JPH0772508B2 - Electronically controlled fuel injection device for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electronically controlled fuel injection device for an internal combustion engine, which includes a fuel injection means and an intake air flow rate detection means in a portion upstream of a branch portion of an intake manifold, In particular, the present invention relates to correction processing of the intake air flow rate detection value during acceleration.

<Prior Art> Conventionally, in an internal combustion engine provided with an electronically controlled fuel injection device, the fuel injection amount is set as follows (actually developed shovel 61-1).
(See No. 83440, etc.).

That is, from the intake air flow rate Q detected by the air flow meter and the engine rotation speed N, the basic fuel injection amount Tp (= K × Q /
N; K is a constant), and this Tp is set based on various correction factors COEF mainly according to the cooling water temperature and the air-fuel ratio detected by the oxygen sensor installed in the exhaust system. The final fuel injection amount Ti is determined by performing a correction calculation using the coefficient LAMBDA and the correction amount Ts based on the battery voltage.

Then, for example, in a single point injection (hereinafter referred to as SPI) system, an injection signal (valve opening drive signal) having a pulse width corresponding to the fuel injection amount Ti is given to the electromagnetic fuel injection valve every 1/2 revolution of the engine. Is output, and fuel is injected and supplied to the engine on / off.

By the way, in the SPI system, since the air flow meter and the fuel injection valve are provided in the upstream portion of the branch portion of the intake manifold, at the time of acceleration, the intake passage volume downstream of the fuel injection valve is filled. Although it is necessary to optimize the air mixing ratio, there is a delay in the detection of the intake air flow rate by the air flow meter that cannot be used to set the required fuel injection amount.Therefore, the air-fuel ratio becomes large and the misfire easily occurs. The acceleration performance was sometimes impaired. In particular, this tendency is large in a hot wire type air flow meter having a large heat capacity.

Therefore, conventionally, the acceleration operation state of the engine is detected when the change in the throttle valve opening is more than a predetermined value in the opening direction, and the latest detected value is detected when the acceleration operation state is detected.
Based on the difference between Q _NEW and the previous detected value Q _OLD , the latest detected value Q _NEW was corrected by the following formula to determine the final intake air flow rate Q.

Q = Q _NEW + A (Q _NEW −Q _OLD ) However, A is a correction coefficient and is a function that can be determined according to the collector volume of the intake manifold and the response of the air flow meter.

According to the above-mentioned correction method of the intake air flow rate Q, when the latest detected value Q _NEW becomes smaller than the previous detected value Q _OLD due to intake pulsation, the correction amount becomes a negative value and the corrected intake air flow rate value. Is smaller than the actual detection value, a correction value smaller than the detection value is not adopted so that the reduction correction is not performed.

<Problems to be Solved by the Invention> However, according to the above-described conventional intake air flow rate correction method, when the throttle valve opening change is more than a predetermined value in the opening direction and it is detected that the engine is in an accelerating operation state, Even if the intake air flow rate Q does not change with the change of the throttle valve opening and is stable, the correction control is performed. Therefore, the intake pulsation in the stable state of the intake air flow rate Q is corrected and controlled. As a result, the fluctuation of the basic fuel injection amount is increased, and the air-fuel ratio controllability of the engine intake air-fuel mixture is deteriorated, which may cause knock or surge.

That is, as shown in FIG. 6, when the throttle valve is opened at a rate higher than a predetermined value and the correction value exceeds the detection value, the correction control conditions are complete and the correction formula is used. The corrected intake air flow rate Q is adopted, and the correction is not limited to the initial stage of acceleration, but the intake air flow rate detected in the engine acceleration state based on the throttle valve rotation rate change rate tends to increase. If it shows, it will be done,
The correction was made even when the intake air flow rate Q increased due to the intake pulsation in a state where the intake air flow rate Q was stable, and by the correction that should be originally made to correct the intake air flow rate detection delay, This is to promote the intake pulsation in the stable state of the intake air flow rate Q that does not require the increase correction.

The present invention has been made in view of the above problems, and the increase correction of the intake air flow rate at the time of acceleration is provided only for the correction of the detection delay to avoid the increase of the intake pulsation and the air-fuel ratio control at the time of acceleration. The purpose is to improve.

