JP2003287453A - Intake-air flow measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that a mean intake-air flow rate to be found by a computing operation does not agree with a mean value of a true intake-air flow rate because in conventional cass a region to be corrected with reference to an output of a flow rate sensor is limited to an inverse region in which a flow-rate converted value of the output of the sensor is negative. <P>SOLUTION: By a correction-reference-value decision means 22, a correction reference value Qx according to an operating state of an engine is found. By a backflow-side output correction means 23, a backflow output value Vg on the side of a backflow direction from the correction reference value Qx is corrected from among an output value V of the flow rate sensor 8 so as to find a backflow-side correction output value Vg'. By a flow-rate calculation means 9, the mean intake-air flow rate Q is found on the basis of an intake-air flow rate Qj to be found from an output value Vj in a forward flow direction from the correction reference value Qx from among the output value V of the flow rate sensor 8 and on the basis of a backflow-side intake-air flow rate Qg to be found from the correction output value Vg'. Therefore, the mean intake-air flow rate Q is measured with high accuracy according to a wide operation of the engine irrespective of the operating state of the engine. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an internal combustion engine (hereinafter,
The present invention relates to an intake air flow rate measuring device sucked into an engine.

[0002]

2. Description of the Related Art An intake pipe of an engine is equipped with a flow rate sensor for measuring a flow rate of intake air taken into the engine. As a flow rate sensor, there is known a flow rate sensor that measures a forward flow rate and a reverse flow rate of air flowing in the intake pipe by using a heating resistor. The solid line A in FIG. 9 shows the output characteristic of the flow sensor when the engine is in the low rotation / high load region (a region where a large backflow occurs). The intake air flow rate calculated from the sensor output of the above type is shown in FIG.
It is shown as the flow rate change of the solid line B of 0. The change in the true intake air flow rate at this time is indicated by the broken line α in FIG. 10.

As is clear by comparing the broken line α and the solid line B in FIG. 10, the flow rate (solid line B) obtained from the sensor output is
The error with respect to the true intake air flow rate (broken line α) is larger on the reverse flow side than on the forward flow side. Therefore, the average intake air flow rate obtained from the sensor output becomes a value larger than the average value of the true intake air flow rate.

As a technique for avoiding the above-mentioned problems, the technique disclosed in Japanese Patent Laid-Open No. 9-15013 is known. In this technique, when the sensor output of the flow rate sensor is in the reverse flow area (the area where the flow rate is negative), the output is corrected as shown by the chain line A'in FIG. When the intake air flow rate is calculated from the correction value thus corrected, the flow rate changes shown by the one-dot chain line B ′ in FIG. 10 when the engine is in the low rotation / high load range, and the average intake air flow rate obtained by the calculation is The average value of the true intake air flow rate is almost the same.

[0005]

As described above, the technique disclosed in the above publication discloses the average intake air flow rate obtained by correcting the output of the flow rate sensor in the low engine speed / high load range. The value can be substantially matched with the average value of the true intake air flow rate. However, the area to correct the output of the flow sensor is limited to the reverse flow area (the area where the flow rate calculated by the sensor output is the negative side) with the forward flow area and the reverse flow area as the boundary, so the average inhalation calculated The air flow rate and the true average value of the intake air flow rate do not match.

Specifically, for example, when the average value of the true intake air flow rate is slightly increased due to an increase in the engine speed or the like, a reverse flow region to be corrected (a region where the flow rate calculated by the sensor output is on the negative side). Is reduced, and the area to be corrected becomes smaller (or disappears), so it becomes impossible to accurately correct the output on the backflow side of the flow sensor,
The average intake air flow rate obtained by the calculation and the average value of the true intake air flow rate do not match.

