JPH0638052B2 - Intake air flow rate measuring device for internal combustion engine - Google Patents

Description

TECHNICAL FIELD The present invention relates to an intake air flowmeter measuring device for an internal combustion engine,
In particular, the present invention relates to a device including a temperature-sensitive resistor provided in an intake passage of an engine.

<Prior Art> In a conventional electronically controlled fuel injection type internal combustion engine, a hot wire type flow meter (actually developed 60-152928) including a temperature sensitive resistor (heat wire) interposed in an intake passage of the engine. Based on an electric signal (voltage) output corresponding to the intake air flow rate Q of the engine (see, for example, Japanese Patent Publication), the intake air flow rate data previously stored in the control unit is retrieved (or calculated), A basic fuel injection amount Tp (← K × Q / N; K is a constant) is calculated from the intake air flow rate Q and the engine rotation speed N detected by a crank angle sensor or the like,
Further, the basic fuel injection amount Tp is corrected according to the engine operating state such as the cooling water temperature Tw, and the final fuel injection amount Ti is obtained.
Is calculated, and an injection pulse signal corresponding to this fuel injection amount Ti is output to the electromagnetic fuel injection valve to intermittently inject and supply the fuel to the engine.

<Problems to be Solved by the Invention> By the way, in the above-mentioned hot wire type flow meter, the temperature sensitive resistor (heat wire) provided in the intake passage of the engine is cooled by the intake air when the intake air flow rate increases, for example. Since the resistance value decreases, the electrical signal (voltage) output correspondingly changes to detect the intake air flow rate Q of the engine.

Therefore, if dust or oil component adheres to the temperature sensitive resistor (heat wire), the adhered substance acts to suppress the temperature drop of the temperature sensitive resistor, and therefore the temperature (resistance value) change characteristic with respect to the intake air flow rate Q is changed. Changes, and an amount smaller than the actual intake air flow rate Q is output as a detection value as shown in FIG. For this reason, when the engine is stopped, a large current is supplied to the temperature-sensitive resistor to heat it to burn off the adhered matter (see Japanese Utility Model Laid-Open No. 61-52228). When the temperature-sensitive resistor deteriorates or remains without being able to satisfactorily burn off the deposit, the hot-wire type flow meter uses the amount smaller than the actual intake air flow rate Q as the detection value as described above. Because of the output, the basic fuel injection amount Tp is set to be smaller than the required amount of the engine, and the air-fuel ratio of the intake air-fuel mixture becomes lean, which may impair the drivability of the engine.

The present invention has been made in view of the above problems, and provides an intake air flow rate measurement device capable of self-diagnosing a decrease in detection accuracy of a hot-wire flow meter and correcting the detection value to correspond to an actual intake air flow rate. The purpose is to

<Means for Solving Problems> Therefore, in the invention, as shown in FIG. 1, intake air for detecting the intake air flow rate of the engine, which is configured to include a temperature-sensitive resistor interposed in the intake passage of the engine The flow rate detecting means, the engine speed detecting means for detecting the engine speed, the throttle valve opening detecting means for detecting the opening degree of the throttle valve interposed in the intake passage, the throttle valve opening degree and the engine speed Intake air flow rate storage means that stores the intake air flow rate in a plurality of measurement point operation states set as parameters, and the measurement point operation state based on the engine speed and throttle valve opening detected by the detection means, respectively. It is determined by the measuring point operating state determining means that determines whether or not the operating state is a predetermined measuring point operating state. The intake air flow rate search means for searching the intake air flow rate storage means for the intake air flow rate at the corresponding measurement point operating state, and the intake air flow rate searched by the intake air flow rate search means and the intake air flow rate detection means Intake air deviation amount calculation storage means for calculating and storing a deviation amount from the detected intake air flow rate, and deviation amount of the intake air flow rate at a plurality of measurement point operating states stored in the intake air deviation amount calculation storage means Intake air flow rate correction formula setting means for setting a correction formula for the intake air flow rate based on the above, and intake air for correcting the intake air flow rate detected by the intake air flow rate detection means based on the set intake air flow rate correction formula And a flow rate correction means.

