JP2001324364A - Thermal air, flow rate measurement device, its flow meter, internal combustion engine using it, and thermal air flow rate measurement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal air flow rate measurement device allowing easy sensitiveness and temperature correction in accordance with the fluid flow direction and having high measurement accuracy, its thermal air flow rate meter, an internal combustion engine using it, and a thermal air flow rate measurement method. SOLUTION: This thermal air flow rate measurement device is provided with at least one heating resistor arranged in gas fluid, temperature measuring resistors 211d-211g formed in the upstream part and the downstream part of the heating resistor 211a, an outputting means outputting at least two signals related to a fluid flow rate, a quantizing means quantizing the outputted value, and a computing means 222 computing a flow rate on the basis of the quantized signal. In this thermal air flow rate measurement method, the flow rate and the direction of the fluid are detected on the basis of a signal about a heat generation amount by at least one heating resistor arranged in the gas fluid, a signal concerning a temperature difference between the upstream part and the downstream part of the temperature measuring resistors formed in a plurality of steps in each of the upstream part and the downstream part of the heating resistor, and a signal corresponding to a fluid flow difference other than the temperature difference.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel thermal air flow measuring device, a measuring method thereof, a thermal air flow meter, an internal combustion engine using the same, and an air flow measuring method suitable for detecting an intake air amount thereof. About.

[0002]

2. Description of the Related Art Conventionally, as an air flow device which is provided in an electronically controlled fuel injection device of an internal combustion engine of an automobile or the like and measures an intake air amount, a thermal type air flow device is widely used because it can directly detect a mass air amount. . At this time, the heating resistor is coated with glass by winding a platinum wire around a bobbin,
The thin film resistor is formed on a ceramic substrate or a silicon substrate.

[0003] The flow rate is detected by heating the heating resistor to a constant temperature and directly detecting the current flowing when the flow is generated, or by arranging the temperature sensing resistor on both sides of the heating resistor. A method of detecting the temperature based on the temperature difference between the resistors may be used.

[0004] In particular, in the case of a pulsating flow in which the pulsating amplitude of the intake air amount is large and a partial backflow occurs, such as when the engine has a low rotational speed and a heavy load of an engine having four cylinders or less, the accuracy of the conventional air flow device is high. Therefore, an output according to the flow direction is required. The method of arranging the temperature detecting resistors on both sides of the heating resistor and detecting the temperature based on the temperature difference between the temperature detecting resistors can obtain an output according to the flow direction, and is suitable for detecting an output such as a backflow.

[0005] Since each system has advantages and disadvantages depending on the application, systems used in combination with analog circuits are described in JP-A-9-318412 and JP-A-11-51954. This is because the temperature difference output of the temperature sensing resistor with relatively high sensitivity is saturated at the high flow rate side and deteriorates, so the direct detection with low sensitivity at the low flow rate side and high sensitivity at the high flow rate side is used. The output and the differential amplifier are added and output.

As described above, as a method of compensating the temperature difference output of the temperature detecting resistor having relatively high sensitivity, a method of compensating the output by dividing the temperature by the rise temperature of the heater, besides the method of compensating for the sensitivity described above. Is Tokuhei 6-63801
The method of temperature compensation is described in Japanese Patent Publication No. 6-64080.

In addition, Japanese Patent Laid-Open No. 6-160142 discloses a method for compensating for the temperature difference output of the temperature detecting resistor for a vehicle, in particular, by detecting the medium temperature.

On the other hand, as a digital method using AD conversion, a method of correcting a zero point by an output of a resistance temperature detector is described in Japanese Patent Laid-Open No. Hei 6-230021. A method of digitally correcting the temperature is disclosed in
-94620.

[0009]

In the above-mentioned prior art, as a method for compensating the accuracy of the temperature difference output of the temperature detecting resistor, various methods mainly using an analog circuit have been proposed. In the case of an analog circuit, in order to obtain a device having a different flow rate measurement range according to various uses and to improve the accuracy, the circuit and adjustment become complicated, which has caused a cost increase. Although a method of digitally compensating for a zero point and a method of compensating for temperature have been studied, adjustment of the sensitivity of the entire sensor has not been considered much.

[0010] It is an object of the present invention to improve the sensitivity by means of arithmetic means using digitalized signals using sensors having different output characteristics, and to output in accordance with the direction of the flow of the fluid. It is an object of the present invention to provide a thermal air flow measuring device and a thermal air flow meter with easy measurement and high measurement accuracy, an internal combustion engine using the same, and a thermal air flow measuring method therefor.

[0011]

SUMMARY OF THE INVENTION The present invention provides at least one heating resistor disposed in a gaseous fluid, and a temperature measuring resistor formed at an upstream portion and a downstream portion of the heating resistor at the fluid. Means for detecting at least two signals related to the flow rate of the fluid, quantization means (digitization means) for quantizing (digital-converting) the detected value, and based on the quantized signal. Computing means for computing the flow rate, or computing means for computing using at least two parameters based on the two or more quantized (digital-converted) signals; and Output means for combining and outputting, or operation means for performing an operation using at least two parameters based on the two or more quantized digitally converted signals; and Output means for synthesizing and outputting signals, wherein at least two signals related to the flow rate are based on a calorific value of the heating resistor and a temperature difference between the temperature measuring resistors formed in the upstream portion and the downstream portion. There is provided a thermal air flow measuring device.

Further, the present invention comprises at least one heating resistor disposed in a gaseous fluid, and the heating resistor for detecting a flow rate of the fluid by driving the heating resistor at a constant temperature by a temperature compensation resistor. Flow rate detecting means, a temperature detecting resistor arranged on both sides of the heating resistor, and a flow rate detecting means for detecting the flow rate based on a temperature difference between the two, and a value from the heating resistor and a value taken as the temperature difference. Quantizing means (digitizing means) for quantizing (digital converting), calculating means for calculating the quantized (digital converted) value, and correcting means for correcting based on the calculated value are provided. It is characterized by the following.

Further, the present invention comprises at least one heating resistor disposed in a gaseous fluid, and a temperature measuring resistor formed on an upstream portion and a downstream portion of the heating resistor with respect to the fluid, The temperature measuring resistor is provided in a thermal air flow meter arranged in a plurality of stages along the longitudinal direction of the heating resistor at each of the upstream portion and the downstream portion, and the heating resistor and the temperature measuring device are connected thereto. Output means for outputting at least two signals related to the flow rate of the fluid from the resistor, quantizing means for quantizing the output value, and the flow rate and direction based on the quantized signal. And a calculating means for calculating the following formula.

