JPS6196417A - Fuel measuring instrument of flying body - Google Patents

Abstract

PURPOSE:To elevate an accuracy by obtaining an actual fuel weight value with calculation based on the values obtd. from a tank unit, compensator unit and fuel density measuring unit. CONSTITUTION:The output of a fuel density measuring unit 10 is inputted into a tank unit 3 and fuel balance arithmetic part 16 from a fuel density arithmetic part 13. The output terminal of the tank unit 3 and the output terminal of a compensator unit 9 are connected and connected to the feedback terminal 16b of the fuel balance arithmetic part 16. And the fuel balance arithmetic part 16 operates the actual fuel weight value based on the value obtd. from the tank unit 3, compensator unit 9 and fuel density measuring unit 10.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention provides a tank unit (hereinafter abbreviated as rT/UJ) that outputs the liquid level of fuel as a capacitance, and a tank unit that outputs the liquid level of fuel as a capacitance, and The compensator unit outputs as (
Relates to a fuel measuring device for an aircraft that calculates and calculates the fuel weight of an aircraft based on the AC voltage signal whose amplitude is proportional to the density of the fuel (hereinafter abbreviated as rC, 'UJ) .

<Prior art> Conventionally known fuel measuring devices for this type of aircraft include: ■
: "Aviation Instruments" of Chijinshokan (published October 5, 1976), and ■: Yokogawa Technical Report (published by Yokogawa Hokushindenei Co., Ltd. in 1988) Vo 1.28 No.

2, page 179.

The technology described above measures the fuel in the fuel tank by utilizing the fact that the output of a capacitive liquid level meter is proportional to the fuel level and the fuel electrostatic coefficient. It is.

FIG. 3 (A> is a diagram showing the type of the basic principle of a capacitor.

In Figure 3 (A>, 1 is a fuel tank that stores fuel 2 of the aircraft, 2a is a capacitance Ct from the liquid level χ of fuel 2
This is the liquid level electrode for taking out the liquid. At this time, the capacitance Ct is CT=CD(1-t χ (K-1))
...(1). However, CD is the capacitance when fuel tank 1 is completely filled with air! (referred to as "dry cap" under D), K is the dielectric coefficient of fuel 2 (the dielectric coefficient of fuel 2 (approximately 2) is approximately twice that of air (1χ).

FIG. 3(B) is a bridge circuit diagram of a simple structure in which the basic principle of the capacitor shown in FIG. 3(A) is used on one side of a bridge similar to a Wheatstone bridge.

In FIG. 3(B), 3 is a capacitance type liquid level sensor T, /U which is a more specific example of the liquid level electrode 2a. This T/LI 3 is composed of coaxial double cylindrical electrodes in which a capacitor is formed between an inner cylinder with a radius of a and an outer cylinder with a radius of a. At this time, the dry cap Go is Co = 24.1 Kl/log 10(a/b) [p F7'mi
++ (2). however,! is the length of the cylinder.

Usually, the dry cap Go is number + DF. E is AC power supply, King is transformer, 4 is ammeter, 50 is capacitor CF
It is a balancing capacitor with Here, the voltage at one end of the transformer T connected to T/U3 is Vl, and the voltage at one end of the transformer T connected to the balancing capacitor 50 is V2.
, the current flowing from T/U3 to connection point 0 is JT, connection point 0
The current flowing from the connection point 0 to the balancing capacitor 50 is (F%) The current flowing from the connection point 0 to the ammeter 4 is Ih. At this time, the current IM is In = IT Ip -ω ■ Blind CT -ω V2CF
... (3). °Substituting equation (1) into this, the current ■gate becomes TM-ωV+Go+ωV1χ
(K-1)C.

-ωV2 Cp (4). However, ω is the angular velocity. In equation (4),
Assuming that it is adjusted so that V+ Co =V2Cp, the current IM becomes Ih=ω■, χ(K-1)Go (5). Therefore, when fuel 2 is empty, χ=0. When the fuel is full, x = 1, and at this time, the ammeter 4 shows IN = O.
A current of ~ωV+ (K 1)Go flows. By reading this current m from the indication of the ammeter 4, the base of the fuel 2 can be known.

The third section (C) is a block diagram showing an instruction system comprising a high-precision servo system, which is a further embodiment of the system shown in FIG. 3(B).

In FIG. 3(C), 5 is a servo amplifier, 6 is a servo motor, 7 is an indicator (M indicates the first shift of the indicator), 8 is a potentiometer, and 60 is a balancing capacitor having a capacity I Ca. Here, the current flowing on each side of the bridge is 1+
, f2. If I3+Io, the current It, 12. I
3. IO is 1+ (-ωVt(Go+χ(
K-1) Go)).