Further, for example, when the opening degree of the throttle valve changes or when the lift amount of the intake valve changes, the ratio of the forward flow rate to the reverse flow rate of the intake pulsation (and the intake pulsation width) is changed. fluctuate. That is, in this case, the backflow region to which correction is applied (the region where the flow rate calculated by the sensor output is on the negative side) fluctuates, and the average intake air flow rate obtained by calculation and the average value of the true intake air flow rate are It will not match.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances and has the following two objects. The first purpose is to accurately correct the backflow side output of the flow rate sensor according to the operating state of the engine, so that the average intake air flow rate can be obtained over a wide operating range of the engine regardless of the operating state of the engine. Measure with high accuracy. The second purpose is to accurately correct the intake air flow rate on the reverse flow side, which is obtained from the flow rate sensor according to the operating state of the engine, so that the average value is obtained over a wide operating range of the engine regardless of the operating state of the engine. Measure the intake air flow rate with high accuracy.

[0009]

Next, the means corresponding to each claim will be described. The reference numerals shown in the respective means are added for the purpose of assisting understanding. [Means of Claim 1] The true air flow flowing in the intake pipe in accordance with the operating state of the engine is such that the intake air flow rate at the branch portion on the forward flow side and the reverse flow side fluctuates or the forward flow rate of the intake pulsation is in the reverse direction. The ratio with the flow rate may change. Therefore, the correction reference value (Qx) is calculated according to the operating state of the engine. Then, of the output value (V) of the flow rate sensor, the correction reference value (Q
x), the output value (Vg) on the backflow side is corrected to obtain the backflow correction output value (Vg '), and the backflow correction output value (Vg') and the output value (V) of the flow sensor are calculated. Among them, the average intake air flow rate (Q) is obtained based on the output value (Vj) on the forward flow direction side of the correction reference value (Qx).

As described above, by adopting the means of claim 1, the output value of the flow rate sensor on the backflow side of the intake pulsation can be appropriately corrected according to the operating state of the engine, so that the operation of the engine is performed. Regardless of the state, the average intake air flow rate can be measured with high accuracy over a wide operating range of the engine.

[Means for Claim 2] The true airflow flowing in the intake pipe in accordance with the operating state of the engine is such that the intake air flow rate at the branch portion on the forward flow side and the reverse flow side fluctuates, or the forward flow rate of the intake pulsation. And the reverse flow rate may change. Therefore, the correction reference value (Qx) is calculated according to the operating state of the engine. Then, of the output values (V) of the flow rate sensor, the intake air flow rate (Qg) obtained from the output value (Vg) on the reverse flow direction side of the correction reference value (Qx) is corrected to correct the reverse flow side corrected intake air flow rate ( Qg ') is calculated, and the intake air flow rate (Qj) is calculated from the output value (Vj) of the flow rate sensor on the side of the forward flow direction of the correction reference value (Qx). Then, the average intake air flow rate (Q) is calculated based on ', Qj).

As described above, by adopting the means of claim 2, it is possible to appropriately correct the intake air flow rate on the reverse flow side of the intake pulsation according to the operating state of the engine. Therefore, the average intake air flow rate can be measured with high accuracy over a wide operating range of the engine.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to two examples and modifications. [First Embodiment] A fuel injection device 2 using an intake air flow rate measuring device 1 will be described with reference to FIGS. As shown in FIG. 1, the fuel injection device 2 includes an intake air flow rate measurement device 1 for measuring the intake air flow rate, and a fuel injection amount calculation device 3 for calculating a predetermined injection amount according to the intake air flow rate. The fuel injection valve 4 injects the injection amount calculated by the fuel injection amount calculation device 3 at a predetermined timing.

The intake air flow rate measuring device 1 is attached to an intake pipe 6 (see FIG. 2) of an engine 5 and is used to detect an intake air flow rate sucked into the engine 5 (see FIGS. 2 and 3). ) And a flow rate calculating means 9 (see FIG. 1) for calculating the intake air flow rate from the output of the flow rate sensor 8 (see FIG. 3) attached to the air flow meter 7.

First, a schematic structure of the intake system of the engine 5 will be described with reference to FIG. The intake system of the engine 5
An intake pipe 6 for guiding the air filtered by the air cleaner 10 to each cylinder 11 of the engine 5 is provided. The intake pipe 6 includes a throttle valve 12 and a surge tank 13 in addition to the air flow meter 7 described above. Has been done. When the piston 14 of the engine 5 descends, the intake valve 15 opens so that the air filtered by the air cleaner 10 is sucked into the cylinder 11 of the engine 5.

