JPS63176636A - Electronic control type fuel injector for internal combustion engine - Google Patents

Abstract

PURPOSE:To suppress surge by concentrating the air fuel ratio when the variation of revolution over a prescribed value is detected in the lean air fuel ratio operation. CONSTITUTION:In the ordinary operation state, the fundamental injection quantity signal supplied from a fundamental injection quantity setting means A is corrected through an air fuel ratio correcting means D by using the correction coefficient of a feed/forward correction coefficient setting means B so that a lean air fuel ratio is obtained. When the revolution variation quantity detected by a revolution variation detecting means C exceeds a prescribed value, the air fuel ratio is corrected by the air fuel ratio correcting means D so that the air fuel ratio becomes larger than an aimed lean air fuel ratio. Therefore, the surge in the lean air fuel ratio operation can be suppressed.

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> The following is a conventional example of an electronically controlled fuel injection device for an internal combustion engine (see Utility 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 C0EF 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, fuel injection during steady operation 1tTi=TpXcO
Calculate EF×α+Ts.

For example, in a single point injection system (hereinafter referred to as SPI system), an injection pulse signal among pulses corresponding to the fuel injection amount Ti is outputted to the fuel injection valve in synchronization with an ignition signal etc. every two revolutions 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 low-speed, low-load operating region of the engine.

In other words, when it is determined that the operation is in a predetermined low-speed, low-load operating region that does not require high output and may allow lean combustion, the fuel injection amount ( A system that controls fuel injection by switching the target air-fuel ratio (hereinafter referred to as stoichiometric air-fuel ratio control) 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 detected value of the oxygen sensor cannot be used during lean air-fuel ratio control, feedbank 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 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 fuel injection device for an internal combustion engine that can suppress surge while enabling lean air-fuel ratio control.

Means for Solving Problems> For this reason, the present invention, as shown in FIG. Feedforward correction coefficient setting means B for setting a feedforward correction coefficient so as to obtain a target lean air-fuel ratio that is leaner than the air-fuel ratio; and rotational fluctuation detection means C for detecting rotational fluctuations of the engine during lean air-fuel ratio control. When the rotational fluctuation is greater than a predetermined value, the set feedforward correction coefficient is adjusted so that the actual air-fuel ratio is enriched relative to the target lean air-fuel ratio in a lean air-fuel ratio region leaner than the stoichiometric air-fuel ratio. an air-fuel ratio correction means for correcting, a fuel injection amount setting means E for setting a fuel injection amount based on the feedforward correction coefficient corrected or set above and the basic injection amount, and a set fuel injection amount. and a driving means G for driving the fuel injection valve F based on the fuel injection valve F.

In this way, when rotational fluctuations exceeding a predetermined value occur, the actual air-fuel ratio is enriched by feedforward control in a lean air-fuel ratio region that is leaner than the stoichiometric air-fuel ratio, thereby suppressing rotational fluctuations. I made it.

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

In FIG. 2, a control bag W1 consisting of a microcomputer, for example, receives 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 a water temperature sensor 4. Coolant temperature signal, vehicle speed signal output from vehicle speed sensor 5, ON/OFF signal from idle switch 6, oxygen sensor 7
(a sensor that can mainly detect the air-fuel ratio near the stoichiometric air-fuel ratio depending on the oxygen concentration in the exhaust gas);
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 basic injection amount setting means, feedforward correction coefficient setting means, air-fuel ratio correction means, and 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 8.

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 the sampling number has reached 11 times or not. If YES, the process advances to S4 and all rotational speeds stored in the rotational 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
10 types of addresses corresponding to each
Data between C and C can be stored.

In S6, the amount of change in rotational speed during the sampling period ΔN (=N, l−N
+ ) is calculated. Here, the sampling period Δt is 1
00m5ec, 200sec, 300sec, 5
00m5ec 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 ΔV3p, and when acceleration driving is determined, the process advances to S9, and when decelerating driving is determined, the process advances to SIO. Furthermore, when determining steady operation, the process proceeds to Sll without determining rotational fluctuation.

In S9, the amount of change ΔN calculated in S6 is compared with the one-sided shift tolerance range -ΔNc, and when it is -ΔNc ΔN, it is determined that the amount of change ΔN is fluctuating toward one side.
The process proceeds to step 2, and when -ΔNc≦ΔN, it is determined that the rotational fluctuation is small, and the process proceeds to step 311.

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, in SIO, the amount of change ΔN is compared with the + side 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 311
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.
While s=O is stored in the RAM or the like, in S12, the state in which a surge has occurred is stored in the RAM or the like as the surge flag Fs""1.

With this surge judgment routine, 100m5ec, 2
Surge determination in lean air-fuel ratio control is performed during sampling periods of 00m5ec+300m5ec, 500m5ec, 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 a RAM or the like 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 322, 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 advances to S23, and if NO, the process advances to S24.

The conditions for establishing lean air-fuel ratio control are that the engine load (for example, 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 within a predetermined 4M (for example, 80
°C) or above, the vehicle speed is set to a predetermined value (e.g. 8 km/h)
) and above, and there are times when the engine is not idling (when the idle switch 6 is OFF).

In S23, it is determined whether the current determination that the lean air-fuel ratio control condition is met is the first determination that the lean air-fuel ratio control condition is met, and the answer is YES.
If , the process proceeds to 325, and if N'O, the process does not pass through S25 (proceeds to S26).

In 325, the air-fuel ratio setting coefficient n stored in the RAM is reset to the initial value (n-#FFH≠0), and then the process proceeds to 326.

