JPS63186937A - Electronically controlled fuel injection device for internal combustion engine - Google Patents

Abstract

PURPOSE:To achieve the restraint of rotational variation or surge, by correcting an air-fuel ratio setting factor so that the target lean air-fuel ratio can be enriched, when the rotational variation of an engine is more than a prescribed value, even if the condition of lean air-fuel ratio is satisfied. CONSTITUTION:A means A which sets a basic injection quantity in response to the operating condition of an engine, and a means B which sets a feedforward correction factor so that the actual air-fuel ratio can reach a target air-fuel ratio leaner than the theoretical air-fuel ratio are provided respectively. And a means C which stores the air-fuel ratio setting factors for correcting the basic injection quantity, a means D which retrieves the air-fuel ratio setting factors, and a means E which detects the rotational variation of the engine during lean air-fuel ratio control are provided respectively. Further, a means F which rewrites the data in the means C into new air-fuel ratio setting factors when the rotational variation is more than a prescribed value is provided. Furthermore, a means G which sets the fuel injection quantity on the basis of the information from respective means A through C, and a means I which drives the fuel injection valve H are provided respectively.

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to an electronically controlled fuel injection device for an internal combustion engine.

(Prior art) Conventional examples of electronically controlled fuel injection devices for internal combustion engines include the following (see Utility Model Application No. 60-066558).
.

That is, from the intake air flow rate Q detected by an air flow meter etc. and the engine rotation speed N, the basic injection amount Tp=Kx
In addition to calculating Q/N (K is a constant), various correction coefficients COEF mainly depending on the water temperature, an air-fuel ratio feedback correction coefficient α set so that the actual air-fuel ratio becomes the stoichiometric air-fuel ratio, and a correction coefficient based on the battery voltage are calculated. After calculating Ts, the fuel injection amount Ti=TpXCOE during steady operation
Calculate F×α+Ts.

For example, in a single point injection system (hereinafter referred to as SP1 system), an injection pulse signal with a pulse width corresponding to the fuel injection amount Ti is output to the fuel injection valve in synchronization with an ignition signal etc. every A rotation of the engine. to provide fuel.

Incidentally, in recent years, for the purpose of improving fuel efficiency and purifying exhaust gas, some engines have been designed to control the air-fuel ratio so that the actual air-fuel ratio becomes thinner than the stoichiometric air-fuel ratio in the constant-speed, low-load operating region of the engine.

In other words, when it is determined that the engine is in a predetermined low-speed, low-load operation region that does not require high output and can be used for lean combustion, fuel injection is performed so that the actual air-fuel ratio becomes approximately the stoichiometric air-fuel ratio! (hereinafter referred to as stoichiometric air-fuel ratio control) is controlled by switching the target air-fuel ratio and setting a reduction so that the actual air-fuel ratio becomes a predetermined lean air-fuel ratio (hereinafter referred to as lean air-fuel ratio control). This aims to reduce fuel consumption and reduce harmful components in exhaust gas.

<Problems to be Solved by the Invention> By the way, when an oxygen sensor that mainly detects a value near the stoichiometric air-fuel ratio is used as an oxygen sensor for detecting the oxygen concentration in exhaust gas, that is, the actual air-fuel ratio, During control, feedback control can be performed to bring the actual air-fuel ratio closer to the stoichiometric air-fuel ratio based on the detected value of the oxygen sensor. However, since the combustion output value of the oxygen sensor cannot be used during lean air-fuel ratio control, feedback control cannot be performed.

For this reason, conventionally, during lean air-fuel ratio control, the fuel injection amount is controlled by feedforward control so as to reach a preset target lean air-fuel ratio.

By the way, in the low injection amount region of the fuel injection valve, the linearity between the injection pulse width and the injection amount is poor, and the fuel injection amount cannot be controlled with high precision.

As a result, when lean air-fuel ratio control is performed by feedforward control, control accuracy to the target lean air-fuel ratio is poor, and when the actual air-fuel ratio becomes excessively leaner than the target lean air-fuel ratio, surges (rotational fluctuations) occur. There is a problem in that this increases the amount of fuel and causes deterioration in drivability.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electronically controlled 411 fuel injection system for an internal combustion engine that can suppress surge while enabling lean air-fuel ratio control.