12 (=(c)V2Cp), I3 (=MωV
3Ca).

It becomes 1o. Here, the bridge equilibrium condition is 1o = I
+ +I2 +13 =O... (6) Therefore, by substituting the values of each current mentioned above, formula (6) becomes V + G
o +1 (K -1) V+ G.

+V2 CF +MV3 C13=O-(7).

Therefore, the indicated value M of the indicator 7 is M−(V+Go+χ(
K1) V+G.

+ V2 GF) / V3 CB...(
8). Now, when the fuel is empty, χ=O, M=O, so equation (7) is: V+ Go '-V2 CF
−(9). On the other hand, when the fuel is full, χ=1
Since 1M=1, equation (7) is: V+CD+(K 1) VIGO +V2 CF +V3 CB =0,', KV+ CD +V2 CF '' V3 Ca
−(10). These equations (9) and (10) are converted into (
8) Substituting into formula, M・=χ...(11)
becomes. ■+ so as to satisfy formulas (9) and (10),
V2. If the values of CD, CF, and CB are determined, Figure 3 (
The bridge circuit in C) can measure fuel and issue instructions.

By the way, if fuel instructions are required in units of weight (for example, for gas turbine aircraft), it is necessary to replace volume with weight. That is, since the T/LI3 is a liquid level sensor, its output is a function of the fuel volume, and in order to determine the weight, it is necessary to multiply it by the fuel density ρ. Therefore, by utilizing the fact that the fuel density ρ is a function of the dielectric constant, a dielectric sensor C of the fuel 2 shown by a broken line is connected in parallel to the balancing capacitor 60.
/U9 is provided, and the circuit characteristics are determined by the density-permittivity correlation formula % formula (1)) (However, TA and Ta are specific values determined by the airplane manufacturer or values determined by MILL, etc.) )
It is possible to obtain the indicated value M proportional to the fuel weight by making it coincide with the fuel weight.

<Problems to be Solved by the Invention> By the way, the above-described correlation equation between fuel density and dielectric constant is a statistical correlation equation, and actually differs depending on the fuel. As a result, there is a problem in that an error of about 4% at maximum occurs.

<Object of the Invention> The present invention has been made in view of the above-mentioned problems, and calculates the true value based on the values obtained from T/U, C/(J, and a fuel density measuring device). It is an object of the present invention to provide a highly accurate fuel measuring device for an aircraft equipped with an arithmetic circuit for obtaining a fuel weight value.

Configuration for Solving the Problems> The fuel measuring device for an aircraft according to the present invention for achieving the above object has the following configuration.

The density of fuel in a fuel tank provided on an aircraft is measured, and based on the measured density, the fuel density measuring device outputs an alternating current voltage signal whose amplitude is proportional to the density. That is, the measured density is converted into a DC voltage proportional to the density, and then further multiplied by an AC voltage, and an AC voltage signal whose amplitude is proportional to the density is converted into an AC voltage signal T,,'U, and the fuel remaining amount calculating section described below. Output to. The capacitance type T/U used as a liquid level sensor for measuring the fuel liquid level is excited by an AC voltage signal from the fuel density calculation section and outputs a capacitance value corresponding to the liquid level. do. One end is connected in series to this T, /U, and the other end is connected to the fuel output terminal of the fuel remaining amount calculation unit (a value proportional to the remaining fuel amount is fed back to C/LJ), and the dielectric constant is measured. C/ which is a rate sensor
U outputs a capacitance corresponding to the dielectric constant (T/
The connection point between lJ and C/U is connected to the feedback terminal of the remaining fuel amount calculating section). On the other hand, in the internal circuit of the fuel remaining amount calculation section, a dry cap cancellation circuit for canceling the dry cap of the T/U is arranged between the input terminal and the feedback terminal, and an operational amplifier and the fuel dielectric between the feedback terminal and the output terminal are arranged. The structure includes a dielectric coefficient cancellation circuit that cancels the influence of the coefficient. Therefore, the remaining fuel amount calculating section can eliminate the dielectric coefficient and the dry cap and obtain an output value proportional to the remaining fuel amount. In other words, this output 1st shift is
T/U is the part immersed in fuel, and T/L
It is also proportional to the excitation voltage of J. As a result, the output for one shift is proportional to fuel volume×density, that is, fuel lff1. This output value can be displayed on the display section.

<Example> Hereinafter, the present invention will be explained in detail with reference to FIG. 1, a block diagram showing a specific example of the fuel measuring device for an aircraft according to the present invention. Note that in FIG. 1, parts that overlap with those in FIG. 3 are given the same numbers and their explanations will be omitted.

