JP2855379B2 - Fuel supply control device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine
Power is supplied from the power supply to the
The amount of intake air is detected from the amount of electricity, and the detected amount of intake air is detected.
Of the internal combustion engine to set the fuel supply amount based on the
The present invention relates to a fuel supply control device .

[0002]

2. Description of the Related Art In an electronically controlled fuel injection device for an internal combustion engine, a basic injection amount is calculated from an intake air amount and an engine speed, and then the fuel injection amount is calculated. For this purpose, an electric resistor type air flow meter is used.

In this electric resistor type air flow meter, an electric resistor such as a so-called hot wire type or a hot film type is interposed in an intake passage, a current is supplied to the electric resistor, and an intake air amount is detected from the supplied current. I have to. This will be described by taking the air flow meter 1 in FIG. 2 as an example. The hot wire resistance 2 and the temperature compensation resistance 3
, The basic resistor 4 and the fixed resistors 5 and 6 form a bridge circuit.

Then, the supply current to the bridge circuit is controlled by an operational amplifier 7 and transistors 8 and 9 for inputting the unbalanced voltage of the bridge circuit, that is, the voltages at points A and B,
For example, the intake air amount is detected based on a voltage change of the fixed resistor 6. For example, intake air speed (intake air volume)
Increases, the resistance of the hot-wire resistor 1 increases, and the resistance tends to decrease. At this time, the potential at the point A increases, the output of the operational amplifier 7 increases, and the current supplied to the bridge circuit increases. Increase.

Thus, the heating value of the hot wire resistor 2 is controlled to be increased and the resistance value is kept constant. And
By reading the flow rate of the intake air from the voltage of the fixed resistor 6, the intake air amount can be detected.

[0006]

The hot wire resistance 5
Since the supporting portion has a predetermined heat capacity, when the power is turned on (when the ignition switch 10 is turned on), a large current flows through the air flow meter 1 to supplement the heat capacity, and the output power is reduced as shown in FIG. After a large rise, it gradually becomes stable. Therefore, in spite of the fact that the intake air is small, the detected value of the intake air amount increases, the fuel injection amount increases, and the air-fuel ratio becomes significantly rich.

When the elapsed time from when the power is turned on to when the starter switch is turned on changes, the detected value of the amount of intake air after the starter switch is turned on also becomes true due to the response delay of the heat ray resistance to the intake air. There is a problem that it deviates from the value of. Specifically, the detected value as shown in FIG. 13 becomes larger than the true value until the elapsed time reaches about 3 seconds, and the air-fuel ratio becomes rich.
Conversely, if the time exceeds seconds, the detected value becomes smaller than the true value, as shown in FIG. 5, and the air-fuel ratio becomes lean.

As a result, the occurrence of engine stall,
There is a problem that emission characteristics are deteriorated. The present invention has been made in view of such a situation, and is intended to be used when starting.
Engine with an appropriate air-fuel ratio in the engine
It is an object of the present invention to provide a fuel supply control device of Seki .

[0009]

SUMMARY OF THE INVENTION Accordingly, the present invention provides an electric resistor provided in an engine intake passage as shown in FIG.
Power from the power supply and the suction air
The amount of fuel detected is determined based on the detected amount of intake air.
A fuel supply control device for an internal combustion engine, wherein the supply amount is set.
The time from when the power to the electric resistor is turned on.
Detects timing means to start and when engine cranking starts
Cranking start time detecting means for detecting whether the power is turned on.
Within the specified time
In some cases, it is set based on the detected intake air volume.
While the fuel supply amount is limited to a predetermined value,
From the start of cranking to the start of cranking
If it exceeds, the response is delayed for the detected intake air volume.
Correction based on the intake air amount after the response delay correction.
Fuel supply amount control means for setting the fuel supply amount by
It was made to consist of.

[0010]

[Function] Then, the power supply to the electric resistor is turned on when the power is turned on.
The elapsed time until the start of Seki's cranking is within the specified time
In some cases (ie, the effect of inrush voltage on the electrical resistor
When the institution starts cranking during a large time period
), Limit the fuel supply to a predetermined value (upper limit)
The power is turned on while preventing the ratio from becoming excessively rich.
The time elapsed from the time until the start of cranking
If it exceeds (that is, the effect of inrush voltage on the electrical resistor)
Became smaller, but the detection response was delayed due to changes in the amount of intake air.
Engine cranking is open during times when the impact of
(If started), respond to the detected intake air volume.
Response delay correction is performed, and based on the intake air amount after the response delay correction,
The fuel supply amount is set based on the This allows
The air-fuel ratio at startup can be optimized,
As a result, the air-fuel ratio control accuracy at the time of starting can be improved.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. The description of the components described in the conventional example is omitted. In FIG. 2, a power supply voltage V is supplied to an air flow meter 1 through an ignition switch 10.
_B is applied. The output voltage of the air flow meter 1 is input via an A / D converter 11 to a microcomputer 12 serving as fuel supply amount control means . Further, a timer 13 is provided as a time measuring means for starting time measurement when the ignition switch 10 is turned on.
The count signal of 3 is input to the microcomputer 12. Signals are input to the microcomputer 12 from the rotation sensor 14 and the starter switch 15.

The microcomputer 12 corrects the output of the air flow meter 1 in accordance with the routine shown in the flowchart of FIG. Next, the operation will be described with reference to the flowchart of FIG. In S1, the output voltage US of the air flow meter 1 is read. In S2,
Based on the read output voltage US, an intake air amount Q is searched from a conversion map.

In S3, the ignition switch 10 is turned on (immediately ) based on the time measured by the timer 13 and the signal of the starter switch 15 (or the rotation speed sensor 14).
When the power is turned on, in other words, move the key switch to the ON position.
Starter switch 15 when on time you dynamic) {i.e. machine
When the Seki starts to start (when cranking starts), in other words,
Switch is in the start position (starter motor drive start position
It is determined whether or not the elapsed time until ｝ is moved to the predetermined position is within a predetermined time (for example, in a range of 3 seconds to 10 seconds). If YES, proceed to S4, and if NO, proceed to S5 without passing through S4. .

In S4, the intake air amount Q obtained from the output voltage US of the air flow meter 1 in S2 is corrected as follows. By the way, when starting the air flow meter 1
When the movement of air starts in the vicinity, the output value of the air flow meter 1 lags behind the actual increase in the amount of intake air as shown in FIG. As a result, detection delay of the intake air amount occurs.
The causes of this detection delay include the fact that the heat capacity of the hot wire resistance 2 is large and that the intake air hardly removes heat from the hot wire resistance 2 (hereinafter referred to as a delay of high frequency components).
A part of the heat to be heated escapes through the support portion and the lead wire (hereinafter, referred to as low frequency component delay). Then, as shown in FIG. 5, the effect of the low frequency component occurs in the entire region where the detection delay occurs, and the effect of the high frequency component occurs in the first half of the detection delay generation region.

Therefore, the correction of the intake air amount will be described separately for a high-frequency component delay and a low-frequency component delay, and the correction of the intake air amount at the time of adding / decreasing operation will be described. First, the delay correction by the high frequency component will be described with reference to FIG. 6. When the high frequency component delay time at which the high frequency component converges is set to T1 and the sampling period of the intake air amount Q is set to ΔT, the sampling period ΔT Is ΔT / T1.

The difference ΔQ (= Q−Q ₋₁ ) between the intake air amount obtained based on the output value of the air flow meter 1 at the previous sampling and the current sampling and the ΔQSS are approximately given by the following equations. To be satisfied. ΔQ = ΔQSS × ΔT / T1 (1) Also, QSS = Q ₋₁ + ΔQSS (2)
Substituting equation (1) into equation (2), QSS = Q- ₁ + ΔQ × T1 / ΔT = Q− ₁ + (Q−Q− ₁ ) × ΔT / T1 (3) Becomes.

Further, as shown in FIG. 7, the high-frequency component delay time T1 decreases as the elapsed time from when the ignition switch is turned on to when the starter switch is turned on, and becomes substantially constant when the elapsed time is further increased. Will be held. Therefore, the QSS
Can be obtained from the output value of the air flow meter 1, the elapsed time, and the sampling period ΔT. here,
The QSS includes an intake air amount based on an output value input of the air flow meter 1 and a high-frequency component delay correction amount. Hereinafter, the QSS is referred to as a high-frequency component delay.

Next, delay correction by low frequency components will be described with reference to FIGS.
Referring to FIG. 10, when the low-frequency component delay time at which the low-frequency component converges is set to T2 and the sampling period of the intake air amount is set to ΔT, the convergence rate within the sampling period ΔT is ΔT / T2. Further, the delay correction AFLE due to the low frequency component includes the delay generated at the time of the current sampling and the delay carried over from the previous sampling, and the sum of the delay correction AFLE is the delay correction amount AFLE.

First, the delay of the low-frequency component at the time of the current sampling will be described with reference to FIG. 8. The ratio of the delay of the low-frequency component AFLE generated this time to the delay of the high-frequency component generated this time (ΔQSS / AFLE) is substantially equal to the ratio (A / B) of the low frequency component and the high frequency component at the time when the increase of the intake air is started, so that ΔQSS / AFLE = A / B, and AFLF = ΔQSS B / A (4)

Next, the delay carry-over will be described with reference to FIG. 9. The delay carry-over AFLE is the carry-over AFLE _-1 at the previous sampling and the sampling period ΔT
AFLE _-1 × △ T /
T2 is multiplied by T2 and can be expressed by the following equation. AFLE = AFLE _-1 × AFLE _-1 × ΔT / T2 = AFLE _-1 × (T2-ΔT / T2) (5) Then, by adding the equations (4) and (5), the low level is obtained. The delay correction amount AFLE of the frequency component is obtained by the following equation.

AFLE = ΔQSS × B / A + AFLE ₋₁ (T2−ΔT / T2) = (QSS−QSS− ₁ ) × B / A + AFLE ₋₁ (T2−ΔT / T2) (6) B / A can be set to a fixed value from the characteristics of the air flow meter 1, and the low frequency component delay time T2 can be set according to the elapsed time from when the ignition switch is turned on to when the starter switch is turned on, as shown in FIG.

Next, the correction of the intake air amount during the acceleration / deceleration operation will be described with reference to FIG. First, at the time of acceleration operation, the amount of intake air increases rapidly, so that heat is easily taken from the hot wire resistance 2 and the amount of electricity supplied to the hot wire resistance 2 increases. Therefore, as shown in the left part of FIG. 11, the ratio of the delay of the high frequency component decreases (A decreases), whereas the ratio of the delay of the low frequency component increases (B increases). In contrast,
At the time of deceleration operation, contrary to the acceleration operation, the amount of intake air decreases rapidly, so that it is difficult to take heat from the heat ray resistance 2,
Since the amount of electricity to the hot wire resistance 2 is reduced, it is difficult to dissipate heat from the hot wire resistance 2 via the supporting portion and the lead wire.
The ratio of the high frequency component delay increases (A increases), while the ratio of the low frequency component delay increases (B decreases).

Thus, the low frequency component delay correction AFL
The transient correction amount AFLG for correcting the intake air amount during the transient operation by multiplying E is set to be large during the acceleration operation and set small during the deceleration operation. In this way, based on the correction amount between the high frequency component, the low frequency component, and the transient operation,
The true intake air amount QS passing through the air flow meter 1 can be expressed as follows.

QS = QSS + AFLE × AFLG = Q ₋₁ + (Q−Q ₋₁ ) × T 1 / ΔT + AFLG × − (QSS−QSS ₋₁ ) × B / A + AFLE ₋₁ (T 2 −ΔT / T 2) 3) Returning to the flowchart of FIG. 3, in S5, S2
Based on the intake air amount Q obtained in the above or the intake air amount QS corrected in S4 and the engine speed N,
The basic injection amount TP = KQ (orQS) / N (K is a constant) is calculated.