<Operation> According to the intake air flow rate measuring device, it is determined by the detected values of the engine speed and the throttle valve opening that the engine operating speed and the throttle valve opening are in the measurement point operating state set using the parameters. Then, the deviation amount between the intake air flow rate stored in advance corresponding to the operating state of the measurement point and the intake air flow rate detected by the intake air flow rate detection unit including the temperature sensitive resistor. Is calculated and the calculation result is stored. Then, when the deviation amount is calculated and stored in a plurality of measurement point operation states, a correction formula for the intake air flow rate is set based on the correlation between the measurement point operation states and the deviation amount thereof. And
The final intake air flow rate is obtained by correcting the intake air flow rate detected by the intake air flow rate detecting means by the intake air flow rate correction formula.

<Embodiment> An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 shows a system outline of an electronically controlled fuel injection type internal combustion engine equipped with an intake air flow rate measuring device according to the present invention.

Throttle valve (not shown) installed in the intake passage of the engine
The throttle valve opening signal α output from the throttle valve opening sensor 1 as the throttle valve opening detection means for detecting the opening α of the throttle valve, the heat ray (temperature-sensitive resistance) interposed in the upstream intake passage of the throttle valve. Output voltage Vs and engine rotational speed N output from the hot-wire flowmeter 2 as an intake air flow rate detecting means configured to include an intake air flow rate Q.
The engine rotation speed signal N output from the rotation speed sensor 3 serving as the engine rotation speed detecting means for detecting the engine speed and the cooling water temperature signal Tw output from the water temperature sensor 4 detecting the temperature Tw of the cooling water in the engine cooling jacket are , Is input to the control unit 5 having a built-in microcomputer.

The control unit 5 corrects the detected value of the intake air flow rate Q based on these signals, sets the fuel injection amount Ti, and outputs an injection pulse signal corresponding to this fuel injection amount Ti to the electromagnetic fuel injection valve 7 Output to the drive circuit 6 of.

That is, in this embodiment, the control unit 5 is
The measurement point operation state determining means, the intake air flow rate search means, the intake air flow rate storage means, the intake air deviation amount calculation storage means, the intake air flow rate correction formula setting means, and the intake air flow rate correction means are also used.

Next, the detected intake air flow rate Q by the control unit 5
The correction formula setting and the setting control of the fuel injection amount Ti based on the corrected intake air flow rate Q will be described with reference to the flowcharts of FIGS. 3 and 4.

The flowchart of FIG. 3 shows a correction formula setting routine for setting a correction formula for correcting the intake air flow rate Q detected by the hot-wire flow meter 2.

Step (denoted as S in the figure, the same applies hereinafter) 1
Then, the throttle valve opening α detected by the throttle valve opening sensor 1, the output voltage Vs of the hot-wire flow meter, and the engine rotation speed N detected by the rotation speed sensor 3 are input.

In step 2, it is determined whether or not the current operating state is the first measurement point operating state.

The first measurement point operation state (# 1) and the second and third measurement point operation states (# 2, # 3) described later are operation states in which the intake air flow rate Q is different as shown in FIG. The intake air flow rate Q ₁ in the first measurement point operation state is the smallest, and the intake air flow rate Q ₃ in the third measurement point operation state is the highest.

The operating state of these measurement points is the throttle valve opening α
And the engine rotation speed N. That is, when the intake air flow rate Q in the measurement point operating state is set, the operating state in which the intake air flow rate Q is obtained is divided by the throttle valve opening α and the engine rotation speed N, and the actually detected throttle valve opening α And whether or not the engine rotation speed N indicates an operating state in which the intake air flow rate Q in the measurement point operating state is obtained.

When it is determined in step 2 that the current operating state is the first measurement point operating state, that is, the throttle valve opening α
When the engine speed N indicates the operating state in which the intake air flow rate Q ₁ is obtained, the process proceeds to step 3, and the voltage output from the hot wire type flow meter 2 in the initial state where the hot wire is not contaminated as shown in FIG. The deviation ΔVs ₁ between s ₁ (corresponding to the intake air flow rate Q ₁ and stored in advance) and the current output voltage Vs from the hot-wire flowmeter 2 input in step ₁ is calculated and stored. The larger the deviation ΔVs ₁ , the lower the detection accuracy of the hot-wire type flowmeter 2 due to contamination of the hot-wire.

On the other hand, when it is determined in step 2 that the current operating state is not the first measurement point operating state, the process proceeds to step 4 and it is determined whether it is the second measurement point operating state in the same manner as in step 2.

