JPH1114418A - Correction method for measurement error of heating resistor-type air-flow-rate measuring instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a correction method in which a flow rate can be measured with high accuracy even in a pulsating flow accompanied by a reverse flow by a method wherein a flowrate signal from a heating resistor is inverted, the generation time of the reverse flow is found so as to know a reverse flow rate and the flow-rate signal before its inversion is corrected and processed. SOLUTION: An air-flow-rate waveform as a detection value from a heating-resistor- type air-flow-rate measuring apparatus which is used for an internal-combustion engine or the like is divided into routines in two systems inside a correction device, and one of them is inverted and processed. By its inversion, a phase is advanced, a pulsating amplitude becomes large, and a waveform in which a reverse flow portion is turned down near the zero of a flow rate is obtained. When a turned-down point is detected precisely, a reverse flow section can be known. By using an inverted result and by using a signal detected by the vehicle-operating-state detection means of the speed of rotation of an engine or the like, a correction amount is computed by a prescribed method. On the basis of the correction amount, an output which is not inverted is corrected and processed so as to be output as an air-flow-rate signal. By this method, the fuel of an engine can be controlled with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for correcting an error in an air flow measuring device for measuring an air flow rate based on a heat radiation amount from a hot wire to air using, for example, a hot wire and the like. The present invention relates to a method for correcting a measurement error of a measuring device caused by intake pulsation when measuring a measured air flow rate.

[0002]

2. Description of the Related Art As a detection error due to a pulsation effect of a heating resistor type air flow measuring device, a minus error caused by a nonlinear output characteristic and a pulsation amplitude of a heating resistor and a plus error caused by a backflow effect generated in an intake pipe. is there.

As a method of reducing an error in the pulsation region, a method of disposing a heating resistor in a sub air passage having at least one bend is known as disclosed in Japanese Patent Publication No. 1-43888.

A technique closest to the present invention is disclosed in Japanese Unexamined Patent Application Publication No. Hei 8-62012, in which an output signal from a heating resistor type air flow measuring device is inversely converted to improve a response delay of the heating resistor. A method of calculating the flow rate by performing a flow rate conversion (linearization) process on the waveform so as to approach a true flow rate waveform is disclosed.

[0005]

It is difficult to detect the direction of flow of the heating resistor which is a flow rate detecting element due to its structure. For this reason, when a backflow occurs, the heating resistor determines that the backflow is also a forward flow and detects it, and detects it as an error.

The air flow flowing in the intake pipe of the engine becomes a pulsating flow as the intake valve opens and closes. The magnitude of this pulsation is small when the throttle valve is relatively closed, and becomes large as the throttle valve is fully opened.

The outline will be described with reference to FIG. When the throttle valve is gradually opened while the rotation speed is kept constant, the pulsation amplitude in the intake pipe gradually increases with an increase in the suction flow velocity (flow rate), and when the throttle valve becomes somewhat large, the output of the heating resistor has its own. A flow rate having a negative error is indicated due to non-linearity and response delay.

FIG. 10 shows the mechanism of this occurrence. When the pulsation amplitude further increases, the flow in the intake pipe becomes a flow accompanied by a backflow. However, the heating resistor is
Due to its structure, it is difficult to detect the direction of the flow, and the flow is detected simply as the flow velocity in both the forward flow and the backward flow. For this reason, even if a backflow occurs, the heating resistor directly detects it as a flow velocity, and as a result, an error on the positive side is shown.

For these reasons, when a heating resistor type air flow measuring device is used, some kind of error correction is necessarily required at the time of backflow.

In the prior art in which the heating resistor is disposed in the sub air passage having at least one bend, it is possible to prevent the negative error caused by the non-linear output characteristic and the pulsation amplitude to some extent. . But,
A sufficient effect cannot be obtained with respect to the reduction of the plus error due to the backflow. With this structure, the backflow from the engine to the air cleaner direction can be reduced by directly forming a backflow on the heating resistor by creating a wall with the auxiliary air passage. The increase cannot be reduced.

Also, in the technique using the inverse transformation,
Since the output signal (voltage signal) from the heating resistor type air flow measuring device is inversely converted and then the flow rate conversion is performed, the accuracy of the inverse conversion itself appears as the accuracy of the detected flow rate. This is because there is no variation because the inverse conversion process itself is performed by a program or the like incorporated in the processing device, but variation at the time of detection due to variation in the response of the heating resistor or the like affects the flow rate accuracy.

