JPS5811015B2 - pressure sensor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pressure sensor that uses a piezoelectric vibrator, particularly a quartz crystal vibrator, to sense force, particularly the pressure of a gas or liquid, and generate an electrical signal proportional to the pressure. .

BACKGROUND ART In conventionally known pressure sensors that use piezoelectric vibrators, especially quartz crystal vibrators, in many cases the point of action of the force to be sensed is localized or point-like. It has not always been possible to obtain a sensor having a good structure for measuring atmospheric pressure, such as when a gas or liquid, ie, a fluid, is exposed to the atmospheric pressure.

On the other hand, when a piezoelectric vibrator, especially a crystal oscillator, is used to sense force, it is possible to form an oscillation circuit and measure the force using the frequency value of the oscillation output.In this case, the resulting signal Since this is suitable for digital processing of frequency values, it is extremely preferable to construct a sensor that senses force or pressure using a piezoelectric vibrator.

OBJECTS OF THE INVENTION The object of the present invention is to obtain a new structure of a sensor using a piezoelectric vibrator suitable for measuring the pressure of gas or liquid.

DISCLOSURE OF THE INVENTION The sensor of the present invention uses a plate-shaped piezoelectric vibrating body, and extracts an electric signal (vibration frequency) generated by the vibration of the central portion of the piezoelectric vibrating body.

A sensing curved body (particularly a spherical body) is attached to cover the central vibrating part of the piezoelectric vibrating body in a non-contact manner, and the periphery of the curved body is fixed to the periphery of the piezoelectric vibrating body.

The force or pressure felt by the curved body is transmitted to the piezoelectric vibrating body through the fixed part, and by deforming the piezoelectric vibrating body, the oscillation frequency (natural frequency) changes according to the deformation, so the frequency You can know the power of sensing based on.

A curved body is a medium that senses and transmits force or pressure, and also functions as a cover that shields the piezoelectric vibrating body, especially its vibrating part and the electrodes attached to the vibrating part, from the atmospheric fluid. It is preferable to cover each of the plate surfaces (the front and back surfaces of the vibrating part of the plate-shaped piezoelectric vibrating body) to which the electrodes are attached with a curved cover.

This also helps to equalize the forces acting on the piezoelectric vibrator.

Effects of the Invention When a spherical surface is set as the curved surface body, the force of the atmospheric fluid to be measured acts uniformly on the sensing part (spherical part), making it possible to measure fluid pressure without error.

Since the oscillation frequency (output signal of the oscillation circuit) is obtained as a digital value, it is suitable for remote transmission, processing of measurement results using a computer, and data processing of the song.

BEST MODE FOR CARRYING OUT THE INVENTION A plate-shaped crystal piece is used as a piezoelectric vibrating body, and electrodes are attached to both the front and back sides of the central part of the crystal piece to form a disk shape, and a vibration frequency signal obtained by the vibration mode of the central region is obtained. Take out.

The curved body is formed to have a spherical curvature, and serves as a cover for each of the front and back surfaces to prevent the electrode portion from being exposed to the atmosphere.

Embodiments will be described below with reference to drawings showing embodiments.

A disc-shaped crystal piece (hereinafter referred to as crystal resonator 1).

) is fixed to the lower surface of the peripheral edge 411 of the upper curved body 41, and the peripheral edge of the lower surface is fixed to the lower surface of the peripheral edge 411 of the upper curved body 41.
It is fixed to the upper surface of the peripheral edge part 421 of No. 2.

The upper curved body 41 also serves as an upper cover, and the lower curved body 42 also serves as a lower cover, and their fixed portions with the crystal resonator 1 are annular at the periphery of the crystal resonator 1.

The dome portions of the upper cover 41 and the lower cover 42 function as sensing portions that sense the atmospheric (external) force or pressure to be measured.

The force acting on the dome portion of the upper cover 41 (other than the edge 411) is made uniform, the force acting on the dome portion of the upper cover 42 is made uniform, and the force acting on the upper cover 41 and the force acting on the lower cover 42 are made uniform. In order to make the same force, an axis that commonly passes through the center of curvature of the upper cover 41 and the center of curvature of the lower cover 42 connects the center of the disc of the crystal resonator 1 with the upper and lower surfaces of the crystal resonator 1 perpendicularly. In this case, the upper cover 41 and the lower cover 42 have the same curvature, and the upper cover 41 and the lower cover 42 have the same structural dimensions (for example, thickness), material, and treatment. Furthermore, the upper and lower surfaces of the crystal resonator 1 are made parallel and the entire thickness is set to be the same.

