JPS6056232A - Manometer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a pressure gauge that is particularly effective for use in aircraft engine control. In more detail, the present invention is
This invention relates to a cylindrical vibrating pressure gauge that uses a cylindrical vibrator and uses the fact that its natural frequency changes depending on the surrounding pressure to determine pressure.

[Description of prior art]

Pressure gauges using cylindrical vibrators are well known in the art. When this cylindrical vibrating pressure gauge is used, for example, to measure the pressure of intake fluid in an aircraft engine, the range of change in pressure to be measured is wide, and the operating conditions of the engine are unrelated to the pressure to be measured. Due to the presence of pulsating pressure noise that changes accordingly, it has been difficult to stably and accurately measure the pressure to be measured.

[Object of the present invention]

The present invention eliminates these problems in the prior art,
The aim is to realize a pressure gauge that can stably and accurately measure the pressure to be measured.

[Summary of the invention]

The device according to the present invention includes a cylindrical vibrator to which a pressure to be measured is applied, a self-excited oscillation circuit formed including this cylindrical vibrator, and a frequency variable filter circuit to which a frequency signal from this oscillation circuit is input. and a detection means for detecting the operating condition of the engine, and is characterized in that the pass band of the variable filter circuit is controlled in accordance with a signal from the operating condition detection means.

[Explanation of Examples]

FIG. 1 is a structural diagram showing an example of a device according to the present invention. In this figure, EG generally represents an aircraft engine, one cylindrical oscillator in the aircraft engine to which suction fluid pressure is applied, and 5 a self-excited oscillation circuit including the cylindrical oscillator 1. 6 is a frequency variable filter circuit that inputs the frequency signal from the oscillation circuit 5, and 7 is a detection means for detecting the operating condition of the engine, for example, a piezoelectric element installed in the engine case is used. ,
From this, a pulsation signal that changes depending on the operating condition of the engine is obtained, and this pulsation signal is given to the control end of the variable frequency filter circuit 6. Reference numeral 8 denotes a measuring circuit which receives the signal from the variable filter circuit 6 and performs predetermined calculations to obtain a pressure signal.

Fig. 2 is a configuration diagram showing an example of the cylindrical vibrator 1, in which 0) is a perspective view showing a part in cross section, and (b) is a line X-X in Fig. 0.
The sectional view in FIG. 3 is a Y-Y sectional view in FIG. 2(A) and an electrical connection diagram including the oscillation circuit 5.

In these figures, the cylindrical vibrator 1 has a thin cylindrical portion 1
1, a thick cylindrical part (7 rank part) 12 continuous to one end of the thin cylindrical part 11, and an end face part 18 that closes the other end of the thin cylindrical part 11. The thick-walled cylindrical portion 12 has countersink holes 13 to 13 extending from its outer peripheral surface to near the inner wall.
16 are provided here. Among these counter-bore holes, the counter-bore holes that are positioned opposite to each other with respect to the central axis of the vibrator 1: L4. : Drive means 21 and 22 for exciting the vibrator 1 are installed in L6, and a detection means 31 for detecting the resonant frequency of the vibrator 1 is installed in the remaining counterbore hole 13.15. .32 is installed.

On the end face portion 13 of the cylindrical vibrator 1, vibration detection means 33,
34 are installed, and the positions of the vibration detection means 33 and 34 are selected so that the line segment connecting them is orthogonal to the line segment connecting the vibration detection means 31 and 32 installed on the flange part 12. There is. Piezoelectric elements can be used as these driving means 21, 22 and vibration detecting means 31, 32, 33, 34. 4 is a case that accommodates the cylindrical vibrator 1;
Its outer diameter is the same as that of the 7-rank section 12, and has an opening at one end into which the tip (end surface section 18) of the vibrator 1 is inserted and fixed. The case 4 is fixed to the seventh rank part 12 and the cylindrical vibrator 1 is fixed to the end face part by means such as welding so that airtightness is maintained.

Reference numeral 41 denotes a pressure introduction port provided on the side wall of the case 4, through which pressure is introduced into the chamber 40 formed between the cylindrical vibrator 1 and the case 4.

In the electric circuit shown in FIG. 3, A□ is an amplifier that amplifies the signal from the vibration detection means 33.34 installed at the end face of the vibrator 1, and A2#i amplifies the signal from the vibration detection means 31.32. The amplifier A3 is an inverting amplifier that inputs the output of the amplifier A□. Both MC□ and MC2 include filter circuits that pass a specific frequency signal and shift the phase to satisfy the self-oscillation condition. 1st.
In the second self-oscillating circuit, the first self-oscillating circuit MO□ includes amplifiers A1. A sum signal e1 of signals eA and eB from each detection means generated at a common connection point of resistors R□ and R2 connected between the output terminals of A2 is input. In addition, the second self-oscillation circuit MC2
is amplifier A3. Resistor R3+ connected between the output terminals of A2
Signals eh from each detection means generated at 14 common connection points
+ eB difference signal e2 is input.

OUT 1. OUT 2, each 1st. Frequency signal f4 obtained from the second self-oscillating circuit MC□, MC2
At the output terminal which outputs □, f4□, each of these frequency signals ff41' 42 is applied to the driving means 21.22 via a resistor R5+Re.

Vibration detection means, 1st. The second self-excited image path and driving means are:
Two self-excited oscillation loops are formed including the vibrator 1, and the cylindrical vibrator 1 has two resonance frequencies f4□ and f42.
multiple oscillation.

The filter circuit 61 receives the frequency signal f□ from the first self-exciting circuit MC□, and the filter circuit 62 receives the frequency signal f2 from the second self-exciting circuit Mc2.

Figure 4 shows signal waveforms showing an example of changes in frequency signals from the self-excitation circuits MC and MC2, where (a) shows when the pressure to be measured is low, and (b) shows when the pressure to be measured is high. are shown respectively.

Each of these frequency signals f1. f2 pulsates depending on the operating condition of the engine, and in particular, as the pressure to be measured becomes higher and the engine speed increases, the period of pulsation becomes shorter, and the amount of change is still large. Therefore, it is no longer possible to accurately calculate pressure from the frequency signals f□ and f2.

FIG. 5 is a circuit diagram showing an example of variable filter circuits 61 and 62. This filter circuit is composed of a capacitor C and an FET functioning as a variable resistor, and a signal from the detection means 7 indicating the operating condition of the engine is applied to the gate of the FET to control its passband.

In the device according to the present invention, the frequency signals f and f2 from the respective excitation circuits MC□ and MC2 shown in FIG.
The voltage is applied to variable filter circuits 61 and 62 having a configuration as shown in the figure, where the pulsation rate that changes depending on the operating condition of the engine is removed.

Therefore, in the measurement circuit 8, the pressure signal can be determined by performing predetermined calculations without being affected by the pulsating wave component.

By adjusting the passing frequencies of the filter circuits included in the respective excitation circuits MC1 and MC2, the density sensitivity is equalized.
Vibration modes with different pressure sensitivities are selected.

That is, let f4□ be the resonant frequency of the fourth-order vibration mode in the circumferential direction and the first-order vibration mode in the axial direction of the cylindrical vibrator 1, and let f4□ be the resonant frequency of the fourth-order vibration mode in the circumferential direction and the second-order vibration mode in the axial direction. For example, each pressure sensitivity s4□.

S42 and density sensitivity 5d41 T 5d42 are (1
) formula, (2) formula.

(It can be expressed in three equations, and the density sensitivity can be made the same.