The structure of the air flow meter 7 will be described with reference to FIG. The air flow meter 7 is an intake pipe 6 of the engine 5.
The sensor body 16 attached to the sensor body 16 and the flow rate sensor 8 held in the sub-flow passage 17 formed in the sensor body 16. The sub-flow passage 17 is provided so that a part of the intake air flowing in the intake pipe 6 bypasses and flows.

The flow rate sensor 8 measures the intake air flow rate in the forward flow direction of the intake air and the intake air flow rate in the reverse flow direction by using a heating resistor, and the detected intake air flow rate is an electrical signal. Output as. Although the flow rate sensor 8 outputs a voltage value according to the intake air flow rate in this embodiment, it may output a current value. Specifically, the flow rate sensor 8 of this embodiment generates the output voltage shown by the solid line A in FIG. 4 with respect to the intake air flow rate passing through the flow rate sensor 8, and the intake air flow rate in the forward flow direction increases. Accordingly, the output voltage rises in a predetermined curve, and as the intake air flow rate in the reverse flow direction increases, the output voltage falls in a predetermined curve (a curve different from the rising curve).

Next, an outline of the intake air flow rate measuring device 1 will be described.
A description will be given with reference to FIG. The output voltage of the flow rate sensor 8 is converted into an average intake air flow rate by the flow rate calculation means 9 provided in the ECU (abbreviation of engine control unit) 20. The flow rate calculation means 9 includes a map or an arithmetic expression in which the intake air flow rate (including forward flow and reverse flow) corresponding to the output voltage of the flow rate sensor 8 is set, and the output of the flow rate sensor 8 that fluctuates due to intake pulsation or the like. The intake air flow rate that fluctuates due to intake pulsation or the like is obtained from the voltage, and the average intake air flow rate is obtained from the value.

When the average intake air flow rate is obtained by using the output characteristic of the flow rate sensor 8 (solid line A in FIG. 4) as in the above-described configuration, the problems described in the section of the prior art occur. That is, the change in the voltage output of the flow rate sensor 8 is shown by the solid line A in FIG. 4, and for example, when the engine 5 is in the low rotation and high load range, the intake air flow rate obtained based on the solid line A is The value becomes the value indicated by the solid line B in FIG. 5, and the change in the actual intake air flow rate (true intake air flow rate) (broken line α in FIG. 5)
On the other hand, the error (the difference between the true intake air flow rate and the calculated flow rate) becomes larger on the reverse flow side than on the forward flow side. Therefore, the average intake air flow rate obtained from the output of the flow rate sensor 8 becomes larger than the average value of the true intake air flow rate.

In order to avoid the above-mentioned problems, the intake air flow rate measuring device 1 of this embodiment corrects the voltage output on the reverse flow side of the voltage output of the flow rate sensor 8 according to the operating state of the engine 5, The average intake air flow rate is determined based on the correction value.

This specific structure is shown in FIGS.
This will be described with reference to FIG. In addition to the configuration shown in FIG. 1A, the intake air flow rate measuring device 1 of the present embodiment has an operating state detecting means 21 for detecting the operating state of the engine 5, and an engine detected by the operating state detecting means 21. The correction reference value determining means 22 for determining the correction reference value Qx according to the operating state of No. 5, and the output value Vg of the output value V of the flow rate sensor 8 on the backflow direction side of the correction reference value Qx are corrected to cause backflow. The reverse flow side output correction means 23 for obtaining the side correction output value Vg ′ (value shown by the alternate long and short dash line in FIG. 4).

