JPS63140838A - Electronic control fuel injection device for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent overleanness from occurring, by selection a feedforward correction factor at the load variation initial stage and also a feedback correction factor afterward, respectively, while compensating it to the rich side when a speed variation is large, in case of a device performing control over a lean side air-fuel ratio. CONSTITUTION:A feedback correction factor setting device G sets a feedback correction factor on the basis of each output out of an air-fuel ratio detecting device A and a desired lean air-fuel ratio setting device B and a feed forward correction factor setting device sets a feedforward correction factor so as to become the set desired lean air-fuel ratio. When a load variation judging device E has judged that a load variation is more than the specified one on the basis of variations in a fundamental fuel injection quantity, a first selector device H selects the feedforward correction factor as long as the specified time, and afterward it selects the feedback correction factor. When a speed variation detecting device L detects a speed variation of more than the specified one, each correction factor or the desired lean air-fuel ratio is compensated and the promotion of richness is carried out.

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.

(Conventional technology) Inner V! The following is a conventional example of an electronically controlled fuel injection system for an engine (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 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, the fuel injection amount Ti=TpXCOB 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 low-speed, low-load operating region of the engine.

That is, when it is determined that the operation is in a predetermined low-speed constant-load operation 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> 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 operation to steady operation, which is an operating range in which lean air-fuel ratio control is possible, there is a sudden switch to lean air-fuel ratio control.
There is a problem in that it is not possible to reduce the Furthermore, when the load fluctuation is large, the torque fluctuation is originally large, so it is necessary to rapidly control and switch the lean air-fuel ratio in order to suppress the torque fluctuation.

However, when this is done using feedback control, the actual air-fuel ratio cannot be rapidly made lean due to the delay in the detection response of the oxygen sensor that detects the actual air-fuel ratio, and even during feedback control, the oxygen sensor changes over time. Therefore, there is a problem that the lean air-fuel ratio cannot be controlled with high precision, and drivability is deteriorated due to the generation of surge.

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. At times, it is difficult to control the actual air-fuel ratio to the target lean air-fuel ratio with high precision, resulting in an increase in NOx emissions and a deterioration in 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.

Therefore, as shown in FIG. 1, the present invention includes an air-fuel ratio detection means A that detects the actual air-fuel ratio of the engine, and a target lean air-fuel ratio that is leaner than the stoichiometric air-fuel ratio. A target lean air-fuel ratio setting means B for setting a target lean air-fuel ratio, a load detecting means C for detecting the engine load, a load change rate calculating means for calculating a load change rate based on the detected load, and a calculated load change rate. a load change rate determining means E for determining whether or not the detected actual Feedback correction coefficient setting means G that sets a feedback correction coefficient so that the actual air-fuel ratio becomes the target lean air-fuel ratio based on the air-fuel ratio; and a feedback correction coefficient setting means G that sets a feedback correction coefficient so that the actual air-fuel ratio becomes the target lean air-fuel ratio; a first selection means H that selects the feedforward correction coefficient for a predetermined period of time and then selects a feedback correction coefficient; A second selection means (■) for selecting a correction coefficient, and a first or second selection means (H, I)
A fuel injection amount setting means J that sets the fuel injection amount based on the correction coefficient selected by , and a drive means that drives the fuel injection valve N according to the set fuel injection amount detect rotational fluctuations of the engine. and the feedforward correction coefficient so that the actual air-fuel ratio is enriched by a predetermined value with respect to the set target lean air-fuel ratio when the detected rotation fluctuation is equal to or greater than a predetermined value. and a feed bank correction coefficient or an air-fuel ratio correction means M for correcting the set target lean air-fuel ratio.

<Operation> In this way, when shifting from acceleration/deceleration operation where the load change rate is above a predetermined value, that is, above the predetermined value, to lean air-fuel ratio control, the actual air-fuel ratio is rapidly changed to lean air-fuel ratio by feedforward control at the initial stage. After the fuel ratio is set, feedback control is performed to bring it closer to the target lean air-fuel ratio. 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 lean air-fuel ratio by feedback control from the start of the lean air-fuel ratio control.

