JPS63140840A - Electronic control fuel injection device for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve a responsiveness as well as to improve fuel consumption and drivability, by selecting a feedforward correction factor at the load variation initial stage, and afterward a feedback correction factor, respectively when performing control over a lean air-fuel ratio, while renewing a learning correction factor by both these correction factors. CONSTITUTION:A feedback correction factor setting device F sets a feedback correction factor on the basis of a deviation between a detection value out of an air-fuel ratio detecting device A and a desired air-fuel ratio at the lean side, and a feedforward correction factor setting device E sets such a feedforward correction factor as becoming the desired air-fuel ratio on the basis of engine speed and fundamental fuel injection quantity. When a load variation judging device D has judged that a load variation is more than the specified one on the basis of variations in the fuel injection quantity, a first selecting device G selects the feedforward correction factor and afterward the feedback correction factor, respectively. A renewal device K renews a learning correction factor of a memory device I corresponding to the engine speed and the fundamental fuel injection quantity on the basis of both these correction factors.

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to an electronically controlled fuel injection system 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 fiTi=TpXcOE during steady operation
Calculate F×α+Ts.

For example, in a single point injection system (hereinafter referred to as SP1 system), the fuel injection valve 1iTi is injected into the fuel injection valve in synchronization with an ignition signal, etc. every A rotation of the engine.
outputs an injection pulse signal with a pulse width corresponding to the pulse width to supply fuel to the engine.

Incidentally, in recent years, for the purpose of improving fuel efficiency and purifying exhaust gas, the air-fuel ratio has been controlled so that the actual air-fuel ratio becomes thinner than the stoichiometric air-fuel ratio in the engine low-speed, low-load operating region.

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 ( (hereinafter referred to as stoichiometric air-fuel ratio control), and fuel injection control (hereinafter referred to as lean air-fuel ratio control) 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. This aims to reduce fuel consumption and reduce harmful components in exhaust gas.

<Problems to be Solved by the Invention> However, in such conventional electronically controlled fuel injection systems, when switching suddenly from stoichiometric air-fuel ratio control to lean air-fuel ratio control during steady operation, the engine output suddenly decreases. The problem is that the driving feeling deteriorates.

In addition, immediately after transitioning from acceleration or deceleration to steady operation, which is an operating range in which lean air-fuel ratio operation is possible, unless you suddenly switch to lean air-fuel ratio control, fuel efficiency or NO
There is a problem that reduction of X cannot be achieved. Alternatively, at the time of the above-mentioned transition accompanied by large load fluctuations, the torque fluctuations occurring at that time can be suppressed by abruptly switching to lean air-fuel ratio control, thereby suppressing deterioration of driving feeling.

However, if this is done using feedback control, the actual air-fuel ratio cannot be suddenly changed to a lean air-fuel ratio due to a delay in the detection response of the oxygen sensor that detects the actual air-fuel ratio. For this reason, when suddenly controlling the actual air-fuel ratio to a lean air-fuel ratio, feedforward control may be considered, but in feedforward control, the shift to lean air-fuel ratio control may occur due to, for example, the injection characteristics of the fuel injector or changes over time. Sometimes, it is difficult to control the actual air-fuel ratio to the target lean air-fuel ratio with high precision, leading to increased NOx emissions and deterioration of drivability due to surge generation.

The present invention has been made in view of the above circumstances, and provides an electronically controlled fuel that can reduce NOx emissions immediately after acceleration driving, improve fuel efficiency, and improve drivability even when lean air-fuel ratio control is performed. The purpose is to provide an injection device.