The flow rate calculating means 9 is provided with a flow rate sensor 8
Of the output value V of the intake air flow rate Qj (value above the correction reference value Qx in FIG. 5) obtained from the output value Vj on the forward flow side of the correction reference value Qx, and the backflow side correction output value Vg ′.
The average intake air flow rate Q is determined based on the backflow side intake air flow rate Qg (value below the correction reference value Qx in FIG. 5) obtained from

The operating state detecting means 21 includes, for example, engine speed, throttle opening, accelerator opening, intake valve 1
One of valve lift amount and average intake air flow rate of 5
One or a combination of a plurality of them is read.
The average intake air flow rate uses a numerical value obtained by the flow rate sensor 8.

Here, the correction reference value determining means 22 is shown in FIG.
As shown in, the correction reference value Qx is continuously (or stepwise) varied within the maximum Qmax range from the Qi set when the engine 5 is idling, in accordance with the operating state such as the intake air flow rate. It is a thing. This upper limit (Qma
x), as shown in FIG. 7, the correction reference value Qx does not intersect the intake pulsating intake air flow rate in an operating state in which the intake air flow rate is larger than the predetermined intake air flow rate and the intake pulsation is small. Is set as follows. By being provided in this way, unnecessary correction can be canceled.

Further, the backflow side output correction means 23 is provided with a correction amount (V) depending on the correction reference value Qx or the engine operating state.
It is provided so as to change (g → Vg ′ change amount). As a concrete example, the output value Vg is corrected to a backflow side corrected output value Vg ′ within the range shown by the broken line in FIG. 4 based on a preprogrammed map or arithmetic expression. The output value Vg is used as an arithmetic expression for varying the correction amount.
Is multiplied by an arbitrary constant, the output value Vg is multiplied by an arbitrary constant and a predetermined value (gain or offset) is added, or the constant for multiplying the output value Vg is used as a function of the flow rate. Is also good.

[Effects of First Embodiment] As described above, the intake air flow rate measuring device 1 of this embodiment obtains the correction reference value Qx according to the operating state of the engine 5 and outputs the output value V of the flow rate sensor 8. Of these, the output value Vg on the backflow direction side of the correction reference value Qx is corrected to obtain the backflow side corrected output value Vg ′.
Then, of the output value V of the flow rate sensor 8, the correction reference value Q
Based on the intake air flow rate Qj obtained from the output value Vj on the forward flow side of x and the reverse flow side intake air flow rate Qg obtained from the reverse flow side corrected output value Vg ′, the average intake air flow rate Q
Are seeking. In this way, the output value V of the flow rate sensor 8 on the reverse side of the intake pulsation can be appropriately corrected according to the operating state of the engine 5, and the wide operating range of the engine 5 can be achieved regardless of the operating state of the engine 5. Thus, the average intake air flow rate Q can be measured with high accuracy.

[Second Embodiment] In the first embodiment, the intake air flow rate Qj obtained from the output value Vj of the flow sensor 8 on the forward flow side of the correction reference value Qx.
And the backflow-side intake air flow rate Qg obtained from the backflow-side corrected output value Vg ′ obtained by correcting the output value Vg on the backflow direction side of the correction reference value Qx are shown as examples in which the average intake air flow rate Q is obtained. It was On the other hand, the intake air flow rate measuring device 1 of the second embodiment adopts the configuration shown in FIG. 8, and in the reverse flow side output correcting means 23 in the ECU 20,
Among the output values V of the flow rate sensor 8, the reverse flow side intake air flow rate Qg obtained from the output value Vg on the reverse flow direction side of the correction reference value Qx is corrected to obtain the reverse flow side corrected intake air flow rate Qg '. Then, in the flow rate calculation means 9, the flow rate sensor 8
Among the output values V of the above, the average intake air flow rate Q is calculated from the intake air flow rate Qj obtained from the output value Vj on the forward flow direction side of the correction reference value Qx and the back flow side corrected intake air flow rate Qg ′ obtained above. It is what you want.

By providing in this way, the intake air flow rate on the backflow side of the intake pulsation can be appropriately corrected according to the operating state of the engine 5, and the engine 5 can be operated widely regardless of the operating state of the engine 5. The average intake air flow rate Q can be measured with high accuracy over the operating range.