[0012]

In order to cope with the above-mentioned problem, first, the sub-air passage structure is devised to suppress a negative error to some extent, and when a sufficiently large back flow occurs, the back flow is generated in the sub-air passage. An auxiliary air passage or the like having one or more bends which are easy to enter is provided, and a heating resistor is disposed inside the auxiliary air passage. Further, in the processing device, the reverse flow is obtained by obtaining the reverse flow generation time and the like without performing the reverse conversion and directly performing the flow rate conversion, and correcting the flow signal before the reverse conversion in accordance with the reverse flow. I decided that.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail with reference to the drawings.

First, the operating principle of the heating resistor type air flow measuring device will be described. FIG. 6 is a schematic configuration circuit diagram of a heating resistor type air flow measuring device. The driving circuit 1 of the heating resistor type air flow measuring device is roughly composed of a bridge circuit and a feedback circuit. Heating resistor 3RH for measuring the intake air flow rate, temperature sensitive resistor 4RC and R10, R1 for compensating the intake air temperature
1 and a feedback circuit using an operational amplifier OP1 so as to maintain a constant temperature difference between the heating resistor 3RH and the temperature-sensitive resistor 4RC.
The heating current Ih flows through H, and an output signal V2 corresponding to the air flow rate is output. That is, when the flow velocity is high, a large amount of heat is taken out of the heating resistor 3RH, so that a large amount of the heating current Ih flows. On the other hand, when the flow velocity is low, the heating resistor Rh
Since the amount of heat taken away from the heater is small, the heating current can be reduced. Here, the amount of heat taken from the heating resistor 3Rh does not depend on the direction of the air flow, and is the same whether it is in the forward flow or in the backward flow. It is.

FIG. 7 is a cross-sectional view showing an example of a heating resistance type air flow meter, and FIG. 8 is an external view seen from the upstream side (left side).

The configuration of the heating resistor type air flow measuring device includes a housing member 1 containing a circuit board 2 constituting a drive circuit and a sub air passage forming member 10 formed of a non-conductive member. A heat generating resistor 3 for detecting the air flow rate and a temperature sensitive resistor 4 for compensating for the intake air temperature are provided in the passage constituting member 10 via a support 5 made of a conductive member. And a housing, a circuit board, a sub air passage, a heating resistor, a temperature-sensitive resistor, and the like, which are configured as an integrated module of a heating resistor type air flow measuring device.

A hole 25 is formed in the wall surface of the main air constituting member 20 constituting the intake pipe, and a sub air passage portion of the heating resistor type air flow measuring device is inserted through the hole 25 from outside. The housing member 1 is fixed to the wall surface of the sub air passage component member with screws 7 so as to maintain mechanical strength.

The main air passage portion into which the sub air passage is inserted is substantially a cylindrical tube, and the effective cross-sectional area of the main air passage through which the air flows is substantially the same at the location of the entrance and exit of the sub air passage. In addition, a seal member 6 is attached between the sub air passage component 10 and the main air passage component to maintain airtightness.

Next, the specific contents of the present invention will be described.

FIG. 1 is a conceptual diagram showing an example of the basic concept of the present invention. First, an air flow waveform which is a detection value from the heating resistor type air flow measuring device is taken into the correction processing device, the output is divided into two routines, and an inverse conversion process is performed only in one of the routines.

Using the result of the inverse conversion and a signal detected by vehicle operating state detecting means such as the engine speed, a correction amount corresponding to the result is calculated, and the correction amount is converted to the other inverse conversion. The correction process is performed on the output from the heating resistor type air flow measuring device that does not perform the above operation, and the result is output as an air flow signal. This correction processing device is constituted by an analog circuit or a digital circuit.

Next, as a specific example of the correction processing device, an engine control unit (EC) for controlling an engine
FIG. 2 shows an example of applying the present invention to U). The detection waveform from the heating resistor type air flow rate measuring device is converted into a digital value using an A / D converter or the like, and then, as in FIG. .

Using the result of the inverse conversion and an engine speed signal or the like as the vehicle operating state detecting means, a correction amount corresponding to the result is calculated, and the correction amount is converted to the other inverse conversion. Correction processing is performed on the output from the heating resistor type air flow measurement device that is not performed, and the correction is output as an air flow signal.

Next, a specific correction method will be described by taking as an example the reduction of detection errors due to backflow. First, FIG. 3 is an example describing a method of detecting a flow waveform and a forward / reverse signal.

By performing the inverse conversion on the signal before the inverse conversion (the waveform detected by the airflow measuring device of the heating resistor type), the phase is advanced and the pulsation amplitude is further increased. It has a folded waveform. Therefore, by accurately detecting the turning point, the reverse flow section (time T
2)

By utilizing this, for example, as shown in the figure, if there is a detection means which becomes HIGH at the time of forward flow and LOW at the time of reverse flow, one cycle time (T1) of the engine and the reverse flow time
(T2) can be known.

Using this, for example, the ratio of the time of T2 to the time of T1 is taken. If this ratio is extremely small, it is determined that the reverse flow is extremely small. Can also be determined to be large. If a map having squares of the engine speed, the ratio of one cycle time (T1) and the backflow time (T2) as shown in FIG. 4 is used, and the correction value in each operation state is input to the map. Therefore, it is possible to correct the error due to the backflow.

The measurement error caused by the pulsation of the intake air of the engine is caused not only by the backflow but also by the pulsation amplitude and the nonlinearity and response delay of the heating resistor.

This indicates that the error caused by the backflow is a plus-side error, while the minus error is a minus side error.

The map shown in FIG. 5 is for taking measures against this negative error. The horizontal axis shows the engine speed,
The vertical axis shows the difference between the signal values from the heating resistor before and after the inverse conversion after the flow rate conversion. The difference on the vertical axis may be a difference between instantaneous and instantaneous values, but is preferably an average value of time during one or more intake strokes of the engine.

The above-mentioned minus error can be prevented by compensating the response and further converting the flow rate. This is as described in the prior art JP-A-8-62012. Therefore, by looking at the difference between the flow values before and after the inverse conversion, it can be seen how much the signal from the heating resistor before the inverse conversion has a negative error. If this difference is corrected, it is possible to take measures against the error on the minus side.

In this case, the correction may be performed by using, for example, the following equation without using the above-mentioned map.

[0033]

Qnew = Q1−k × (Q1−Q2) Qnew: Air flow rate after correction Q1: Air flow rate conversion value before inverse conversion Q2: Air flow rate conversion value after inverse conversion k: Coefficient Finally, FIG. An embodiment in which the present invention is applied to an internal combustion engine of an electronic fuel injection system using the present invention will be described.

The intake air 67 sucked from the air cleaner 54 passes through the body 53 of the heating resistance type air flow measuring device, the suction duct 55, the throttle body 58, and the intake manifold 59 having the injector 60 to which fuel is supplied. It is sucked into the cylinder 62. On the other hand, gas 63 generated in the engine cylinder is discharged through an exhaust manifold 64.

The air flow signal output from the circuit module 52 of the heating resistance type air flow measuring device, the intake air temperature signal from the temperature sensor, the throttle valve angle signal output from the throttle angle sensor 57, and the exhaust manifold 64 are provided. The control unit 66 that inputs these signals, such as the oxygen concentration signal output from the oximeter 65 and the engine speed signal output from the engine speed meter 61, sequentially calculates these signals to obtain the optimum fuel The injection amount and the idle air control valve opening are obtained, and the injector 60 and the idle control valve 66 are controlled using the values.

[0036]

According to the present invention, it is possible to provide a method for correcting a measurement error of a heating resistor type air flow measuring device which measures an air flow with high accuracy even under a pulsating flow which is sucked into an automobile engine or the like and involves a backflow. . Also, by using this, it becomes possible to perform the fuel control of the engine with high accuracy.

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing an outline of the present invention using an engine control unit.

FIG. 3 is a pulsation waveform showing correction contents at the time of backflow according to the present invention.

FIG. 4 is a diagram showing an example of a correction map according to the present invention.

FIG. 5 is a diagram showing an example of a correction map according to the present invention.

FIG. 6 is a drive circuit diagram of a heating resistor type air flow measuring device.

FIG. 7 is a cross-sectional view of a heating resistor type air flow measuring device.

FIG. 8 is a view of FIG. 7 as viewed from the upstream side.

FIG. 9 is a diagram showing a pulsation error of the heating resistor type air flow measuring device.