According to the present invention, there is provided a signal relating to an amount of heat generated by at least one heat generating resistor disposed in a gaseous fluid;
A signal relating to a temperature difference between the upstream portion and the downstream portion of the temperature measuring resistor formed in a plurality of stages at each of an upstream portion and a downstream portion of the fluid of the heating resistor, and a flow of the fluid other than the temperature difference And quantizing (digital-converting) these signals based on a signal corresponding to the difference between the two, and calculating the flow rate and direction based on the quantized signal. Thermal measurement method of the air flow rate.

That is, according to the present invention, there is provided a heating resistor, means for driving the heating resistor at a constant temperature by means of a temperature compensating resistor to detect a flow rate, and a temperature sensing resistor provided on both sides of the heating resistor. Means for detecting a flow rate based on a temperature difference between the two elements, a quantization means (digitizing means) for inputting a signal corresponding to the flow rate of the heating resistor and a signal corresponding to the flow rate of the temperature difference, and a quantization operation based on both signal inputs. (Digital operation) to perform correction and adjustment.

According to the present invention, even in applications having different measurement ranges, output sensitivity can be easily adjusted by digital optimization calculation using flow rate signals using two different detection principles, thereby improving accuracy. Becomes possible.

In the present invention, the function of the above-mentioned linear expression or higher is (q1 = a1 × f1 + b1, q2 = f2,...)
(Q1 = f1, q2 = a2 × f2 + b2,...) And (q
1 = a1 × f1 + b1, q2 = a2 × f2 + b2,...)
And the function for the temperature is (a1 = c1 × Ta + d1, b1 = c2 × Ta + d
2,...) And the function for the quantized signal are:
(A1 = g1 × f1 + h1, b1 = g2 × f1 + h2,
…). As the above function, a quadratic or cubic function can be used.

According to the present invention, it is possible to easily adjust output sensitivity and improve accuracy by digital optimization calculation using flow rate signals using two different detection principles even in applications having different measurement ranges. It becomes possible.

In a hot-wire type air flow meter for measuring an intake air amount of an internal combustion engine of an automobile or the like, a device having a different flow rate measurement range according to various applications is provided, and the sensitivity of the whole sensor is adjusted to improve accuracy. It is an improvement and a simplified circuit and adjustment.

By obtaining an air flow meter with good sensitivity and high accuracy by the digital correction as described above, there is an effect that the optimization of the engine control of the automobile is achieved and the exhaust gas from the engine can be reduced.

[0021]

(Embodiment 1) FIG. 1 is a drive circuit diagram of a thermal air flow meter according to the present invention. The hot-wire drive circuit 1 is connected to the power supply 101 and outputs an output according to the air flow rate. The heating wire driving circuit 1 includes a heating resistor 211a, a temperature compensation resistor 211c,
The Wheatstone bridge circuit composed of the resistors 13, 14, and 17 generates the heating resistor 2 by the differential amplifier 15 and the transistor 16 so that the potential difference at the bridge midpoint becomes zero.
It is configured to adjust the current flowing through 11a.
If the heating temperature of the heating resistor 211a is low, the differential amplifier 1
The output of No. 5 increases, and it operates to further heat.
With this configuration, the current flowing through the heating resistor 211a is controlled so that the resistance value of the heating resistor 211a is constant regardless of the air flow velocity, that is, the temperature is kept constant. At this time, a signal corresponding to the air flow velocity by the heating resistor 211a is obtained by converting a current flowing through the heating resistor 211a into a voltage by the resistor 13 to obtain a voltage signal V2 and input to the digital correction circuit 220.

The heating resistor 211a is formed, for example, by forming a thin film or a thick film of platinum or tungsten as a heating element on a plate-shaped glass or ceramic substrate.

In particular, the heating resistor 211a is formed by forming a thin film or thick film of platinum or tungsten, a polysilicon resistor, or a single crystal silicon resistor as a heating element on a semiconductor substrate such as silicon.

The heating resistor 211a is provided in an intake passage of an internal combustion engine of an automobile or the like, and obtains a voltage output V2 corresponding to a flow rate of air flowing through the intake passage. Amplifying this voltage with a differential amplifier and using it is the configuration of a normal direct detection type thermal air flow meter.

On the other hand, temperature detecting resistors 211d, 211e, 211f, 211g are arranged on both sides of the heating resistor 211a, and the temperature detecting resistors 211d, 211e, 211f,
A bridge is constituted by 211g and the potentials Vb1 and Vb2 at the middle point
In the method of detecting the temperature difference of the resistor from the difference, the output according to the flow direction can be obtained. Here, the temperature detection resistor 211
d, 211e, 211f, 211g are the power supply voltage Vref
1 is driven at a constant voltage. This method of detecting the temperature difference of the resistor has good sensitivity on the low flow rate side because it is differentially detected, and is suitable for detecting bidirectional flow such as reverse flow. Sensitivity is likely to be limited.

FIG. 2 is an example of a pattern diagram in which a heating resistor 211a is formed on a silicon semiconductor substrate 211 by a thin film. The heating resistor 211a has a vertically elongated pattern in which the resistance is turned back.
1e, 211f, and 211g are arranged. The heat generating resistor 211a and the temperature detecting resistors 211d, 211e, 211f, and 211g are, for example, formed by etching the back surface of the silicon substrate 211 and disposing the resistors in a diaphragm structure having a small heat capacity.
The temperature compensating resistor 211c is disposed in a place where the temperature of the heating resistor 211a is not easily affected by the temperature.

A specific principle of detecting the flow rate of the temperature difference will be described. Here, the normal air flow flows from A to B.
Even when there is no flow, the heater is heated by the heating resistor 211a and a temperature distribution occurs in the heater. Resistor 21 for temperature detection
In a state where there is no flow, 1d, 211e, 211f, and 211g ideally have the same resistance values, and no output is generated even if a bridge circuit is configured. Here, when air flow occurs, the temperature distribution on both sides of the heating resistor 211a changes, and an output corresponding to the flow rate is obtained. More specifically, the temperature detecting resistors 211d, 2d on the upstream side of the heating resistor 211a,
The resistance value of the resistor 11e decreases as the temperature decreases, and the resistance values of the temperature detecting resistors 211f and 211g on the downstream side decrease.
When the temperature rises due to the heat of the heating resistor 211a, the temperature rises, and a temperature difference between the upstream and downstream sides can be obtained as a change in the resistance value.

As described above, if a bridge is formed by using a plurality of resistors for temperature detection in the longitudinal direction of the heating resistor 211, the sensitivity for detecting a temperature difference can be particularly improved. In principle, the same detection is possible even if two resistors for temperature detection are arranged on the upstream side and the downstream side, and a bridge is formed in combination with two resistors that do not detect temperature in particular. However, the sensitivity of the output voltage to the change of the temperature detecting resistor is lower than the case where a plurality of temperature detecting resistors are used in the longitudinal direction of the heating resistor 211a. In the case where the temperature dependency of the temperature detecting resistor is high, it is sufficient to provide a total of two temperature detecting resistors, one each for the upstream side and the downstream side. If it is difficult to obtain output sensitivity due to low temperature dependency of
It is desirable to provide a plurality of, especially two, resistors for temperature detection on the upstream side and on the downstream side, respectively.