<Means for Solving the Problems> For this reason, as shown in FIG. Feedforward correction coefficient setting means B for setting a feedforward correction coefficient so that the target lean air-fuel ratio is leaner than the air-fuel ratio; and rewritable storage means C for storing the air-fuel ratio setting coefficient for correcting the basic injection amount. , a search means A for searching the air-fuel ratio setting coefficient from the storage means, a rotation fluctuation detection means E for detecting rotation fluctuations of the engine during lean air-fuel ratio control, and when the detected rotation fluctuations are above a predetermined value, The retrieved air-fuel ratio setting coefficient is corrected so that the actual air-fuel ratio becomes richer by a predetermined amount than the target lean air-fuel ratio, a new air-fuel ratio setting coefficient is set, and this new air-fuel ratio setting coefficient is stored in the storage means. a rewriting means F for rewriting data; a fuel injection amount setting means G for setting a fuel injection amount based on the calculated basic injection amount, feedforward correction coefficient, and air-fuel ratio setting coefficient; A driving means I for driving the fuel injection valve H based on the amount of fuel is provided.

In this way, even when the lean air-fuel ratio control conditions are met, when the engine rotational fluctuation is greater than a predetermined value, the air-fuel ratio setting coefficient is corrected to enrich the target lean air-fuel ratio, thereby suppressing the rotational fluctuation. I decided to do so.

Furthermore, by storing the air-fuel ratio setting coefficient, it is possible to suppress rotational fluctuations when the lean air-fuel ratio control is resumed after stopping the lean air-fuel ratio control.

<Example> An example of the present invention will be described below based on FIGS. 2 to 7.

In FIG. 2, a control device 1 consisting of, for example, a microcomputer includes an ignition signal (rotational speed signal) output from an ignition coil 2, an intake air flow rate signal output from an air flow meter 3, and an output from a water temperature sensor 4. Cooling water temperature signal output from the vehicle speed sensor 5, vehicle speed signal output from the vehicle speed sensor 5, ON-OFF signal from the idle switch 6, oxygen sensor 7 (a sensor that can mainly detect the air-fuel ratio near the stoichiometric air-fuel ratio based on the oxygen concentration in the exhaust gas) air-fuel ratio detection signal from
is entered. The control device 1 operates according to the flowcharts shown in FIGS. 3 to 7, and outputs a drive pulse signal to the fuel injection valve 8 via the drive circuit 9.

Here, the control device 1 constitutes a basic injection amount setting means, a feedforward correction coefficient setting means, a storage means (CRAM), a retrieval means, a rewriting means, and a fuel injection amount setting means. Further, the control device 1 and the drive circuit 9 constitute a drive means, and since the rotational speed is detected by the ignition signal of the ignition coil 2, the ignition coil 2 constitutes a rotation fluctuation detection means.

Next, the operation will be explained according to the flowcharts shown in FIGS. 3 to 7.

First, the surge determination routine will be explained based on the flowchart of FIG.

This routine is started every 100 m5ec by inputting a start signal.

Sl reads the rotational speed signal and vehicle speed signal from the ignition signal.

In S2, +1 is added to the number of sampling times n stored in the number of times memory (RAM), and the result is stored in the number of times memory as a new number of sampling times n.

In S3, it is determined whether or not the number of sampling times has reached 11. If YES, the process advances to S4, and all rotation speeds stored in the rotation speed memory (RAM) are set to initial values (for example, 0), while if NO, the process proceeds to S4. Sometimes, the process proceeds to S5 without initializing the rotational speed memory.

In S5, the detected rotational speed is stored in the address of the rotational speed memory corresponding to the newly set number of sampling times. Here, the rotation speed memory contains 100m5e.
Number of rotational speed samplings detected every c (100s
ec) 10 types of addresses corresponding to 1 s
Data between ecs can be stored.

In S6, the amount of change in rotational speed during the sampling period ΔN (=N-N+
) is calculated. Here, the sampling period Δt is 100
m5ec, 200sec, 300sec, 500
ssec and 1 sec. Therefore, at the beginning of sampling, the amount of change ΔN in the rotational speed is calculated in a sampling period of 100 m5ec.

In S7, the unit time is calculated from the detected vehicle speed VSF.

In S8, the current driving state is determined from the calculated vehicle speed change rate ΔVSF, and when acceleration driving is determined, the process proceeds to S9, and when deceleration driving is determined, the process proceeds to 310.Furthermore, when steady driving is determined, the process proceeds to Sll without determining rotation fluctuation. .