In S26, 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 air-fuel ratio setting routine will be explained according to the flow chart of FIG. 5. In S31, it is determined whether the lean flag FL is 1 or O, and when F t = 1, that is, when the lean air-fuel ratio control condition is satisfied, the lean flag FL is set to 332. Proceed to F=O
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, proceed to 333.

In S33, a correction coefficient such as a mixture ratio correction coefficient K m l' + water temperature correction coefficient KTo, which will be described later, is set to O so that the air-fuel ratio becomes approximately the stoichiometric air-fuel ratio.

On the other hand, in S34, a correction coefficient such as A1 is searched from the map for the mixture ratio correction coefficient.

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

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, the basic injection amount Tp is determined from the engine speed N obtained from the ignition signal and the intake air flow rate Q (= In KS52, it is determined whether the lean flag FL is 1 or 0, and FL=1
In other words, when the lean air-fuel ratio control condition is satisfied, the process proceeds to 353, and when FL-0, the process proceeds to S54.

In S53, it is determined whether the surge flag F is 1 or 0,
When F3-0, that is, no surge has occurred, the process proceeds to S55, and when FS=1, that is, it is determined that a surge has occurred, the process proceeds to 356.

In S55, the air-fuel ratio setting coefficient n stored in the RAM is
It is determined whether or not is the initial value (n=#FFH), and if YES, it is assumed that no surge has occurred after the engine has started, and S57
If the answer is No, it is determined that there has been a history of surge occurrence after the engine was started, and the process advances to 364.

At 356, +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 858.

In S58, the newly set injection time setting value i is 10.
If it is YES, the process proceeds to S59, and if NO, the process proceeds to 360 without passing through S59.

In S59, +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 zero. Therefore, this routine is started every 10 m5ec, and the air-fuel ratio setting coefficient n takes the same value until the injection time setting value i goes from 0 to 10, that is, 100m5ec.
A new air-fuel ratio setting coefficient n is set every 00 m5ec.

In 360, it is determined whether the newly set air-fuel ratio setting coefficient n has reached the maximum value nmax (for example, n - # F E H), and if YES, the process advances to 361 and NO.
If so, proceed to 362.

In 361, the air-fuel ratio setting coefficient n is set to the maximum value nl1la so that the air-fuel ratio setting coefficient n does not exceed the maximum value nmax.
Clamp to x and proceed to 362. Here, the maximum value n
1sX 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 S62, 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 S63, various correction coefficients C0EF are calculated and set by the following equations based on the correction coefficients obtained in S33.
Proceed to 67.

CoEF=1+KIIr+KT11...+KHo7 Therefore, since a correction coefficient such as - is set to O in 333 as a mixture ratio correction coefficient, various correction coefficients C'OE F
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 following equation is calculated based on the mixture ratio correction coefficient obtained in the various correction coefficients C0EFt-334 in 354 and the correction coefficients such as □. Calculate and set, and proceed to 366.

C0EF=1 +Kmr+Kt, 4+...10KHoT
Therefore, at this time, the various correction coefficients C0EF are 1
is set to a value greater than .

In S65, the air-fuel ratio feedback correction coefficient α is set as a feed bank correction coefficient 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 S66.

Furthermore, when the lean flag FL=1, that is, the lean air-fuel ratio control condition is satisfied, and when the surge flag F3=0, and no surge has occurred after the engine is started, the lean burn searched in 332 is performed in S57. The correction coefficient L B CMA P is set, and the process proceeds to S63.

Further, even if FL=1 and FS=0, if it is determined that a surge has occurred even once after the engine is started, a lean burn correction coefficient LBC is calculated in S64 in the same manner as in 362 above. Note that the air-fuel ratio setting coefficient n at this time is, for example, the maximum value n, .

At 366, the fuel injection amount Ti is calculated using the following equation.

Ti=TpXα (orLBCMAP, LBC)XCO
EF+TS Note that T is a battery correction coefficient. Then, based on the calculated fuel injection amount Ti, 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 condition is satisfied and no surge has occurred at present or in the past immediately after engine startup, the lean burn correction coefficient L
Lean air-fuel ratio control is performed by feedforward control based on B CMA P so that the actual air-fuel ratio becomes the lean air-fuel ratio (S57, 363. and 566). 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, 365, and 5).
66).

Furthermore, immediately after 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 increase the actual air-fuel ratio (lean air-fuel ratio) by feedforward control. become

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

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

In this embodiment, when a surge occurs, the lean air-fuel ratio control is performed to gradually enrich the air-fuel ratio, but it may be possible to enrich the air-fuel ratio instantaneously.

<Effects of the Invention> As explained above, the present invention enriches the lean air-fuel ratio when a surge occurs during lean air-fuel ratio control, thereby preventing the actual air-fuel ratio from becoming excessively lean. Since it is possible to prevent surge generation, it is possible to improve fuel efficiency and suppress the occurrence of surges.
This allows for improved drivability.

[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

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; rotation fluctuation detection means for detecting rotational fluctuations of the engine during lean air-fuel ratio control; an air-fuel ratio correction means that corrects the actual air-fuel ratio in a lean air-fuel ratio region leaner than the air-fuel ratio, so that the actual air-fuel ratio is richer than the target lean air-fuel ratio;
a fuel injection amount setting means for setting a fuel injection amount based on the basic injection amount and a feedforward correction coefficient that has been corrected or set; and a driving means that drives a fuel injection valve based on the set fuel injection amount. An electronically controlled fuel injection device for an internal combustion engine, comprising: