JPS6352014A - Fluid measuring instrument - Google Patents

Abstract

PURPOSE:To measure pressure and temperature simultaneously at the same place and to calculate the mass, etc., of fluid by using a diffusion type semiconductor sensor. CONSTITUTION:The diffusion type semiconductor sensor 16 is constituted by forming a bridge circuit of four diffusion gauge resistances 20 on a silicon substrate 18 and detects pressure. This sensor 16 is arranged against a flow of fluid and a constant current is supplied 22 to both ends of the resistances 20. Then if there is a flow fluid at the periphery of the sensor 16, piezoelectric resistance effect is caused according to the flow velocity and the value of the resistances 20 varies. The terminal voltage across the bridge impedance and bridge unbalanced voltage vary according to said variation and those are amplified 26 and 28, A/D-converted 31, and inputted to a CPU 32. Consequently, the CPU 32 obtain the pressure and temperature of the fluid from the respective voltages to perform temperature compensation and sensitivity compensation, and then computes accurate dynamic pressure, thereby obtaining density from a specific table. Then, those values are substituted in a specific expression and the square root of the values is computed to find the mess flow rate of the fluid, which is outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fluid measuring device, and particularly to a fluid measuring device that measures the dynamic pressure and t of a fluid that changes depending on the fluid velocity in a fluid passage in an internal combustion engine.
l! The present invention relates to a fluid measurement device that detects 1ffiffil by 1 degree and detects density based on the static pressure and temperature of the fluid that changes depending on the atmospheric pressure of the fluid.

[Prior art]

In general, a vane flowmeter or a pressure receiving plate flowmeter is used as a dynamic pressure flowmeter that determines the flow rate of fluid flowing through a fluid passage (see Japanese Patent Laid-Open No. 49-29675).

Vane flowmeters have vanes installed inside the fluid passage.
The flow rate is calculated by converting the dynamic pressure acting on the vane into a vane displacement angle.

Therefore, it is not possible to measure the lit flow rate, and
The vanes block part of the fluid passage, resulting in large pressure loss and poor response. Furthermore, it requires a movable part, which poses a problem in durability.

On the other hand, the pressure-receiving plate flow rate needle similarly has the same problem as the vane flowmeter because it calculates the dynamic pressure acting on the pressure-receiving plate by converting it into strain produced in the pressure-receiving plate.

Furthermore, since the gas flow rate changes depending on the density, correction is required. For this reason, the temperature and pressure of the gas are measured separately (for example, the pressure is measured with an aneroid barometer and the temperature is measured with a 7Sman psychrometer), and the density of the gas is calculated and corrected from these.

However, in this case, the temperature needs to be measured within a range where there is no large change in pressure.

[Problem that the invention seeks to solve]

In consideration of the above facts, the present invention provides a fluid measuring device that can measure pressure and temperature simultaneously and at the same location using a diffusion type semiconductor sensor, and can calculate the mass flow rate and/or density of a fluid. It is a purpose.

[Means for Solving the Problems (Part 1)] The fluid measurement device according to the first invention includes a diffusion type semiconductor sensor including a silicon substrate and a diffusion gauge resistor forming a bridge circuit on the substrate; A constant TS that supplies a constant current to both ends of the bridge circuit, a flow supply means, a fluid temperature detection means that detects the temperature of the fluid by the voltage across the bridge, and an unbalance of the bridge that changes due to the piezoresistive effect due to fluid pressure. a fluid dynamic pressure detection means for detecting the dynamic pressure of a fluid using a voltage; a dynamic pressure compensating means for compensating the dynamic pressure detected by the fluid dynamic pressure detection means with a fluid temperature detected by the fluid temperature detection means; jQ means for storing fluid density according to;
The apparatus includes a mass flow rate calculation means for calculating the mass flow rate of the fluid based on the dynamic pressure and density of the fluid, and a control means for outputting the mass flow rate.

[Effect (Part 1)] Generally, the mass flow rate (G, c...) of fluid flowing through a pipe is expressed by the following equation.

