JPH04255552A - Temperature sensing intake air flow measuring device - Google Patents

Abstract

PURPOSE:To suppress leanness of air-fuel ratio while preventing promotion of a pulsation by canceling only high frequency delay correction when a low frequency delay correction amount is a positive value, at the time of high load easily generating an intake pulsation. CONSTITUTION:In a temperature sensing flow meter, by assuming QA for intake air flow detection value, QA-1 for preceding time detection value and AFMTC>1 for constant, a high frequency delay correction amount Qss= QA-1+(QA-QA-1)XAFMTC is calculated. By assuming QSS-1 for preceding time arithmetic value of Qss and AFLEG, AFLETC(<1) for constant, a low frequency delay correction amount AFLE=(Qss-QSS-1)XAFLEG+AFLE-1XAFLETC is obtained to output Qs=Qss+AFLEXAFLEA as a measured value. On the other hand, at the time of high load where a throttle valve opening theta=theta0 (theta0 is predetermined opening of throttle valve easily generating intake pulsation), when a relation is AFLE>0, high frequency delay correction is canceled to obtain a measured value suited for a request value.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the intake air flow rate of an internal combustion engine based on a signal from a temperature-sensitive flowmeter using a temperature-sensitive resistance.

0002

[Prior Art] This type of measuring device is conventionally shown in Fig. 4.
There is something like the one shown in Figure 5.
(See Publication No. 920, etc.). In FIG. 4, a hot film element 1 as a temperature-sensitive resistor has a cylindrical body whose surface is coated with platinum that functions as a hot film, and a glass coating is applied from above.
The structure is such that the leads 1b protrude, and the leads 1a, 1
b is the opening 2a of the plug 2 installed in the intake passage of the engine.
It is connected by brazing to a pair of terminals 3a and 3b erected on the bottom wall. In addition, a temperature compensating resistor 4 has a pair of terminals 5 in the opening 2a of the plug 2 with both ends erected in the opening 2a.
a, 5b, and a coil-shaped reference resistor 6 is further wound around one end of the plug 2.

As shown in FIG. 5, a bridge circuit is constituted by the hot film element 1, temperature compensation resistor 4, reference resistor 6, and two fixed resistors 7 and 8 provided outside the intake passage. The potential US at the voltage dividing point a on the side where the hot film element 1 and the reference resistor 6 of this bridge circuit are connected in series (terminal voltage of the reference resistor 6),
The potential at voltage dividing point b on the side where temperature compensation resistor 4 and fixed resistors 7 and 8 are connected in series (terminal voltage of fixed resistor 8) is input to differential amplifier 9. Differential amplifier 9 and transistors 10 and 11 constitute a control circuit that controls the current supplied to the bridge circuit.

Therefore, when the intake air flow rate increases in a state where the bridge circuit is balanced, the element 1 is further cooled and its resistance value decreases, the bridge circuit becomes unbalanced, and the terminal voltage of the reference resistor 6 increases. As US increases, the output of the differential amplifier 9 increases. This increases the current supplied to the bridge circuit controlled by transistors 10, 11, heats element 1 and increases its resistance value, restoring the equilibrium condition of the bridge circuit.

Here, when the intake air flow rate decreases, for example, the element 1 is cooled and its resistance value decreases, but the element 1
The temperature compensation resistor 4 in the same atmosphere as is also cooled at the same time,
Since the resistance value decreases, changes in the current value supplied to the bridge circuit due to intake air temperature are suppressed. That is, the intake air flow rate and the current supplied to the bridge circuit correspond to each other regardless of the intake air flow rate, and for example, the intake air flow rate is measured by detecting the terminal voltage US of the reference resistor 6.

[0006] Incidentally, an intake air flow rate measuring device using such a hot film element has an aspect in which the responsiveness is inferior to that using a platinum wire as the temperature-sensitive resistor. Some devices correct detected values in this way. That is, when the intake air flow rate changes stepwise as shown by the solid line in FIG. 6, the response delay of the detected value shown by the dotted line is divided into a delay A due to high frequency change and a delay B due to low frequency change. .