It is desirable that the vibration frequency of the crystal resonator 1 is not affected by changes in ambient temperature.

For this purpose, an AT cut or, to a lesser extent, a BT cut, is used (however, this does not mean that cuts with other angles than these cuts cannot be used).

In general, the purpose of use of the sensor, the magnitude of the pressure to be measured, the range of change, and the usage environment (including the fluid to be measured).

) and the temperature and atmosphere conditions (temperature values and their changes), etc., and select one with an appropriate cutting angle.

The materials of the upper cover 41 and the lower cover 42 have appropriate flexibility (elasticity) and rigidity, and the temperature characteristics of the crystal resonator 1 (when considering the influence of the oscillation frequency deviation temperature characteristics) A material having the same temperature characteristics as that of the crystal resonator 1 is selected.

Materials suitable for such requirements can be found, for example, in nickel chrome steel, permalloy, stainless steel, and the like.

Regarding the balance between flexibility and rigidity, the upper cover 41
, the thickness of the lower cover 42 is also considered.

The electrode 21 on the top surface is an electrical signal extraction lead (hereinafter referred to as lead).

) 31, and the electrode 22 on the lower surface is connected to a lead 32.

An internal upper space 51 is formed between the upper surface of the crystal resonator 1 and the upper cover 41, and an internal lower space 52 is formed between the lower surface of the crystal resonator 1 and the lower cover 42.

These upper space 51 and lower space 52 are filled with an appropriate fluid so as to maintain a known reference pressure (for example, the material of the crystal resonator 1, the material of the electrodes 21 and 22, and the material of the upper cover 41).
, filling the material of the lower cover 42 with a gas, etc. that does not have a chemical effect: In addition to selecting the type and properties of the gas, etc., it is necessary to mechanically or electrically influence the parts that come into contact with the gas, etc. It is also possible to apply a film coating using a type of substance that is not attacked by gas or the like in such a manner that it does not cause any damage.

) or vacuum, and the upper space 51 and lower space 52 are both set to have the same known pressure (reference or standard pressure, or the same degree of vacuum).

When measuring the pressure of a liquid or gas, it is attached to an appropriate support structure and placed in the atmosphere of the liquid or gas to be measured.

In the case shown in FIG. 4, the sensor is placed in the box (or chamber) 6 as necessary, and the fluid is introduced from one side of the distribution lower 172 and the other, or the on-off valve 8 of the distribution lower 1 is introduced.
The measurement is performed by closing one of the on-off valves 82 of No. 1 and 72 and introducing from the other.

The pressure P introduced into the inside of the box 6 acts on the upper cover 41 and the lower cover 42 as either a pressing force P1 or a pulling force P2, and this force P1 or P2 acts on the edge 411,
421 to the internal crystal oscillator 1 (when pressure acts as a pressing force P1 on the upper cover 41 and lower cover 42) or inward compressive force F2 (when pressure acts on the upper cover 41 and the lower cover 42 as a pressing force P1) (when acting as a pull-out force P2 on the cover 41 and lower cover 42), and the oscillation frequency of the crystal resonator 1 shifts to a value corresponding thereto.

In this case, if the pressure P of the introduced fluid is larger than the pressure in the upper space 51 and lower space 52 inside the sensor, it acts as a pushing force P1, and if it is smaller than the pressure in the upper space 51 and lower space 52, it acts as a pulling force P2. .

Note that if the upper space 51 and the lower space 52 are in a vacuum, a pressing force P1 is applied.

The greater the curvature of the dome portions of the upper cover 41 and lower cover 42, the better the sensitivity, and the smaller the curvature, the lower the sensitivity.
Set to an appropriate value depending on the purpose of use, etc.

Even if there is no box 6 and there is an open atmosphere, the measurement operation is the same.

Note that although the structure supporting the sensor is not shown in FIG.
1 or the side ends of the crystal oscillator 1 between them), the sensor can be attached to any location of the box 6 or any appropriate location of the music device.

Further, the leads 31 and 32 are also led out by appropriate means, such as using the mounting structure as a support base.

If it is necessary to prevent the crystal oscillator 1 from being chemically affected by atmospheric fluid, the side edges (between edges 411 and 421) should be made of a material that is not affected by chemical effects from the atmosphere. Cover appropriately.