11 and --1(2) 42 ρo-R-H'(2πf42o)8d41"
Sd4 However, R: Radius of cylindrical oscillator 1 H: Thickness of cylindrical oscillator 1 g: Gravitational acceleration ρ: Density of cylindrical oscillator 1 Ro: Case inner diameter ρ: Constant determined by gas density and two vibration modes, In the case of the vibration mode described above, K = 132 f: Resonance frequency of the 4th order vibration mode in the circumferential direction and the 1st order vibration mode in the axial direction of the cylindrical vibrator in a vacuum state f: 20 cm circumference of the cylindrical vibrator in a vacuum state As is clear from the resonance frequency equation (1) of the fourth-order vibration mode in the direction and the second-order vibration mode in the axial direction, the pressure sensitivity ss is 41'
42 Resonant frequency f4□. " is inversely proportional to the square of 420. On the other hand, the density sensitivities Sa4□+sd4□ are equal and independent of the resonant frequency.

In this device, the cylindrical vibrator 1 is operated in two imaging modes: 4th order in the circumferential direction and 1st order in the axial direction (4th order in the circumferential direction and 2N in the axial direction (however, N
=4.2.3...) It is self-oscillating in a double mode with the following vibration mode. The resonance frequencies f4□ and f42 of these two modes are equal to the pressure P1 inside the cylindrical vibrator 1 and the pressure p outside, if higher-order nonlinear terms are ignored. Differential pressure P
, Equation (4) holds true for the fluid density ρ.

(If the density ρ is eliminated in the 4-n equation, the 5-n equation is obtained.

p=A((f,□/f4□o-1) -(f4゜/f4
2o-1)・BH3) However, A and B are calibration constants. Therefore, the measurement circuit 8 has each variable filter 61°62
By inputting the resonant frequency signals f4□, f4□ from the respective self-excitation circuits MC1, MC2 applied through the Furthermore, the target differential pressure P can be measured without being affected by pulsating wave pressure noise that changes depending on the operating status of the engine.

In the above embodiment, the cylindrical vibrator 1 is self-oscillated in a double mode so as not to be affected by the density of the fluid, and fl
, f2 is obtained, but if the influence of density can be ignored, the cylindrical vibrator 1 can be self-excited in one mode and the pressure can be determined from the resonance frequency. You can do it like this.

In addition, in the above explanation, the vibration modes of the cylindrical vibrator 1 are exemplified as 4th order in the circumferential direction, 1st order in the axial direction, 4th order in the circumferential direction, and 2Nth order in the axial direction. Also, a vibration mode that is least affected by the pulsating wave component may be selected depending on the operating condition of the engine.

Further, in the above description, the pressure measurement of the intake fluid of the engine has been described, but the same effect can be obtained even if the present invention is applied to general pressure measurement related to the engine.

[Effects of the present invention]

As explained above, according to the present invention, the bandpass characteristics of the variable filter circuit are changed according to the operating conditions of the engine, and the pulsating wave component mixed in the measured pressure is removed. Pressure can be measured stably and accurately.

[Brief explanation of the drawing]

FIG. 1 is a configuration block diagram showing an example of the device according to the present invention, FIG. 2 is a configuration diagram showing an example of the cylindrical camera element used in the device shown in FIG. 1, and (A) is a perspective view; (b) is (b)
Figure 5 is a Y-Y cross-sectional view in Figure 2 (a), Figure 4 is a waveform diagram of a frequency signal containing a pulsating wave component from the self-excited oscillator, and Figure 5 is a waveform diagram of the frequency signal containing the pulsating wave component from the self-excited oscillator. FIG. 2 is a circuit diagram showing an example of a variable filter circuit. 1... Cylindrical vibrator, EG... Engine, 5...
Self-oscillation circuit, 6... variable frequency filter circuit, 7...
- Operating condition detection means, 8... measurement circuit.

Claims (1)

[Claims] (1) A cylindrical vibrator to which measurement pressure is applied, a self-excited oscillation circuit formed by including this cylindrical vibrator, a variable frequency filter circuit to which the frequency signal from this self-excited oscillation circuit is input, and the operating status of the engine. a measuring circuit for inputting a frequency signal from the frequency variable filter circuit and performing a predetermined calculation to obtain a measured pressure signal, the pass band of the frequency variable filter circuit being determined by the signal from the driving condition detecting means. A pressure gauge characterized by controlling according to.