FIG. 3 is a sectional view of a resistor formed on a silicon substrate. The location where the resistance pattern is located has the thickest structure. In this embodiment, the potentials Vb1 and Vb2 at the bridge midpoints of the temperature detecting resistors 211d, 211e, 211f, and 211g are also input to the digital correction circuit 220. The digital correction circuit 220 has two analog / digital converters 221a and 221b, converts a voltage value corresponding to the flow rate into a digital value, reads it, adjusts it as a digital quantity by calculation, and adjusts the digital / analog converter 224. A signal is sent to the engine control unit or the like as the output voltage Vout. Here, the digital correction circuit 220 includes a CPU 222a, a RAM,
An arithmetic circuit 222 including a ROM 222c and a ROM 222c, an oscillator 226, a PROM 223, and the like. Here, the PROM 223 is not limited to an electrically rewritable EEPROM, a flash ROM, or the like as long as the PROM 223 can record a variation or the like of the output sensitivity of the individual sensor as an adjustment value at least once. .

The voltage Vcc supplied from the outside is input to the internal power supply / protection circuit 228 as a power supply, and the power supply voltage Vref1 depending on the external voltage Vcc is supplied to the analog / digital converter 221a via the switches 225a and 225b. 221b, digital / analog converter 2
24 and used as a reference. Here, the switches 225a and 225b are connected to the voltage Vref2 generated by the reference voltage circuit 229 inside the digital correction circuit 220.
And a power supply voltage Vref1 depending on the external voltage Vcc.
Is to switch. Here, the analog / digital converters 221a and 221b output the output Vb of the bridge circuit.
Since 1, Vb2, V2, etc. are directly input, accuracy is required. However, in order to ensure accuracy and reduce the circuit scale, for example, a ΔΣ type analog-digital converter may be used.

In this embodiment, the voltage signal V2 obtained by converting the current flowing through the heating resistor 211a into a voltage by the resistor 13 and the temperature detection resistors 211d, 211e,
The analog of digitalization of the potentials Vb1 and Vb2 at the bridge midpoint indicating the temperature difference according to the flow rates of 211f and 211g.
The digital converter is provided separately. This is based on the principle of both flow rate detections, and is configured to be easily optimized for each.

The voltage signal V2 changes the bridge voltage of the hot-wire drive circuit 1 by feedback, and its output does not depend on the power supply Vcc of the digital correction circuit 220 or the like. Therefore, an independent reference voltage is required for analog-to-digital conversion, and the reference voltage Vref
2 is provided for application as a reference to the analog / digital converter 221b.

On the other hand, the temperature detecting resistors 211d,
11e, 211f, and 211g are driven at a constant voltage by the power supply voltage Vref1.
Due to the fluctuation of f1, the potentials Vb1 and Vb2 at the bridge midpoint increase or decrease. One method for removing this is to change the reference voltage of the analog / digital converter 221a to the power supply voltage V.
As ref1, the read value at the time of digital conversion is changed similarly to the power supply voltage Vref1. In this embodiment, in particular, a switch 225a is provided to switch the reference voltage of the analog / digital converter 221a. When the fluctuation of the power supply voltage Vref1 is very small, the reference voltage Vref2 of the reference voltage circuit 229 may be used.

The digital / analog converter 224
Similarly, the reference voltage can be changed by the switch 225b. This is to freely select the standard when interfacing with analog values.
When the reference voltage of the digital converter and the voltage Vcc supplied from the outside fluctuate in the same or synchronous manner, the power supply voltage Vref1 is used as a reference, and when there is no relation with the control unit, an independent reference voltage Vref2 is used. The configuration is such that it is easily handled by the selected and corresponding control unit, and the error due to the unmatching of the analog interface is small.

With the above-described configuration of the digital correction circuit 220, the output sensitivity is improved, and an air flow meter that can be easily adjusted can be obtained. The detailed operation will be described with reference to FIG. The output characteristic with respect to the flow rate of the voltage signal V2 obtained by converting the current flowing through the heating resistor 211a into a voltage by the resistor 13 as described above is represented by f1, and the flow rate of the temperature detection resistors 211d, 211e, 211f, and 211g is obtained. The output characteristic of the difference voltage dV between the potentials Vb1 and Vb2 at the bridge midpoint indicating the corresponding temperature difference with respect to the flow rate is represented by f2.

The output characteristic f1 is an offset output voltage characteristic that does not pass through the origin because the heating current of the heating resistor 211a flows even when the flow rate is zero. The output characteristics are such that when the flow rate is zero, the zero point fluctuates easily due to natural convection or the like during self-heating, but at high flow rates, the output does not saturate within the range permitted by the power supply voltage. For this reason,
In particular, when the heat generating resistor 211a having a small heat capacity is used, the sensitivity on the low flow rate side is deteriorated, but the sensitivity is excellent on the high flow rate side.

On the other hand, the output characteristic f2 takes the output of the difference between the bridges, and ideally has a characteristic of passing the origin at zero flow rate. In particular, the sensitivity on the low flow rate side from zero flow rate becomes better, but on the high flow rate side, the temperature difference of the resistance is less likely to occur, and the characteristics tend to be small and the output is saturated.

To actually use the above characteristics, a zero span adjustment for amplifying with a differential amplifier or the like and adjusting a zero point is usually performed in an analog manner. As a result, the apparent sensitivity characteristics are relatively improved, but the basic sensitivity trends of the output characteristics f1 and f2 do not change. That is, the output characteristic f1 has low sensitivity at the low flow rate and has high sensitivity on the high flow rate side, whereas the output characteristic f2 has the sensitivity at the low flow rate and good sensitivity at the high flow rate side. In order to improve these characteristics, it is conceivable to change the characteristics using an analog arithmetic circuit composed of a differential amplifier or the like. However, making all analog calculations for sensitivity compensation and adjustments for compensating for individual differences among sensors all analog requires a complicated adjustment circuit, a complicated adjustment method, and an increase in cost. .

In order to improve the above points, the object can be achieved by performing a digital operation using the digital correction circuit 220 described above. Specifically, the output characteristics f1,
The respective sensitivities of f2 are corrected by a first-order or higher functional expression.

[0040]

Next, the results of sensitivity correction are multiplied by each other.

[0042]

As a result, it is possible to obtain a good sensitivity characteristic from the low flow rate side to the high flow rate side with respect to the basic sensitivity tendency of the output characteristics f1 and f2. As shown in FIG.

