JPH09273951A - Device for measuring heating resistance type flow rate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To conduct uniformly highly precise air flow rate measuring by correcting the error of output characteristics at an arbitrary correction point, and replacing it with an output signal approximate to an output characteristic line as reference. SOLUTION: The output voltage of a drive circuit 2 for air flow rate detection using a heating resistor 5 and an induction resistor 6 is digitized 3 and read by an arithmetic circuit 1. In addition, the arithmetic circuit 1 reads a correction function stored to EEPROM 8. At this time, for instance, the flow rate characteristics are divided into four sections, a primary function is set so that in each section both the ends of the section is an error 0% for the output characteristics of reference. Operation processing is performed by the correction function read from EEPROM for the output value of the drive circuit 2 to obtain a normal flow rate value. Furthermore, an output table is referred, an output value is calculated for a present flow rate value, and a signal is output from an output circuit 4. Thereby signal deterioration of a flowmeter is corrected at the time of flow rate correction and intake air flow rate of an internal combustion engine can be more accurately detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating resistor type air flow meter for measuring the intake air flow rate of an internal combustion engine.

[0002]

2. Description of the Related Art In the prior art, as described in Japanese Patent Application No. 56-64149, the output adjustment of a heating resistor type air flow meter is performed by adjusting the span by a resistor connected to a current detecting element of the heating resistor. The adjustment of the zero point was performed only by adjusting the reference voltage of the differential amplifier circuit.
For this reason, the adjustment can absorb the product variation under the adjusting condition and maintain high accuracy, but under other conditions, the product variation must be reduced as much as possible.

[0003]

SUMMARY OF THE INVENTION The present invention is intended to reduce the characteristic error of the output characteristic of a heating resistor type air flow meter, and particularly to reduce the heating resistance which is the cause of the characteristic error of the heating resistor type. An object of the present invention is to provide a uniform and highly accurate heating resistor type air flow meter in which the influence of manufacturing variations on the characteristics is reduced.

[0004]

[Means for Solving the Problems] A characteristic error due to manufacturing variation of a heating resistor, which is a main factor of the characteristic variation of a heating resistor type air flow meter, causes a slight characteristic difference as compared with a reference output characteristic line. To do.

Therefore, the flow rate correction means according to the present invention corrects the error in the output characteristic at at least three arbitrary correction points and replaces it with the output signal which is close to the reference output characteristic line, thereby eliminating the output characteristic error. Measures to reduce are adopted.

However, when the flow rate correction is individually performed at each corrected flow rate point, the corrected output characteristics between the correction points become irrelevant before and after the correction point, resulting in a stepwise output characteristic.

The flow rate correcting means according to the present invention does not correct the output value stepwise, but provides a flow rate correcting means which reproduces a smooth output characteristic by correlating before and after the correction points. Further, it is a correction means that can also temporarily convert the flow rate value and rewrite it to the output value to reproduce the output characteristic that matches the existing characteristic curve.

[0008]

Embodiments of the present invention will be specifically described with reference to the drawings.

FIG. 1 shows an example of a typical system configuration of a heating resistance type flow rate measuring device according to the present invention. FIG. 2 is an example of a specific component structure of the heating resistor type air flow meter according to the present invention.

Here, the main claim of the present invention is not limited to the basic constitution of the heating resistor type air flow meter for correcting the output characteristic and the means for correcting the heating resistor type air flow meter. .

According to the present invention, the heating resistor 5, the thermosensitive resistor 6 and the drive circuit 2 for driving the resistor element generate a voltage signal according to the air flow rate. This voltage signal is
It is digitized by the / D converter 3 and taken into the arithmetic circuit 1 for calculation processing.

The ROM 7 stores a program for output characteristic correction processing according to the present invention. The EEPROM8 stores the correction data necessary for correcting the output characteristics of the heating resistor type air flow meter, and the necessary correction data is transferred according to the request of the arithmetic circuit.

Here, the flow of flow rate correction according to the present invention will be described with reference to FIG.

The output voltage of the drive circuit for detecting the air flow rate, which uses the heat generating resistance element 5 and the heat sensitive resistance element 6, is connected to the A / D converter 3 incorporated in the heat generating resistor type air flow meter, and an analog voltage is obtained. Digitize.

The arithmetic circuit 1 reads the output value of the drive circuit 2 via the A / D converter 3, and reads the correction function stored in the EEPROM 8 based on the output value of the drive circuit 2.

Here, the correction function is an arbitrary constant.
The output value of the drive circuit 2 is arithmetically processed using the correction value read from the EEPROM 8 to obtain a normal flow rate value.

Further, referring to the output table, the output value for the current flow rate value is calculated and the signal is output from the output circuit 4.

FIG. 4 shows an example of a method of correcting an output signal according to the present invention.

The output value 12 of the drive circuit before correction is not uniform due to manufacturing variations of the heat generating resistor and the heat sensitive resistor.
As shown in the embodiments of the present invention, the error of the characteristic is different for each section.