[0007] Therefore, the high frequency delay correction amount QSS is set using the following equation. QSS=QA-1 + (QA-QA-1) ・A
FMTC Here, QA is the latest intake air flow rate detection value, QA-1 is the previous intake air flow rate detection value (for example, 4 ms ago), and AFMTC is an amplification constant greater than 1. Furthermore, the low frequency delay correction amount AFLE is calculated using the following equation.

[0008]AFLE=(QSS-QSS-1)・
AFLEG +AFLE-1・AFLETC Here, QSS-1 is the previous calculated value of QSS, AFLE
G, AFLETC (<1) are constants, AFLE
-1 is the previous calculated value of AFLE. Then, using these high frequency delay correction amount QSS and low frequency delay correction amount AFLE, the measured value QS of the intake air flow rate is determined by the following equation.

[0009]QS=QSS+AFLE×AFLEA
Here AFLEA is a constant. In addition, in the measurement method that performs high-frequency correction and low-frequency correction as described above, when the engine load increases to a high load close to full throttle as shown in FIG. 7a, intake pulsation occurs as shown in FIG. 7b, If the above-mentioned correction is performed in this case, the pulsation will be amplified and promoted, so a method is adopted in which the above-mentioned correction is canceled when the load is higher than a predetermined value and the pulsation is likely to occur.

0010

[Problem to be Solved by the Invention] However, if cancellation is performed at a high load as described above, at the time of cancellation, the low frequency delay still remains, so the correction for the low frequency delay is also canceled as shown in FIG. 7c. As a result, there are steps in the measured values, and when the air-fuel ratio is controlled based on the measured values, the air-fuel ratio becomes lean as shown by the solid line in e of the figure, which results in a decrease in acceleration performance and the like.

The present invention has been made in view of these conventional problems, and provides an internal combustion engine in which a highly accurate measured value of intake air flow rate can be obtained by appropriately setting the cancellation method and timing. The purpose of the present invention is to provide a temperature-sensitive intake air flow rate measuring device.

0012

[Means for Solving the Problems] Therefore, the temperature-sensitive intake air flow measuring device for an internal combustion engine according to the present invention includes a temperature-sensitive resistor and a plurality of resistors arranged in the intake passage of an internal combustion engine, as shown in FIG. and a control circuit that controls the current supplied to the bridge circuit based on the unbalanced voltage of the bridge circuit that changes due to a change in the resistance value of the temperature-sensitive resistor according to the intake air flow rate, A temperature-sensitive flowmeter is provided that outputs a voltage corresponding to the supply current as a signal of the intake air flow rate, and the detected value by the temperature-sensitive flowmeter is QA, and the previous detected value is QA-1. , a high-frequency delay correction amount calculating means for calculating a high-frequency delay correction amount QSS for correcting a detection delay in response to a high-frequency change in the intake air flow rate, and a low-frequency delay correction for correcting a detection delay in response to a low-frequency change in the intake air flow rate. A low frequency delay correction amount calculating means for calculating the amount AFLE, and QS calculated from the high frequency delay correction amount QSS and a predetermined ratio AFLEA of the low frequency delay correction amount AFLE is calculated as a measured value of the intake air flow rate. In a temperature-sensitive intake air flow rate measuring device, the temperature-sensitive intake air flow rate measuring device includes: a load detection means for detecting engine load; and a load detection means for detecting engine load; When the load is high and the low frequency delay correction amount AFLE is a positive value that increases the intake air flow rate, QA-1 = QA.
(QA-1 is the previous value of QA), QSS-1=Q
A (QSS-1 is the previous value of QS), and a canceling means for canceling the correction by the high frequency delay correction amount calculating means is provided.

[0013]

[Operation] Since pulsation is likely to occur when the load is higher than a predetermined value, the cancellation means that promotes the pulsation sets QA-1 = QA and QSS-1 = QA, thereby reducing the high-frequency delay correction amount QSS. In the arithmetic expression
(QA - QA-1) becomes 0 and QSS = QA
As a result, the high frequency delay correction is canceled and the promotion of pulsation is prevented, and in the calculation formula for the low frequency delay correction amount AFLE, (QSS-QSS-1) becomes 0, so AFLE=AFLE-1×AFLETC, AFL
Since ETC<1, the low frequency delay correction amount AFLE gradually decreases, and the air-fuel ratio characteristics that meet the required value during acceleration improve acceleration performance.