In order to actually use the calculation result of Equation 3, it is necessary to further adjust the output level at the time of interface.

[0044] However, A = ga ・ a1 ・ a2, B = ga ・ a1 ・ b2, C = ga ・ a2 ・ b1, D = ga ・ b1 ・ b2 +
Set to off.

As described above, the provision of digital correction means makes it possible to simultaneously and easily perform basic sensor sensitivity correction and output correction. Like above

From Equation 1

Up to Equation 4 may be calculated in order,

The calculation may be performed collectively, as in Equation 5.

In the case of the formula (5), by calculating the parameters in advance and recording the results, there is an advantage that the number of variables can be reduced as compared with the case where the correction parameters are individually provided.

According to this embodiment, the output characteristics f1, f
When two sensors having different characteristics are used, the sensitivity is improved by digital operation means, and the number of variables for the sensitivity correction is reduced, and the adjustment is simplified.

FIG. 6 is a diagram showing an example of sensor output voltage characteristic correction according to the embodiment of the present invention. This is an embodiment in the case where digital correction means is used in consideration of the flow direction of the air flow rate. As described above, the temperature detection resistor 211d,
An output characteristic f2 of the output characteristic with respect to the flow rate of the difference voltage dV between the potentials Vb1 and Vb2 at the bridge midpoint indicating the temperature difference according to the flow rates of 211e, 211f, and 211g is obtained with a sign according to the flow direction. FIG. 6 shows output characteristics f1 and f2.
Is an output obtained by correcting the sensitivity by a first-order or higher functional expression, q1,
q2.

The output q2 of the temperature difference equation is a positive output when the flow rate is positive, and a negative output when the flow rate is negative. This is because, for example, the digital correction circuit 22
This is achieved in the case where the analog-to-digital converter 221a of "0" is capable of differential input, and converts positive and negative analog differential inputs into signed digital signals. In particular, if the sensitivity differs depending on the direction of the flow,

In Equation 2, a plurality of parameters a2, b2 are prepared as a2u, b2u, a2d, b2d according to the direction of the flow,
It is also possible to optimize by changing the sensitivity.

On the other hand, the output q1 of the direct heating type has a positive output regardless of whether the flow rate is positive or negative, and has no sign in the flow direction. This is achieved, for example, in a configuration in which the analog-to-digital converter 221b of the digital correction circuit 220 can be input with reference to the ground, and the positive analog input is converted into an unsigned digital signal. Is done. Especially in this case

In the formula (1), the sensitivity is adjusted by the parameters a1 and b1 so that the zero point of q2 and the zero point of q1 coincide.

The output q2 of the signed temperature difference equation as described above
And even if the unsigned direct heat output q1 is used,
As mentioned in the previous embodiment

The calculation of the sensitivity correction may be performed by Equation 3, but the multiplication result q3 must also be signed.

According to this embodiment, the output characteristics f1, f
2, even if the characteristics are different in sign such as unsigned output and signed output, it is possible to easily realize signed operation by digitally correcting, and to achieve sensitivity regardless of the flow direction of flow. There is an effect that correction can be made and performance is improved.

FIG. 7 is a diagram showing the relationship between the sensor output voltage and the flow rate when digital correction means is used in consideration of the flow direction of the air flow rate. As described above, the output q2 of the temperature difference equation is obtained with a sign depending on the flow direction. On the other hand, the output q1 of the direct heat type has no sign with respect to the flow direction. However, especially in this case

In the equation 1, the output q2 of the temperature difference equation is exceeded on the high flow rate side by the parameters a1 and b1, and the zero point of q2 and q1
Adjust the sensitivity to match the zero point of. Further, by determining the sign of the output q2 of the temperature difference equation, the output −q obtained by adding a sign to the output q1 of the direct heat type when the flow rate is negative.
Prepare 1

In order to make the sensitivity on the low flow rate side and the sensitivity on the high flow rate side compatible, the magnitude of the output q2 of the temperature difference type and the output q1 of the direct heat type are determined. This is realized by, for example, a condition determination that a larger flow rate is selected when the flow rate is positive and a smaller flow rate is selected when the flow rate is negative. In this case, it is as follows.

[0054]

Here, the minus sign indicates a sign. By optimizing the parameters, the flow rate output q3 selected according to the flow rate can also obtain a smooth curve with few steps when switching. In addition, the determination

The multiplication process as shown in Expression 3 can be omitted.

According to this embodiment, the output characteristics f1, f
2, the sensitivity can be corrected by digital correction and determination means even if the characteristics have different signs, such as an unsigned output and a signed output.

FIG. 8 is a diagram showing an example of an error due to the intake air temperature and characteristic correction. In particular, the temperature characteristics are improved when a combination of characteristics having different output characteristics f1 and f2 is used. Considering the output error when the intake air temperature changes with respect to the room temperature, the direct heating type output ft1 tends to have a positive temperature characteristic with respect to the intake air temperature because the heating temperature also increases according to the intake air temperature. . On the other hand, the output ft2 of the temperature difference equation tends to have negative temperature characteristics when driven at a constant voltage. Among these temperature characteristics, the output ft1 of the direct heating type can be changed by changing the temperature compensation resistor 17 in the bridge. However, in that case, the adjustment becomes complicated because the temperature characteristics are not always uniform. On the other hand, by performing digital operation correction, the temperature characteristics can be easily improved by changing the ratio of the error of each characteristic to the temperature.

This is described above.

[Equation 1]

In Equation 2, it becomes possible by setting each parameter according to the rate of change with respect to the intake air temperature. For example, assuming that the output ft1 of the direct heating type is opposite in polarity to the output ft2 of the temperature difference type and is twice as large,

[Equation 1]

The parameters qt1 and qt2 having the opposite temperature characteristics are obtained by adjusting the parameters of the equation (2). this

By performing the calculation using Equation 3, it is possible to obtain a good characteristic qt3 of the intake air temperature characteristic.

The parameters of the equation (1) are corrected for the intake air temperature Ta as follows, for example.

[0059]

According to this embodiment, the output characteristics f1, f
2 and the temperature characteristics are different, the use of digital correction means has the effect of improving the temperature characteristic performance.

FIG. 9 is a diagram showing an example of error due to flow rate and characteristic correction. In particular, the present invention is intended to improve the flow rate dependency when the output characteristics f1 and f2 are used in combination. This indicates how the basic characteristics of the output according to the flow rate fluctuate due to ambient temperature, variations in elements, and the like. In general, both the direct heat type output fe1 and the temperature difference type output fe2 have a large error on the low flow rate side. This is because, because of a relative error, the smaller the flow rate, the smaller the allowable amount for the fluctuation, and the higher the ratio of the error even if the apparent fluctuation is the same. Even in such a case, the flow rate dependency is improved by adjusting the parameters in the same manner as in the correction of the intake air temperature. For example, characteristics qe1 and qe2 in which the flow rate dependency is minimized with respect to the error of the output fe1 of the direct heat type and the output fe2 of the temperature difference type are obtained. this

By performing the calculation using Expression 3, it is possible to obtain the characteristic qe3 having a good flow rate dependency.