In FIG. 1, reference numeral 10 measures the density ρ of the fuel 2 in the fuel tank 1 provided in the aircraft, and based on the measured density ρ, an AC voltage signal whose amplitude is proportional to the density (for example, voltage n, ρVrer (However, n1 is a constant))) This is a fuel density measuring device that calculates and outputs. This fuel density measuring device 10 includes a density sensor 11 that detects the density ρ of the fuel 2.
, input the density ρ from this density sensor 11, and obtain the density ρ
A density calculation circuit 12 calculates a DC voltage signal n1ρ proportional to , and an AC voltage (Vref
) and whose amplitude is proportional to the density 71+
/) fuel density calculation unit 13 that outputs Vref. Here, the fuel vM degree calculation unit 13 calculates the AC voltage vrer
, and a multiplier 15 that multiplies the AC voltage VTef and the DC voltage n1ρ. T/
lJ3 is an AC voltage signal n from the fuel density measuring device 10
It is excited by 1ρvTer and outputs a capacitance corresponding to the liquid level χ of the fuel 2 as an output current ■a. One end of C/L19 is connected in series to T/U3 (the connection point is α), and the other end is connected to the output terminal of the remaining fuel amount calculation section described below, and corresponds to the dielectric constant K of fuel 2. The output current 1c is outputted from the capacitance. 16 is an AC voltage signal nIρVr
e t is input from the input terminal 16a, and T/U 3 and C are input from the feedback terminal 16b connected to the connection point α.
/Ll This is a remaining fuel amount calculating section which inputs the combined current (Ia+Ic) of 9, eliminates the dielectric coefficient K and the dry cap, and outputs an output value Vo proportional to the remaining fuel amount from the output terminal 16c. The remaining fuel amount calculating section 16 is configured as follows. A dry cap canceling circuit 17 is arranged between the input terminal 16a and the operational amplifier Q2, which is composed of an amplifier Q1 with a gain of (-1) and a capacitor 17a with a capacitance fncyo, and cancels the dry cap of the T/Ll3. The output current of the dry camp cancellation circuit 17 is equal to Ib). A connection point between the dry cap cancellation circuit 17 and the input terminal of the operational amplifier Q2 is connected to the feedback terminal 16b. The output terminal of operational amplifier Q2 is connected to output terminal 16C.

Furthermore, the input terminal of the operational amplifier Q2 is connected to the operational amplifier Q2. The output Vo of the radiator Q2 is an amplifier Q3 with a gain (-1) and a capacitor 1c.
A feedback current ■d is fed back through a dielectric coefficient canceling circuit 18 that cancels the influence of the dielectric coefficient of the fuel, which is composed of a capacitor 18a of CO.

The operation of this remaining fuel amount calculating section 16 will be explained below.

If the dry cap is CTO, the capacitance JE1Cvu of T/U3 is calculated as follows from equation (1): Cru = Cro (1+χ(K-1))
...(12), and on the other hand, the capacitance of C/U 9 is
Ccυ becomes Ccu=-Cco-(13) if the dry cap is Cco. On the other hand, each current ra to Id is calculated as follows, where S is the operator, Ia = SCv u ・n + ρvr e r = SCv
o(1+χ (K-1)) ・n1ρVTef ... (14) Ib = -8CT D -n+ ρvTef
=(1,5)Ic =SCc u −V.

=SKCco −Vo −(16)
Id = 5Cco −Vo
−(17). Since the equilibrium condition of the bridge is la + Ib + Ic + Id = O - (18), the relationship between equations (14) to (17) is 5CTO (1
+r (K 1)) ・n+
ρ Vrsr 5CroFI+ρVrer+5KCc
o -Vo 5Cco ・Vo -(1
9). Therefore, the output (ltV
o is Vo−−[((Cyo+χ(K−1)−CTO
)−CTD)/(KCco Cco)]・n)ρVver=(20). Here, Cvo-Cvos Gco = Cc.

If CTO, Cco are selected so that the equation (20) is obtained, the output value vO becomes one shift proportional to (fuel volume) x (density) = (fuel weight).

Note that the dry cap cancellation circuit and the dielectric coefficient cancellation circuit are not limited to the circuits described here; for example, (-
1) Amplifier Q+ with a gain of.

When Q3 has a gain of (-N), box>
-7” capacity of 4t17a, 18a (CTD/N)
.

(Cco/N), no difference in characteristics will occur.

Further, the output value Vo can be displayed, for example, on a display section φ, which is constituted by a digital-to-analog conversion circuit and a display indicated by a broken line.

<Other Examples> The configuration of the fuel density calculation section of the present invention is not limited to that shown in FIG. FIG. 2 is a block diagram showing another embodiment of the invention. In FIG. 2, explanations of parts that overlap with those in FIG. 1 will be omitted by giving the same numbers.