However, due to the influence of pulsation, the response delay correction due to low frequency changes may be corrected to the negative side, and if you cancel the high frequency delay correction at that time, the low frequency delay correction amount AFLE will cause the correction to be reversed until it reaches steady state after acceleration. Since the direction correction is applied and the lean air-fuel ratio is promoted, the high frequency lag correction is canceled only when the low frequency lag correction amount AFLE is on the positive side.

[0015]

[Embodiments] Examples of the present invention will be described below with reference to the drawings. In FIG. 2 showing the overall configuration of one embodiment, a bridge circuit is configured by a hot film element 1, a temperature compensation resistor 4, a reference resistor 6, and fixed resistors 7, 8, and a differential amplifier 9, transistors 10, 11 The bridge circuit and the control circuit constitute a temperature-sensitive flowmeter K, and the temperature-sensitive flowmeter K is installed in the intake passage of an internal combustion engine (not shown), as in the past. It is.

[0016] Then, the analog measurement signal of the temperature-sensitive flowmeter measured as the terminal voltage US of the reference resistor 6 is
After being converted into a digital signal via the D converter 12, it is input to the microcomputer 13. Further, a throttle sensor 14 as a load detection means for detecting the opening of the throttle valve is provided in the intake passage, and the throttle valve opening signal from the throttle sensor 14 is also digitalized via the A/D converter 12. After being converted into a signal, it is input to the microcomputer 13.

The microcomputer 13 performs correction calculation processing on the measurement signal from the temperature-sensitive flowmeter as described later. The arithmetic processing by the microcomputer 13 will be explained according to the flowchart of FIG. Step (Denoted as S in the figure. The same applies below) In step 1, the temperature-sensitive flowmeter K
Detection value QA of intake air flow rate from , previous detection value Q
A-1, previously calculated high frequency delay correction amount QSS-1,
Read the previously calculated low frequency delay correction amount AFLE-1.

In step 2, the high frequency delay correction amount QSS
is calculated using the following formula. QSS=QA-1 + (QA-QA-1) ×A
FMTC; AFMTC is a constant greater than 1...(1
) That is, the function of step 2 corresponds to the high frequency delay correction amount calculation means. In step 3, the low frequency delay correction amount AF
LE is calculated using the following equation. AFLE= (QSS-QSS-1) ×AFLEG
+AFLE-1×AFLETC; AFLEG, AFL
ETC is a constant smaller than 1 (2) That is, the function of step 3 corresponds to the low frequency delay correction amount calculation means.

In step 4, it is determined whether the throttle valve opening θ detected by the throttle sensor 11 is greater than or equal to a predetermined opening θ0 at which intake pulsation is likely to occur. If it is determined in step 4 that θ<θ0, step 5
Then, the measured value of the intake air flow rate is calculated using the following equation and output. QS=QSS+AFLE×AFLEA ;AFLEA
is a constant smaller than 1 (3) That is, the function of step 5 corresponds to the measured value output means.

On the other hand, when it is determined in step 4 that θ≧θ0, the process proceeds to step 6, and it is detected whether the low frequency delay correction amount AFLE calculated in step 3 is a positive value. When it is determined that the value is not positive, that is, the value is less than or equal to 0, the process proceeds to step 5, where the measured value QS is calculated and outputted using equation (3). Also, step 6
When it is determined that the low frequency delay correction amount AFLE is a positive value, the process proceeds to step 7, and QA-1 = QA, Q
After setting SS-1=QA, in steps 8 and 9, the high frequency delay correction amount QSS and the low frequency delay correction amount A are determined, respectively.
Recalculate FLE.

As a result, QSS becomes equal to the detected value QA, and the high frequency delay correction is canceled, and at the same time, QSS becomes equal to the detected value QA.
Since SS-QSS-1 becomes 0, the low frequency delay correction amount becomes AFLE=AFLE-1×AFLETC. That is,
The function of step 7 corresponds to a canceling means. In step 10, it is determined whether or not the recalculated low frequency delay correction amount AFLE has become 0 or less, and if it has become 0 or less, the process proceeds to step 11 and the low frequency lag correction amount AFLE is
After holding FLE=0, the process proceeds to step 5, and if the low frequency delay correction amount AFLE is a positive value, the process directly proceeds to step 5, where the measured value QS is calculated by the above equation (3) and output.