Further, when a rotational fluctuation of a predetermined value or more is detected, the actual air-fuel ratio is corrected to the rich side to suppress the occurrence of a surge during 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, for example, a control device L consisting of a microcomputer 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 depending on the oxygen concentration in the exhaust gas) (sensor that can detect)
The air-fuel ratio detection signal from

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 includes a load change rate calculation means, a load change rate determination means, a feedforward correction coefficient setting means, a feedback correction coefficient setting means, first and second selection means, a fuel injection amount setting means, and an air-fuel ratio correction means. constitutes.

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.

Further, since the rotational speed is detected based on the ignition signal of the ignition coil 2, the ignition coil 2 constitutes rotational fluctuation detection means.

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

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, a basic injection amount 'rp (=KN- is a constant) is calculated from the engine rotational speed N obtained from the ignition signal and the intake air flow rate Q.

In steps 83 to S7, lean air-fuel ratio control conditions are determined.

That is, in S3, it is determined whether or not the calculated basic injection amount Tp is within the range from the set value Tpl to T1)z. If YES, the process proceeds to S4; if NO, the process proceeds to S22.

In S4, it is determined whether the engine rotational speed N is within the range from set value N1 to N2, and if YES, S4 is determined.
If the answer is No, the process advances to S22.

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 closed) or OFF, and 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).
h) Determine whether or not it is greater than or equal to
If the answer is NO, the process advances to S22.

When the lean air-fuel ratio control condition (see FIG. 9) is thus determined, the basic injection amount 'rpO difference Δ'rp calculated last time and this time is calculated in S8-.

In S9, the absolute value lΔTpl of the calculated difference is set to a predetermined value Δ
It is determined whether or not TpL has been exceeded. If YES, the process proceeds to S10; if NO, the process proceeds to S15.

At 310, 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 'r+ (for example, 13.
(See Figure 10) in step c, and determine if YES has passed.
If so, the process advances to S12, and if No, the process advances to S22.

In S12, the second set time T8 (for example, 1.2
sec (see Figure 10) has elapsed, and Y
When the answer is ES, the process advances to S17, and when the answer is 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 amount 'rp.

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

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 proceeds to 322.

In S17, the detection signal of the oxygen sensor 7 is read and S17 is performed.
At step 18, the actual air-fuel ratio is searched from the air-fuel ratio map based on the detection signal of the oxygen sensor 7, and the process proceeds to step S19.

In step 319, 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 rich, the process advances to S20, and if it is lean, the process advances 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, in S21, a predetermined value ΔL is added to the previously set lean burn correction coefficient LBC, and a new lean burn correction coefficient L is added so that the actual air-fuel ratio approaches the target lean air-fuel ratio.
Set BC. Note that when the actual air-fuel ratio is the target lean air-fuel ratio, the previous lean burn correction coefficient LBC is used.

Then, in S14, the fuel injection amount Ti is calculated by the following equation based on the lean burn correction coefficient LBC retrieved in S13 or the lean burn correction coefficient LBC set in S20 or S21.

Ti = Tpx LBC

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

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 S14 or S22 is determined by the reference signal (rotational speed) from the ignition coil 2, for example, according to the flowchart shown in FIG.
In synchronization with this, the signal is output to the fuel injection valve 8 via the drive circuit 9 to perform fuel injection.

Further, the target lean air-fuel ratio is set according to the flowchart shown in FIG. That is, in S41, 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 amount Tp, and in S42, the searched target lean air-fuel ratio is stored in a RAM or the like, and the value is stored in the RAM or the like. It is used in the flowchart in Figure 3.

Next, 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.

In S51, the rotational speed signal and vehicle speed signal from the ignition signal are read.

In S52, +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 step 353, it is determined whether or not the number of sampling times has reached 11. If YES, the process advances to step S54, where all the rotational speeds stored in the rotational speed memory (RAM) are set to the initial value (
For example, if the answer is NO, the process proceeds to S55 without initializing the rotation speed memory.