In FIG. 2, 19 is a fuel density measurement position.

This fuel density measuring device 19 includes a density meter 20 which is connected to a connection point α and which measures the density ρ of the fuel 2 in the fuel tank 1 and outputs a density signal IO which is a constant DC current proportional to the density of the fuel. , a density detection circuit 21 connected to a connection point α, which inputs this density signal 1o and outputs, for example, a DC voltage signal Vo proportional to the density signal io, and a fuel density calculation unit 13.

Here, the density detection circuit 21 includes a series circuit of a resistor 21b having a resistance value R2, an operational amplifier Q4 having, for example, low-pass filter characteristics, and a feedback resistor 21a having one resistor R1 connected in parallel to the series circuit. It consists of

Now, if a current of feedback resistor 21aG, :i of the density detection circuit 21 flows, the operational amplifier Q2 of the remaining fuel amount calculation section 16
A DC voltage -iR is output, and the operational amplifier Q4 of the density detection circuit 21 detects the DC component of the output voltage of the operational amplifier Q2, and generates a DC voltage (Vo> that cancels this.This DC voltage The voltage (vO) is fed back to the operational amplifier Q2 through the resistor 21b.

As a result, the DC component appearing at the output of the operational amplifier Q2 becomes zero, and the current ro from the density meter 20 all flows into the density detection circuit 21. That is, Vo=R21o'' (fuel density) (22), and the DC voltage (Vo) of the density detection circuit 21 is proportional to the fuel density.
Similarly to the figure, the DC voltage input to the multiplier 15 is Vo=n+
(Although the fuel leak resistance is parallel to the feedback resistance R2 when transmitting the density signal, a change in the resistance R7 does not affect the operation of the operational amplifier Q4 and therefore does not result in an error).

The present invention can also be realized in this manner.

<Effects of the Invention> As described above in detail with reference to specific examples, the present invention includes a fuel density measuring device that outputs a value proportional to the density of fuel, and a fuel density measuring device that is excited by the output from this fuel density measuring device. T>U to measure the liquid level of the fuel, and C/ to measure the dielectric constant of the fuel.
A fuel measuring device for an aircraft according to the present invention, which comprises a fuel density measuring device, a fuel density measuring device, a T/U, and a C/U, and a fuel remaining amount calculation unit that outputs a fuel proportional to the remaining fuel amount (fuel weight). Since this multiplies the volume and density, there is no error of up to 4% that occurs when using a statistical [fuel density-permittivity correlation formula] as in the prior art, and the true fuel It is possible to obtain the weight and provide an extremely effective technique for measuring the fuel of an aircraft. In addition, by using a density detection circuit that uses a direct current balance method as a circuit that converts the density signal, which is a current, into a voltage (by configuring it as shown in Figure 2), it is possible to convert the density signal ('DC) and It is possible to transmit fuel residual signal (AC) on the same line.

There is an effect.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a specific embodiment of the fuel measuring device for an aircraft according to the present invention, and FIG. 2 is a Bron line diagram showing another embodiment of the fuel measuring device for an aircraft according to the present invention. Figure 3 is a diagram showing the prior art, and individually, Figure 3 (A>
Figure 3 shows the basic principle of capacitors.
B) is a bridge circuit diagram of a simple structure in which the basic principle of the capacitor shown in Fig. 3(A) is used on one side of a bridge similar to a Wheatstone bridge. B
) is a block diagram showing an instruction system comprising a high-precision servo system that further embodies the system.

Claims (1)

[Claims] (1) An aircraft comprising a tank unit that outputs the liquid level of fuel in a fuel tank provided in the aircraft as a capacitance, and a compensator unit that outputs the dielectric constant of the fuel as a capacitance. In the fuel measuring device, A: a fuel density measuring device (for example, 10, 19) that inputs the density measurement value of the fuel and outputs a value proportional to the density, and B: one end is connected to the fuel density measuring device. the tank unit (for example, 3), the other end of which is connected to one end of the compensator unit (for example, 9); C: the fuel density measuring device is connected to the input terminal, and the other end of the compensator unit is connected to the output terminal; is,
A connection point between the compensator unit and the tank unit is connected to a feedback terminal, and a dry cap canceling circuit (for example, one
7), an amplifier (for example Q_2) and a dielectric coefficient cancellation circuit (for example 18) for canceling the influence of the dielectric coefficient of the fuel are provided between the feedback terminal and the output terminal, and A fuel measuring device for an aircraft, comprising: a remaining fuel amount calculating section (for example, 16) that calculates and outputs a value proportional to the remaining fuel amount.