Means for Solving the Problems> Therefore, as shown in FIG. 1, the present invention provides air-fuel ratio detection means A for detecting the actual air-fuel ratio of the engine, and load detection means B for detecting the engine load. a load change rate calculation means 0 for calculating a load change rate based on the detected load; a load change rate determination means 0 for determining whether the calculated load change rate is equal to or greater than a predetermined value; and a stoichiometric air-fuel ratio. Feedforward correction coefficient setting means E for setting a feedforward correction coefficient so as to obtain a substantially constant lean air-fuel ratio; a feedback correction coefficient setting means F that sets a feedback correction coefficient to the feedforward correction coefficient during a predetermined time period at the beginning of the lean air-fuel ratio control when the load change rate is determined to be equal to or greater than a predetermined value; a first selection means G for selecting a feedback correction coefficient;
a second selection means H that selects the feedback correction coefficient from the start of the lean air-fuel ratio control when the load change rate is determined to be less than a predetermined value; and a rewritable second selection means H that stores a learning correction coefficient that corrects the fuel injection amount. a storage means (2), a search means J for searching the learning correction coefficient from the storage means, and setting a new learning correction coefficient based on the set feedforward correction coefficient and feedback correction coefficient, and performing the new learning correction. The updating means updates the data stored in the storage means I to the coefficients, the feedforward correction coefficient selected by the first selection means G, the searched or newly set learning correction coefficient, or the first or A fuel injection setting means for setting the fuel injection amount based on the feedback correction coefficient selected by the second selection means G, H, and a driving means N for driving the fuel injection valve M according to the set fuel injection amount. I made sure to prepare the following.

(Function) In this way, when transitioning from acceleration/deceleration operation where the load change rate is above a predetermined value, that is, above a predetermined value, to lean air-fuel ratio control, the feedforward control is used to rapidly change the actual air-fuel ratio to lean air-fuel ratio control at the initial stage. After the fuel ratio is set, the actual air-fuel ratio is brought closer to the target lean air-fuel ratio by feedback control.On the other hand, when the load change rate is less than a predetermined value, the actual air-fuel ratio is brought closer to the target air-fuel ratio by feedback control at the same time as starting the lean air-fuel ratio control. do it like this.

Further, a fuel injection amount during feedforward control is calculated based on a learning correction coefficient obtained from a feedforward correction coefficient and a feedback correction coefficient during feedforward control.

<Example> An example of the present invention will be described below based on FIGS. 2 to 6.

In FIG. 2, a control device 1 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. A cooling water temperature signal, a vehicle speed signal output from the vehicle speed sensor 5, an ON/OFF signal from the idle switch 6, an oxygen sensor 7 as an air-fuel ratio detection means (a wide range of air-fuel ratios including the stoichiometric air-fuel ratio of 4 depending on the oxygen concentration in the exhaust gas) The air-fuel ratio detection signal from a sensor that can detect the air-fuel ratio is manually generated. The control device 1 operates according to the flowcharts shown in FIGS. 1 to 6, and outputs a drive pulse signal to the fuel injection valve 8 via a drive circuit 9.

Here, the control device 1 includes a load change rate calculation means, a load change rate means, a feedforward correction coefficient setting means, a feedback correction coefficient setting means, first and second selection means, a storage means (RAM), a search means, and an update means. and a fuel injection amount setting means.

Further, the control device 1 and the drive circuit 9 constitute a drive means. Furthermore, since the rate of change in the basic injection amount calculated from the flow rate of intake air per engine revolution is used as the rate of change in load, the air flow meter 3 constitutes a load detection means.

Next, the operation will be explained according to the flowcharts shown in FIGS. 3 to 6.

First, the fuel injection amount calculation routine will be explained based on FIG. 3. At Sl, various signals such as an ignition signal and an intake air flow rate signal are read.

In S2, the basic injection amount Tp (=KQ) is determined from the engine rotational speed N obtained from the ignition signal and the intake air flow rate Q.

−, is a constant).

33 to $7, lean air-fuel ratio control conditions are determined. That is, in S3, the calculated basic injection amount Tp is set to the set value T.
It is determined whether or not it is within the range from pl to Tp2. If YES, proceed to s4; if NO, proceed to S2.

In S4, it is determined whether the engine rotation speed N is within the range from the set value N to N2, and if YES, the S
If the answer is No, the process advances to 322.

In S5, it is determined whether or not the detected cooling water temperature Tw is equal to or higher than a predetermined value (for example, 80° C.). If YES, the process proceeds to S6; if NO, the process proceeds to S22.

In S6, it is determined whether the idle switch 6 is ON (when the intake throttle valve is fully open) or OFF. If it is OFF, the process proceeds to S7, and if it is ON, the process proceeds to S22.