G-ρ・g-fi, -v...(1) where ρ; fluid density (g, sec"/m') g;
Velocity (9.13 m/sec) A: Cross-sectional area of pipe (a) V: Fluid flow velocity (m/sec) Next, both sides of equation (1) are squared.

G" = g"・A"-9-12-V" ・ (
2) On the other hand, the flow velocity (V) of the fluid is expressed using the dynamic pressure (ΔP) of the fluid as shown in the following equation.

Square both sides of this equation (3) and rearrange it.

ρ·v2−2·ΔP (4) Next, by substituting this equation (4) into equation (2), it is expressed as the following equation.

G"=k・ρ・ΔP...(5) Here K=2・g2・A" (constant) According to equation (5), the square of the mass flow rate (G is the density (ρ) and the dynamic pressure (Δ
P).

The diffused half-quad sensor consists of four diffused gauge resistors forming a bridge circuit on a relatively temperature-sensitive silicon substrate.
It detects pressure. Therefore, the rate of change of diffusion gauge resistance with temperature is greater than the rate of change of resistance with pressure.

In the present invention, paying attention to this fact, the power supply supplied to the bridge circuit is made to be a constant current. As a result, the voltage across the bridge impedance changes depending on the temperature, and the bridge unbalance voltage is proportional to the pressure, so the temperature and pressure of the fluid can be obtained at the same time at the same location.

A diffusion type semiconductor pressure sensor is disposed in a fluid flow path so as to face each other in the fluid flow direction, and a constant current is supplied to both ends of a diffusion gauge resistor constituting a bridge circuit by a constant current generating means. When a fluid flows around a diffusion type semiconductor pressure sensor, a piezoresistance effect occurs depending on the flow velocity of the fluid, and the value of the diffusion gauge resistance changes. As shown in Figure 1, depending on this variation, the voltage across the bridge impedance (7) and the bridge unbalance voltage (Vp)
changes.

FIG. 2 shows the temperature-bridge impedance voltage (■?) characteristic. With this characteristic graph,
■Since 〒 is proportional to temperature, temperature can be easily obtained from the value of ■7.

Figure 3 shows the fluid pressure-bridge unbalance voltage (VP).
The zero span temperature-bridge unbalance voltage (VP) characteristics of fluid pressure are shown in FIG.

These characteristic graphs show that even if the fluid pressure is constant, the output of the bridge unbalance voltage (VP) is affected by the fluid degree.

First, the temperature of the fluid corresponding to the voltage (Vt) across the bridge impedance is obtained from FIG.

Next, the fluid pressure corresponding to the bridge unbalance voltage (■,) is obtained from FIG. This pressure is expressed as the offset voltage (■.F3) shown in Fig. 3, the zero shift (T, ,) shown in the temperature characteristics of the diffusion type semiconductor pressure sensor in Fig. 5,
The sensitivity is corrected by the temperature decrease rate (T, , ), and temperature compensation is performed to obtain accurate pressure.

Next, the density corresponding to the fluid temperature is obtained from the temperature-density characteristics shown in FIG. 6, and by substituting this density and the fluid pressure into the above equation (5), an accurate mass flow rate can be obtained. .

[Means for Solving the Problems (Part 2)] The fluid measurement device according to the second invention includes a diffusion type semiconductor sensor including a silicon substrate and a diffusion gauge resistor forming a bridge circuit on this substrate, and constant current supply means for supplying a constant current to both ends of the bridge circuit; fluid temperature detection means for detecting the temperature of the fluid based on the voltage across the bridge circuit; ′
a fluid static pressure detecting means for detecting the static pressure of the fluid with i voltage; a static pressure compensating means for compensating the static pressure detected by the fluid static pressure detecting means by the fluid temperature detected by the fluid temperature detecting means; and a control means for outputting the density.

[Effect (Part 2)] Generally, the density (ρ) of a gas is expressed by the following equation using the gas state equation.

ρ=P/ (,g-R-T)...(6) where g; gravitational acceleration (g, sec"/m') R; gas constant (n+
/K ) T: Temperature (6K) P: Static pressure (g/n() Here, reference pressure (760 mtlg), reference temperature (2
ρ is the gas density at 0℃). Then, the density (ρ) is expressed by the following equation.