In S9, the amount of change ΔN calculated in S6 is compared with the m-tolerance range ΔNc, and when -ΔNc>ΔN, it is determined that the amount of change ΔN is largely fluctuating in one direction, and S1
The process proceeds to step 2, and when -ΔNc≦ΔN, it is determined that the rotational fluctuation is small, and the process proceeds to Sll.

In this way, during acceleration operation, it is determined that a surge has occurred when the amount of change ΔN is significantly fluctuating to one side.

On the other hand, at 510, the amount of change ΔN is compared with the + side shift tolerance range ΔNc, and when ΔNc<ΔN, the amount of change ΔN
It is determined that Δ has changed significantly to the + side, and the process proceeds to S12, where
When Nc≧ΔN, it is determined that the rotational fluctuation is small and Sll
Proceed to.

In this way, during deceleration operation, it is determined that a surge has occurred when the amount of change ΔN is significantly fluctuating on the positive side.

In Sll, the surge flag F indicates the state where no surge occurs.
, = 0, and stored in the RAM, etc., and in S12, the state in which a surge has occurred is stored in the RAM, etc., as the surge flag F, = 1.

With this surge judgment routine, 100m5ec, 20
Surge determination in lean air-fuel ratio control is performed during sampling periods of 0 m5 eC+ 300 m5 eC+ 500 m5 eC and 1 sec.

Furthermore, when it is determined that a surge has occurred, S1
In step 3, it is determined whether the current surge determination is the first surge determination, and if YES, the process proceeds to S14, and if NO, the surge determination routine is ended.

In S14, an air-fuel ratio setting coefficient n and an injection time setting value i, which will be described later, stored in the RAM are reset to zero.

Next, the lean air-fuel ratio control determination routine will be explained based on FIG. 4. In S21, various signals such as an ignition signal and an intake air flow rate signal are read.

In S22, it is determined whether the lean air-fuel ratio control condition is satisfied based on the detected various operating states, and if YES, the process proceeds to S23, and if NO, the process proceeds to S24.

The conditions for establishing lean air-fuel ratio control are that the engine load (e.g., basic injection amount) is in a low load range within a predetermined range, the rotation speed is in a low rotation range within a predetermined range, and the cooling water temperature is at a predetermined value (e.g., 80°C).
As described above, there are times when the vehicle speed is higher than a predetermined value (for example, 8 km/h) and the vehicle is not idling (when the idle switch 6 is OFF).

In S23, the fact that the lean air-fuel ratio control condition is satisfied is stored in the RAM as a lean flag FL=1.

On the other hand, in S24, the fact that the lean air-fuel ratio control condition is not satisfied is stored in the RAM as a lean flag FL=O.

Next, the target lean air-fuel ratio setting routine will be explained according to the flowchart in FIG. 5. In S31, the lean flag F
It is determined whether L is 1 or 0, and when FL=1, that is, when the lean air-fuel ratio control condition is satisfied, the process advances to S32 and FL=0.
If so, the process advances to S34.

In S32, the lean burn correction coefficient LBCMAP is set as a feedforward correction coefficient so that the air-fuel ratio becomes a target lean air-fuel ratio leaner than the stoichiometric air-fuel ratio. After searching from the fuel ratio map, the process advances to S33.

In S33, correction coefficients such as a mixture ratio correction coefficient Kljrl water temperature correction coefficient KTW, which will be described later, are set to 0 so that the air-fuel ratio becomes approximately the stoichiometric air-fuel ratio.

On the other hand, in S34, correction coefficients such as the mixture ratio correction coefficient Ksr are searched from the map.

Further, as shown in the flowchart of FIG. 6, the air-fuel ratio setting coefficient n is reset to 0 when the ignition switch is turned on.

Next, the fuel injection amount control routine will be explained according to the flowchart shown in FIG. This routine is started every 10m5ec.

In S51, a basic injection amount Tp (=K□·K is a constant) is calculated from the engine rotation speed N obtained from the ignition signal and the intake air flow i1Q.

In S52, it is determined whether the lean flag FL is 1 or O,
When Ft''1, that is, when the lean air-fuel ratio control condition is satisfied, the process proceeds to S53, and when FL=0, the process proceeds to S54.