Here, when it is determined that the current operating state is the second measurement point operating state, the process proceeds to step 5 and, similarly to step 3, in the second measuring point operating state, the hot wire system is used in the initial state where the heating wire is not contaminated. A deviation ΔVs ₂ between Vs ₂ output from the flow meter 2 (corresponding to the intake air flow rate Q ₂ and stored in advance) and the current output voltage Vs from the hot-wire flow meter 2 input in step 1 is calculated. ·Remember.

When it is determined in step 4 that the operating state is not the second measurement point, it proceeds to step 6 to check whether the current operating state (throttle valve opening α and engine speed N) is the third measurement point operating state. It is determined in the same manner as steps 2 and 4 above.

Here, when it is determined that the operating state is the third measurement point operation, the process proceeds to step 7, and in the third measurement point operation state, the voltage Vs ₃ output from the hot-wire flow meter 2 in the initial state in which the heating wire is also clean. (Intake air flow rate Q
₃ ), which is stored in advance) and the deviation ΔVs ₃ between the current output voltage Vs from the hot-wire flowmeter 2 input in step 1 is calculated and stored.

On the other hand, when it is determined in step 6 that the current operating state is not the third measurement point operating state, that is, when the current operating state does not correspond to any of the first, second and third measurement point operating states , This routine is finished as it is.

When the deviations ΔVs _{1 to} ΔVs ₃ (the deviation amount increases as the contamination of the heat ray in the heat ray type flow meter 2 progresses) are calculated in steps 3, 5 and 7, in steps 8 and 9 respectively. A correction formula for the output voltage Vs in the correction zone is set.

In step 8, between the first measurement point operating state and the second measurement point operating state (the intake air flow rate Q is Q ₁ and Q ₂
The correction equation in the first correction zone (between and) is set according to the following equation.

Vs ← Vs + ΔVs ₁ + {(ΔVs ₂ −Δs ₁ ) / (Vs ₂ −Vs ₁ )} × {(Vs + Vs ₁ y) / (Vs ₂ y−Vs ₁ y)} Here, Vs ₁ y and Vs ₂ y a first respectively a deviation Delta] s ₁ in the second measurement point operating condition, a hot-wire flow meter 2 output voltage Vs used to calculating the Delta] s _2, deviation Delta] s ₁ in step 3 or step 5, Delta] s ₂ It is the one that was stored when the calculation was performed.

On the other hand, in step 9, between the second measurement point operating state and the third measurement point operating state (when the intake air flow rate Q is Q ₂
The correction equation in the second correction zone (between Q and Q ₃ ) is set according to the following equation.

Vs ← Vs + ΔVs ₂ + {(ΔVs ₃ −Δs ₂ ) / (Vs ₃ −Vs ₂ )} × {(Vs + Vs ₂ y) / (Vs ₃ y−Vs ₁ 2)} where Vs ₃ y is Vs ₁ Similar to y and Vs ₂ y, the output voltage Vs of the hot-wire flow meter 2 used to calculate the deviation ΔVs ₃ in the operating state at the third measurement point, and the step 7
It is stored when the deviation ΔVs ₃ is calculated in.

The above correction formula is for raising the output voltage Vs, which is lowered when the heat wire of the heat wire type flow meter 2 is dirty as shown in FIG. 5, to the initial value, and is between the measurement point operating states. As the deviation amount linearly increases or decreases, the deviation amount between the measurement point operation states is estimated based on the deviations ΔVs _{1 to} ΔVs ₃ in the measurement point operation state to increase and correct the output voltage Vs. Therefore, as shown in FIG. 5, the correction formula is set so as to correspond to the output voltage Vs which actually changes in a curve with respect to the intake air flow rate Q.

The correction formula for the intake air flow rate Q set in this way is
It is used in the fuel injection amount setting routine shown in the flowchart of FIG.

In step 11, the throttle valve opening α detected by the throttle valve opening sensor 1, the output voltage Vs of the hot-wire flow meter 2, the engine rotation speed N detected by the rotation speed sensor 3, and the water temperature sensor 4 are detected. Enter the cooling water temperature Tw.

In step 12, the hot-wire flow meter 2 entered in step 11
The output voltage Vs of is converted into the intake air flow rate Q.

In step 13, the intake air flow rate Q converted in step 12
The correction zone is determined based on. Here, when it is determined that the first correction zone (Q ₁ <Q <Q ₂ ), the process proceeds to step 14, and the output input in step 11 based on the correction formula set in step 8 of the flowchart of FIG. The correction calculation of the voltage Vs is performed to increase the output voltage Vs lowered due to the contamination of the heating wire to the output voltage Vs in the initial state.