<Means for Solving the Problem> Therefore, in the present invention, as shown in FIG. 1, the fuel injection means and the intake air flow rate detection means are provided in the upstream portion of the branch portion of the intake manifold, and the engine speed is detected. And a fuel injection amount calculation unit that calculates a fuel injection amount based on an intake air flow rate and an engine rotation speed, and the amount of fuel calculated by the fuel injection amount calculation unit is the fuel. In an electronically controlled fuel injection system for an internal combustion engine configured to inject and supply from an injection means to an engine, the opening change rate of a throttle valve interposed in an engine intake system is detected, and the detected opening change rate is used in the opening direction. In the state in which the engine acceleration state is determined by this acceleration state determination means, the acceleration state determination means determines that the engine is in the acceleration state when it is equal to or more than the predetermined value. Intake air flow rate comparison means for detecting the magnitude of the latest detected value of air flow rate and the previous detected value, and when the latest detected value is the comparison result of this intake air flow rate comparison means, the difference between the two detected values Based on the intake air flow rate correction means for increasing and correcting the latest detected value based on the intake air flow rate detection value, and the comparison result of the intake air flow rate comparison means becomes the acceleration state from when the latest detection value becomes small. The correction prohibiting means for prohibiting the increase correction of the intake air flow rate by the intake air flow rate correcting means until the acceleration determination by the determining means is interrupted is provided.

<Operation> In this configuration, the acceleration state determination means determines that the engine is in the acceleration state when the opening change rate of the throttle valve is equal to or more than the predetermined value in the opening direction, and thus the acceleration state is determined. When it is present, the intake air flow rate comparison means detects the magnitude of the latest detected value of the intake air flow rate and the previous detected value.

Then, when the latest detection value of the comparison result of the intake air flow rate comparison means is large, the intake air flow rate correction means increases the latest detection value based on the difference between the two detection values to increase the intake air flow rate detection value. However, from the time when the latest detected value of the comparison result of the intake air flow rate comparison means becomes small until the acceleration determination by the acceleration state determination means is interrupted, the intake air flow rate correction means inhales by the correction prohibition means. The correction of the air flow rate is prohibited, and even if the intake air flow rate comparison means detects that the latest detected value is large during this period, the intake air flow rate correction means does not perform the correction.

<Examples> Examples of the present invention will be described below with reference to the drawings.

Referring to FIG. 2 showing the structure of one embodiment, an intake manifold 2 of an engine 1 has a throttle valve 3 upstream of a branch portion for controlling an intake air flow rate in cooperation with an accelerator pedal.
And an air flow meter 4 as an intake air flow rate detecting means for detecting the intake air flow rate Q and a fuel injection valve 5 as a fuel injection means are provided on the upstream side of the control unit 6 including a microcomputer. The valve is driven to open by an injection pulse signal of, and fuel supplied under pressure from a fuel pump (not shown) and controlled to a predetermined pressure is injected into the intake manifold 2.

Further, a water temperature sensor 7 for detecting the temperature of the cooling water in the cooling jacket of the engine 1 is provided, and an oxygen sensor 9 for detecting the oxygen concentration in the exhaust passage 8 is provided. Further, a distributor (not shown) has a built-in crank angle sensor 10 that also serves as engine speed detection means, and counts a crank angle unit signal output from the crank angle sensor 10 in synchronization with the engine rotation for a certain period of time. Alternatively, the engine rotation speed N is detected by measuring the cycle of the crank reference angle signal.

Further, the axis of the throttle valve 3 has a throttle valve opening TV
A throttle sensor 11 for detecting O is provided, and
An idle switch 12 that is turned on at the fully closed position (idle position) of the throttle valve 3 is provided, and a neutral switch 13 that is turned on when the transmission is in a neutral state is provided. The throttle sensor 11 together with the control unit 6 constitutes acceleration state determination means.

Next, the contents of the basic fuel injection amount setting control including the increase correction control of the intake air flow rate Q during acceleration will be described according to the routines shown in the flowcharts of FIGS. 3 and 4.
In this embodiment, the functions as the fuel injection amount calculation means, the intake air flow rate correction means, the correction prohibition means, and the intake air flow rate comparison means are configured by software as shown in the above flow chart.