In S6, it is determined whether or not the calculated basic injection amount TP is smaller than the maximum basic injection amount TPMAX at the time of starting.
In the case of ES, the process proceeds to S7, and in the case of NO, the process proceeds to S8.
In S7, the calculated basic injection amount TP is selected, and in S8, the starting maximum basic injection amount TPMAX is selected. By the way, immediately after the ignition switch 10 is turned on, that is, immediately after the power supply to the air flow meter 1 is turned on, an excessive current flows through the hot wire resistance 2 (see FIG. 12). Therefore, TPMAX is provided for the purpose of suppressing the enrichment due to the characteristic (see FIG. 13). Therefore, when TPMAX is selected, the starter switch 15
Is turned on within about 3 seconds.

Then, the selected TP or TPMA
A fuel injection amount is calculated based on X, and a fuel injection valve (not shown) is driven according to the fuel injection amount to supply fuel to the engine. As described above, the ignition switch 1
Since the intake air amount detected by the air flow meter 1 can be obtained in accordance with the elapsed time from when the starter switch 15 is turned on to when the starter switch 15 is turned on, the air-fuel ratio can be optimally maintained, and engine stall at the time of starting can be prevented. Deterioration of emission and smoldering of the spark plug can be prevented. In particular, since the response delay of the hot-wire resistance 2 is corrected by dividing it into a high-frequency component, a low-frequency component, and a transient correction component, a true intake air amount can be secured with high accuracy.

The reason why the maximum elapsed time until the start of starting is set to 10 seconds in the present embodiment is that it is hardly longer than that in a normal start operation. Therefore, even if the maximum elapsed time is not set. Good.

[0028]

According to the present invention, as described above, the power supply is turned on.
Elapsed time from start to cranking start
(Ie, the inrush voltage to the electrical resistor)
Engine cranking is started during the time when
The fuel supply is limited to a specified value (upper limit).
To prevent the air-fuel ratio from becoming too rich.
On the other hand, from the power-on to the start of cranking,
If the elapsed time exceeds a predetermined time (that is, the electric
The effect of the rush voltage on the resistor is small and the suction
During times when the effect of the response delay on changes in
(If Seki's cranking was started), it was detected
A response delay correction is performed on the intake air amount to correct the response delay.
Set the fuel supply amount based on the amount of intake air after
To optimize the air-fuel ratio at startup.
To improve air-fuel ratio control accuracy at startup.
Can be. Therefore, occurrence of engine stall, deterioration of emission, smoldering of the spark plug, and the like can be prevented.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to claims of the present invention.

FIG. 2 is a configuration diagram showing one embodiment of the present invention.

FIG. 3 is a flowchart of the above.

FIG. 4 is a diagram showing a response delay of an output value of an air flow meter with respect to intake air.

FIG. 5 is a diagram for explaining the response delay in FIG. 4 in detail.

FIG. 6 is a diagram for explaining a high-frequency component delay according to the first embodiment;

FIG. 7 is a characteristic diagram of the above.

FIG. 8 is a diagram for explaining a low-frequency component delay according to the first embodiment;

FIG. 9 is another diagram for explaining a low-frequency component delay according to the first embodiment.

FIG. 10 is a characteristic diagram of the above.

FIG. 11 is a diagram for explaining correction of an intake air amount during a transient operation.

FIG. 12 is a diagram for explaining a conventional defect.

FIG. 13 is another diagram for explaining a conventional defect.

[Description of Signs] 1 ... Air flow meter 2 ... Heat wire resistance 10 ... Ignition switch 12 ... Microcomputer 13 ... Timer 15 ... Starter switch

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F02D 41/00-45/00

Claims (1)

(57) [Claims] 1. An electric resistor provided in an engine intake passage is energized from a power supply from a power supply, and an amount of intake air is detected from an amount of electric current supplied to the electric resistor. Fuel is supplied based on the detected amount of intake air.
To the fuel supply control device for the internal combustion engine,
Oite, the course of the time counting means for starting counting from the time of power supply to the electrical resistor, and cranking start detection means for detecting a cranking start of the engine, from the time the power is turned on until the cranking start time
Is within the predetermined time, the detected intake air amount
Limit the fuel supply amount set based on the
From the power-on to the start of cranking
If the time exceeds a predetermined time, the detected suction air
The response delay correction is performed on the air volume, and the response delay correction is performed.
Fuel supply amount that sets fuel supply amount based on intake air amount
Control means for supplying fuel to the internal combustion engine.
Control device.