In step 13, the second correction zone (Q ₂ <Q <Q ₃ )
If it is determined that the output voltage Vs input in step 11 is corrected based on the correction equation set in step 9 of the flowchart of FIG.

On the other hand, when it is determined in step 13 that the operating state is outside the correction zone, the process jumps to step 17 without performing the correction based on the correction formula.

When the correction calculation based on the correction formula of the output voltage Vs is performed in step 14 or step 15, the corrected output voltage Vs is converted into the intake air flow rate Q in step 16.
That is, the intake air flow rate Q converted in step 16
Is a value obtained by correcting a decrease in detection accuracy due to contamination of the heat ray of the heat ray type flow meter 2, and is a value close to an actual value.

In step 17, the intake air flow rate Q obtained by converting the output voltage Vs in step 12 or 16 and step 11
The basic fuel injection amount Tp (← K × Q / N; K is a constant) is calculated on the basis of the engine rotational speed N input in (1).

In step 18, the cooling water temperature Tw input in step 11
And various correction factors COEF are set by the throttle valve opening α (indicating the idle state and the acceleration state),
A voltage correction amount Ts for correcting the change in the effective valve opening time of the fuel injection valve 7 due to the battery voltage is set.

In step 19, the basic fuel injection amount Tp calculated in step 17 is corrected and calculated by the correction coefficient COEF and the voltage correction amount Ts set in step 18, and the final fuel injection amount Ti (← Tp × COEF + Ts) is set. To do.

In step 20, a predetermined amount of fuel is injected and supplied to the engine by outputting an injection pulse signal corresponding to the set fuel injection amount Ti to the drive circuit 6 of the fuel injection valve 7 at a predetermined timing.

In the present embodiment, the correction formula for the intake air flow rate Q is derived by setting the measurement point operating states at three locations.
It is obvious that the correction can be made to be closer to the actual value by increasing the operating state of the measurement points.

<Effects of the Invention> As described above, according to the present invention, the decrease in the accuracy of detecting the intake air flow rate due to the contamination of the temperature sensitive resistor (heat wire) is caused by the difference between the initial intake air flow rate and the detected value in a plurality of measurement point operating states. Self-diagnosis is performed based on the deviation, and the detected value is corrected based on the correction formula set based on this diagnosis result, so even if dirt on the temperature-sensitive resistor occurs, the inhalation approximates the actual value. The effect is that the air flow rate can be detected.

[Brief description of drawings]

FIG. 1 is a block diagram of the present invention, FIG. 2 is a system block diagram showing an embodiment of the present invention, FIG. 3 is a flow chart showing a correction formula setting routine in the same embodiment, and FIG. FIG. 5 is a flowchart showing the fuel injection amount setting routine, and FIG. 5 is a graph showing the relationship between the output voltage of the hot wire type flow meter and the intake air flow rate. 1 ... Throttle valve opening sensor, 2 ... Hot wire type flow meter,
3 ... Rotation speed sensor, 5 ... Control unit

Claims (1)

[Claims] 1. An intake air flow rate detecting means for detecting an intake air flow rate of the engine, the intake air flow rate detecting means including a temperature sensitive resistor interposed in an intake passage of the engine, and an engine rotational speed detecting means for detecting an engine rotational speed. , A throttle valve opening detecting means for detecting the opening of a throttle valve interposed in the intake passage, and the intake air flow rate in a plurality of measurement point operating states set with the throttle valve opening and the engine rotation speed as parameters Intake air flow rate storage means, measurement point operation state determination means for determining the measurement point operation state based on the detected engine speed and throttle valve opening, and predetermined measurement by the measurement point operation state determination means When it is determined that it is in the point operation state, the intake air flow rate corresponding to the measurement point operation state is retrieved from the intake air flow rate storage means. An intake air flow rate search means, and an intake air deviation amount calculation memory for calculating and storing a deviation amount between the intake air flow rate searched by the intake air flow rate search means and the intake air flow rate detected by the intake air flow rate detection means. Means, and intake air flow rate correction formula setting means for setting a correction formula for the intake air flow rate based on the deviation amounts of the intake air flow rate in a plurality of measurement point operating states stored in the intake air deviation amount calculation storage means, An intake air flow rate measuring device for an internal combustion engine, comprising: an intake air flow rate correcting means for correcting the intake air flow rate detected by the intake air flow rate detecting means based on the intake air flow rate correction formula.