[Modification] In the first embodiment described above, the intake air flow rate Qj obtained from the output value Vj on the forward flow direction side of the correction reference value Qx and the reverse flow side intake air obtained from the reverse flow side correction output value Vg ′. An example of obtaining the average intake air flow rate Q from the air flow rate Qg has been shown. However, the output value Vj on the forward flow direction side of the correction reference value Qx and the reverse flow side correction output value Vg '
The average intake air flow rate Q may be directly obtained from That is,
For example, the output value Vj on the forward flow direction side of the correction reference value Qx
And the backflow side corrected output value Vg ′ may be averaged, and the average intake air flow rate Q may be obtained from the average value.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of a fuel injection device (first embodiment).

FIG. 2 is a schematic diagram showing an intake system of the engine (first embodiment).

FIG. 3 is a sectional view of an air flow meter (first embodiment).

FIG. 4 is a graph showing the relationship between the output of the flow rate sensor and the intake air flow rate (first embodiment).

FIG. 5 is a graph showing a change in intake air flow rate obtained by calculation (first embodiment).

FIG. 6 is a graph showing the relationship between the correction reference value and the intake air flow rate (first embodiment).

FIG. 7 is a graph showing a change in intake air flow rate during normal operation (first embodiment).

FIG. 8 is a schematic block diagram of a fuel injection device using an intake air flow rate measurement device (second embodiment).

FIG. 9 is a graph showing the relationship between the output of the flow rate sensor and the intake air flow rate (conventional example).

FIG. 10 is a graph showing a change in intake air flow rate obtained by calculation (conventional example).

[Explanation of symbols]

1 Intake air flow rate measuring device 5 Engine 6 Intake pipe 8 Flow rate sensor 9 Flow rate calculating means 21 Operating state detecting means 22 Correction reference value determining means 23 Reverse flow side output correcting means Q Average intake air flow rate Qg Output value of flow rate sensor on the reverse flow side Intake air flow rate Qg 'calculated from the reverse flow side corrected intake air flow rate Qj Intake air flow rate Qx calculated from the output value of the flow rate sensor in the forward flow direction V reference value V Output value of the flow rate sensor Vg Output value of the flow rate sensor in the reverse flow direction Vg 'Reverse flow side corrected output value Vj Forward flow direction side flow sensor output value

Claims (2)

[Claims] 1. A flow rate sensor, which is disposed in an intake pipe of an engine and is capable of measuring an air flow amount in a forward flow direction and an air flow amount in a reverse flow direction of intake air flowing in the intake pipe by using a heating resistor. (B) an operating state detecting means for detecting an operating state of the engine; and (c) a correction reference value determining means for determining a correction reference value according to the operating state of the engine detected by the operating state detecting means, (D) Of the output values of the flow rate sensor, backflow side output correction means for correcting the output value on the backflow direction side of the correction reference value to obtain the backflow side corrected output value, and (e) the output of the flow rate sensor. Of the values, an output value on the forward flow direction side of the correction reference value and a flow rate calculation means for obtaining an average intake air flow rate based on the backflow side corrected output value obtained by the backflow side output correction means. Inhalation empty Air flow measurement device. 2. A flow rate sensor, which is disposed in an intake pipe of an engine and is capable of measuring an air flow amount in a forward flow direction and an air flow amount in a reverse flow direction of intake air flowing in the intake pipe by using a heating resistor. (G) operating state detecting means for detecting an operating state of the engine; (h) correction reference value determining means for determining a correction reference value according to the operating state of the engine detected by the operating state detecting means; (I) Backflow-side output correction means for calculating a backflow-side corrected intake air flow rate by correcting the intake airflow rate obtained from the output value on the backflow direction side of the correction reference value among the output values of the flow rate sensor, j) Of the output values of the flow rate sensor, from the intake air flow rate obtained from the output value on the forward flow direction side of the correction reference value, and the reverse flow side corrected intake air flow rate obtained by the reverse flow side output correction means. An intake air flow rate measuring device comprising: a flow rate calculating means for determining an average intake air flow rate.