JPS5930440Y2 - pressure transducer - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a pressure transducer that converts pressure or differential pressure into electrical signals.

Pressure transducers, such as differential pressure transmitters using resonant wires 4, have been known in which pressure is varied by a vibrating differential pressure of a vibrator and the sound of this variation is electrically detected.

However, in this spring-type pressure transducer, the wire and pressure-receiving diaphragm are mechanically connected using gold, making the structure complicated and expensive, and it is necessary to apply bias tension to the twisted wire with a spring. Therefore, there were drawbacks such as an error sound occurring when the bias tension of the lever changes due to temperature or other factors.

This invention was made to eliminate these conventional disadvantages, and its purpose is to have a simple structure,
The objective is to provide pressure conversion benefits that enable accurate and stable pressure detection.

In order to achieve such a target sound, this invention has a structure in which a moving body is provided in the liquid facing the vibrator, and the facing distance from the vibrator changes depending on the sound receiving pressure of the moving body. By taking advantage of the fact that the frequency of vibration changes when an object 4 is brought close to a vibrating vibrator in a liquid, output sound can be detected without contacting the vibrator.

Hereinafter, a detailed explanation will be given based on this design drawing.

FIG. 2 is a sectional view of an embodiment of the pressure transducer according to this invention.

In the figure, a main body 1 has an internal space and a central key metal extending from the internal space to both sides, and a terminal body 2 is fitted and welded into the opening of the internal space.

Further, diaphragms 3 and 4 as pressure receiving elements are welded and attached to both side surfaces of the main body 1 through gap metals, respectively.

A sealed space surrounded by the main body 1, diaphragms 3 and 4, and the terminal body 2 is filled with a liquid made of incompressible silicone oil.

On the other hand, from the inner surface of the terminal body 2, there is a cantilever beam 5 as a moving body.
The cantilever beam 5 is provided with tuning fork-shaped vibrators 6 and 7 facing each other on both sides of the cantilever beam 5.
are fixed with screws.

Piezoelectric elements 8 and 9 are fixed to the vibrators 6 and 7, respectively, and the electrodes of the piezoelectric elements 8 and 9 are connected to terminals 12 and 13, which are hermetically sealed to the terminal 2 with an insulating material 10 and 11, respectively, using lead wires. It is connected.

Note that 14 is a terminal that is directly inserted into the terminal body 2 and welded.

The tips of the cantilever beams 5 are connected to the diaphragms 3 and 4 by pins 15 and 16 arranged in the center hole of the main body 1, respectively.

Figure 2 explains the vibration state of the vibrator, where A is a surface view and Figure 2 is a front view.

The vibrator 7 is formed into the shape of a flat tuning fork made of a constant elastic metal sheet made of Elinba, Ni 5panC, etc. A piezoelectric material such as Zno is deposited on one leg, and a thin film electrode is deposited with gold on this piezoelectric material to form a piezoelectric element. A lead wire is connected to this thin film electrode.

The other electrode of the piezoelectric element 9 is formed by the vibrator 7 itself, and this electrode is commonly connected to the terminal 14.

Note that 7a is a mounting hole for mounting the vibrator 7 to the terminal body 2.

When an alternating current voltage is applied between both electrodes, each leg of the vibrator 7 is deflected in the opposite direction as shown by the arrow in A, and vibrates at a natural frequency.

The shape and operation of the vibrator 6 are exactly the same.

For such a configuration, terminals 12 and 14 and terminal 1
When an oscillation circuit is connected between 3 and 14, the oscillators 6 and 7
each vibrates automatically at its own natural frequency.

Here, when a difference occurs in the pressure applied to the left and right diaphragms 3 and 4, the cantilever beam 5 is deflected in the left-right direction in FIG. 7 and the cantilever beam 5 vary differentially.

Due to this change in the facing distance, the influence of the surrounding liquid on the Equation 1 Ryo L7, that is, the equi-oblique added mass and the damping characteristics, changes, and each frequency moves in the opposite direction (if one increases, the other decreases). change to).

Therefore, if the frequency change of the vibrators 6 and 1 is detected,
Be able to measure the pressure difference applied to diaphragms 3 and 4.

In this case, since the frequency changes differentially depending on the deflection of the cantilever beam 5, the effects of changes in the density and viscosity of the surrounding liquid due to humidity are canceled out and do not appear in the measurement results.

Therefore, highly accurate pressure detection is possible.

Next, the operation of the electric circuit of this pressure transducer will be explained.

FIG. 3 is a circuit diagram of this electric circuit.

In the figure, 20a and 20b are excitation parts, and the amplification element 21
A well-known identification circuit is formed using 22 gold.