The basic fuel injection amount setting routine shown in the flowchart of FIG. 3 is executed every 1/2 rotation of the engine 1 based on the signal from the crank angle sensor 10.

In step (denoted as "S" in the figure, the same applies hereinafter) 1, the integrated value Q _SUM of the intake air flow rate QA detected by the air flow meter 4 while the engine 1 is rotating 1/2 is used as the sample number I. By dividing by
Simple average value of intake air flow rate QA during rotation Q _SIMPL
Calculate (← Q _SUM / I).

The integrated value Q _SUM and the sample number I are set by the integrated value setting routine shown in the flowchart of FIG. Note that this routine is executed every 1 ms.

Here, in step 31, the output voltage Us of the air flow meter 4 is AD-converted, and in the next step 32, the output voltage Us is previously converted.
Intake air flow rate QA stored in the map corresponding to Us
Output voltage obtained by AD conversion in step 31 from the data of
Search for and obtain the intake air flow rate QA data corresponding to Us.

Then, in step 33, the intake air flow rate QA obtained by the search in step 32 is added to the accumulated value Q _SUM so far, and in step 34, the counter I is added every time the detected value QA of the air flow meter 4 is added in step 33. The value of is increased by 1 and the integrated value Q
Count the number I of _SUM samples.

The integrated value Q _SUM and the number of samples I thus obtained are used in the step 1 and the intake air flow rate QA (detection value of the air flow meter 4) during the 1/2 revolution of the engine 1
The simple average value of Q _SIMPL is calculated.

In the next step 2, the integrated value Q _SUM and the sample number I are reset to zero in order to newly set the integrated value Q _SUM and the sample number I in the routine shown in the flowchart of FIG.

In step 3, since it is used later as a value indicating the engine load state, the intake air flow rate QA currently detected by the air flow meter 4 is divided by the engine rotation speed N. It should be noted that the simple average value Q _SIMPL of the intake air flow rate QA during one half rotation of the engine 1 calculated in step 1 may be divided by the engine rotation speed N.

In step 4, it is determined whether the current engine operating state is the idle operating state. Specifically, when the idle switch 12 is ON and the neutral switch 13 is ON, it is determined that the engine is in the idle operation state.

If it is determined in step 4 that the engine is not in the idle operation state, the process proceeds to step 5 to determine whether the engine 1 is in the deceleration operation state based on the change rate ΔTVO of the throttle valve opening TVO detected by the throttle sensor 11. To judge. Whether or not the engine 1 is in the decelerating operation state is determined to be in the decelerating operation state when the rate of change ΔTVO is, for example, −1.6 ° / 30 ms or less.

Here, when it is determined that the engine 1 is in the decelerating operation state, the routine proceeds to step 6, where the current operating state is the Q flat region (even if the throttle valve opening TVO changes, the intake air flow rate Q
Whether A is included in the unchanged operating region) is determined based on, for example, the current throttle valve opening TVO and the engine speed N, and when it is not included in the Q flat region, the process proceeds to step 11, , Q, it is determined that the engine 1 is not in the decelerating operation state in step 5, and the process proceeds to step 7.

In step 7, as in step 5, it is determined based on the throttle valve opening change rate ΔTVO whether the engine 1 is in the accelerating operation state. Here, for example, the change rate ΔTV
When O is 1.6 ° / 100ms or more, it is judged to be in the acceleration operation state.

Then, when it is determined in step 7 that the engine 1 is in the acceleration operation state, the process proceeds to step 8 and the weighting constant in the weighted average calculation formula when _{performing the} weighted average calculation of the simple average value Q _SIMPL of the intake air flow rate QA. X _REV calculated in step 3
Search based on QA / N. That is, as shown in the graph in the flowchart of FIG. 3, the X _REV corresponding to the current QA / N is retrieved from the data of the weighting constant X _REV stored in the map in advance according to the QA / N. X _REV is set to be larger as the engine 1 having a higher QA / N is operated at a higher load, and the weighting with respect to the past weighted average value Q _AVREV is increased.