The parameters of the formula (1) are corrected for the output f1 of the direct heating type, for example, as follows.

[0062]

By previously calculating the optimum parameters for each characteristic and performing digital correction using the optimum parameters for each sensor as described above, the sensitivity is optimum and the intake air temperature characteristics and flow rate dependency are improved. A good air flow meter can be obtained.

According to this embodiment, the output characteristics f1, f
(2) By using different sensors and optimizing each use condition using digital correction means, an air flow meter with optimum sensitivity, good intake air temperature characteristics and good flow rate dependency can be manufactured at low cost. There is an effect that it can be obtained.

In particular, when sensors having output characteristics f1 and f2 different from each other are used, the sensitivity is further improved by digital calculation means, and the number of variables for sensitivity correction is reduced, and adjustment is simplified. Has a significant effect. At the same time, sensitivity correction and temperature correction are facilitated according to the flow direction of the flow rate, and the performance is improved. Further, since the air flow measurement accuracy is improved, there is an effect that the exhaust gas of the engine can be reduced when used for controlling the engine of an automobile.

(Embodiment 2) FIG. 10 is a drive circuit diagram of a thermal air flow meter according to the present invention. This is an example of a configuration in the case where a reference voltage in the digital correction circuit 220 is provided externally with respect to FIG. The hot-wire drive circuit 1 is connected to the power supply 101 and outputs an output according to the air flow rate. Similarly, the power supply circuit 5 is connected to the power supply 101 and generates the voltage Vref3 by the reference voltage circuit 51. This voltage Vref3 is supplied to the digital correction circuit 220, the temperature detection resistors 211d and 211e,
The power is supplied to the bridge circuit of 211f and 211g.

In the present embodiment, the potentials Vb1 and Vb2 at the bridge midpoints of the temperature detecting resistors 211d, 211e, 211f and 211g are determined by the resistors 32, 33, 34, 3
5, 36, and 37, and a temperature difference voltage Vb3 amplified by the differential amplifier 31 with reference to the offset voltage Voff, and input to the analog / digital converter 221c of the digital correction circuit 220.

The voltage signal V 2 obtained by converting the current flowing through the heating resistor 211 a into a voltage by the resistor 13, and the applied voltage V 1 of the bridge circuit of the hot-wire drive circuit 1.
The voltage Vr1 obtained by dividing the voltage by the resistors 212 and 213 is similarly input to the analog / digital converter 221c of the digital correction circuit 220. Analog-to-digital converter 22
1c is a voltage Vref generated by the reference voltage circuit 51.
3, a voltage value corresponding to the flow rate is converted into a digital value, read and adjusted as a digital amount by calculation, and a signal is sent to the engine control unit or the like as the output voltage Vout of the digital / analog converter 224.

Here, the digital / analog converter 224
Is the voltage Vref3 generated by the reference voltage circuit 51.
And the external voltage Vcc can be switched by the switch 225b. This is to freely select the standard when interfacing with analog values.
Reference voltage of analog / digital converter on the control unit side to be connected and voltage Vc supplied from outside
If c is the same or fluctuates synchronously, the voltage Vc
When the reference is not related to the control unit side, an independent reference voltage Vref3 is selected, and the configuration is such that the corresponding control unit can easily deal with the reference voltage Vref3 and the error due to the unmatching of the analog interface is small.

Here, the analog / digital converter 221
Since a and 221b have a large number of inputs, it is desirable that one analog-digital converter be used by switching with a switch. To secure the conversion speed and reduce the circuit scale, for example, a successive approximation type analog-to-digital converter may be used. In this case, the analog-to-digital converter 221c is configured to be able to input with reference to ground, and to convert a positive analog input into a digital signal without a sign.

FIG. 11 is a diagram showing an example of sensor output voltage characteristic calculation correction for a bidirectional air flow rate. Even when the digital correction circuit 220 is configured as described above, the output sensitivity is improved as in the previous embodiment, and an easily adjustable air flow meter can be obtained with a smaller circuit scale. As described above, the current flowing through the heating resistor 211a is
The output characteristic with respect to the flow rate of the voltage signal V2 obtained by converting the voltage into the voltage at 3 is f1, and the temperature detection resistor 211
The output characteristic with respect to the flow rate of the temperature difference voltage Vb3 obtained by amplifying the potentials Vb1 and Vb2 at the bridge midpoints of d, 211e, 211f and 211g with reference to the offset voltage Voff is defined as f2.

Here, when the output characteristic is f1, the voltage signal V2
Instead of applying the bridge circuit applied voltage V1 to the resistor 212,
The voltage Vr1 divided in step 213 may be used. V
2. The difference between V1 and V1 is a difference in temperature characteristics. The temperature characteristics are adjusted by the resistor 17, but V1 is easier to reduce the temperature dependency than V2. Further, by measuring the voltage at both ends of the heating resistor 211a, the heating temperature Th of the heating resistor 211a can be calculated, and the temperature compensation using the heating temperature Th can be performed to reduce the temperature dependency. The calculation of each parameter in this case is as follows, for example.

[0073]

The output characteristic f2 with respect to the flow rate is obtained by increasing or decreasing the output according to the flow direction. Output q of temperature difference equation
Reference numeral 2 denotes a positive output when the flow rate is positive with respect to the offset flow rate q0, and a negative output when the flow rate is negative. In particular, since there is no sign, a correction calculation considering the offset flow rate q0 is required. The output q1 of the direct heating type has only a positive output regardless of whether the flow rate is positive or negative, and there is no need to consider the flow direction.

When the output q2 of the unsigned offset temperature difference equation as described above and the output q1 of the unsigned direct heat equation are used, it is necessary to perform a correction operation in consideration of the flow direction. .

As an example, the

[Equation 1]

## EQU2 ## From the output characteristics f1 and f2, q1 and q2 with sensitivity corrected are obtained. Here, the range where the flow rate is positive is defined as area a, the output of the temperature difference equation in that case is q2a, the output of the direct heat type is q1a, and the range of negative flow rate is area b, and the output of the temperature difference equation in that case. Is q2b, and the output of the direct heating type is q1b. The correction output obtained by multiplying these is performed by separating the conditions according to the flow rate.