The terminal 12 is connected to the input end of the amplification element 21, the terminal 13 is connected to the input end of the amplification element 22, and the terminal 14 is connected in common.

The excitation gH (20a constitutes the oscillation circuit of the vibrator 6, and the excitation section 20b constitutes the oscillation circuit of the vibrator 7.

30a. Reference numeral 30b denotes a counter section, each of which is constructed by connecting flip-flops, and divides the frequency of the oscillation output sound of the excitation sections 20a and 20b.For example, when obtaining a resolution of 4 of 0.05%, it is formed into 12 focal points. .

Reference numeral 40 denotes a logic operation section, which consists of an exclusive OR gate 41 which outputs four divided outputs from the counter sections 30a and 30b, and an AND gate 42 as well.

The output of the AND gate 42 is the counter section 30a.

Use it as a reset signal to reset the flip-flop of 30b synchronously.

50 is the analog output section, exclusive or get 4
1, an amplifier 52 that compares the smoothed output sound with a constant voltage, and an FE controlled by the output of the amplifier 52.
FE that provides a constant drive current of 4 to T53, amplifier 52, etc.
T54, a resistor 55 for feeding back a voltage corresponding to the load current to the gold amplifier 52, and the like are included.

Although not shown, a power source and a load are connected to the output terminals 17 and 18.

Next, the operation of such a circuit will be explained with reference to the time chart shown on the fourth page.

When the frequency of the vibrator 6 becomes higher than the frequency of the vibrator 7 due to the pressure difference, the output of the counter section 30a first changes from "L" to "H", and the output of the counter section 30a changes from "L" to "H".
It is reset simultaneously with the change of the output to "H".

Figure 4 A9 is the counter g1530a, 30 at this time.
The waveforms of each output of b.

When the frequencies of the vibrators 6 and 7 are equal, the counter section 30
Since the outputs of a and 30b are in phase, their waveforms are as shown in Fig. 4, c and 2.

In addition, when the frequency of the vibrator 7 becomes higher than the frequency of the vibrator 6, the output of the counter section 30b becomes "L" first.
to 'XH', and is reset at the same time as the output of the counter section 30a changes to 'H'.

FIGS. 4E and 4B show waveforms 4 of the respective outputs of the counter sections 30a and 30b at this time.

Therefore, from exclusive or gate 41,
As shown in FIG. 4, a pulse width signal having a pulse width corresponding to the difference in frequency between the two plate movers is output.

This pulse width signal is smoothed through a capacitor 51 and then amplified, and an analog signal corresponding to the frequency difference is output from output terminals 17 and 18.

FIG. 5 is an explanatory diagram of another embodiment of the vibrator.

The vibrators 6 and 7 made of constant elastic metal are formed into a normal U-shape, and the ends of the legs repeatedly approach and separate from each other to vibrate in the direction of the arrow.

The inner leg faces the cantilever 5, and piezoelectric elements 8 and 9 are fixed to the outer legs, respectively.

In the above embodiment, two vibrating springs were provided for differential pressure, but pressure measurement is also possible even with two vibrating rings.

The casing was made of constant elastic metal Kongo for the oscillator, but it was made of crystal.

A piezoelectric element such as a piezoelectric ceramic can also be used as a gold vibrator.

1.The two diaphragms on both sides were used to displace the cantilever beam by 4 degrees due to the differential pressure, but it is also possible to apply 4 pressures from only one side and use it as a pressure gauge.

In this way, according to the pressure transducer according to this invention, since it is not directly connected to the vibrating metal pressure receiving element,
The structure is simplified and the vibrator can be easily mounted and fixed.

Since there is no need to add bias tension 4,
It has many excellent effects, such as enabling accurate and stable pressure detection without temperature errors.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of one embodiment of the pressure transducer according to this invention, Fig. 2 is an explanatory diagram of the vibrator, Fig. 3 is a circuit diagram of the electric circuit, Fig. 4 is a time chart, and Fig. 5 is It is an explanatory view of other examples of a vibrator. 1... Main body, 2... Terminal body, 3, 4...
...Diaphragm, 5...Cantilever beam, 6
, 7... Vibrator, 8°9... Piezoelectric element, 12, 13, 14... Terminal, 15.16.
·····pin.

Claims (1)

[Scope of utility model registration request] A vibrator disposed in a liquid filled in a quadruple space between a pressure receiving element and a main body, an oscillation circuit for vibrating this vibration, and an oscillation circuit disposed in the liquid facing the vibrator, the pressure receiving element A pressure conversion system comprising: a movable body whose facing distance with a vibrator changes according to the displacement of the metal; vessel.