Here, t: Temperature ('C) According to equation (7), the density (ρ) can be easily calculated by the pressure and temperature of the fluid.
can be obtained.

Note that the same applies to liquids because they expand depending on temperature.

First, the temperature and pressure (static pressure) of the fluid are obtained using a diffusion type semiconductor sensor arranged parallel to the flow of the fluid.

By substituting this value into the above equation (7), the density can be obtained. Note that when obtaining the density in (6) 2 above, the gravitational acceleration and gas constant may be stored in advance.

[Means for solving the problem (part 3)] In the fluid measuring device according to the third invention, a silicon substrate is disposed in a fluid so as to face each other in the flow direction of the fluid, and a bridge circuit is configured on this substrate. a first diffusion type hemiwind sensor equipped with a diffusion gauge resistor; a second diffusion sensor equipped with a silicon substrate disposed in the fluid parallel to the flow direction of the fluid and comprising a bridge circuit on this substrate; shaped semiconductor sensor,
A constant current supply means for supplying a constant current to both ends of the bridge to the first and second diffusion type semiconductor sensors, and a temperature of the fluid based on the voltage across the bridge in the bridge circuit of the first diffusion type semiconductor sensor. a first fluid temperature detection means for detecting the fluid temperature; dynamic pressure compensating means for compensating the dynamic pressure detected by the dynamic pressure detecting means in accordance with the temperature of the fluid; and a second diffusion type semiconductor sensor for detecting the temperature of the fluid using a voltage across the bridge in the bridge circuit of the second diffusion type semiconductor sensor. a fluid temperature detection means, a fluid static pressure detection means for detecting the static pressure of the fluid by the unbalanced voltage of the second diffusion type semiconductor sensor that changes due to the piezoresistive effect due to the atmospheric pressure of the fluid, and this fluid static pressure detection means. static pressure compensating means for compensating the static pressure detected by the second fluid temperature detecting means according to the temperature detected by the second fluid temperature detecting means; and fluid density calculating means for calculating the density of the fluid based on the compensated static pressure and temperature. and a mass fL amount calculation means for calculating the mass flow rate of the fluid based on the compensated dynamic pressure and the density detected by the fluid density detection means, and a control means for outputting the mass flow rate.

[Effect (Part 3)] In this way, the density of the fluid is also determined by temperature and static pressure, so when obtaining the mass flow rate, instead of using the characteristic graph in Figure 6, substitute the value obtained here. It is being calculated. Therefore, mass 2i! Accurate values of LH can be obtained.

[First Embodiment] A first embodiment of the fluid measuring device 10 according to the present invention is shown in FIGS. 7(A) and CB) and the eighth section.

The fluid flows into the conduit 12 of the tube 11 from the left side to the right side as shown by arrow A in FIG.

A support 15 is attached to the inner circumferential surface of the conduit 12, and its tip extends in the axial direction. The support body 15 is made thin and there is no fluid pressure loss.

The tip of the support 15 is slightly bent in the direction of fluid inflow, and a diffusion type semiconductor pressure sensor 16 is attached to the end face thereof.

As shown in FIG. 8, this diffusion type semiconductor pressure sensor 1
6 is composed of a silicon substrate 18 and four diffused gauge resistors 20, and the diffused gauge resistors 20 constitute a bridge circuit.

At diagonal corners of the bridge circuit in the vertical direction in the drawing, 22B are connected to the flashing wires 22□ from the constant current generating means 22, respectively. Also, this I ε cotton 22. 22B is extended and connected to the amplifier 26 of the microcomputer 24 to detect the voltage across the bridge impedance. Further, the diagonal sides of the bridge circuit on the left and right sides in the drawing are connected to an amplifier 28 via signal lines 25A and 25B, respectively, to detect the bridge unbalanced voltage.

This constant current generating means 22 and microcomputer 24
is housed in a control section 30 attached to the outer periphery of the tube 11, as shown in FIG.