In step 55, the detected rotational speed is stored in the address of the rotational speed memory corresponding to the newly set sampling number. Here, the rotation speed memory contains 100m5e.
The rotation speed detected every c is the sampling number (100
10 types, that is, 1 for the address corresponding to
Data for sec can be stored as shown in FIG.

In S56, the amount of change in rotational speed during the sampling period ΔN (-N, -N
Calculate O. Here, the sampling period Δt is 10 sec, 200 sec, 300 sec, 500 m
It is set to 5ec and 1 sec. therefore,
At the beginning of sampling, the amount of change ΔN in the rotational speed is calculated during a sampling period of 100 m5ec.

In S57, the unit time is calculated from the detected vehicle speed vsp.

In 35B, the current driving state is determined from the calculated vehicle speed change rate Δvsp, and when acceleration driving is determined, the process proceeds to 359, and when deceleration driving is determined, the process proceeds to S60.Furthermore, when steady driving is determined, the process proceeds to S61 without determining rotation fluctuation. .

At step 359, the amount of change ΔN calculated at S56 is compared with the m-tolerance range -ΔNc, and when -ΔNc>ΔN, it is determined that the amount of change ΔN is greatly fluctuating to one side, and step 362 When -ΔNc≦ΔN, it is determined that the rotational fluctuation is small and the process advances to S61.

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 S60, 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 S62, where
When Nc≧ΔN, it is determined that the rotational fluctuation is small and S61
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 S61, a state in which no surge has occurred is stored as a flag -0 in a RAM, etc., while in S62, a state in which a surge has occurred is stored in a RAM, etc. as a flag =1.

With this surge judgment routine, 100m5ec, 2
00+5sec, 300m5ec, 500m5ec
Then, a surge determination is performed during a sampling period of 1 sec.

Next, the air-fuel ratio correction routine will be explained based on the flowchart of FIG. This routine runs every 10m5ec.

In S71, various signals such as a vehicle speed signal and an air-fuel ratio detection signal are read.

In S72, a vehicle speed change rate Δvsp per unit time is calculated from the detected vehicle speed.

In S73, it is determined whether or not the vehicle is in steady operation based on the calculated vehicle speed change rate ΔVSF, and if YES, the process advances to S74 and NO.
If so, the process advances to S76.

In S74, it is determined whether the flag stored in the RAM or the like is 1 or 0. If the flag is 1, the process proceeds to S75, and if the flag is O, the process proceeds to 376.

In S75, ΔA/F is calculated from the detected actual air-fuel ratio A/F.
The air-fuel ratio detected by subtracting F is corrected to be leaner by ΔA/F than the actual one, and this corrected air-fuel ratio is used in S18 of FIG. 3.

At S76, the detected actual air-fuel ratio A/F is set without correction, and this value is used at 318 in FIG.

By doing this, when a surge occurs, the detected air-fuel ratio A/F will be leaner than the actual one by ΔA/F, so S
The lean burn correction coefficient LBC during feedback control set in steps 20 and S21 is corrected so as to be on the rich side with respect to the target lean air-fuel ratio by an amount corresponding to ΔA/F. As a result, even if the actual air-fuel ratio shifts to 0 point within the surge generation zone in FIG. Since the air-fuel ratio is controlled to be on the rich side compared to that in FIG. 11, the air-fuel ratio shifts from point 0 in the surge generation zone to point D in the surge non-occurrence zone, and surge generation can be prevented.

In addition, as shown in FIG. 10, from the time when the lean air-fuel ratio control condition is determined until the first set time T has elapsed, the actual air-fuel ratio remains the same as immediately before the determination, regardless of the magnitude of the absolute value of the difference 1ΔTpl. is feedback-controlled so that it becomes, for example, the stoichiometric air-fuel ratio. As a result, even if the lean air-fuel ratio control condition is determined by temporarily passing through the lean air-fuel ratio control area during acceleration operation from point A to point B outside the lean air-fuel ratio control area as shown in FIG. Since lean air-fuel ratio control is not performed during the first set time T, it is possible to prevent the actual air-fuel ratio from becoming leaner and maintain good acceleration performance.