On the other hand, if it is determined in step 7 that the engine 1 is not in the acceleration operation state, the process proceeds to step 9 to search for the weighting constant X _REV based on QA / N as in step 8. However, the weighting constant X _REV searched in step 9 when the engine 1 is not in the accelerating operation state is larger than that in the accelerating operation state.
The QA / N is set to a larger value, which effectively suppresses intake pulsation and ensures responsiveness in the acceleration operation state.

Then, in step 8 or step 9, the weighting constant X
_{When REV} is set, in the next step 10, using the simple average value Q _SIMPL of the intake air flow rate QA calculated in step 1 this time and the weighted average value Q _AVREV calculated in step 10 last time, the weight is calculated according to the following equation. Performs averaging.

On the other hand, when it is determined in step 4 that the engine 1 is in the idle operation state and when it is determined in step 6 that the engine 1 is not in the Q flat region (in the decelerating operation condition and not in the Q flat region), the process proceeds to step 11 and the weighting is performed. The constant X _REV is set to zero, the simple average value Q _SIMPL calculated in step 1 this time is set as the weighted average value Q _AVREV this time, and the weighted average calculation in step 10 is not performed.

When the calculation / setting of the weighted average value Q _AVREV is completed as described above, in the next step 12, whether or not the engine 1 is in the rapid acceleration operation state is determined based on the throttle valve opening change rate ΔTVO. Here, for example, when the throttle valve opening change rate ΔTVO is 1.6 ° / 30 ms or more, it is determined that the engine 1 is in the rapid acceleration operation state, and when the rapid acceleration determination is made, the process proceeds to step 13.

In step 13, it is determined whether or not the rapid acceleration determination in step 12 is the first time, and if it is determined that it is the first time, the process proceeds to step 14 to set the flag to 1, but if it is not the first time, step 14 is performed. Jump to step 15.

In step 15, the correction amount ΔQ for correcting the detection delay of the air flow meter 4 in the rapid acceleration operation state of the engine 1
Is calculated according to the following formula.

ΔQ ← (Q _AVREV -Previous Q _AVREV ) K _MANI That is, the correction amount ΔQ is obtained by multiplying the coefficient K _MANI by the value _obtained by subtracting the previous weighted average value Q _AVREV from the weighted average value Q _AVREV calculated or set this time. To be The coefficient K _MANI
Is determined according to the collector volume of the intake manifold 2 and the responsiveness of the air flow meter 4, for example, 2.
The value should be around 6.

In the next step 16, the correction amount ΔQ calculated in step 15
Is determined to be a value exceeding zero, and the correction amount ΔQ>
When it is 0, the routine proceeds to step 17, where the flag is judged, and only when the correction amount ΔQ> 0 and the flag is 1, the routine proceeds to step 18 where the intake air flow rate Q is increased and corrected. On the other hand, when it is determined in step 16 that the correction amount ΔQ ≦ 0, the flag is set to zero in step 19 and then the process proceeds to step 20.

In step 18, the final intake air flow rate Q (final Q) is set by increasing the correction amount ΔQ by adding the correction amount ΔQ to the weighted average value Q _AVREV calculated in step 10 this time. Weighted average value Q calculated in 10
_AVREV is set as the final Q and no increase correction is performed.

That is, since the air flow meter 4 and the fuel injection valve 5 are provided in the upstream portion of the branch portion of the intake manifold 2, the optimum amount of air filled in the intake passage volume on the downstream side of the fuel injection valve 5 at the time of sudden acceleration. Although it is necessary to perform the mixing ratio, there is a detection delay of the intake air flow rate Q that cannot be used for setting the fuel injection amount of the air flow meter 4, so step 15
Although it is necessary to perform the increase correction using the correction amount ΔQ calculated by, even if the intake air flow rate Q is stabilized after the rapid acceleration, if the increase amount correction is performed by the correction amount ΔQ, the intake pulsation is promoted. _Therefore , in the present embodiment, in order to solve this, once the weighted average value Q _AVREV shows a decreasing tendency, the increase correction is not performed until a new sharp acceleration is made thereafter.