FIG. 10 is a diagram showing a non-linearity of a heating resistor, a response delay, and a negative measurement error caused by a pulsation amplitude.

FIG. 11 is a diagram showing a system configuration of an internal combustion engine.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Housing constituent member, 2 ... Circuit board, 3 ... Heating resistor, 4 ... Temperature sensitive resistor, 5 ... Conductive support, 6 ... Sealing material, 10 ... Sub air passage constituent member, 11 ... Sub air passage entrance , 12: Sub air passage outlet, 13: Vertical passage, 14: Horizontal passage, 20: Main air passage constituent member, 22: Main air passage, 2
3 ... forward air flow, 24 ... reverse air flow, 25 ...
Holes, 51: intake air temperature sensor, 52: module, 53 ...
Body, 54 ... Air cleaner, 55 ... Duct, 56 ... Idle air control valve, 57 ... Throttle angle sensor, 58 ... Throttle body, 59 ... Intake manifold, 60 ... Injector, 61 ... Tachometer, 62 ...
Engine cylinder, 63 gas, 64 exhaust manifold, 65 oxygen meter, 66 control unit,
67 ... intake air.

Claims (7)

[Claims] 1. A method for correcting a measurement error caused by a pulsating flow of a heating resistor type air flow measuring device which generates heat by flowing a heating current used in an internal combustion engine and measures an air flow rate based on a heat release amount to intake air, Compensates for the response delay of the output signal obtained from the heating resistor (advance phase and increase amplitude)
Means for determining a correction value of a measurement error caused by the pulsating flow via the means for compensating for the response delay, and correcting the flow rate signal before compensating for the response delay to reduce the detection error. A method for correcting a measurement error of the heating resistor type air flow measuring device. 2. A method for correcting a measurement error caused by a pulsating flow of a heating resistor type air flow measuring device which generates heat by flowing a heating current used in an internal combustion engine and measures an air flow rate based on a heat release amount to intake air, Means for countermeasure the output negative error caused by the non-linear output characteristics and pulsation amplitude of the heating resistor, and compensation for the response delay of the output signal obtained from the heating resistor (advance phase to increase amplitude ) Means for correcting a measurement error of the heating resistor type air flow measuring device. 3. A method for correcting a measurement error caused by a pulsating flow of a heating resistor type air flow measuring device which generates heat by flowing a heating current used in an internal combustion engine and measures an air flow rate based on a heat release amount to intake air, Means for countermeasure the output negative error caused by the non-linear output characteristics and pulsation amplitude of the heating resistor, and compensation for the response delay of the output signal obtained from the heating resistor (advance phase to increase amplitude And means for judging the presence or absence of a backflow in the intake pipe through the means for compensating for the response delay, and, if a backflow occurs, a value corresponding to the backflow and compensating for the response delay. A method for correcting a measurement error of a heating resistor type air flow measuring device, wherein the detection error is reduced by correcting the flow signal before the flow. 4. A method for correcting a measurement error caused by a pulsating flow of a heating resistor type air flow measuring device which generates heat by flowing a heating current used in an internal combustion engine and measures an air flow rate based on a heat release amount to intake air, Compensates for the response delay of the output signal obtained from the heating resistor (advance phase and increase amplitude)
Means for converting the output signal after compensating for the response delay to flow rate; means for converting the output signal before compensating the response delay obtained from the heating resistor to flow rate; Means for comparing with the flow rate conversion value, and corrects one of the outputs before and after the response delay compensation in accordance with the difference between the flow rate conversion values before and after the response delay compensation to reduce a detection error due to pulsation. A method for correcting a measurement error of a heating resistor type air flow measuring device, characterized in that: 5. A method for reducing a detection error of a heating resistor type air flow measuring device according to claim 1,
A map is created from the value obtained by digitizing the information obtained from the detection waveform that compensated for the response delay and the engine speed signal, and a correction value is entered in the map to reduce the detection error of the heating resistor type air flow measurement device. Method for reducing the measurement error of the heating resistor type air flow measurement device that performs the measurement. 6. A heating resistor type air flow measuring device according to claim 1, further comprising means for correcting a measurement error caused by a pulsating flow. 7. An engine control unit for an internal combustion engine, wherein the heating resistor type air flow measuring device according to claim 1 further comprises means for correcting a measurement error caused by a pulsating flow.