As shown in FIG. 8, the outputs of amplifiers 26 and 28 are A/
After being A/D converted by the D converter 31, it is input to the CPU 32. The CPLI 32 has a storage device 3 in which the outputs from the amplifiers 26 and 28 and the data of the graphs shown in FIGS. 2 to 5 described above are input in advance.
The mass flow rate is calculated based on the data from 4.36 and is output.

The operation of the first embodiment will be explained below.

First, the constant current generating means 2 is applied to the diffusion type semiconductor pressure sensor 16.
Supply current from 2. In this case, the current value is 1-2mA
The diffusion gauge resistor 20 generates heat when a relatively large current is supplied.

Since the diffusion type semiconductor pressure sensor 16 is installed facing the direction of fluid inflow, the diffusion type semiconductor pressure sensor 16
The pressure experienced by the fluid, that is, the dynamic pressure, is proportional to the square of the fluid flow rate. The flow velocity is obtained as the bridge unbalance voltage (Vp) and is input to amplifier 28.

On the other hand, when the fluid collides with the diffusion type semiconductor pressure sensor 16, the resistance value of the diffusion gauge resistor 20 installed on the surface thereof changes depending on the temperature of the fluid.

Here, as described above, a minute constant current (1 to 2 mA) flows through the diffusion gauge resistor 20, and thereby the temperature change of the fluid can be obtained as the bridge impedance voltage (■, ). The impedance voltage (■, ) bridging this temperature change is input to the amplifier 26.

Each voltage (VT, VT
) is A/D converted by the A/D converter 31 and input to the CPU 32.

The memory devices 34 and 36 store in advance the offset voltage of the diffusion type half-four body pressure sensor 16, the shift of the zero point due to the temperature of the fluid, the sensitivity reduction due to the temperature, and the constant (K) applicable to the above-mentioned equation (5). The CPU 31 controls each voltage (V
t, VP) Based on the pressure and temperature of the fluid obtained from d, temperature compensation and sensitivity compensation are performed to calculate an accurate dynamic pressure (ΔP), and the density (ρ) is taken in from FIG.

Next, by substituting these values (K, ΔP, ρ) into equation (5) and calculating the square root of the values, the mass flow rate (G) of the fluid is determined and output.

Note that by disposing the diffusion type semiconductor pressure sensor 16 applied in the first embodiment in parallel to the fluid flow,
It is also possible to determine the density (ρ) of the fluid, and this case will be described below.

The density (ρ.) at a reference temperature <20°C) and a reference pressure (760 mmHg) is stored in advance in the storage device 34.36. Here, the bridge impedance voltage (V
The density (ρ) can be easily determined by substituting it into equation (7) together with the static pressure (P) obtained through calculation processing based on t).

In addition, if the storage device stores the gravitational acceleration 1 (g) and the gas constant (R) instead of the reference density (ρ.), then (
The density can also be determined using equation 6).

In this way, one diffusion-type semiconductor pressure sensor 16 can measure the pressure and temperature of the fluid at the same place in the pipe line 12 at the same time, making it possible to obtain accurate quality II quantity or density. can.

Furthermore, since the fluid flow path is not obstructed by vanes, pressure receiving plates, etc., there is almost no pressure loss.

Note that in the first embodiment, the diffusion type semiconductor pressure sensor 16
was placed in the center of the conduit 12 via the support 15, but
As shown in FIGS. 9(A) and 9(B), a small diameter pipe 40 may be provided around the diffusion type semiconductor pressure sensor 16 to form a center venturi type sensor.

In addition, as shown in FIGS. 10(A) and (B), the tube 11
The thickness of the wall is set to 1, and a bypass path 42 is provided in a part of the wall.
A diffusion type semiconductor pressure sensor 16 may be installed within this bypass path 42.

Further, the diffusion type semiconductor pressure sensor 16 used in the first embodiment may be of either a differential pressure type or an absolute pressure type, however, when detecting density, an absolute pressure type is preferable.

[Second Embodiment] FIGS. 11(A), 11(B), and 12 show a second embodiment of the fluid measuring device according to the present invention.

In the second embodiment, the first diffusion type semiconductor pressure sensor 16 disposed opposite to the fluid flow applied in the first embodiment is used.
Separately, a second diffusion type semiconductor pressure sensor 44 is attached to the support body 1.
5 (a surface perpendicular to the fluid flow direction).