[0077]

FIG. 12 is a diagram showing an example of the sensor output voltage characteristic determination correction with respect to the bidirectional air flow rate. FIG.
As shown in (1), this is to perform sensitivity correction by magnitude determination using region determination based on the offset flow rate and the flow direction. In each case, the same effects as those of the previous embodiment can be obtained.

According to this embodiment, the output characteristics f1, f
2, even if the output characteristics are different and have no sign, it is possible to easily realize a considerable operation with a sign by digitally correcting it, and to perform sensitivity correction regardless of the flow direction of the flow rate, improving performance. It has the effect of doing. Further, since the configuration of the digital correction circuit 220 for realizing this is simplified, there is an effect that the achievement is easy even if a general-purpose microcomputer is used.

(Embodiment 3) FIG. 13 is a drive circuit diagram of a thermal air flow meter according to the present invention. As shown in FIG. 13, even if the external voltage Vcc is directly input to the analog-to-digital converter 221c and the calculation of the dependence on the external voltage is performed in the digital correction circuit 220, the same effect as before can be easily obtained. Is obtained. Also, by inputting the voltage between both ends of the temperature compensation resistor 211c, the intake air temperature can be calculated, and can be used for correcting the intake air temperature and outputting the intake air temperature. In this embodiment, a digital / analog converter 224b is provided to realize an analog output of the intake air temperature. According to the present embodiment,
By using an analog / digital converter having a large number of channels, a more accurate and highly functional air flow meter can be obtained.

(Embodiment 4) FIG. 14 is a drive circuit diagram of a thermal air flow meter according to the present invention. As shown in FIG. 14, when the bridge voltage V1 is divided and detected, one of the voltage dividing resistors is replaced with a resistor 21 having a temperature coefficient similar to that of the temperature compensating resistor 211c.
By using 1h, a thermistor, or the like, the temperature characteristics of the V1 output can be separately improved. By doing so, the temperature detecting resistors 211d, 211e, 211f,
With respect to the temperature characteristics of 11 g, the temperature dependency can be more finely improved to the desired characteristics in advance. By changing the arrangement of the voltage dividing resistors, the directionality of the temperature characteristic (whether the temperature characteristic is positive or negative) can be changed. In addition, for the temperature compensation resistor 211h disposed in the intake passage, the voltage dividing resistor 213 is disposed inside the digital correction circuit 220 or on the substrate on which the digital correction circuit 220 is mounted, in order to detect the substrate temperature. By using a resistor having a desired temperature coefficient, the influence of the substrate temperature can be reduced.

FIG. 15 is a diagram showing the temperature dependence of each resistor with respect to the intake air temperature. As shown in the figure, vta obtained by improving the characteristics of the original direct heat type temperature characteristics vt1 by the temperature compensation resistor 211h is obtained. On the other hand, the output vt3 in which the intake air temperature and the substrate temperature are compensated can be obtained by the vtm in which the substrate temperature is compensated.

By calculating the above result in the digital correction circuit 220, it is possible to obtain an output with good temperature characteristics. In this embodiment, the resistor 211 depending on the intake air temperature is used.
By providing h and compensating the intake air temperature in advance, an air flow meter with good temperature characteristics can be obtained even if an analog / digital converter having a small number of channels is used.

(Embodiment 5) FIG. 16 is a circuit diagram showing an example of calculation correction and output switching output. The input / output software processing of the present invention will be described. FIG. 16 shows the signal f obtained by the analog-to-digital conversion processing 311a, 311b.
2 and f1 are converted into parameters a1, a2, b1, by the digital operation correction process 312 as described in the previous embodiment.
A signal q3 with improved characteristics is obtained using b2 and the like. A signal qv3 obtained by converting the signal q3 into an air flow rate by the air flow rate conversion processing 313a is obtained. Here, for example, the air flow rate is obtained by converting a voltage into a flow rate using a table called a voltage-flow rate conversion map. This table called a voltage-flow rate conversion map may be prepared individually for each sensor, or a correction table may be separately prepared separately for each sensor using the representative characteristics. They are,
The data is recorded in a storage element or the like called a PROM which can be written once or more and retains the record even without a power supply.

In this embodiment, as for the signal, the software switch 316a which can switch the signal q3 after the calculation and the signal qv3 converted into the air flow rate by an external signal.
As for the output, the output fout converted into the frequency by the pulse conversion processing 314 and the voltage value Vout subjected to the digital / analog conversion processing 315 are switched by the soft switches 316b and 316c, as shown in FIG.
Can be arbitrarily obtained. This can be easily realized by digitization. By realizing a plurality of output interfaces by one digital correction circuit 220, the components can be shared and the cost can be reduced.

(Embodiment 6) FIG. 18 is a circuit diagram showing an example of calculation correction and output switching output. Another input / output software process will be described. FIG. 18 shows a signal f2 obtained by the analog-digital conversion processing 311a, 311b,
f1 is individually converted into a voltage by using a table called a voltage-flow rate conversion map as shown in FIG. This is to prepare separate tables because the characteristics of the two signals are different. Individual air flow conversion processing 313
b, 313c, the signals qv2, qv1 are
The signal qv3 in which the output sensitivity is compensated as in the previous embodiment is obtained by the arithmetic processing 312, and the digital signal is converted into the duty of the pulse signal by the pulse conversion processing 314.
This is changed by a soft switch 316d that can be switched by an external signal to a filter 3 having a plurality of different characteristics.
By switching between 17a, 317b, no filter, etc., a pulse output or a smoothed analog signal can be obtained. In particular, it is possible to obtain a highly accurate analog output by changing the characteristics of the filter according to the application. Generally, when such a pulse is subjected to filter conversion,
Since the relationship between the accuracy and the responsiveness is a trade-off, even when the responsiveness is required or the accuracy is required, it is possible to easily cope with the digitization. FIG. 20 shows an example of the output characteristic. An output signal corresponding to the flow rate can be obtained by linearizing the output signal in the same manner for both the duty α and the output voltage. According to the above result, there is an effect that a high-precision output can be obtained at low cost.

(Embodiment 7) FIG. 21 is a circuit diagram showing an example of switching output after calculation correction and air flow rate conversion. Another input / output software process will be described. FIG.
The signals f2 and f1 obtained by the analog-to-digital conversion processes 311a and 311b are individually converted into voltages by using a table called a voltage-flow rate conversion map as shown in FIG. This is to prepare separate tables because the characteristics of the two signals are different. The signal qv2, which is individually converted by the air flow rate conversion processes 313b and 313c,
As for qv1, a signal qv3 in which the sensitivity of the output is compensated by the operation processing 312 as in the previous embodiment is obtained. This is changed to a soft switch 316e that can be switched by an external signal.
Thus, three different air flow rates can be obtained as the voltage value Vout subjected to the digital / analog conversion processing 315. FIG. 22 shows the output characteristics. In addition, the arithmetic processing 31
2, a plurality of correction parameters k1, k2, k
3, k4. . . . By preparing the two flow rate signals q
The correlation between v2, qv1 and the output qv3 after the operation can be adjusted. This is particularly effective in adjusting the output, etc.
Easy and accurate adjustment is possible. Here is an example,
First, the signals qv2 and qv1 having different characteristics and different temperature characteristics in the initial characteristics are read as analog values by the soft switch 316e, and correction parameters a1 and a
2, b1, b2, k1, k2, k3, k4. . . . To obtain a corrected signal qv3. In particular, when the signals qv2 and qv1 vary, parameters can be easily extracted, and a signal with higher accuracy with respect to sensitivity and temperature can be obtained.

