numerator s are correction coefficients for correcting the fuel injection amount, but they have little relation to the present invention. Therefore, detailed explanation will be omitted. Note that the final injection amount Ti is I10
It is stored in the output register of the boat 45 as a voltage pulse width having a predetermined duty value, and an injection signal Stt corresponding to this Ti is output to the injector at a predetermined crank angle.

FIG. 5 is a flowchart showing a program for calculating the transient correction amount KATHO3.
This corresponds to step P described in the figure. First, the equilibrium adhesion amount MFH (MFH=func (Tw, Qa, N)
Calculate. This equilibrium adhesion fiMFH indicates the amount of wall flow bone of adhering fuel as a function of Tw, Qa and N.
The value tends to increase rapidly as the throttle opening approaches full opening. Then, the proportion KMF in pH
(KMF=func (Tw, Qa, N) is calculated. This quantity ratio KMF is Tw, Q as in the above-mentioned MFH.
It is calculated as a function of a and N, and corresponds to the evaporation rate of the wall flow bone of attached fuel. At pHs, the adhesion speed VMF is calculated according to the following equation (2); however, when the start SW is 0, VMF=0), and at P+a, the current adhesion amount MF is calculated according to the following equation (2).

VMF= (MFH-MF)XKMF ・・・・・・
■However, MF: Previous adhesion amount MF = MF -1+ V MF...
...■ However, MF-1: Previous adhesion amount VMF: Value calculated using the 0th formula. Next, PI5 calculates the correction factor GI (F) according to the following formula (■), and PI& performs transient correction according to the following formula Quantity KATHO3
is calculated and the current process ends.

G HF = G HF Q A CY L x G
HF F B Y A・・・・・・■ However, GHFQACYL: Deceleration correction factor GHFFBYA
: Air-fuel ratio correction factor K A T HOS = V M F x G HF
---...-■ However, the value obtained by VMF: PI3 Therefore, when the accelerator is closed and the engine reaches a predetermined deceleration state, the waveforms of each signal during deceleration up to idling are as shown in Figure 6. (see (a) in the same figure), the transient correction amount KAT HOS is calculated based on the operating state of the engine. Then, the transient correction amount KA is added to the basic injection amount 'rp.
The value added THO3 (i.e. TpF) is below the injector NG level LINJNG and 'rp is LINJ
When Tp is larger than NG, as shown by the solid line in the same figure (b),
F is restricted to LINJNG. Therefore, the same figure (C
), injection in the injector NG zone where the accuracy of the injector 7 deteriorates is avoided, and fluctuations in the air-fuel ratio are suppressed to prevent engine stalling (see the solid line in Figure 6(a) or the injector NG zone). (See Figure 4(e)). Furthermore, when the transient correction amount K A T 110S is negative, TpF=Tp
Since deceleration correction is not performed as shown in FIG. 6(d), misfires and instability during deceleration can be eliminated, and a smooth feeling of deceleration can be obtained.

(Effects) According to the present invention, when the engine is in a predetermined deceleration state, the basic injection amount is corrected by the deceleration correction amount to calculate the fuel injection amount, and when the fuel injection amount is below the predetermined value and the basic injection amount is Since the fuel injection amount is limited to the predetermined value so that the fuel injection amount does not reach the predetermined value when It is possible to suppress fluctuations in the air-fuel ratio, prevent engine stalling, and improve exhaust emission characteristics and driving sensation.

[Brief explanation of drawings]

Fig. 1 is a basic conceptual diagram of the present invention, Figs. 2 to 7 are diagrams showing an embodiment of the present invention, Fig. 2 is an overall configuration diagram thereof, and Fig. 3 is a diagram showing an embodiment of the present invention.
The figure is a flowchart showing the fuel injection control program, and Figure 4 is a waveform diagram showing the waveforms of each signal during deceleration.
Figure 5 is a flowchart showing the program that calculates the amount of transient correction, Figure 6 is a waveform diagram showing the waveform of each signal during deceleration to explain its effect, and Figure 7 shows the flow rate characteristics of the injector. It is a characteristic diagram. 1...Engine, 7...Injector (injection means), 41...
...Control unit (basic injection amount calculation means, deceleration correction amount calculation means, fuel injection amount calculation means, restriction means, control means).

Claims (1)

[Scope of Claims] a) Operating state detection means for detecting the operating state of the engine; b) Deceleration state detection means for detecting that the engine has transitioned to a predetermined deceleration state; c) Based on the operating state of the engine. d) deceleration correction amount calculation means for calculating a deceleration correction amount to correct the basic injection amount of fuel based on the deceleration state of the engine; e) deceleration correction amount calculation means for calculating a basic injection amount based on the deceleration state of the engine; a fuel injection amount calculating means for calculating a fuel injection amount by correcting a basic injection amount of fuel by the deceleration correction amount when in a deceleration state; g) limiting means for limiting the fuel injection amount to the predetermined value so that the fuel injection amount does not become less than the predetermined value when the fuel injection amount is greater than or equal to the predetermined value; g) outputting an injection signal corresponding to the fuel injection amount; an internal combustion engine, comprising: a control unit that outputs an injection signal corresponding to the predetermined value when fuel injection control device.