In this case, the upper cover 41 and the lower cover 42 are also made of a material that is not susceptible to chemical effects from the atmosphere (the outer surface may be coated with a film).

In addition, in the above explanation, spatial symmetry such as upper, lower, upper surface, lower surface, etc. is a measure for convenience of explanation, and is not equivalent or essential, and is based on the view of the drawings of the embodiment. They are simply used interchangeably.

Advanced Embodiment FIG. 5 shows an embodiment of a structure that integrally functions as a structure supporting the entire sensor and a structure supporting the leads. Reference numerals 41 and 42 denote the upper cover and lower cover, respectively, which have already been described. It has the same meaning as cover (the phrases ``up'' and ``down'' are for convenience, and there is no need to restrictively understand the symmetry of directions such as ``up'' and ``down'').

In this example, the edge portions indicated by symbols 411 and 412 are the peripheral edges of the upper cover 41 and the lower cover 42, respectively, and the crystal resonator 1, the upper cover 41, and the lower cover 4.
In addition to functioning as a fixed connection with the edge 411, the leg 412 is integrally formed with the edge 411 and extends from the edge 411, and a leg 422 is formed integrally with the edge 421 and extends from the edge 421, respectively. Legs 412, 422 function as structures that support the entire sensor.

In practice, the part of the annular body corresponding to the edge 421 and the leg 42
The annular body part of the two parts integrally made is brought into contact with the edge 421 of the lower cover 42, and the contact part is fixedly joined or bonded.

The same applies to the legs 412 of the upper cover 41.

The tips 413 of the legs 412 and the tips 423 of the legs 422 are plug terminals (although they are shown as male terminals in FIG. 5, they may also be female terminals).

) is designed to function as

The lead 31 is provided on one side of the leg, for example, by printing, and is led to the tip of the plug terminal 413.

In this regard, the parts of the legs 412 (including the parts of the circumferential annular edge 411 if necessary) are made of an electrically insulating material, or at least the parts that carry the printed leads 31 are made of an insulating material as appropriate. It is assumed that the following processing has been applied.

Leg 422 has another lead 32 (not visible in FIG. 5).

) are set up in the same way.

By inserting the plug terminals 413, 423 into appropriate connection points such as the jack terminals of the connector, the oscillation frequency signal of the crystal resonator 1 can be taken out to the outside of the sensor.
Moreover, the sensor itself can be supported spatially.

In this case, instead of inserting the tips 413 and 423 into the connector, the tips 413 and 423 are inserted into the hole where the print is introduced on the board.
423 may be inserted to make an electrical connection between the printed leads 31 and 32 and printed conductors on the board.

FIG. 6 shows an embodiment in which the legs supporting the sensor are also used as leads for deriving the oscillation signal of the crystal resonator 1.

In this case, the edges 412, 422 and the legs 412, 422 are made of conductive metal, and the legs 412 are formed integrally with the dome portion of the upper cover 41 and its edges 411, and the separate legs 412 are joined. (The dome part 41, the edge 411, and the legs 412 are made integrally from the beginning by stamping molding from the same material, etc.), similarly, the legs 422 are made integrally with the dome part of the lower cover 42 and its edges 421. form.

In this case, the legs 412 and 422 double as the leads 31 and 32 of FIGS. 1, 2, and 3, respectively.

The materials listed above for the upper cover 41 and the lower cover 42 can be used as lead materials for deriving the oscillation signal in this case.

The electrode 22 at the center of the circle, which extracts the vibration signal of the crystal oscillator 1, is guided to a conductor 221 at its periphery, and this circumferential conductor 221
Overlap the annular edge 421 of the lower cover 42 on top and join (
(structural bonding and electrical connection) to derive the oscillation signal of the crystal resonator 1 to the leg 422.

The same goes for leading out to the leg 421.

As in the case of FIG. 5, the tips 413 and 423 are inserted into, for example, a printed conductor on a board to support the sensor itself and to make an electrical connection.

The legs 411 and 421 are shown bent in FIG. 6 for convenience in providing structural cushioning properties.

Industrial Applicability The sensor according to the present invention is used as an element constituting an oscillation circuit in which the piezoelectric vibrator is the main element that determines the oscillation frequency.

The force sensed by the piezoelectric vibrator is understood as the frequency value of the output signal of the oscillation circuit, and the change in the sensed force is observed as a change in the frequency value.