In particular, when the characteristics change due to dirt or the like, the signals qv2, qv1, and qv3 are individually obtained, so that the error can be easily corrected and readjusted, and the long-term characteristics can be compensated. become able to. In the present embodiment, it is possible to provide a highly accurate sensor at a low cost by performing more advanced adjustment.

By obtaining an air flow meter with good sensitivity and high accuracy by the digital correction as described above, there is an effect that the engine control of the automobile is optimized and the exhaust gas from the engine can be reduced.

[0090]

According to the present invention, the sensitivity can be improved by the arithmetic means using digitalized signals using sensors having different output characteristics, and an output corresponding to the direction of fluid flow can be obtained. Thus, it is possible to obtain a thermal air flow measuring device, a measuring method thereof, and a thermal air flow meter having high measurement accuracy, which facilitates sensitivity and temperature correction thereby. Furthermore, by obtaining an air flow meter with good sensitivity and high accuracy by the above digital correction, the control of the engine of the vehicle is optimized, so that the effect of reducing the exhaust gas from the engine can be obtained.

[Brief description of the drawings]

FIG. 1 is a drive circuit diagram of a thermal air flow measuring device according to the present invention.

FIG. 2 is a pattern diagram of a thermal air flow meter having a heating resistor formed on a silicon substrate.

FIG. 3 is a sectional view taken along a line AB in FIG. 2;

FIG. 4 is a diagram showing an example of output voltage characteristic correction of the thermal air flow meter of the present invention.

FIG. 5 shows the presence or absence of output adjustment of the output voltage characteristic of the thermal air flow meter with respect to the air flow rate.

FIG. 6 is a diagram showing an example of calculation correction of output voltage characteristics of a thermal air flow meter with respect to a bidirectional air flow rate.

FIG. 7 is a diagram illustrating an example of determination correction of output voltage characteristics of a thermal air flow meter with respect to a bidirectional air flow rate.

FIG. 8 is a diagram showing an example of an error due to intake air temperature and characteristic correction.

FIG. 9 is a diagram illustrating an example of an error due to a flow rate and characteristic correction.

FIG. 10 is a drive circuit diagram of the thermal air flow measuring device of the present invention.

FIG. 11 is a diagram illustrating an example of calculation correction of output voltage characteristics of a thermal air flow meter with respect to a bidirectional air flow rate.

FIG. 12 is a diagram showing an example of determination correction of output voltage characteristics of a thermal air flow meter with respect to a bidirectional air flow rate.

FIG. 13 is a drive circuit diagram of the thermal air flow measuring device of the present invention.

FIG. 14 is a drive circuit diagram of the thermal air flow measuring device of the present invention.

FIG. 15 is a diagram illustrating an example of an error due to an intake air temperature and a substrate temperature and a characteristic correction.

FIG. 16 is a diagram showing an example of calculation correction and output switching output.

FIG. 17 is a diagram illustrating an example of a sensor output characteristic with respect to an air flow rate.

FIG. 18 is a diagram illustrating an example of calculation correction and output switching output.

FIG. 19 is a diagram showing conversion characteristics of an analog-to-digital conversion input value into an air flow rate.

FIG. 20 is a diagram illustrating an example of a sensor output characteristic with respect to an air flow rate.

FIG. 21 is a diagram showing an example of switching output after calculation correction and air flow rate conversion.

FIG. 22 is a diagram illustrating an example of a sensor output characteristic with respect to an air flow rate.

[Explanation of symbols]

1. hot wire drive circuit, 5 power supply circuit, 101 power supply, 211 silicon substrate, 211a resistance heating element, 211c temperature compensation resistance, 211d, 211e, 2
11f, 211g ··· Temperature detection resistor, 13, 14, 1
7, 32, 33, 35, 36, 37, 212, 213
..Resistance, 15, 31 .. differential amplifier, 16 .. transistor, 51 .. reference voltage, 220 .. digital correction circuit, 221a, 221b, 221c .. analog-digital converter, 222 .. arithmetic circuit, 222a C
PU, 222b..RAM, 222c..ROM, 2
23 ··· PROM, 224, 224b · · · digital
Analog converter, 225a, 225b, switch, 2
26 .. oscillator, 227 .. serial communication interface, 228 .. power supply and protection circuit, 31
1a, 311b ... analog-to-digital conversion processing, 31
2 ··· Calculation processing, 313a, 313b, 313c ··· Air flow conversion processing, 314 ··· Pulse conversion processing, 315 ·
・ Digital-to-analog conversion processing, 316a, 316b,
316c, 316d, 316e, soft switch, 3
17a, 317b filter.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Masamichi Yamada 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Shinya Igarashi 2477 Takaba, Hitachinaka City, Ibaraki Prefecture Hitachi Car Engineering Co., Ltd. (72) Inventor Hiroshi Yoneda 2477 Takaba, Hitachinaka-shi, Ibaraki Pref. Hitachi Car Engineering Co., Ltd. (72) Kenji Ota 2520 Odaikoba, Hitachinaka-city, Ibaraki Prefecture Hitachi, Ltd. F term in the automotive equipment group (reference) 2F035 AA02 EA05 EA08 EA09

Claims (25)