In S7, the detected vehicle speed is set to a predetermined value (for example, 8 km/h).
) or more, and if YES, proceed to S8; if NO, proceed to S22.

When the lean air-fuel ratio control condition is thus determined (see FIG. 7), in S8, the difference ΔTp in the basic injection amount 'rpO calculated last time and this time is calculated.

In S9, the absolute value 1ΔTpl of the calculated difference is set to the predetermined value Δ
It is determined whether or not the TpL is exceeded. If YES, the process proceeds to SIO; if NO, the process proceeds to 315.

In SIO, the count value of the timer is reset and a new count is started, and the process proceeds to Sll.

In Sll, the first set time TI (for example, l s
ec (refer to Figure 8) has elapsed, and select YES.
If so, the process advances to S12, and if No, the process advances to S22.

In S12, the second set time T2 (for example, 1.2
38C (see Figure 8) has passed, and YE
If S, the process advances to S17, and if No, the process advances to S13.

In S13, a lean burn correction coefficient LBC as a feedforward correction coefficient is searched from the three-dimensional map based on the engine rotational speed N and the basic injection tTp.

Here, the lean burn correction coefficient is stored in a three-dimensional map so that the air-fuel ratio becomes the leanest during road driving, and as the load increases, the air-fuel ratio approaches the stoichiometric air-fuel ratio.

314, the lean burn learning correction coefficient LBCL, which will be described later, is
RN is searched from a learning map such as PAM based on the engine rotational speed N and the basic injection amount 'rp.

On the other hand, in S15, +1 is added to the count value of the timer to obtain a new count value, and the process proceeds to S16.

In S16, the count value of the timer is equal to the first set time T.
, it is determined whether or not the period has elapsed, and if YES, the process proceeds to S17.
If the answer is NO, the process advances to S22.

In S17, the detection signal of the oxygen sensor 7 is read, and 31
At step 8, the actual air-fuel ratio is searched from the air-fuel ratio map based on the detection signal of the oxygen sensor 9, and the process proceeds to step S19.

In S19, the searched air-fuel ratio, that is, the actual air-fuel ratio, is compared with the target lean air-fuel ratio, and if the actual air-fuel ratio is lean, the process proceeds to S20, and if it is lean, the process proceeds to S21.

In S20, a predetermined value ΔL is subtracted from the previously set lean burn correction coefficient LBC as the feedback correction coefficient to set a new lean burn correction coefficient LBC so that the actual air-fuel ratio approaches the target lean air-fuel ratio.

On the other hand, when the actual air-fuel ratio is the target lean air-fuel ratio, the previous lean burn correction coefficient LBC is set as is.

On the other hand, in S21, a predetermined value ΔL is added to the previously set lean burn correction coefficient LBC to create a new lean burn correction coefficient' so that the actual air-fuel ratio approaches the target lean air-fuel ratio.
Set LBC.

Then, in S23, the lean burn correction coefficient LBC and the lean burn learning correction coefficient LBCLR retrieved in S13 are
Lean burn correction coefficient L set in N or S21
Based on BC, the fuel injection amount Ti is calculated using the following equation.

T i =TpX (LBC+LBCLRN)XCOE
FXKBLRC+Ts COEF is various correction coefficients including water amount etc. Ts is correction coefficient based on battery voltage KBLRC is a learning coefficient set at the time of stoichiometric air-fuel ratio control to correct changes over time of the fuel injection valve 8 and the like.

It should be noted that during the feedback control from 315 to S21, the lean burn learning correction coefficient LBCLRN is set to zero.

On the other hand, during the first set time T+ even if the lean air-fuel ratio control condition is not determined or is determined, the fuel injection amount Ti is calculated by the following formula in S22 so that the actual air-fuel ratio becomes approximately the stoichiometric air-fuel ratio. do.

Ti=TpXαXC0EFXKBLRC+Tsα is an air-fuel ratio feedback correction coefficient set so that the actual air-fuel ratio becomes the stoichiometric air-fuel ratio, as in the conventional example.