In S53, it is determined whether the surge flag F is 1 or O,
When FS=o, that is, no surge has occurred, the process proceeds to S55, and when F,=1, that is, it is determined that a surge has occurred, the process proceeds to S56.

In S55, the air-fuel ratio setting coefficient n stored in the RAM is
is 0 or not, and if YES, it is determined that no surge has occurred after the engine has started, and the process proceeds to S57. If NO, it is determined that there has been a history of surges occurring after the engine has been started, and S5
Proceed to step 6.

In S56, the air-fuel ratio setting coefficient n is retrieved from the RAM based on the basic injection 1tTp and the rotational speed N.

Here, an air-fuel ratio setting coefficient n is stored in the RAM in association with Tp and N.

In 558, +1 is added to the previous injection time setting value i to set a new injection time setting value i, and then the process proceeds to 359.

In S59, the newly set injection time setting value i is 10.
It is determined whether or not the current value has been reached, and when the answer is YES, the process proceeds to S60, and when the answer is No, the process proceeds to S61 without passing through S60.

In S60, +1 is added to the previous air-fuel ratio setting coefficient n to set a new air-fuel ratio setting coefficient n, and the injection time setting value i is reset to O. Therefore, this routine is started every 10m5ec, and the air-fuel ratio setting coefficient n takes the same value until the injection time setting value i goes from O to 9, that is, during the period of 100IIIsec.
A new air-fuel ratio setting coefficient n is set every 100 m5ec.

In S61, it is determined whether the newly set air-fuel ratio setting coefficient n has reached the maximum value nmax (for example, n=1oo%). If YES, the process advances to S62, and if NO, the process advances to S63.

In S62, the air-fuel ratio setting coefficient n is set to the maximum value nIII so that the air-fuel ratio setting coefficient n does not exceed the maximum value n+nax.
Clamp to ax and proceed to S63.

Here, the maximum value n max is set so that the actual air-fuel ratio becomes a lean air-fuel ratio that is leaner than the stoichiometric air-fuel ratio.

In S63, a new lean burn correction coefficient LBC is calculated using the following equation.

LBC=LBCMAP+nXΔF Note that ΔF is a clamp concentration coefficient.

In S64, the newly set air-fuel ratio setting coefficient n is stored in the RAM.
to be memorized.

In this way, the air-fuel ratio setting coefficient n is increased to an air-fuel ratio at which no surge occurs.

In S65, various correction coefficients C0EF are calculated and set by the following equations based on the correction coefficients obtained in S33.
Proceed to 67.

Co E F ” 1 + @1.+ Ktw-+ K
Hot Therefore, since the first correction coefficient in the mixture ratio correction coefficient is set to 0 in 833, various correction coefficients C0
EF is set to 1.

On the other hand, when the lean flag FL=0, that is, when the lean air-fuel ratio control condition is not satisfied, the various correction coefficients C0EF are changed to the mixture ratio correction coefficient K obtained in S34 in S54.
Based on the correction coefficients such as sr, the following equation is used to calculate and set, and the process proceeds to S66.

C0EF=1 +K1. lr+Kt@+”・10K MO
? Therefore, at this time, the various correction coefficients C0EF are set to values exceeding 1.

In step 368, the air-fuel ratio feedback correction coefficient α is set so that the air-fuel ratio becomes the stoichiometric air-fuel ratio based on the actual air-fuel ratio detected by the oxygen sensor 7, and the process proceeds to S69.

Furthermore, when the lean flag FL=1, that is, the lean air-fuel ratio control condition is satisfied, and when the surge flag F=0 and no surge has occurred after the engine is started, the lean The burn correction coefficient L B CMAP is set, and the process proceeds to S65.

Furthermore, even if FL=1 and F, -〇, if it is determined that a surge has occurred even once after the engine has started, in S66,
After retrieving the air-fuel ratio setting coefficient n from the RAM, a lean burn correction coefficient LBC is calculated in S67 in the same manner as in S63.

In step 369, the fuel injection amount Ti is calculated using the following equation.

Ti=Tpxα(orLBCMAP,LBC)XCOE
F+Ts Note that T is a buffer correction coefficient.

Based on the calculated fuel injection ITi, it is output to the fuel injection valve 8 via the drive circuit 9 in synchronization with, for example, a reference signal (rotation speed) from the ignition coil 2 to perform fuel injection.