[Claims] At least one heat generating resistor disposed in a gaseous fluid, a temperature measuring resistor formed at an upstream portion and a downstream portion of the heat generating resistor with respect to the fluid, and measuring the heat generating resistor. At least two related to the flow rate of said fluid from the thermal resistor
Thermal means, comprising: output means for outputting two signals; quantizing means for quantizing the output values; and calculating means for calculating the flow rate based on the quantized signal. Air flow measurement device. 2. A heating element disposed in a gaseous fluid, a temperature measuring resistor formed on an upstream portion and a downstream portion of the heating resistor with respect to the fluid, and the heating resistor. At least two related to the flow rate of said fluid from the thermal resistor
Output means for outputting two signals, quantization means for quantizing the output values, operation means for operating the two or more quantized signals using at least two parameters, And a combining output means for combining and outputting the combined signals. 3. The method according to claim 1, wherein the heating resistor is driven at a constant temperature by at least one heating resistor disposed in a gaseous fluid and a temperature compensating resistor provided near the heating resistor to control the flow rate of the fluid. An output unit that outputs a signal; an output unit that outputs a signal related to the flow rate based on a temperature difference between a temperature measuring resistor formed at each of an upstream portion and a downstream portion of the fluid of the heating resistor; Quantizing means for quantizing a signal from a body and a signal based on the temperature difference; calculating means for calculating the quantized value using at least two parameters; and correcting means for correcting the calculated value And a thermal air flow measuring device. 4. A heating resistor disposed in a gaseous fluid, a temperature measuring resistor formed at each of an upstream portion and a downstream portion of the heating resistor, and the heating resistor. And output means for outputting at least two signals related to the flow rate of the fluid from the resistance temperature detector, quantizing means for quantizing the output value, and outputting the two or more quantized signals. Computing means for computing using at least two parameters, and combining output means for combining and outputting the computed signals, wherein at least two signals related to the flow rate are the amount of heat generated by the heating resistor and A thermal air flow measuring device, which is a signal relating to a temperature difference between a resistance temperature detector formed at an upstream portion and a downstream portion. 5. At least one heating resistor disposed in a gaseous fluid, a temperature measuring resistor formed at an upstream portion and a downstream portion of the heating resistor with respect to the fluid, and measuring the heating resistor. At least two related to the flow rate of said fluid from the thermal resistor
Output means for outputting two signals, quantizing means for quantizing the output value, and calculating means for calculating the flow rate and direction of the fluid based on the quantized signal,
The thermal air flow measuring device, wherein the temperature measuring resistors are arranged in a plurality of stages along the longitudinal direction of the heating resistor in each of the upstream portion and the downstream portion. 6. The apparatus according to claim 1, wherein at least one of the signals quantized by said quantizing means is adjusted by a plurality of parameters represented by a function of a linear expression or higher. A thermal air flow measuring device, wherein a plurality of signals are multiplied and output. 7. The method according to claim 1, wherein at least one of the signals quantized by said quantization means is:
Thermal air flow measurement characterized by adjusting by a plurality of parameters represented by a function equal to or greater than the linear expression, determining the magnitude of the adjusted plurality of signals, and outputting a larger one of the signals. apparatus. 8. The method according to claim 6, wherein at least one of the signals quantized by the quantization means is a code related to a direction of a flow of the fluid, and the function is selected according to a type of the code. A thermal air flow measuring device, wherein a plurality of flow directions of the fluid can be detected by a signal adjusted by adding a sign to the signal. 9. The method according to claim 8, wherein at least one of the signals quantized by said quantizing means has a reference point with respect to the flow direction of said fluid, and said function is selected according to the magnitude of the signal with respect to said reference point. A thermal air flow measuring device, wherein the signal adjusted by adding a sign to the signal is used. 10. The thermal air flow measuring device according to claim 1, wherein at least one of the plurality of parameters is a function relating to temperature. 11. The apparatus according to claim 1, wherein two or more signals quantized by said quantizing means are adjustable by said plurality of parameters and an external signal. Thermal air flow measurement device. 12. The method according to claim 1, wherein said quantizing means comprises a plurality of quantizing means independently set with respect to a reference voltage which is a reference for quantization. Thermal air flow measurement device. 13. A thermal air flow measuring device according to claim 1, wherein at least one of said plurality of quantizing means is a signed quantizing means having a differential input. 14. A thermal air flow measuring apparatus according to claim 1, wherein at least one of said plurality of signals has a temperature characteristic previously added by a temperature compensating resistor. 15. An apparatus according to claim 1, wherein said plurality of quantized signals are calculated with said plurality of parameters and then converted into an air flow rate, and an output can be selected by an external signal. Thermal air flow measurement device. 16. The method according to claim 1, wherein said plurality of quantized signals are converted into an air flow rate in advance.
A thermal air flow measurement device characterized in that the output is selectable by an external signal, calculated by parameters. 17. The method according to claim 1, wherein said plurality of quantized signals are converted into an air flow rate in advance.
A thermal air flow measuring device, wherein an output can be selected by an external signal from a value calculated by a parameter and an individual air flow value converted into an air flow. 18. The method according to claim 15, wherein
The output to be selected is any of an analog value obtained by converting a quantized digital value corresponding to an air flow rate into an analog value, a frequency obtained by converting the digital value into a pulse, or a duty obtained by converting the digital value into a PWM pulse. Thermal air flow measurement device. 19. The method according to claim 15, wherein
A thermal air flow measuring device, wherein the output to be selected is selectable from a filter for converting a quantized digital value into an analog signal after pulse conversion. 20. At least one member disposed in a gaseous fluid.
Two heating resistors, and a temperature measuring resistor formed at an upstream portion and a downstream portion of the fluid of the heating resistor. A thermal air flow meter, which is arranged in a plurality of stages along the longitudinal direction of the thermal air flow meter. 21. At least one member disposed in a gaseous fluid.
A heating resistor, a temperature measuring resistor formed at an upstream portion and a downstream portion of the fluid of the heating resistor, and a temperature compensating resistor provided at an upstream side of the temperature measuring resistor. A thermal air flowmeter, wherein the temperature measuring resistors are arranged in a plurality of stages along the longitudinal direction of the heating resistor at each of an upstream portion and a downstream portion of the fluid. 22. An internal combustion engine equipped with the thermal air flow measuring device according to claim 1 or the thermal air flow meter according to claim 20 or 21. 23. At least one member disposed in a gaseous fluid.
A signal relating to the amount of heat generated by the two heating resistors, and the upstream of the temperature measuring resistor formed in a plurality of stages in the longitudinal direction of the heating resistor at each of an upstream portion and a downstream portion of the fluid of the heating resistor. A signal regarding the temperature difference between the upstream and downstream sections,
A method of measuring a thermal air flow rate, comprising detecting a flow rate and a direction of the fluid based on a signal corresponding to a difference in flow of the fluid other than the temperature difference. 24. At least one member disposed in a gaseous fluid.
A signal related to the amount of heat generated by the two heating resistors, and a signal related to a temperature difference between the upstream portion and the downstream portion of the temperature measuring resistor formed in a plurality of stages in each of the upstream portion and the downstream portion of the fluid of the heating resistor. And a signal corresponding to a difference in the flow of the fluid other than the temperature difference, quantizing these signals, and calculating a flow rate and a direction of the fluid based on the quantized signal. Thermal air flow measurement method. 25. A method for measuring the air flow rate of an internal combustion engine, comprising measuring the air flow rate by the thermal air flow rate measuring method according to claim 23.