[0022] Here, in step 7, QA-1 = QA
= QSS-1, so as mentioned above, QSS = QA
Therefore, when proceeding directly from step 8 to step 5, AFLE = AFLE - 1 × AFLETC, and the measured value QS is QS = QA + AFLE × AFLEA =
QA + AFLE - 1 x AFLETC x AFLEA. Here, since AFLETC is a constant smaller than 1, the low frequency delay correction amount AFLE converges to 0 each time the calculation process is repeated.

Furthermore, when AFLE=0 in step 9, the measured value QSS matches the detected value QA. With such a configuration, only the high frequency delay correction is canceled when the low frequency delay amount is a positive value during high loads that are likely to cause pulsation, thereby reducing the low frequency delay in the positive direction without promoting pulsation. Since the correction can be made close to the required value shown by the dotted line in Figure 7d, the air-fuel ratio can be smoothly enriched and shifted to the required air-fuel ratio after acceleration as shown by the dotted line in Figure 7e, resulting in a good result. Acceleration performance can be obtained. Note that if you cancel the high frequency delay correction when the low frequency delay correction amount AFLE becomes a negative value due to the influence of pulsations, the correction in the opposite direction to the original positive direction will continue to be performed until a steady state is reached. This promotes a leaner fuel ratio, further deteriorating acceleration performance. According to the present invention, such a situation can be prevented.

[0024]

As explained above, according to the present invention, there is provided a temperature-sensitive intake air flow rate sensor that performs high-frequency delay correction and low-frequency delay correction on the intake air flow rate detected by the temperature-sensitive flowmeter and outputs the resultant value as a measured value. The measuring device is configured to cancel only the high frequency delay correction when the low frequency delay correction amount is a positive value during high loads that are likely to cause intake pulsation.
While preventing the promotion of pulsation, it is possible to suppress the air-fuel ratio from becoming leaner and bring it closer to the required value, thereby improving acceleration performance.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention.

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

FIG. 3 is a flowchart showing an intake air flow rate measurement routine of the embodiment.

FIG. 4 is a front view showing a conventional example of a temperature-sensitive flowmeter.

FIG. 5 is a circuit diagram of the temperature-sensitive flowmeter shown above.

FIG. 6 is a diagram showing the response delay of the temperature-sensitive flowmeter.

FIG. 7 is a diagram showing differences in the state of each part between the embodiment and the conventional example.

[Explanation of symbols]

1 hot film element 4 temperature compensation resistor 6 reference resistor 7, 8 fixed resistor 9 differential amplifier 10, 11 transistor 13 microcomputer 14
throttle sensor

Claims (1)

[Claims] 1. A bridge circuit formed by a temperature-sensitive resistor and a plurality of resistors disposed in an intake passage of an internal combustion engine, and a bridge circuit that changes by a change in resistance value of the temperature-sensitive resistor according to an intake air flow rate. and a control circuit that controls the current supplied to the bridge circuit based on the unbalanced voltage, and includes a temperature-sensitive flowmeter configured to output a voltage corresponding to the supplied current as a signal of the intake air flow rate. High frequency delay correction amount calculating means for calculating a high frequency delay correction amount QSS for correcting a detection delay with respect to high frequency changes in intake air flow rate, where the detected value by the thermal flowmeter is QA and the previous detected value is QA-1. and a low frequency delay correction amount AFLE for correcting the detection delay due to low frequency changes in the intake air flow rate.
a low frequency delay correction amount calculating means for calculating the low frequency delay correction amount, and outputs QS obtained by calculating from the high frequency delay correction amount QSS and a predetermined ratio AFLEA of the low frequency delay correction amount AFLE as a measured value of the intake air flow rate. A temperature-sensitive intake air flow rate measuring device comprising: a load detection means for detecting engine load; and a load detection means for detecting engine load; QA-1=
QA (QA-1 is the previous value of QA), QSS
-1=QA (QSS-1 is the previous value of QS). A temperature-sensitive intake air flow rate measuring device comprising a canceling means for canceling the correction by the high frequency delay correction amount calculating means.