In this way, the fuel injection amount Ti calculated in S23 or S22 is used to inject fuel via the drive circuit 9 in synchronization with the reference signal (rotation speed) from the ignition coil 2, for example, according to the flowchart shown in FIG. It outputs to valve 8 and performs fuel injection.

Further, the target lean air-fuel ratio is set according to the flowchart shown in FIG. That is, in step 341, a target lean air-fuel ratio is searched from the air-fuel ratio map based on the engine rotational speed N and the basic injection 1tTp, and in step S42, the searched target lean air-fuel ratio is stored in a RAM or the like, and its value is stored in FIG. Used in flowcharts.

Next, learning control of the lean burn learning correction coefficient will be explained according to the flowchart of FIG.

In S51, various signals from the oxygen sensor 7 and the like are read.

In 85.2, is there a feedback system in the lean air-fuel ratio control region? I (i.e. 815~ in the third flowchart)
It is determined whether or not the control area in which S21 is being performed has been started, and if YES, the process proceeds to S53, and if NO, the process returns to 351.

In S53, it is determined whether or not the detected actual air-fuel ratio is fluctuating within the allowable range of the target lean air-fuel ratio, that is, whether it has entered the feedback control range. If YES, the process proceeds to S54; if NO, the process proceeds to Return to S51.

In S54, the lean burn correction coefficient LBC is retrieved from the three-dimensional map based on the engine rotational speed N and the basic injection amount 'rp (engine load).

In S55, the coefficient difference ΔLBC between the lean burn correction coefficient LBC set during stable feedback control and the lean burn correction coefficient LBC searched by the three-dimensional map is calculated.
(See Figure 8).

In S56, the data of the learning map is updated as a learning correction coefficient by making the calculated coefficient difference ΔLBC correspond to the engine rotational speed N and the basic injection 1tTp.

The learning correction coefficient data updated in this way is
It is used as the lean burn learning correction coefficient LRCLRN in the flowchart of the figure.

The first set time T from the time when it is determined that the lean air-fuel ratio control condition is met.
Until 1 has passed, regardless of the magnitude of the absolute value 1ΔTp1 of the difference, feedback control is performed so that the actual air-fuel ratio becomes, for example, the stoichiometric air-fuel ratio in the same way as immediately before the determination. As a result, as shown in FIG. 7, even if during acceleration operation from point A to point B outside the lean air-fuel ratio control region, the lean air-fuel ratio control region is temporarily passed and the lean air-fuel ratio control condition is determined. , because the lean air-fuel ratio control is not performed during the first set time T,
It is possible to prevent dilution of the actual air-fuel ratio and maintain good acceleration performance.

Further, after the first set time T1 has elapsed, if the absolute value 1ΔTpl of the difference exceeds the predetermined value ΔTpL, the lean burn correction coefficient LBC searched by the three-dimensional map is Since the fuel injection iTi is calculated based on, as shown in FIG.
After the first set time T has elapsed, the actual air-fuel ratio is maintained at a constant lean air-fuel ratio that is leaner than the stoichiometric air-fuel ratio (referred to as feedforward control) until the second set time T3 has elapsed. As a result, when lean air-fuel ratio control is performed immediately after acceleration driving, the actual air-fuel ratio rapidly decreases from the stoichiometric air-fuel ratio to the lean air-fuel ratio after the first set time T has elapsed, so that the transition to lean air-fuel ratio control is performed. At times, it is possible to improve fuel efficiency by controlling the lean air-fuel ratio while reducing the amount of NOx emitted in the exhaust gas.

On the other hand, when the absolute value 1ΔTpl of the difference is less than or equal to the predetermined value, that is, when transition is made from ultra-slow acceleration operation or steady operation to lean air-fuel ratio control, the first set time T.

Since the feedback control is performed so that the actual air-fuel ratio detected by the oxygen sensor 7 becomes the target lean air-fuel ratio after the elapse of time, as shown by the broken line in FIG. , after gradually approaching the target lean air-fuel ratio over time, feedback control is performed near the target lean air-fuel ratio. Here, the target lean air-fuel ratio during feedforward control and during feedback control are the same. Thereby, since the engine output gradually decreases over time when shifting to lean air-fuel ratio control, it is possible to suppress deterioration of driving feeling.