Further, if the absolute value 1ΔTpl of the difference exceeds the predetermined value ΔTpL after the first set time T1 has elapsed, the lean burn correction coefficient LBC searched by the three-dimensional map will not be used until the second set time T8 has elapsed. Since the fuel injection amount Ti is calculated based on the following, as shown in FIG.
The actual air-fuel ratio is maintained at a constant lean air-fuel ratio that is leaner than the stoichiometric air-fuel ratio until the second set time Tt has elapsed after the first set time T1 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 TI has elapsed, so when transitioning to lean air-fuel ratio control, It is possible to improve fuel efficiency by controlling the lean air-fuel ratio while reducing the amount of NOx emissions 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 after the elapse of time becomes the target lean air-fuel ratio, the actual air-fuel ratio at the beginning of the feedback control is 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. 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.

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 from the rate of change of the throttle valve opening, torque, opening area of the throttle valve, etc.

In addition, in this embodiment, when a surge occurs, the actual air-fuel ratio is corrected to be on the rich side during feedback control during lean air-fuel ratio control, but the lean burn correction coefficient LBC set by the map The lean burn correction coefficient LBC may also be corrected so that the actual air-fuel ratio becomes rich when performing feedforward control. Furthermore, when a surge occurs, the target lean air-fuel ratio is set to a predetermined value flt?
It may be corrected to be on the a side.

<Effects of the Invention> As explained above, the present invention performs lean air-fuel ratio control by rapidly approaching the lean air-fuel ratio by feedforward control and then by feedback control when the load change rate is equal to or higher than a predetermined value. Since lean air-fuel ratio control is performed by feedback control when the load change rate is less than a predetermined value, for example, when performing lean air-fuel ratio control immediately after acceleration operation, N.

While reducing X emissions and improving fuel efficiency, for example, during lean air-fuel ratio control during steady operation, engine output is gradually reduced by gradually bringing the air-fuel ratio closer to the lean air-fuel ratio. You can improve your feeling.

In addition, since the air-fuel ratio is corrected so that it becomes rich when the rotational fluctuation is greater than a predetermined value, the actual air-fuel ratio may shift from the target lean air-fuel ratio to the lean side due to changes in the oxygen sensor or fuel injection valve over time. Even if rotational fluctuation occurs due to deviation, this rotational fluctuation can be prevented.

[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 7 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 Sasashima Figure 3, Part 2 Figure 4, Figure 5, Figure 7, Figure 8 Figure 9 Big Gunda Kangi

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 an actual air-fuel ratio of the engine; target lean air-fuel ratio setting means for setting a target lean air-fuel ratio leaner than the stoichiometric air-fuel ratio; load detection means for detecting engine load; load change rate calculation means for calculating the load change rate based on the load change rate; load change rate determination means for determining whether the calculated load change rate is equal to or greater than a predetermined value;
Feedforward correction coefficient setting means for setting a feedforward correction coefficient so that the set lean air-fuel ratio is achieved; and feedback so that the actual air-fuel ratio becomes the target lean air-fuel ratio based on the detected actual air-fuel ratio. Feedback correction coefficient setting means for setting a correction coefficient; and when it is determined that the load change rate is equal to or higher than a predetermined value, the feedforward correction coefficient is selected for a predetermined time at the beginning of the lean air-fuel ratio control, and then the feedback correction coefficient is selected. a first selection means for selecting the feedback correction coefficient from the start of lean air-fuel ratio control when the load change rate is determined to be less than a predetermined value; a fuel injection amount setting means for setting the fuel injection amount based on the set correction coefficient; a driving means for driving the fuel injection valve according to the set fuel injection amount; and a rotation fluctuation detection means for detecting engine rotation fluctuation. , at least the feedforward correction coefficient and the feedback correction coefficient so that when the detected rotational fluctuation is equal to or greater than a predetermined value, the actual air-fuel ratio is enriched by a predetermined value with respect to the set target lean air-fuel ratio. An electronically controlled fuel injection device for an internal combustion engine, comprising an air-fuel ratio correcting means for correcting one or the set target lean air-fuel ratio.