As is well known, since the oscillation frequency of the piezoelectric vibrator (crystal resonator), that is, the output of the oscillation circuit, and the sensing force of the piezoelectric vibrator (crystal resonator) can be obtained through a proportional relationship, the output signal of the oscillation circuit Sensitivity can be determined based on the frequency value of .

If a fluid with a known pressure is sealed in the upper and lower spaces inside the sensor, set it so that the reference oscillation frequency is obtained when the external pressure is in equilibrium with the internal pressure (the external pressure to be measured). is the reference state, and if the external pressure increases or
Set the cutting angle and the factors of the song so that when the external pressure increases, the oscillation frequency increases or decreases accordingly. The oscillation frequency can be set to either decrease or increase when the external pressure decreases, but if the oscillation frequency increases when the external pressure increases, then the oscillation frequency increases when the external pressure decreases. The combination is set so that the oscillation frequency decreases, and if the oscillation frequency decreases when the external pressure increases, the oscillation frequency increases when the external pressure decreases.

When the internal upper space and lower space are vacuum, external absolute pressure is measured, and in this case, the change in oscillation frequency corresponding to a monotonous change in external pressure is monotonous.

The sensor of the present invention is used to measure force in a field that has a uniform distribution over a wider area than the sensing area of the force sensing part (upper cover, lower cover), especially pressure of gas or liquid. Suitable as a sensor.

However, the application is not limited to such cases, and as long as the force felt in the sensing part is transmitted through the deformation of the sensing part and the deformation of the piezoelectric vibrating body through the edge part, the sensing part can be used. It can also be used as a sensor to measure the force felt only at a partial location within the sensing part.

The sensor of this invention can generally be obtained as a small and lightweight one, and when a crystal resonator is used as the piezoelectric vibrator, the oscillation frequency changes sensitively (highly sensitive) in response to changes in external pressure. In this case, a device whose internal space is set to a vacuum can be used as an atmospheric pressure sensor for measuring atmospheric pressure in the sky by suspending it from a radiosonde and emitting hot water during weather observation.

[Brief explanation of drawings]

Each of the figures from Fig. 1 to Fig. 6 is for explaining this invention, Fig. 1 is a front view, and Fig. 2 is a plan view (
3 is a side sectional view taken along arrow A-A in FIG. 2, and FIG. 4 is a conceptual diagram showing an example of pressure measurement.
5 and 6 are perspective views of a further embodiment of that shown in FIG. 1; FIG. The meanings of the main symbols are as follows. 1...Crystal resonator (piezoelectric vibrator), 21, 22...
Electrode, 221... Conductor, 31, 32... Lead (electrical signal extraction lead) 41... Upper cover (upper curved body), 42... Lower cover (lower curved body), 411
... Edge of upper cover, 421... Edge of lower cover,
412゜422... Leg, 413,423... Plug, 51... Upper space inside, 52... Lower space inside, 6... Box or chamber, 71, 72... Distribution port , 81
, 82... Opening/closing valve, Pl, F2... Force acting on the upper cover and lower cover, Fl, F2... Force acting on the crystal resonator.

Claims (1)

[Scope of Claims] 1. A plate-shaped piezoelectric vibrating body, which covers the piezoelectric vibrating body at a distance from the vibrating part of the piezoelectric vibrating body, and has a peripheral edge fixed to the peripheral edge of the piezoelectric vibrating body, and has flexible elasticity. A pressure sensor characterized by having a curved surface. 2. The pressure sensor according to claim 1, wherein the piezoelectric vibrator is a crystal oscillator. 3. The pressure sensor according to claim 1, wherein both sides of the piezoelectric vibrating body are covered with curved bodies. 4. The pressure sensor according to claim 1 or 3, wherein the curved body is a surface having spherical curvature. 5. a plate-shaped piezoelectric vibrating body; a curved body that is spaced apart from the vibrating part of the piezoelectric vibrating body, covers the piezoelectric vibrating body, has a peripheral edge fixed to the peripheral edge of the piezoelectric vibrating body, and has flexible elasticity; A pressure sensor characterized by having legs that are integrally formed with the periphery of the curved body and extend and project. 6. The pressure sensor according to claim 5, wherein the legs are used as supporting bases for leads that derive oscillation signals from the piezoelectric vibrating body. 7. In the pressure sensor according to claim 5, a conductor ring is provided at the edge of the piezoelectric vibrator and connected to an electrode for extracting a vibration signal of the piezoelectric vibrator, and a leg made of a conductor is attached to the conductor ring. pressure sensor bonded with