When fuel injection control is performed in this way, when the lean air-fuel ratio control conditions are met and a surge does not occur immediately after engine startup, feedforward control is performed based on the lean burn correction coefficient LBCMAP to adjust the actual air-fuel ratio to Lean air-fuel ratio control is performed to maintain the fuel ratio (357
．． S65 and 569).

Therefore, in this operating range, it is possible to improve fuel efficiency and purify exhaust gas.

On the other hand, when the lean air-fuel ratio control condition is not satisfied, the fuel injection control is controlled by feedback control so that the actual air-fuel ratio becomes the stoichiometric air-fuel ratio (S54, S68, and 569).

Furthermore, when a surge occurs, even if the lean air-fuel ratio control conditions are met, the air-fuel ratio setting coefficient n is increased every 100 m5ec to gradually enrich the actual air-fuel ratio (lean air-fuel ratio) through feedforward control. .

Then, when the predetermined lean air-fuel ratio is reached, the air-fuel ratio is controlled to become the actual air-fuel ratio.

As a result, even if the injection characteristics of the fuel injector 8 in the low injection amount range are poor and the actual air-fuel ratio is excessively lean due to the lean air-fuel ratio control and a surge occurs, the actual The air-fuel ratio is enriched and surge generation can be suppressed, thereby improving drivability.

The air-fuel ratio setting coefficient, which is set to enrich the target lean air-fuel ratio when a surge occurs, is updated and stored.
When the lean air-fuel ratio control is resumed after the lean air-fuel ratio control is stopped, the actual air-fuel ratio is richer than the target lean air-fuel ratio.

Therefore, the generation of surge can be suppressed at that time.

Furthermore, when the ignition switch is turned on, the RA
Since the air-fuel ratio setting coefficient n of M is reset to O, the surge can be suppressed even when the injection amount of the fuel injection valve temporarily decreases and a surge occurs.

In this embodiment, when a surge occurs, the air-fuel ratio control is gradually enriched from the lean air-fuel ratio control to the stoichiometric air-fuel ratio control, but the air-fuel ratio control may be enriched instantly.

<Effects of the Invention> As explained above, the present invention enriches the lean air-fuel ratio in control when a surge occurs during @lean air-fuel ratio control, so the actual air-fuel ratio is not excessively adjusted. Since dilution can be prevented, surge generation can be suppressed while improving fuel consumption, thereby improving drivability.

Furthermore, since the air-fuel ratio selection coefficient is newly set and stored, it is possible to suppress the occurrence of surge when switching to lean air-fuel ratio control again.

[Brief explanation of the drawing]

FIG. 1 is a diagram corresponding to claims of the present invention, FIG. 2 is a configuration diagram showing an embodiment of the present invention, and FIGS. 3 to 7 are flowcharts of the same. 1... Control device 2... Ignition coil 3...
Air flow meter 7...Oxygen sensor 8...Fuel injection valve 9...Drive circuit Patent applicant Japan Electronics Co., Ltd. Representative Patent attorney Fujio SasashimaFigure 2Figure 4Figure 5Figure 6

Claims (1)

[Claims] Electronically controlled fuel for an internal combustion engine that performs lean air-fuel ratio control using feedforward control so that when a predetermined lean air-fuel ratio control condition is detected in a predetermined operating region, the actual air-fuel ratio is leaner than the stoichiometric air-fuel ratio. The injection device includes a basic injection amount setting means for setting a basic injection amount according to engine operating conditions, and a feed for setting a feedforward correction coefficient so that the actual air-fuel ratio becomes a target lean air-fuel ratio leaner than the stoichiometric air-fuel ratio. forward correction coefficient setting means; rewritable storage means for storing an air-fuel ratio setting coefficient for correcting the basic injection amount; search means for searching the air-fuel ratio setting coefficient from the storage means; and an engine under lean air-fuel ratio control. rotational fluctuation detection means for detecting rotational fluctuation of the engine; and when the detected rotational fluctuation is equal to or greater than a predetermined value, the retrieved air-fuel ratio setting coefficient is configured to make the actual air-fuel ratio richer than the target lean air-fuel ratio by a predetermined amount. rewriting means for rewriting data in the storage means to the new air-fuel ratio setting coefficient; An internal combustion engine comprising: a fuel injection amount setting means for setting a fuel injection amount based on a fuel ratio setting coefficient; and a driving means for driving a fuel injection valve based on the set fuel injection amount. Electronically controlled fuel injection device.