When the engine 1 is rapidly accelerated and the first determination is made in step 13, the flag is set to 1 and the weighted average value Q _AVREV shows a decreasing tendency (until it is determined in step 16 that the correction amount ΔQ ≦ 0). Is corrected in step 18, but when the weighted average value Q _AVREV shows a decreasing tendency, the flag is set to zero in step 19, so that the engine 1 Even if the rapid acceleration state is determined, the final Q is set in step 20 so that the increase correction is not performed, and until the rapid acceleration operation state is again determined for the first time and the flag is set to 1. This prohibition state of the increase correction continues.

Therefore, after the rapid acceleration of the engine 1 is determined, the weighted average value Q
_{While the AVREV} continues to rise, that is, while the detection delay of the air flow meter 4 occurs, an increase correction is made based on the correction amount ΔQ, but the intake air flow rate Q shows a decreasing tendency. If it is stable and the detection delay reaches a level where there is no problem, unnecessary increase correction is avoided, and as shown in FIG. 5, the peak of the intake air flow rate Q generated by the increase correction is only once at the beginning. Therefore, the peak of the intake pulsation is not increased in the subsequent stable state of the intake air flow rate, and the fluctuation of the basic fuel injection amount Tp calculated based on the final Q is not increased.

When the final Q is set in step 18 or step 20, the basic fuel injection amount Tp (← K × final Q / N; K is a constant) is calculated using the final Q in the next step 21. Since this basic fuel injection amount Tp is used to set the optimum ignition timing when the ignition timing is variably controlled, the ignition timing is also optimized by optimizing the intake air flow rate increase correction as in the present embodiment. be able to.

Although omitted in the present embodiment, the correction amount Ts based on the battery voltage, the air-fuel ratio feedback correction coefficient LAMBDA based on the air-fuel ratio detected by the oxygen sensor 9 and the cooling water temperature detected by the water temperature sensor 7 in another routine, etc. The basic fuel injection amount Tp is corrected and calculated by various correction factors such as COEF based on the above, and the final fuel injection amount Ti is set, and the injection pulse signal corresponding to this fuel injection amount Ti is injected in synchronization with the engine rotation. The fuel is output to the valve 5 and the fuel is injected and supplied to the engine 1 on / off.

<Effects of the Invention> According to the present invention as described above, the increase correction of the intake air flow rate is prohibited from when the latest detected value becomes smaller than the previous value until the acceleration determination is interrupted.
Since the increase correction control can be performed only when there is a detection delay of the intake air flow rate during acceleration, there is an effect that it is possible to improve the air-fuel ratio control by avoiding the promotion of intake pulsation.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of the present invention, FIG. 2 is a system diagram showing an embodiment of the present invention, FIGS. 3 and 4 are flow charts showing control contents of the same embodiment, and FIG. FIG. 6 is a time chart for explaining the effect of the present invention, and FIG. 6 is a time chart for explaining the conventional problems. 1 ... Engine, 2 ... Intake manifold, 3 ... Throttle valve, 4 ... Air flow meter, 5 ... Fuel injection valve, 6 ...
Control unit, 10 Crank angle sensor, 11
...... Throttle sensor

Claims (1)

[Claims] 1. An engine rotational speed detecting means for detecting an engine rotational speed, comprising a fuel injection means and an intake air flow rate detecting means at a portion upstream of a branch portion of an intake manifold.
An electronic device for an internal combustion engine, comprising: a fuel injection amount calculation means for calculating a fuel injection amount based on an intake air flow rate and an engine rotation speed, and configured to inject and supply the calculated amount of fuel to the engine from the fuel injection means. In the control fuel injection device, the opening change rate of the throttle valve interposed in the engine intake system is detected, and when the detected opening change rate is a predetermined value or more in the opening direction, the engine is in the acceleration state. An acceleration state determination means for determining, and an intake air flow rate comparison means for detecting the magnitude of the latest detection value of the intake air flow rate and the previous detection value in a state where the acceleration state determination means determines the engine acceleration state. When the comparison result of the intake air flow rate comparison means is the latest detection value is large, the latest detection value is increased and corrected based on the difference between the two detection values and output as an intake air flow rate detection value. And the increase correction of the intake air flow rate by the intake air flow rate correction means is prohibited from when the latest detection value of the comparison result of the intake air flow rate comparison means becomes small until the acceleration determination by the acceleration state determination means is interrupted. An electronically controlled fuel injection device for an internal combustion engine, comprising: a correction prohibiting unit;