That is, this diffusion type semiconductor pressure sensor 44 is not opposed to the flow of fluid, and is capable of measuring the static pressure of the fluid. Here, the diffusion type semiconductor pressure sensor 44 that measures the static pressure of the fluid is preferably an absolute pressure type pressure sensor.

A constant current (1 to 2 mA) is supplied from a constant current generating means 46 to a diffusion type semiconductor pressure sensor 44 composed of a silicon substrate 45 and four diffusion gauge resistors 20, similarly to the diffusion type semiconductor pressure sensor 16. , the bridge impedance voltage and the bridge unbalance voltage are connected to the amplifier 4.
8.50 to the A/D converter 31.

The structure after the A/D converter is the same as that in the first embodiment, so a description of the structure will be omitted.

The operation of the second embodiment will be explained below.

A constant current (1 to 2 mA) is supplied from constant current generating means 22.46 to each of the diffusion type semiconductor pressure sensors 16.44. This allows two diffusion type semiconductor pressure sensors 16.4
It is possible to measure the bridge impedance voltage and bridge unbalance voltage of each of the four components.

The above four types of data are amplified by amplifiers 26, 28, 48, and 50 and A/D converted by A/D converter 31, and then
Based on the offset voltage of the two diffusion type semiconductor pressure sensors 16.44 inputted to U32 and stored in advance in the storage device 34.36, zero point shift depending on the temperature of the fluid, pressure anger reduction, and flow rate conversion constant. The calculation is processed.

Since the diffusion type semiconductor pressure sensor 16 faces the direction of fluid inflow, the dynamic pressure (ΔP) of the fluid is detected similarly to the first embodiment.
and temperature (T) can be obtained.

On the other hand, the diffusion type semiconductor pressure sensor 44, which is parallel to the flow direction of the fluid, obtains the static pressure (P) and temperature of the fluid by changes in the bridge impedance voltage and the bridge unbalanced voltage, and substitutes these into equation (7). By doing so, the density (ρ) corrected for atmospheric pressure can be obtained.

Next, the temperature of the fluid obtained by the diffusion type semiconductor pressure sensor 16 (
T) and the density (ρ) of the fluid obtained by the diffusion type semiconductor pressure sensor 44 are determined.

Next, dynamic pressure (ΔP), density (ρ), flow rate conversion constant (K)
By substituting into equation (5) and finding the square root of that value, the quality! ff1l (G) is output.

In this way, the density (ρ) can be calculated from the diffusion type semiconductor pressure sensor 44.
Since it is determined from the static pressure (P) obtained in , it is more accurate than obtaining the density by reading it using the graph of FIG. 6 as in the first embodiment.

[Third Embodiment] FIGS. 13 and 14 show a third embodiment of the fluid measuring device according to the present invention.

In the third embodiment, the microcomputer 24 shown in the first embodiment is replaced with an IC5 such as a bipolar IC or a MOS-IC.
2 is disposed on the silicon substrate 18. This IC
52 is an input A1 lead 56 for supplying constant current power to a bridge circuit composed of a diffusion gauge resistor 20 that is a part of the diffusion type semiconductor pressure sensor 16, and an output lead 56 for outputting the mass flow rate of fluid. The Al lead 57 and these GND AI leads 58 are connected.

In this way, by integrating the peripheral circuits other than the diffusion type half-quad body pressure sensor 16 onto the silicon substrate 18, the fluid measuring device itself becomes compact.