Further, it is a known fact that it is also affected by variations in the shape of the main passage 11 in which the heating resistor type air flow meter according to the present invention is arranged.

In this embodiment, the entire flow rate characteristic is divided into four sections, and a linear function is set so that both ends of the section have an error of 0% with respect to the reference characteristic in each section. A linear correction between each section is used.

Here, the function used for the correction is not limited to a linear function, but may be a quadratic or cubic function depending on the output characteristics.

Since the correction function is individually set in each of the four sections, the output characteristic error can be maintained with higher accuracy than the zero-span adjustment of the operational amplifier incorporated in the drive circuit.

Further, according to the present invention, since the correction values can be set individually for each of the four sections, when an attempt is made to perform the correction more optimally in each section, a characteristic error is suddenly generated at the joint of the correction sections as shown in FIG. The part that changes to occurs.

Such a stepwise change is not useful for fuel control of, for example, an internal combustion engine using the heating resistor type air flow meter according to the present invention.

Therefore, in the present invention, each correction function is set so that there is no sudden characteristic error due to the correction being associated with the correction function in each correction section.

In this embodiment, the output signal of the drive circuit is temporarily converted into a temporary flow rate value by referring to the flow rate conversion data previously written in the ROM 7 inside the heating resistor type air flow meter. Thereafter, appropriate characteristic correction is performed, and further, an appropriate output signal is generated from the output circuit at any time with reference to the output characteristic data which is electrically written in advance in the ROM 7 inside the heating resistor type air flow meter.

In another embodiment of the present invention, the provisional flow rate conversion means temporarily obtained is converted into a flow rate value by a functional expression representing the output characteristics of the heating resistor type air flow meter, and an appropriate correction is made. There is also one that is converted into a reference output signal and then output from the output circuit.

Further, an appropriate correction function of the flow rate value is woven into the reference output characteristic data used when converting the temporarily obtained flow rate value into the reference output signal, and the reference output characteristic data itself. Some have been corrected.

Further, the output form of the output circuit of the heating resistor type air flow meter according to the present invention may be an analog signal or a digital signal.

[0031]

The effect of the present invention is to correct the signal deterioration of the heating resistor type air flow meter at the time of flow rate correction so that the intake air flow rate of the internal combustion engine can be detected more accurately.

[Brief description of drawings]

FIG. 1 is a block diagram of a system configuration of a heating resistor type air flow meter showing an embodiment of the present invention.

FIG. 2 is an explanatory view of a heating resistor type air flow meter showing an embodiment of the present invention.

FIG. 3 is a flowchart of output characteristic correction according to the present invention.

FIG. 4 is a characteristic diagram of an example of correction of output characteristics.

FIG. 5 is an explanatory diagram of a cause of an error in output characteristic correction and a solution.

[Explanation of symbols]

1 ... Arithmetic circuit, 2 ... Heating resistor driving circuit, 3 ... A / D converter, 4 ... Output circuit, 5 ... Heating resistor, 6 ... Thermal resistor, 7 ... ROM, 8 ... EEPROM.

Claims (7)

[Claims] 1. An output characteristic of a heating resistor type air flow meter, which is provided in an intake passage of an internal combustion engine, has at least one heat-sensitive resistor installed in the intake passage, and measures the amount of intake air. With respect to the reference characteristic at the flow rate point of, the output characteristic is corrected by the arithmetic circuit previously arranged in the heating resistor type air flow meter and the correction value electrically recorded and output. Heating resistor type air flow meter. 2. The heating resistor type air flow meter according to claim 1, wherein the correction means between the three or more correction flow rate points corrects and outputs by an arbitrary function. 3. The correction means between any three or more correction points is corrected by a correction function associated with each correction point, and the corrected output characteristic is stepwise. A heating resistor type air flow meter that corrects so that it does not change suddenly. 4. The output characteristic of the heating resistor type air flow meter according to claim 1, 2 or 3, after converting the output characteristic into a temporary flow rate value and converting into an air flow rate value, at least with respect to the flow rate value. A heating resistor type air flow meter that corrects the output characteristics with three or more correction points and then replaces it with an output signal corresponding to the air flow rate and outputs. 5. The heating means according to claim 4, wherein the conversion means for temporarily converting the flow rate value is converted by using an arbitrary function, and the conversion means for converting the temporary flow rate value into an output signal after correction. A heating resistor type air flow meter that converts the flow rate data recorded by using an electrical means into a body type air flow meter into an output signal. 6. The heating resistor type air flow meter according to claim 4, wherein the conversion means for temporarily converting the flow rate value and the conversion means for converting the temporary flow rate value into an output signal after correction are electrically connected to the heating resistor type air flow meter in advance. A heating resistor type air flow meter that converts the flow rate data recorded using various means into an output signal. 7. The method according to claim 4, wherein after temporarily converting into the flow rate value, the correction means for the temporary flow rate value is recorded in advance in the heating resistor type air flow meter by using electric means. A heating resistor type air flow meter that is woven into conversion data that refers to flow rate value data and converts it into an output value, corrects the conversion data itself and outputs it.