Furthermore, during feedforward control, the fuel injection amount is corrected based on the learning correction coefficient set by the difference ΔLBC between the lean burn correction coefficient LBC during feedforward control and stable feedback control. According to the lean burn correction coefficient, the actual air-fuel ratio may deviate from the target lean air-fuel ratio due to, for example, the injection characteristics of the fuel injector 8 or changes over time. This can be compensated for by the lean burn correction coefficient LBC set based on this.

Therefore, the actual air-fuel ratio during feedforward control can be controlled to the target lean air-fuel ratio with high accuracy, reducing NOK emissions, improving fuel efficiency, and improving drivability by reducing surge.

In this embodiment, the engine operating state immediately before the start of lean air-fuel ratio control is determined from the rate of change of the basic injection amount per unit time, that is, the absolute value 1ΔTpl of the difference between the previous and current times. The determination may be made based on the rate of change of the throttle valve opening or the like.

<Effects of the Invention> As explained above, the present invention performs lean air-fuel ratio control by feedback control after rapidly approaching the lean air-fuel ratio by feedforward control when the load change rate is equal to or higher than a predetermined value. Lean air-fuel ratio control is performed by feedback control when the load change rate is less than a predetermined value, so, for example, when controlling the lean air-fuel ratio immediately after acceleration, it is possible to reduce NOx emissions and improve fuel efficiency. On the other hand, when controlling the lean air-fuel ratio from, for example, steady operation, the engine output is gradually reduced by gradually bringing the air-fuel ratio closer to the lean air-fuel ratio, thereby improving the driving feeling.

Furthermore, a learning correction coefficient was set using the correction coefficient during feedforward control and the correction coefficient during feedback control, and was used to calculate the fuel injection amount during feedforward control, so that the actual air-fuel ratio during feedforward control was set as the target. The lean air-fuel ratio can be controlled with high precision, reducing NOx emissions and improving fuel efficiency while reducing surge and improving drivability.

[Brief explanation of the drawing]

Fig. 1 is a diagram corresponding to the claims of the present invention, Fig. 2 is a configuration diagram showing an embodiment of the present invention, Figs. 3 to 6 are flowcharts of the same, and Figs. It is a figure for explaining. 1... Control device 2... Ignition coil 3...
Air flow meter 4...Water temperature sensor 5...
Vehicle speed sensor 6... Idle switch 7...
Oxygen sensor 8...Fuel injection valve 9...Drive circuit Patent applicant Japan Electronics Co., Ltd. Agent Patent attorney Fujio SasashimaFigure 3-Figure 4Figure 5 Engine rotation VL degree

Claims (1)

[Claims] In an electronically controlled fuel injection system for an internal combustion engine that performs lean air-fuel ratio control such 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. air-fuel ratio detection means for detecting the actual air-fuel ratio of the engine; load detection means for detecting the engine load; load change rate calculation means for calculating the load change rate based on the detected load; and load change rate calculation means for calculating the load change rate based on the detected load. load change rate determining means for determining whether or not the ratio is equal to or higher than a predetermined value; a feedback correction coefficient setting means for setting a feedback correction coefficient so that the actual air-fuel ratio becomes a target lean air-fuel ratio based on the actual air-fuel ratio that has been determined; A first selection means selects the feedforward correction coefficient and then selects a feedback correction coefficient during a predetermined time at the initial stage of fuel ratio control, and lean air-fuel ratio control is performed when the load change rate is determined to be less than a predetermined value. a second selection means for selecting the feedback correction coefficient from the start; a rewritable storage means for storing a learning correction coefficient for correcting the fuel injection amount; a search means for searching the learning correction coefficient from the storage means; updating means for setting a new learning correction coefficient based on the set feedforward correction coefficient and feedback correction coefficient, and updating the data stored in the storage means to the new learning correction coefficient; fuel injection setting means for setting the fuel injection amount based on the selected feedforward correction coefficient, the searched or newly set learning correction coefficient, or the feedback correction coefficient selected by the first or second selection means; An electronically controlled fuel injection device for an internal combustion engine, comprising: a driving means for driving a fuel injection valve according to the set fuel injection amount.