(Effects of the Invention) As explained above, the fluid measuring device according to the present invention can measure pressure and temperature simultaneously and at the same location using a diffusion type semiconductor sensor, and can calculate the mass flow rate and/or density of a fluid. It has the excellent effect of being able to

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a diffusion type semiconductor pressure sensor applied to the present invention, Fig. 2 is a temperature-bridge impedance voltage (vl) characteristic diagram, and Fig. 3 is a pressure-bridge unbalance voltage (V,). Characteristic diagram, Figure 4 is the zero span temperature of fluid pressure vs. bridge unbalance voltage (V,) characteristic diagram, Figure 5 is the temperature characteristic diagram of the diffusion type semiconductor pressure sensor, and Figure 6 is the temperature vs. density characteristic of the fluid. 7(A) and CB) are the first embodiment of the present invention.
A side view and a front view of the vicinity of the fluid measuring device according to the embodiment, FIG. 8 is a circuit diagram of the fluid measuring device according to the first embodiment, and FIGS. 9 (A) and CB) are when the pipe line is a venturi type. (A) and (B) are side views and front views of the fluid measuring device when the pipeline is a bypass type, and FIG. 11 (A) and (B) are side views and front views of the fluid measuring device. B) is a side view and a front view of the fluid measuring device according to the second embodiment, and FIG. lO...Fluid measuring device, 1゛4...Fluid, 16...Diffusion type semiconductor pressure sensor, 18...Silicon substrate, 20...Diffusion gauge resistance, 22...Constant IT flow generation means , 24...Microcomputer.

Claims (3)

[Claims] (1) A diffused semiconductor sensor equipped with a silicon substrate and a diffused gauge resistor forming a bridge circuit on this substrate;
constant current supply means for supplying a constant current to both ends of the bridge circuit; fluid temperature detection means for detecting the temperature of the fluid based on the voltage across the bridge; and unbalanced voltage of the bridge that changes due to a piezoresistive effect due to fluid pressure. a fluid dynamic pressure detecting means for detecting the dynamic pressure of the fluid; a dynamic pressure compensating means for compensating the dynamic pressure detected by the fluid dynamic pressure detecting means by the fluid temperature detected by the fluid temperature detecting means; A fluid measuring device comprising: a storage means for storing a corresponding fluid density; a mass flow rate calculation means for calculating a mass flow rate of the fluid based on the dynamic pressure and density of the fluid; and a control means for outputting the mass flow rate. (2) a diffused semiconductor sensor comprising a silicon substrate and a diffused gauge resistor forming a bridge circuit on this substrate;
constant current supply means for supplying a constant current to both ends of the bridge circuit; fluid temperature detection means for detecting the temperature of the fluid based on the voltage across the bridge circuit; a fluid static pressure detecting means for detecting the static pressure of the fluid with a voltage; a static pressure compensating means for compensating the static pressure detected by the fluid static pressure detecting means by the fluid temperature detected by the fluid temperature detecting means; A fluid measuring device comprising: a density calculation means for calculating the density of a fluid based on static pressure and temperature; and a control means for outputting the density. (3) A first diffusion type semiconductor sensor including a silicon substrate and a diffusion gauge resistor forming a bridge circuit on this substrate, and a silicon substrate and a bridge disposed in a fluid parallel to the fluid flow direction. a second diffused type semiconductor sensor including a diffused gauge resistor constituting a circuit; constant current supply means for supplying a constant current to both ends of the bridge to the first and second diffused semiconductor sensors; 1
A first fluid temperature detection means detects the temperature of the fluid by the voltage across the bridge in the bridge circuit of the diffusion type semiconductor sensor;
a fluid dynamic pressure detecting means for detecting the dynamic pressure of a fluid using an unbalanced voltage of a diffusion type semiconductor sensor; and a dynamic pressure compensating means for compensating the dynamic pressure detected by the fluid dynamic pressure detecting means according to the temperature of the fluid. , a second fluid temperature detection means for detecting the temperature of the fluid by the voltage across the bridge in the bridge circuit of the second diffusion type semiconductor sensor; and a second diffusion type semiconductor that changes due to the piezoresistive effect due to the atmospheric pressure of the fluid. Fluid static pressure detection means for detecting the static pressure of the fluid using the unbalanced voltage of the sensor, and compensating the static pressure detected by the fluid static pressure detection means according to the temperature detected by the second fluid temperature detection means. a static pressure compensation means, a fluid density calculation means for calculating the density of the fluid based on the compensated static pressure and temperature, and a mass flow rate of the fluid based on the compensated dynamic pressure and the density detected by the fluid density detection means. A fluid measuring device comprising a mass flow rate calculation means for calculating, and a control means for outputting the mass flow rate.